MASTER-30-99-00-0103-1

ENGINEERING SPECIFICATION

ES 30-99-00-0103

PIPELINES LAUNCHER & RECEIVER SYSTEMS

2 25.03.2007 SPrE (HH) SSpE (KG) HE (JD/FG) Promoted to be ADCO Standard

1 3.11.2004 ILF SME (KG)/ SPrE (AW) HE (JD/FG) Project Specific

REV. DATE ORIGINATOR REVIEWED (Custodian)

APPROVED (Forum Facilitator)

DESCRIPTION

THIS DOCUMENT IS INTENDED FOR USE BY ADCO AND ITS NOMINATED CONSULTANTS, CONTRACTORS, MANUFACTURERS AND SUPPLIERS.

ORIGINATOR: ENGINEERING SUPPORT DEPARTMENT

ADCO Doc. No. ES30-99-00-0103-1 Project No. MASTER Pages 61

Project No.: MASTER DOCUMENT TITLE:

ADCO DOC. NO. 30-99-00-0103-1

REV. 2 DATE :March 07

PIPELINES LAUNCHER & RECEIVER SYSTEMS PAGE 2 OF 61

TABLE OF CONTENTS

1. INTRODUCTION 3

2. TECHNICAL DESIGN SPECIFICATION 9

3. LAY-OUT, ANCILLIARY FACILITIES AND OTHER CONSIDERATIONS 46

4. DESIGN CONSIDERATIONS FOR SOUR SERVICE 50

5. OPERATING PROCEDURES 53

6. SAFEGUARDING SYSTEM AND PHILOSOPHY 53

7. SUGGESTED PIGGING SCHEDULING 58

8. SAFETY PRECAUTIONS 58

9. EMERGENCY SHUTDOWN (OPTIONAL) 59

10. SHARED (TEMPORARY) PIG TRAPS 59

11. PIG TRAP DATA SHEET 60

12. TYPICAL PIG LANUCHER/RECEIVER SYSTEM ARRANGEMENT 60

13. MECHNICAL INTERLOCK SEQUENCE – A CASE EXAMPLE 61

ATTACHMENTS

APPENDIX - 1 : DATA SHEETS – LAUNCHER & RECEIVER

APPENDIX - 2 : TEMPLATE PID AND OPERATING SEQUENCE FOR OIL PIG

TRAPS

APPENDIX - 3 : TEMPLATE P& ID AND OPERATING SEQUENCE FOR GAS

PIG TRAPS

APPENDIX - 4 : TEMPLATE P& ID AND OPERANTING SEQUENCE FOR MULTI

PHASE FLOW PIG TRAPS

APPENDIX - 5 : PIPELINE PIGGING REQUIREMENTS

APPENDIX - 6 : INTRUSIVE AND NON-INTRUSIVE PIG SIGNALLER VENDOR

SKETCHES

APPENDIX - 7 : FLOW RAE VS VELOCITY GRAPH – LIQUID & GAS

APPENDIX - 8 : BARRED TEE

APPENDIX - 9 : PIG TRAP INTERLOCK SYSTEM – CASE EXAMPLE


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1 INTRODUCTION

1.1 Scope

This Standard Design Specification (SDS) specifies requirements and gives recommendations for the design of pig trap systems across all ADCO Fields having a diameter of 200 mm to 1400 mm (8 to 56 inch). It is provided for use by the project teams and design contractors. It is written in the context of onshore horizontal pig trap systems for liquid, gas and multi-phase hydrocarbon fluids either permanent or temporary installations and shall not cover Automatic and Bi-directional Pigging. This SDS consists of specific design directives, recommended practices and typical operational requirements. Exact direction has been provided where possible. In addition, it incorporates all the requirements of Shell Design Engineering Practice (DEP) titled “Design of Pipeline Pig Trap Systems” DEP 31.40.10.13-Gen (December 1998 issue including DEP circular 18/02).

1.2 Intended Use and Regulatory Considerations

This SDS is intended for use while designing pigging facilities for new pipeline. This specification shall standardise the minimum safety measures and configurations for launcher / receiver systems. It will serve as a basis for ongoing and/ or new projects and shall be used to scrutinize the existing systems to determine their deficiencies. If UAE local regulations exist in which some of the requirements may be more stringent than SDS, the Contractor shall determine by careful scrutiny which of the requirements are more stringent and which combination of requirements will be acceptable as regards safety, environmental, economic, and legal aspects. In all cases the Contractor shall inform ADCO of any deviation from the requirements of SDS which is considered to be necessary in order to comply with UAE local regulations.

1.3 General Definitions

The Contractor is the party that carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project, or operation or maintenance of a facility. ADCO may undertake all or part of the Contractor duties. The Manufacturer/Supplier is the party that manufactures or supplies equipment and services to perform the duties specified by the Contractor.


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ADCO (Abu Dhabi Company for Onshore Oil Operations) is the party that initiates the project and ultimately pays for its design and construction. ADCO will generally specify the technical requirements or may also include an agent or consultant authorised to act for, and on its behalf. The word “must/shall” indicates a mandatory requirement. The word “should” indicates a preferred course of action. The word “may” indicates one acceptable course of action.

1.4 Specific Definitions

Balance Line A small-bore line that allows pressurisation of the barrel on

both sides of a pig at the same time. Barred Tee A tee-piece provided with bars across the internal bore of the

side branch to prevent entry of a pig. Bypass Line Piping between the pipeline and associated plant or facility

through which fluid flows under normal operational conditions. Cup/Disc Flexible membrane forming a seal between the pig and the

pipe wall. Drain Line A small-bore line used to drain fluid from the barrel. End Closure A fitting, including a removable part or assembly that provides

quick and easy access to the major barrel when open and seals the bore when closed.

Kicker Line Piping connection from pig trap to incoming/outgoing pipeline used to promote movement of pig into/out of a pig trap.

Main Line The major portion of a pipeline, between pig traps. Major Barrel Enlarged pipe section used for used for loading or retrieval of

pigs. Minor Barrel Pipe segment between reducer and pig trap isolation valve, of

the same diameter as the pipeline. Pig A mechanical device driven through pipeline-by-pipeline fluids

to prepare, gauge, inspect or maintain a pipeline in a suitable condition.

Pig Launcher A pig trap for launching pigs into the pipeline and comprises major and minor barrel with reducer, end closure and instruments.

Pig Receiver A pig trap for receiving pigs from the pipeline and comprises major and minor barrel with reducer, end closure and instruments.

Pig Signaller A device installed on a pipeline or pig trap to give an indication of the passage of a pig.

Pig Trap General terminology for pig launcher and receiver.


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Pig Trap System

A pig trap together with all associated piping, valves, supports and instruments.

Piping Pipework associated with the pipeline but not part of the main line.

Pressurising Line

A small-bore line with valves to allow equalisation of pressure across a larger valve, avoiding damage to the seats of the larger valve.

Catch Pit or Drip Tray

Draining facility underneath an end closure.

Tell-tale vent or Safety bleeder

A safety device as part of the end closure door locking mechanism to safeguard personnel during door opening.

1.5 Applicable Codes and Standards

All design, engineering and materials shall generally conform to the latest issue of Shell DEP’s except where ADCO standards, philosophies, specifications, local statutory codes and regulations and the Technical provisions of this section indicate otherwise. The order of precedence of requirements shall generally be as follows, unless otherwise directed in writing by ADCO:

UAE Local Statutory Codes and Regulations,

Project Specific Features and Design Requirements.

Technical Specific Features and Design Requirements under this SDS,

Shell DEP’s and all referenced Codes and Standards therein,

ADCO HSE Manual and ADCO HSE Risk Management

International Codes and Standards

1.5.1 SHELL DEP Standards

[Ref 1] Design of Pipeline Pig Trap Systems

: 31.40.10.13-Gen

[Ref 2] Pipeline Fittings

: 31.40.21.30-Gen

[Ref. 3] Pig signallers : Intrusive type

: 31.40.21.33-Gen

Pressure vessels (Amendments/Supplements to ASME VIII, Div. 1 and Div. 2)

: 31.22.20.31-Gen


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Data/requisition sheet for design of a pig trap system for a pipeline

: 31.40.10.93-Gen

Data/requisition Sheet for pig trap end closure

: 31.40.21.94-Gen

Pressure relief, emergency depressurising, flare and vent systems.

: 80.45.10.10-Gen

EP HSE Manual (Shell Standard)

: EP-95000

1.5.2 International Standards (Latest Applicable Revision)

Process Piping : ASME B 31.3 Liquid transportation systems for hydrocarbons, LPG, anhydrous ammonia, and alcohols

: ASME B 31.4

Gas Transmission and distribution piping systems : ASME B 31.8 ASME Boiler and Pressure Vessel Unfired pressure vessels

: ASME Section VIII

Sizing, Selection & Installation of Pressure Relieving Devices in Refineries. Isolation stop valves in pressure relief piping.

: API RP 520 part II, section 4

IP Model code of Safe Practice: Area Classification code for Installation & Handling of Flammable fluids

: IP 15

Pipeline Safety Regulation : BS8010 Parts 2 & 3

Sulphide stress cracking resistant metallic material for oil field equipment

: NACE MR0175

Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-Induced Cracking

: NACE TM0284

1.5.3 ADCO Standards for HSE

Health, Safety and Environment Management Policy Guidelines

:

Guidelines for Preparation of the Health, Safety and Environment (HSE) Philosophies Document

:

Environmental Protection and Occupational Health Management – Policy and Guidelines

:

Health, Safety and Environmental Risk Management Guidelines

:


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1.6 Climatic Conditions

Wind

i) Prevailing Direction From NNW ii) Mean Speed 8.0 m/s iii) Maximum Design Speed 44.7 m/s iv) Airborne Particles Saliferous dust and sand

with frequent sandstorms

Temperature

i) Maximum Solar 85 ° C ii) Maximum Shade 58 ° C iii) Average Shade Summer 36 ° C iv) Average Shade Winter 22 ° C v) Average Shade Yearly 28 ° C vi) Average Minimum Shade 4 ° C

Humidity

i) Relative Maximum at 43 °C 95% ii) Relative Maximum at 54 °C 60%

Solar Radiation => 946 W/m2 Rainfall

Dew => Heavy Mists => Early morning mists causing evaporative cooling loss

i) Frequency Infrequent ii) Maximum 51mm/year iii) Minimum Trace iv) Highest Rate Jan-Apr 25mm in 24 hrs


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1.7 Abbreviations

ADCO : Abu Dhabi Company for On shore Oil Operations

ADNOC : Abu Dhabi National Oil Company

API : American Petroleum Institute

ASME : American Society for Mechanical Engineers

CAPEX : Capital Expenditure

DEP : Design Engineering Practises

ESD : Emergency Shutdown

H2S : Hydrogen Sulphide

HAZOP : Hazard and Operability Study

HC : Hydrocarbon

HIC : Hydrogen Induced Cracking

HSE : Health, Safety and Environment

ID : Inside Diameter

IPS : Intelligent Pigging System

NACE : National Association for Corrosion Engineers

NPS : Nominal Pipe Size

P & ID : Piping and Instrument Diagram

PPM : Parts per Million

QOEC : Quick Opening End Closure

SDS : Standard Design Specification for Pig Trap system (Engineering

Specification for Pig Trap System)

UAE : United Arab Emirates

2 TECHNICAL DESIGN SPECIFICATION


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This SDS specifies requirements and recommendations for the design of horizontal pig trap systems for onshore pipelines liquid, gas and multi-phase hydrocarbon fluids, permanent or temporary installations. This Standard Design Specification shall be used for design purposes only and not for material procurement.

2.1 Description

A simple definition of Pig Trap is – a piece of pipeline equipment that allows easy loading or unloading of a pig into, or out of, the pipeline. Its purpose is to provide in a safe manner and without flow interruption the means to either insert and launch a pig into the pipeline or receive and retrieve a pig from a pipeline. A pig trap comprises the following basic components that are illustrated in attached template P & ID’s, Appendix 2, 3 and 4:

A quick opening closure or blanked flanged end, which provides quick and easy access to the major barrel when open and seals the bore when closed.

A major diameter section, referred to as the Major Barrel. An eccentric reducer for connecting the major and minor barrels. A minor diameter section corresponding to the line pipe size and referred to

as the minor barrel. Various nozzles such as vent, drain, pressure indicator, kicker, bypass,

relief, equalizing and pig signaller. Lifting lugs, supports and earthing lugs

The boundaries of a pig trap system are depicted in Figure 1 and are defined as:

A point on the incoming/outgoing pipeline, on the pipeline side of the main tee but including the main line pig Signaller.

The pipeline side of the isolation valve of connecting facilities. Kicker line and valves. Pig trap isolation valves. Instruments like pressure indicator, thermal relief valve

The sections below describe each pig trap and pig trap system component, in order to give a clear understanding of its purpose, and give detailed minimum requirements. The main components and configuration of typical pig trap are shown in template P & IDs. The requirements for additional components not shown in template P & IDs shall be determined in accordance with the Design Codes and standards specified in this document, based on actual service conditions.

2.2 Design Parameters


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In designing a pig trap system special attention shall be paid to the following features:

Safe operations with proper positive isolation this is achieved by fitting a

blank, insertion of a spade or by rotating a spectacle blind; Operational flexibility to facilitate commissioning and decommissioning

operations; Adequate venting, draining and purging facilities; Facilities for possible chemical injection, sampling, water dousing, etc.; Types of pigging operations (e.g. cleaning, intelligent, etc.) and

frequencies. General environmental criteria (maximum & minimum ambient

temperatures, etc); Pipeline fluid properties, including any corrosive or erosive materials; Pig trap layout and orientation; Operating conditions, design & test pressures and temperatures; Mechanical design codes, material of construction.

The design shall be based on the most onerous type of pigging operation, which is envisaged for the pipeline. This shall, in most cases, mean designing for intelligent pigs. Where intelligent pigging is not required, all aspects of this SDS remain except pig trap lengths and access area.

Pig traps system are designed and fabricated based on:

Basic design parameters Functional design parameters

The following sections describe the design parameters in detail.

2.3 Basic Design Parameters

The basic design parameters cover the following aspects of pig trap design.

2.3.1 Design Code and Code break

The pipeline design shall be based on ASME B31.4 or ASME B31.8, depending on the product.


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For the purpose of code break locations it is also assumed that the piping of the facilities to which the pipeline/pig trap system is connected is designed in accordance with ASME B31.3. Where this is not the case e.g. at intermediate pig trap stations (e.g. Mile Stations) or where the pig trap ties into a slug catcher designed to ASME B31.8, the code break is not applicable. The entire pig trap system should be designed, constructed and tested according to the same code as the pipeline. There are 4 options of design code break between ASME B31.8/B31.4 and ASME B31.3 [Ref 1]. The design code break between ASME B31.8/B31.4 and ASME B31.3 shall be as depicted in Figure –1 when pig traps are procured as prefabricated item.

Wall thickness transitions shall meet the welding configuration requirements as specified in the design codes ASME B31.4 (clause 434.8.6) and ASME B31.8 (Appendix I, Figure I5). The distance between welds for fittings and branch connections shall be at least one pipeline diameter, but not less than 300 mm. The maximum thickness for design pressures shall not be greater than 1.5 t, where t is the nominal thickness of the thinner pipe. Pipes with a wall thickness less than 5.6 mm shall not be used.


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2.3.2 Design Factor

For pipelines designed with a hoop stress design factor higher than 0.6, the pig trap systems shall be designed with a factor of 0.6, to increase safety margins. For pipelines designed with a hoop stress design factor equal to 0.6, the pig trap systems shall be designed with a factor of 0.5, to increase safety margins. For pipelines designed with a factor of less than 0.6, the pig trap systems shall be designed with a factor equal to that of the pipeline. This design factor shall be applied to the pipe work within the boundaries of the pig trap system plot, including any corrosion monitoring pits associated with the pig traps. The above approach has the advantage that conversion of an oil pipeline to a gas pipeline can in practice be done without any modifications to the pig trap systems.

2.3.3 Design Pressure

The entire pig trap system shall be designed, constructed and tested according to the same code as the pipeline. The pig trap design pressure shall be equal to that of the associated pipeline.

2.3.4 Design Temperature

The maximum design temperature shall not be less than the maximum temperature, which the pig trap system could attain or to which it could be exposed during operation, start-up or shutdown. The minimum design temperature shall be based on minimum ambient temperature and on the conditions (e.g. blowdown), which could occur during operations. See Climatic Conditions para 1.6.

2.3.5 Design Velocities for Piping Diameter

The recommended maximum velocities for the purpose of piping diameter selection are: For piping in intermittent service: In case of liquid 8 m/s. In case of gas 40 m/s.


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For piping in continuous service: In case of liquid 4 m/s. In case of gas 20 m/s. Based on these velocities and the assumption that parts of the pig trap are in intermittent service, piping diameters are suggested in (Table 3). For every design, however, it should be checked that the velocities do not exceed designated maximum and that piping pressure drops are not excessive. For pigging speeds in the pipeline refer paragraph 2.4.1.3.

2.3.6 Test Pressure

The pig trap shall be hydrostatically tested in shop based on code requirements as indicated in the relevant data sheet.

2.3.7 Corrosion Allowance

In absence of other guidelines a minimum corrosion allowance of 3 mm shall be considered for minor barrel, reducer and major barrel. Caution: Due to 3mm corrosion allowance, the minor barrel ID would be less than the pipeline ID. This transition in thickness shall be smooth and verified as part of pipeline pigging studies to avoid pig getting stuck in the minor barrel.

2.3.8 Materials

The materials of construction shall be as indicated in the Pig Trap data sheet. To aid the selection process the line product shall be specified i.e. sour, toxic, corrosive along with impurities etc. This will influence the selection of metallic as well as elastomeric materials typically the sealing elements.

Metallic Materials:

All components in sour service shall be resistant to HIC (Hydrogen Induced Cracking) and conform to NACE specifications. All main line items shall be compatible with the line pipe with respect to weld ability, wall thickness/ material grade transitions and dimensions.


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Dimensional considerations include actual internal diameter, ovality and wall thickness transition taper angles.

All items shall be designed and manufactured to avoid brittle fracture at possible low service temperatures. Although transmission pipelines are excluded from its scope it may be relevant for many of the pig trap components especially the vent / blowdown line in high pressure gas systems. For selection of metallic materials refer DEP 30.10.02.11 - Gen.

Non-metallic Materials (especially the elastomer seals):

The properties of elastomeric seals are strongly influenced by the choice of compounding ingredients for the base polymer, fillers, additives, curing system, and by the compounding process. For the selection of a seal, it is therefore important to specify the desired performance properties, which the seal must meet instead of selecting on the basis of an elastomer type.

Elastomeric seals have to meet three basic requirements:

1) the material must be chemical resistant to the environment with which it

will be in contact; 2) the material must be able to withstand the temperature in service and

during storage; 3) the material must be able to withstand mechanical loads as pressure,

stress or abrasion. When selecting a suitable material for seal application the following mechanical properties shall be specified:

1) The required hardness: quoted in shore A or IRHD, the normal hardness for sealing application lies between 60 - 95 IRHD (according to ASTM D 2240 or ISO 48);

2) Compression set: this is the ability of an elastomer to recover from a deformed state to original dimensions; a low compression set is usually preferred in seal applications, testing according to ASTM D 395 or ISO 815;

3) Tensile strength, elongation, modulus at 100 % elongation: characterises the material strength and stiffness, according to ASTM D 412.


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4) Attention shall be paid to some special seal problem areas as: a. Explosive decompression (ED): sudden decompression from a high

pressure gas environment can lead to the production of blisters and surface splits in most elastomers. For further information, see DEP 30.10.02.13-Gen.

b. High pressure extrusion: a seal must have sufficient strength to resist extrusion out of its containment groove when subjected to high pressure and temperature. High pressure performance is mainly determined by the seal hardness and the seal stiffness at high temperature. Techniques to avoid extrusion in high pressure application include decreasing the clearance gap of the seal groove, increasing modulus and hardness and the use of back-up rings.

c. Effect of corrosion inhibitors: in some cases corrosion inhibitors attack elastomeric seals. High pH amines are the most hostile chemical. Three main degradation mechanisms are known when up to a few per cent of such chemicals are added to a fluid.

d. Methanol resistance: the swelling effect of methanol is greater than that of other alcohols.

For selection of non-metallic materials refer DEP 30.10.02.13.

2.4 Functional Design Parameters

The functional design parameters are discussed below.

2.4.1 Pigging Operation and PIG

Pigging operations are required in order to prepare, operate and maintain pipelines. These operations can be summarised as follows however requirements will vary for individual pipelines:

Dewatering after hydrotest; Cleaning the pipeline both during commissioning and after it is in operation; Gauging internally; Inspection of the pipeline both internally and externally (geometric

verification); Structural integrity evaluation (investigation on metal loss and material

defect) Controlling of liquid hold-up in gas pipelines; and Application of internal coating for corrosion protection.


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A Pig can be defined as a mechanical device that is inserted in the pipeline to carry out pre-defined tasks along the length of the pipeline depending on its construction.

2.4.1.1 Pig Selection

Pigs must first be selected to carry out the intended function (task). The pig can generally be described by its function like cleaning pig, gauging pig, de-watering pig, intelligent pig etc. These pre-defined functions all rely on one or combination of the following aspects of the pig’s design characteristics:

Ability to seal Ability to clean Ability to gauge Ability to withstand the operating conditions Compatibility with service or pigging medium Ability to last the entire pig run

Some of the characteristics may need to be enhanced in order to provide the best pig for the task. This will be influenced by the pipeline development stage at which the pig must carry out its task. These stages are - construction, pre-commissioning, commissioning, Inspection, maintenance, repair, decommissioning etc. Pigs designed to carry out tasks at one stage of pipeline may not possess features that are suitable to enable them to carry out the same task at other stages. This is due to a combination of the following factors:

Pigging distance Frictional resistance of the materials in contact Lubrication Pigging speeds and Pipeline design factors like:

Pipeline construction feature - bend radius, tees, wyes, diverters,

multiple pipeline diameters, material, internal coating/ lining etc Service – liquid, gas, multiphase Temperature Pressures Flow Types of deposits – rust, wax, mineral deposits, condensate, water etc


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2.4.1.2 Types of Pig

Based on their function, specific features and operating mode, pigs can be classified into one of the following categories:

Conventional Pigs These are passed through a pipeline to perform a specific function related to construction, operation or maintenance (e.g. cleaning, dewatering, batching). They do not generate or collect any data related to the pipeline condition. Those typically used in pipeline construction and operation are: • Foam pigs - are used for liquid sweeping and are cylindrical in shape with a

conical or parabolic nose and made of resilient polyurethane foam. The diameter is normally 0.5 inch – 2 inch larger than the internal diameter and the length is usually twice the diameter. They can be bare with a back disc or coated to achieve different duties.

• Cleaning pigs equipped with polyurethane driving cups - usually consist of

a disc pig or conventional cup pig provided with polyurethane blades or hardened steel brush units, which are attached to a steel body with springs to maintain pressure against the pipe wall. In some cases cleaning blades are shaped to induce rotation of the pig to provide uniform wear of the blades and pig cups during operation.

• Gauging pigs equipped with polyurethane driving cups and aluminium

gauging plate(s) - designed for gauging new pipelines to prove the pipe is circular and that there is no excessive weld penetration or construction debris remaining in the pipe. One pass will assure passage of other units. Constructed of a tubular steel body fitted with easily replaceable neoprene or polyurethane cups and a gauging plate made from steel or aluminium alloy. Gauge plates may be installed on either the front or rear of the pig or at both locations.

Specialty Pigs

These are designed to perform ‘special’ functions as internal coating application, line plugging for maintenance and repair, wet buckle prevention, etc. They do not generate or collect any data.


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Intelligent Pigs

These are used to gather information on the pipeline geometry, configuration and wall conditions. Information obtainable from intelligent inspection tool runs includes:

geometry measurement, e.g. wall thickness and mechanical defects external/internal metal loss, including general and pitting corrosion mill defects, i.e. laminations and inclusion clusters hydrogen induced cracking crack detection metal detection in padding material close to the pipeline.

Various criteria are important for the selection of the tool to be used. Briefly, the tool to be used should:

not-interfere with pipeline operation detect all significant defects discern spurious indications from actual defects determine defect sizes, position and location distinguish internal from external metal loss give an accurate view of the overall pipeline integrity

2.4.1.3 Pigging Speeds

The pigging speeds are dependant on the product flow and failure to operate within the specified optimum range will affect the performance and may require additional runs. The velocity can also affect the efficiency with respect to the sealing capability of cups, discs and cleaning capability of brushes. Excessive velocities may damage both pig and pipeline. Below are listed some criteria’s and pigging velocity however, it is advisable to take Vendor feedback for pig velocity on case-to-case basis.

General

The pressure required to move a pig depends upon a number of factors like:

The pressure in front of the pig Condition of the pipe wall surface Pressure exerted by the seals on the pipe wall (the ‘fit’ of the pig in the pipe) The presence of a lubricant and for Intelligent Pigs on the working principle and on the capabilities of devices

used for data logging.


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Pigs move in the pipeline under the influence of the ‘differential ‘pressure across them i.e. the pressure behind the pig (P1) minus the pressure in front of the pig (P2). This differential pressure (‘delta P) gives the pig a velocity. (i.e. It gives the pig both speed and direction). If P1 is less than P2 the pig will move backwards. The differential pressure contributes to the efficiency of pigging operations by improving the sealing efficiency i.e. it forces the seals against the pipe wall, making them act like non-return valves.

Pigging with Liquid

Liquid flows improve cleaning efficiency by allowing the pig to maintain a constant velocity. Velocities can be maintained, within limits. They can be lowered or controlled at the pump or globe valve. Seal wear rates are also reduced as the product or pigging medium acts as a lubricant. The recommended pig velocities irrespective of pipe size are:

Cleaning Pigs => 0.5 – 2.5 m/sec Intelligent Pigs => 1.0 – 2.5 m/sec

Pigging with Gas

Compressed air operations impose several conditions on the pig – no lubrication is available and pigging occurs in a series of high speed ‘excursions’ between localized restrictions. The pig stops and the pressure builds until there is sufficient energy to launch the pig past the obstacle. As the pig moves forward rapidly, the pressure is dissipated until the pig reaches the next restriction, causing the process to be repeated. The velocity profile is erratic when pigging with gasses, due to their ability to be compressed. Once the pig begins to move this energy is released very rapidly. Aside from the safety aspects, pigging in this manner is inefficient; increases wear on the pig seals due to friction heat build-up and are generally more destructive to the pig. Increased speed also causes a decreased pressure differential across the pig, which, in turn, results in decreased sealing efficiency. The recommended pig velocities irrespective of pipe size are: Cleaning Pigs => 0.5 – 2.0 m/sec Intelligent Pigs => 1.0 – 2.0 m/sec

It is recommended to use lower velocity limits in case of pigging with gas.


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Pigs with BY-PASS facility It is possible to design pigs with a by-pass facility to run pigs at lower speeds than the product flow speed. ‘By-Pass’ is the controlled flow of pigging medium, gas or liquid, through and/or past the pig. It has two effects:

It reduces the pressure (P1) behind the pig and hence the differential pressure

(delta P) across the pig – variations in the differential pressure affects the speed of the pig. The pig slows down as the differential pressure decreases.

The by-pass facility can also be equipped with Jetting head which provides the necessary jetting action to increase the efficiency of cleaning pigs by preventing brushes from becoming blocked with loosened deposits and holding these deposits in suspension in front of the pig rather than allowing them to form into a solid ‘slug’. These slugs are difficult to deal with at the receiver, also they may cause the pig to stuck.

With a by-pass facility pigging can be done at product flow speeds upto 10 m/sec, while the pig moves at a lesser speed of 3 to 5 m/ sec depending on design.

2.4.1.4 Pigging Pressure and Flow

It is not possible to recommend minimum pressures while pigging because it is dependant on many factors like function and type of pig, seal material and type, pipeline condition, types of deposits, lubricant, liquid or gas pigging, temperature, viscosity etc. Refer Appendix- 7 for flowrate Vs Velocity graph for liquid and gas. The Graph -1 shows the flowrate in a pipe against the velocity for liquid. For gas it is not possible to provide a single graph showing the flowrate in pipe Vs velocity. This is due to the compressibility nature of the gas. The gas velocity in the pipe is a function of the actual system pressure. The pressure will change along the gas pipeline also the gas velocity will increase with lower pressures. The Graph –2, 3 and 4 shows the flowrate in a pipe against the velocity for gas at pressure 10 bara, 50 bara and 100 bara respectively for different pipe sizes. The graphs are valid for following gas condition:


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Model Gas => Methane (100%)

Gas Density at Standard condition of 1 atm/ 60°F => 0.68 Kg/m^3

Gas Density at 10 bara @ 20°C => 6.71 Kg/m^3



Note that these diagrams should only be used as a reference for the worst-case conditions i.e. low pressure (high speed) section at the end of a pipeline.

2.4.1.5 Pigging Frequency

During normal operation of pipeline the pigging frequency is determined by quantum risk of internal corrosion to the pipeline. This shall be determined by ADCO’s Corrosion specialist and is outside the scope of this document. Nevertheless some guidelines for pigging frequencies are shown in Appendix 5.

2.4.2 Barrels

The barrel is the section of the pig trap, from the pig trap valve up to and including the end closure, which is required to launch and receive pigs. It consists of four parts:

End Closure. As defined under 1.4.

Major Barrel. As defined under 1.4. To facilitate the insertion and removal of pigs, for pipelines smaller than 20-inch diameter the major barrel (for launcher and/or receiver) should be 2 inches more than the pipeline diameter. However if the barrel wall thickness is greater than 15mm then the barrel becomes tight to push the inspection tool in. This case shall be discussed with Vendor before finalizing the major barrel diameter. For pipelines with diameter of 20 inch and larger the major barrel oversize should be 4 inches. Typical sizes for major barrels are given in (Table 1).

Reducer. As defined under 1.4.

The transition connection between major and minor barrels shall be an eccentric reducer with the bottom of the entire barrel at the same level. The length of the reducer section shall be in accordance with ASME B16.9.

Minor Barrel. As defined under 1.4.


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Internal diameter of the minor barrel shall match the minimum inside diameter of the pipeline to which it is attached. This may be particularly relevant if thick wall low-grade pipe is used for the major barrel and the pipeline is thin wall high-grade material. The internal diameter of the minor barrel should be the same as that of the main line. However, transitions in the internal diameter due to wall thickness variations greater than 2.4 mm shall be tapered to a maximum angle of 14° to the pipe axis to allow for the smooth passage of a pig. The internal surfaces shall be flush and designed to allow free passage of pigs. All nozzle connections shall be flanged and 2” NPS minimum. Outlet connection 3” NPS and larger shall be internally contoured. Outlet connections 4” NPS and larger shall be fitted with scraper bars. All nozzles except drain connections shall be located on the side or top of the pig trap.

Table 1 Typical Diameter of Major Barrel and Pipe work [Ref 1]

Pipeline Diameter, mm (inches) Major Barrel, mm (inches) 200 (8) 250 (10)

250 (10) 300 (12) 300 (12) 400 (16) 350 (14) 400 (16) 400 (16) 450 (18) 450 (18) 500 (20) 500 (20) 600 (24) 600 (24) 700 (28) 650 (26) 750 (30) 700 (28) 800 (32) 750 (30) 900 (36) 800 (32) 900 (36) 900 (36) 1000 (40) 950 (38) 1 050 (42)

1 000 (40) 1 100 (44) 1 050 (42) 1 150 (46) 1 200 (48) 1 300 (52) 1 400 (56) 1 500 (60)


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2.4.3 Launcher For launchers, the minor barrel provides “head” space for the pig cups to engage and prevents the nose of the pig coming into the contact with pig launcher isolation valve providing that the balance line is open. This section is relatively short compared to major barrel. For launchers the barrel shall be sloped (typically 1:100) down towards the drain outlet. Pig traps should be designed for the longest pig that will be used (usually an intelligent pig) plus a margin of 10%. Refer Table 2 and Figure 2A [Ref 1] for dimensions of pig launchers designed for intelligent pigs.


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2.4.4 Receiver For receivers the minor barrel must be long enough for the pig to trigger the pig signaller and the length shall accommodate intelligent pigs so that the isolation valve(s) can be closed without damage to the pig or valve. The length of the pig receiver unit shall be designed as a minimum to receive one intelligent pig and one cleaning pig plus 10% margin. For receivers the barrel shall be sloped (typically 1:100) down towards the end closure to improve draining of liquids from the barrel. If there is a chance of solids getting collected ahead of the pig, then additional lengths should be considered.

Refer Table 2 and figure 2B [Ref 1] for dimensions of receivers designed for intelligent pigs.

2.4.5 Bi-directional Traps

The application of bi-directional traps is not foreseeable within ADCO installations.

2.4.6 Barrel Reducer

A standard eccentric-type reducer (in accordance with ANSI B16.9) or a fabricated reducer (with a minimum length of no less than that of the standard reducer) shall be used. The reducing section shall be oriented with the bottom flat.


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Table 2 Barrel Lengths for Intelligent Pigs [Ref 1]

Approx. Minimum Barrel

Length, (m) Launcher Receiver

Pipeline Diameter,

mm (inches)

Approximate Maximum Tool

Length, m

Approximate Maximum Tool

Weight, kg AL BL AR BR 200 (8) 3.9 170 4.1 1.5 3.9 3.9

250 (10) 4.3 300 4.3 1.5 4.3 4.3 300 (12) 4.3 365 4.3 1.5 4.3 4.3 350 (14) 4.8 380 4.8 1.5 4.8 4.8 400 (16) 5.1 700 5.1 1.5 5.1 5.1 450 (18) 5.1 810 5.1 1.5 5.1 5.1 500 (20) 5.1 840 5.1 1.5 5.1 5.1 600 (24) 5.7 1 600 5.7 1.5 5.7 5.7 650 (26) 5.8 2 000 5.8 1.5 5.8 5.8 700 (28) 5.8 2 000 5.8 1.5 5.8 5.8 750 (30) 6.0 2 000 6.0 1.5 6.0 6.0 800 (32) 6.6 2 270 6.6 1.5 6.6 6.6 900 (36) 6.6 3 560 6.6 1.5 6.6 6.6 950 (38) 6.6 3 600 6.6 1.5 6.6 6.6

1 000 (40) 6.6 4 090 6.6 1.5 6.6 6.6 1 050 (42) 6.6 4 550 6.6 1.5 6.6 6.6 1 200 (48) 6.6 Vendor to confirm 6.6 1.5 6.6 6.6 1 400 (56) 6.6 Vendor to confirm 6.6 1.5 6.6 6.6

2.4.7 End Closures

2.4.7.1 General

The barrel closure shall be a quick opening door with side hinges or a swivel davit, provided with lubrication facilities. The quick acting design should allow opening and closing by one man in a period of approximately one minute, without the use of additional devices. Closures 18” and larger shall be hand wheel operated. Large size heavy closures shall be fitted with mechanical means to break seal when opening door and compress seal when closing.


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The end closure shall be installed in the vertical plane. Closure door shall be equipped with an interlocking device to prevent it being opened while the barrel is still under pressure. The end closure shall conform to the general requirements of ASME VIII, Division 1, Section UG-35 (b) (Quick Actuating Closures). In particular a fail-safe design of the opening mechanism shall ensure that the failure of any part of the opening mechanism shall leave the closure closed rather than open. End closures with exposed screw expanders or captive ratchet braces are not recommended because of the high maintenance requirements and the non-fail-safe aspects of some opening mechanism designs. For certain services, end closure leak through the seal ring grooves. In such cases it is advisable to overlay the seal ring grooves with Inconel 625. However this shall be decided during detail design of the project based on Operations feedback.

2.4.7.2 End Closure Components

The end closure shall consist of the following components:

A removable door, which provides full-bore access when open, and terminates

and seals the bore when closed. A welding end hub, for joining to the major barrel of a pig trap. The material used

for the welding end hub shall be compatible with the major barrel material. A closure-handling device, suitable to lift, hinge or swing the door. When the

handling device is attached to the closure, it shall be attached to the welding hub, not to the major barrel of the pig trap.

Ring seals for pressure containment. The activation of the seals shall be such that the fluid within the trap is contained at any pressure between 1 bar (abs) and the pig trap design pressure. Elastomeric materials for ring seals shall resist explosive decompression and shall be suitable for long-term exposure to the transported fluid at the design pressure and temperature conditions. The cross-section of the seals shall not exceed 7 mm in diameter for design pressures of 150 bar and above. The ring seal material shall be compatible with transported fluid.

Two safety devices to prevent inadvertent opening of the closure before the pig trap is depressurised as detailed under Safety Devices below.


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Note: An end closure with a flanged-end for joining to the major barrel has recently become available. This may have application in certain circumstances, e.g. where the use of a temporary barrel extension piece is proposed to allow intelligent pigging. This specification does not recommend using such end closures due safety reasons. This type of barrel extension adds one more flange joint and can be compared to portable pig traps. Also the barrel extension is possible only on launcher. On receivers extending the neck pipe would be difficult and would mean moving the entire installation.

2.4.7.3 Safety Devices

The end closure shall have the following safety devices:

A pressure-locking device to prevent opening of the door when the pig trap is

pressurized. A safety bleeder/ tell tale vent that when released will alert the operator to a

possible hazard unless pressure in the pig trap is relieved completely. Opening of the door shall not be possible unless the bleeder is released. Engaging the bleeder shall only be possible when the closure is closed. The bleeder shall be designed such that there is no risk of blockage.

The devices shall be constructed and located so that they cannot readily be rendered inoperative. The devices shall be easily accessible for inspection.

The interlock system shall be through mechanical trapped key systems. Refer ’Safety and Interlock Systems paragraph 6.0 for further details.

2.4.8 Pipe work

2.4.8.1 Bypass Line

A bypass line is required to connect the pipeline with related facilities such as a booster station, tank farm, etc. Typical sizes for the bypass line are given in (Table 3), based on fluid velocities for continuous service. However the bypass line is outside the scope of this standard document.


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2.4.8.2 Kicker Line / Receiving line

A kicker line is required to connect the major barrel with the bypass line to enable diversion of the fluid through the barrel to launch or receive a pig. For a launcher the kicker line shall be connected to the major barrel as close as possible to the end closure and for a receiver as close as possible to the reducer. Typical sizes for the kicker line are given in (Table 3), based on fluid velocities for intermittent service. Install barred tees on kicker/ receiving line to avoid broken pigs passing through.

2.4.8.3 Balance Line

A balance line shall be provided on launchers to enable filling and pressurising or depressurising (equalizing) of the barrel on both sides of the pig at the same time. This is to prevent a pig, which is ready to be launched from moving either forwards (and thereby hitting and possibly damaging the pig trap valve) or backwards (and losing the seal in the reducer). To ensure this, the balance line, branching off from the kicker line, shall be connected to the minor barrel as close as possible to the pig trap valve. Consideration should also be given to the provision of a balance line on receivers to prevent any possible pressure differential across a received pig. The drain line configuration as depicted in P & ID, Appendix-2, 3 and 4 can also be used as balance line. However it is recommended that the drain lines shall not be used as balance line for new installation.

2.4.8.4 Pressurising Line

The pressure equalising line across the kicker valve shall be provided for operating pressure higher than 1000 psig in oil service. For gas and multiphase service the pressurising line across kicker valve shall be provided for line size 6” @ 600# rating and above. This smaller diameter pressurising line around kicker valves serves to control speed of operation, control of barrel pressurisation and/or to avoid damage to the kicker valve seats or other internals. The pressurising line should be at least 2-inch diameter.

2.4.8.5 Safety Relief Line

A pig trap system shall be protected against overpressure by providing relief valves. The valve shall be provided at the highest point on the pig trap major barrel and piped to flare/vent system.


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Where flare/vent system is not available, the valve shall be piped to a safe location (atmosphere). Relief valves discharging to atmosphere should be located at the maximum practical elevation to keep discharge piping (to safe location) as short as possible. Dispersion analysis shall be performed to determine the safe distances. To keep this discharge pipe free from liquid a small (8 mm dia) weep hole shall be drilled at the lowest point.

2.4.8.6 Drain Line

Drain points shall be provided near end closure and near the pig trap valve at lowest point of the barrel to allow maximum drainage of liquid accumulated in the barrel. Connection of drain lines to pressurized systems should be avoided to enable the contents of the barrel to be emptied as necessary. In addition, before opening the drain valve(s) the barrel shall be depressurised and vented to minimise vapour release or over pressurisation of the drain system. Diameters of drain lines are as shown in (Table 3). The barrel drain lines shall be sloped (at least 1:300) towards a closed drain system or a designated open drain. To provide positive isolation of the barrel from the closed drain system during opening of the pig trap end closure, a double block and bleed valve arrangement shall be installed on the barrel drain line with spectacle blind. The first drain valve shall be located as close as possible to the barrel to avoid accumulation of dirt/debris in the branch that may render the drain valve inoperative. A back flushing connection on the drain line underneath the vessel should be installed if there is a possibility of blockage from deposits of sludge, sand, etc. in the barrel.

2.4.8.7 Vent/flare/blowdown Lines

A vent line shall be provided near the end closure to vent/purge the barrel and near the pig trap isolation valves to ensure depressurisation behind a pig in the event of it being stuck in the minor barrel. The vent line shall be sized based on liquid content, blow down calculations etc. However the diameter of the vent line(s) shall be at least 50 mm (2 inch). The vent line shall be equipped with isolation valve with interlock to ensure that it cannot be opened when the end closure is also open. For high-pressure gas and multi phase flow systems consideration should be given to the provision of a blowdown line, incorporating a globe valve or restriction orifice sized (such that over


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pressurisation of the vent/flare system is avoided) for controlled depressurisation. During depressurisation, pig traps in gas service and associated piping may become cold. Protection of personnel should be by means of operating procedure rather than insulation.

Table 3 Typical Diameters of Pipe work [Ref 1]

Pipeline Diameter, mm

(inches)

Bypass Line, mm (inches)

Kicker Line, mm (inches)

Balance Line, mm (inches)

Drain Line, mm (inches)

200 (8) 100-150 (4-6) 100 (4) 50 (2) 50 (2) 250 (10) 150 (6) 100 (4) 50 (2) 50 (2) 300 (12) 150-200 (6-8) 100 (4) 50 (2) 50 (2) 350 (14) 150-250 (6-10) 100 (4) 50 (2) 50 (2) 400 (16) 200-300 (8-12) 150 (6) 100 (4) 100 (4) 450 (18) 250-300 (10-12) 200 (8) 100 (4) 100 (4) 500 (20) 250-400 (10-16) 200 (8) 100 (4) 100 (4) 600 (24) 300-450 (12-18) 200 (8) 100 (4) 100 (4) 650 (26) 400-500 (16-20) 250 (10) 100 (4) 100 (4) 700 (28) 400-500 (16-20) 250 (10) 100 (4) 100 (4) 750 (30) 400-550 (16-24) 250 (10) 100 (4) 100 (4) 800 (32) 400-600 (16-24) 250 (10) 100 (4) 100 (4) 900 (36) 450-650 (18-28) 300 (12) 100 (4) 100 (4) 950 (38) 500-650 (20-28) 300 (12) 100 (4) 100 (4)

1 000 (40) 500-800 (20-32) 300 (12) 100 (4) 100 (4) 1 050 (42) 500-900 (20-36) 400 (16) 100 (4) 100 (4) 1 200 (48) 600-900 (24-36) 450 (18) 100 (4) 100 (4) 1 400 (56) 800-1 000 (32-40) 500 (20) 100 (4) 100 (4)

2.4.8.8 Orientation

The orientation of branches on the Pig Trap System shall be as follows:

Drains: bottom of pipe (at 180° position) Vents, pressure gauges, purge connection, thermal relief and pig signaller:

top quadrant of the pipe (at 0° position) Kicker line, balance line and by-pass line: side of pipe (at 90° position)

The diameters of the branch connections are specified in Table 3.


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2.4.8.9 Pressure Indicator Connections

Pressure indicator connections shall be installed at the following locations:

On the major barrel near the end closure. On the minor barrel near the pig trap valve. On the bypass line on the pipeline side of the bypass valve. On the main line downstream of the ESD, if an ESD valve is installed in the

main line, or On the bypass line upstream of the ESD valve, if an ESD valve is installed in

the bypass line.

The diameter of these connections shall be 2-inch, with 2-inch double block and bleed valve with ½” NPT outlet for instrument connection. All pressure indicators shall be visible to those operating the closure mechanism.

2.4.8.10 Pressure Transmitter

A Pressure Transmitter shall be installed on the Pig trap for the Control Room to know the status of pig trap during stand-by condition, wherever facility to transfer instrumentation signals exists.

2.4.8.11 Audible Local High Pressure Alarm

A local audible high pressure alarm for receivers in gas service including the trunk lines shall be provided so that the Operator is alerted well in advance of the pressure rise to take necessary action. This requirement applies to stations where power or pneumatic supply is available.

2.4.8.12 Purge Connections

A 2” flanged purge connection with two isolation valves and check valve shall be provided for all systems. It should be located near to the pig trap valve or near the end closure to allow purging and/or flushing the full length of the barrel with nitrogen before opening the end closure. The adjacent vent valve should remain closed during purging.

2.4.8.13 Chemical Injection Connection

A flanged off, 2-inch connection with two isolation valves and check valve shall be provided for launchers on the bypass line.


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2.4.8.14 Spectacle Blinds

A provision of positive isolation facility like spectacle blinds is not normally required in pig trap systems where the work duration is considerably small. Hence the risk of swinging and re-swinging the spectacle would be greater and time consuming than the actual work with only valved isolation. Secondly for hazardous service if a spectacle blind is fitted with the spade in position, then the flange bolts shall not be loosened for swinging the spade unless it is certain that the valves are not passing.

As per SHELL guidelines the spectacle blind may be provided for following systems:

For all flashing liquids and toxic systems in ASME class 600 and below. For all systems in service of ASME class 900 and above.

It is recommended to provide spectacle blind on Kicker line and drain / vent lines when connected with to other facilities with the spacer in place during normal operations. Since the spectacle blinds are required for isolation of the trap from the pipeline, these shall be located on the pig trap side of the valves. The spectacle blind on the main line is not recommended as it may interfere with pigging.

2.4.8.15 Sample Connection

A suitable sample connection shall be installed in the pig receiver area on the drain line, primarily for sampling sludge for any bacterial growth & effectiveness of chemical injection. The orientation of the sample tapping shall be from bottom of pipeline or horizontal for liquid service, horizontal for multi phase flow and from top of pipeline or horizontal in gas service. The sample points shall be designed for safe operations. There shall be no spill-over or sour gas venting during sampling. The venting and draining philosophy as outlined for vent and drain shall be applicable for sample point drain and vent if any. The minimum size of sample tap shall be 2”, reducing further to suit sample connection.

2.4.8.16 Water Inlet Connection

Hydrogen Sulphide (H2S) reacts with iron and forms iron sulphide (pyrophoric scale/ dust). Pyrophoric scale may accumulate in the debris collected by the pig. In a dry condition this material may smoulder i.e. when exposed to atmosphere. The debris must be kept wet and disposed off in a suitable area by burning. Hence a water inlet connection shall be provided on launchers and receivers in gas service containing H2S in order to soak the pyrophoric dust and douse the pig in the traps before opening the end closure.


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2.4.8.17 Branch Connections The configuration of the branch connections between the various lines and ancillary items should be as shown in (Table 4), based on the typical pipe diameters listed in (Table 3). The diameter of all branch connections shall be at least 50 mm (2 inch).

Table 4 Branch connection configurations [Ref 1]

Branch Connection

Location Sizes

mm (inches)

Configurations

Bypass line on main line

75 on 100 (3 on 4) Tee

Size 4” & larger Barred tee Kicker line/ receiving line on major barrel

Size 4” & larger Welded branch connection (see note 1)

Balance line on minor barrel, Balance line on Kicker line/ receiving line

50-100 on 150 (2-4 on 6) and above

Welded branch connection (see note 1)

Drain on minor and major barrel

Kicker line/ receiving line on bypass line

Size 4” and above Tee

Pressuring line to Kicker line/ receiving line

50 (2) and larger Welded branch connection (see note 1)

Small items (e.g. vents and gauges)

50 (2) Weldolet

Notes: 1) "Welded branch connections" include tees, extruded outlets/sweepolets and

weldolets as well as fabricated items. In all cases they shall conform to the design codes (ASME B31.4 and B31.8).

2) The distance between branch connections should be addressed to ensure that it does not coincide with pig cup/disc separation as this may result in pig stoppage. Barred tees shall be installed on all branches larger than 50% of the pipeline diameter. However it is advisable to install barred tees on kicker/ receiving line to avoid broken pigs passing through the kicker/ receiving line. The reducing barred tees shall minimum satisfy the requirements of Figure-3 (Refer Appendix – 8)


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2.4.9 Pig Signaller

2.4.9.1 General

Pig signallers are used to provide confirmation that the pig: Has been successfully launched from the launcher or arrived at the receiver; and

Has successfully passed through the pig trap valve, barred tee etc.

There are two types of pig signallers: 1. Intrusive Pig Signallers and 2. Non-intrusive Pig Signallers

2.4.9.2 Intrusive Pig Signallers

The intrusive type pig signaller has a trigger penetrating into the bore of the pipeline and into which the transported fluid will enter and pressurise the housing. Intrusive pig signallers are, by definition, static, mechanically actuated and provide a momentary indication of a pig’s presence at a specific point in the pipeline. Because the actuating mechanism is a mechanical trigger that intrudes into the pipeline, a signaller must also incorporate a satisfactory means of retaining the pressure within the pipeline. The main features of intrusive pig signaller are:

Reliable and provides visual signal. Proven track record. Active type of sensor. Debris entering the signaller clogs up and prevents the trigger movement.

This trips the external flag / switch. The external flag arrangement requires greasing.


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2.4.9.3 Non-Intrusive Pig Signaller

This type of pig signaller is externally mounted on the pipeline and therefore is not exposed to the transported fluid or the internal pressure in the pipeline. These signallers are easy to maintain. There are number of non-intrusive systems on the market:

a. Monitoring change in magnetic field by the movement of the metallic body of

the pig - This approach is very difficult to set because there should not be any other moving metallic parts in the vicinity, i.e. steel capped boots, tool boxes etc, this can change the field and inadvertently trip the signaller.

b. Ultrasonic systems - This approach again can be fooled by pressure surges

and therefore give a false reading. c. Monitoring movement of a magnet fitted into the pig body - This devise relies

on a small coin sized magnet being fitted on to the pig body, which the external non-intrusive signaller can pick-up. This gives a more reliable signal. The non-intrusive signallers system can be fitted with a number of accessories, including LCD read outs to give time and date and number of pigs passed. This can be linked to either mobile phones, or pagers to send SMS style messages.

The salient features of non-intrusive pig signaller are:

Acoustic, passive type intelligent sensor Detects the passage of pig at speeds up to 0.5 m/sec. Data on

detection of pig for pig speed below 0.5 m/sec is not available. The pipeline wrapping and coating has to be removed to provide bare

metal-to-metal contact between the line pipe and instrument. Requirement of power plus computer and hence expensive. Practically with no maintenance.

2.4.9.4 Pig Signaller Assembly

Pig signallers shall be robust and designed to be installed for long periods. In addition, they are installed at points along the pipeline where the course of the pig must be confirmed (e.g. wyes, tees) and for providing a warning of approach at receiver.


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The pig signallers shall be installed at the following locations as a minimum:

On the minor barrel of launcher and receiver. For launcher it shall be towards the pig trap valve while for receiver it shall be near the small diameter side of the reducer,

On the mainline, one intelligent pig length downstream and beyond the barred tee on each trap to confirm that the pig has successfully passed both the pig trap valve and the barred tee,

At approximately 1.0 km upstream of pig launcher (Note 1)

Note: (1) Optional requirement for new facilities. The requirement shall be finalized in consultation with Operations during detail design stage. Considering the salient features mentioned in paragraph 2.4.9.2 and 2.4.9.3 and the vendor feedback that the non-intrusive pig signallers are still in the developmental / field trial stage, it is concluded to use Intrusive type Pig Signallers and requirements for this type are given in DEP 31.40.21.33-Gen. The proposed assembly shall be as indicated in Figure-4 below.


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Pig Signallers shall be bi-directional, shall give positive indication of pig passage and shall not solely dependent on a superficial or painted marking or other method that can become obliterated. The indicators shall be designed for manual reset and allow replacement of all moving parts with pressure in the line Every signaller must incorporate a mechanism that will provide a positive indication that a pig has passed. This is normally done in one of two ways:

Mechanical/Visual (a local flagged indicator) Electrical (magnetically linked proximity switch provides an electrical signal to

a controller) The pig signallers shall always be provided with full-bore ball valves and a system to allow removal and/or maintain under full pressure. Proprietary signallers designed for removal under pressure normally have small-size flange and bolt assemblies and consideration should be given to the use of a standard 50 mm (2-inch) flange assembly for such items. It is recommended to use Pig Signallers from the below mentioned vendors or equivalent:

GD Engineering Pipeline Engineering INPIPE Products

Refer Appendix –6 for vendor sketches of Intrusive and Non-intrusive pig signallers and pig signaller removal tool consisting mainly of jacking bracket.


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2.4.10 Valves

2.4.10.1 General and Valve Operations

Most of the valves are required for isolation purposes i.e. on/off use. Depending on the intended frequency and operations requirement the pig trap and kicker valves may require power-operation (hydraulic or motor actuated). Irrespective of frequency of use, large valves may require power operation (i.e. motor operated valve – MOV). The motor operated valve especially on the trap isolation, bypass line and kicker line shall be able to stop immediately and reverse the stroke if needed. Actuated valves shall have provision for a hand wheel or hand pump on the actuator. Wherever MOV’s are provided and SCADA exists the valves shall be provided with position indicators for display in central control room / DCS. The pig trap valve and Kicker valve are the main isolating valves between the pipeline and pig trap. Also these valves are subjected to pigging debris and hence it is advisable to have these valves as tight shut-off valves. The main pipeline valves (downstream of launcher and upstream of receivers) for 16” and above for all ratings shall be motorized if power is available. The kicker valves need not be motorized. In the absence of motorization the valve shall be provided with gear operation inline with ADCO specifications. All gear operated valve shall have the option to fit portable pneumatic tool to facilitate valve operation. A set of Portable Pneumatic Tool shall be provided for each location. The locations where power is available, valves on mainline below 16” size could be motorized depending on project specific decision. Refer paragraph 6.0 for ’Safety and Interlock Systems’ to be used for valves.

2.4.10.2 Valve type Selection The pig trap valve needs to be piggable. They shall be full-bore ball valves or through-conduit type gate valves. The kicker valve do not need to be full-bore but since they may be subject to pipeline debris a ball valve or through-conduit gate valve should be used.

A comparison between ball valves and through-conduit gate valves are listed below. A through-conduit gate valve may be slab-gate or expanding-gate type.


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There are reverse slab gate valves. These are used to reduce the actuator size in pneumatic or hydraulic actuated valves. The reverse slab design helps in reducing the torque requirement for close/ open operation. Since the present design for pig trap valves is with electric motor operated valves, the reverse slab type gate valves are not considered.

Table 5 : Comparison of Ball Valves & Gate Valves

Ball Valves Gate Valves Advantages

Compact size Lighter weight Lower cost for high pressure (Class 600 and above)

Faster operation

Advantages Lower cost for low pressure service (Class 300 and below)

Better resistance to dirt in the open position (expanding-gate type)

Maintainable in-situ Upstream and downstream sealing Better fire resistance

Disadvantages Soft seats may be damaged in dirty service

Only top entry type maintainable in-situ

More sensitive to foreign hard particles

Disadvantages Slower operation larger height larger weight

Based on the above criteria it is concluded that for main oil lines and oil transfer lines gate valves shall be preferred. For the gas service including the trunk lines, the use of gate or ball valve shall be project specific.

2.4.10.3 Additional Consideration in Valve Design

It is reported that ADCO is facing severe valve-passing problem at most of their pig trap installations. Following are some of the recommendations ADCO may consider to overcome the problem. It is to be emphasized that the suggestions below are only general and do not replace the ADCO valve specifications in any way. However the suggestions might help to evaluate the existing valve specifications. It is to be noted that the suggestions below are based on our experience & in no way attempts to prepare valve specifications, which is outside the scope of this document.


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General

In corrosive services, consideration should be given to overlaying critical areas in the valve (e.g. seal pockets).

Where the service is erosive (e.g. presence of solids), harder seating areas (i.e. seat rings and closure elements) and/ or hardfacing overlay should be used.

Where CO2 is present, elastomer selection should consider the possibility of explosive decompression.

Electroless- nickel plated coatings often fail after continuous long immersion in salt water. Their uses should be limited to the less severe services (neutral PH’s and temperatures < 93.3 degree C) or to locations/ services where successful use has been documented.

Suggestions

Ball valves in corrosive service (i.e. on all piping material classes having a minimum corrosion allowance of 3mm) shall receive a 3 mm thick weld overlay in stainless steel grade 316L on all seal pockets and related contact faces. This requirement only applies to dynamic seals (i.e. seat-to-body and also upper stem seals). It does not apply to static seals such as body seals or to parts already made of stainless steel having minimum nominal chromium content of 17%.

The mainline pig trap valve shall have the following additional features: Metal to metal contact (no soft seat seal) Tungsten carbide coating of all surfaces subject to metal-to-metal

contact (seats and ball). This coating shall be of 400 microns minimum thickness, in complement of the 75 microns ENP coating, which has to be applied on the remaining parts of the trim (i.e. ball, stem, seats).

3 mm thick weld overlay in Inconel 625 of all the seal pockets and related contact faces (whatever the corrosion allowance of the relevant piping material class). This requirement only applies to dynamic seals (i.e. seat-to-body and also upper stem seals). It does not apply to static seals such as body seals or to parts already made of stainless steel having minimum nominal chromium content of 17%.


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In case of solid particles in the fluid the valve design shall incorporate the following:

No lip seals are permitted. No soft seals are permitted for the seat-to-ball seals: valve must be

metal-to-metal seating. Seats and ball contact faces must be Tungsten Carbide coated in

order to achieve a minimum surface hardness of 1100 Vickers. The thickness of the Tungsten Carbide coating must be a minimum of 400 microns (thickness of the finished, machined surface).

Operating procedures are to be followed to prevent the valve seats from getting damage i.e. the ball valves shall not be opened against differential pressure. For large bore valves a 2” pressure equalizing line shall be provided and upon equalization of pressure the main ball valve shall be opened.

2.4.10.4 Double block and Bleed Philosophy

A double block and bleed system shall be installed at the location of the pig trap isolation valve as follows:

1. All Main Oil Lines with 600# and above. 2. Transfer lines with 300# and above.

The bleed requirements shell be as follows:

1. Wherever double block valves are provided for isolation, provide a bleed connection with a valve for lines of sixes 6” and above.

2. For hydrocarbon systems having H2S concentration exceeding 500 ppm,

the bleed should preferably be connected to a closed system (flare/drain). In instances where this can not be applied, proper dispersion analysis be carried out for routing bleed o a safe location.


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2.4.10.5 Pig trap isolation valve

The pig trap isolation valve(s) shall be full-bore tight shut-off ball valve or gate valve, installed to isolate the barrel from the rest of the pipeline. The minimum internal diameter of the valves shall be consistent with that of the pipeline to avoid difficulties in pigging activities.

2.4.10.6 Bypass valve

The bypass valve shall be provided with “Inching” facility.

2.4.10.7 Kicker valve

The kicker valve(s) shall be a tight shut-off ball valve or gate valve installed to isolate the bypass line from the barrel.

2.4.10.8 Pressurizing valves

A pressurizing line shall be installed and it shall include an isolating valve (ball valve) and should preferably include a throttling valve (globe valve). The isolating valve shall be installed on the bypass line side for tight shut-off of the pressurizing line and the throttling valve shall be installed on the balance line side to control the flow in the pressurizing line.

2.4.10.9 Balance valve

To cater for possible low flow conditions and to ensure that pigs can always be launched, a balance valve (ball valve) shall be provided in the balance line, so that all flow may be diverted behind the pig by closing the balance valve during launching. This valve should be normally open.

2.4.10.10 Drain valves

The drain valves shall be tight shut-off ball valve for isolation and globe valve for throttling as depicted on P & IDs.

2.4.10.11 Vent valves

The vent valves shall be tight shut-off ball valve for isolation and globe valve for throttling as depicted on P & IDs.


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2.4.10.12 Blowdown valve For gas service the blowdown valve shall be a tight shut-off valve with a downstream globe valve or an orifice restriction for controlled depressurisation of the barrel. It is recommended to manually depressurise by opening the valves locally.

2.4.10.13 Purge connection valve

Two 50 mm (2 inch) isolating valves and a 50 mm (2 inch) check valve shall be installed in the purge connection. The isolating valve shall be installed on the barrel side for tight shut-off of the purge connection. (The check valve is intended to prevent hydrocarbons entering the purge/flush line.)

2.4.10.13 Chemical injection valves

If a chemical injection connection is required it shall include two tight shut-off valve to isolate the chemical injection line from the pipeline and a check valve to prevent reverse flow. The diameter of the connection shall be at least 2 inch.

2.4.10.14 Pressure Relief valve

Pig traps designed as per pipeline system shall be protected against overpressure. The main causes of pipeline pressure are (DEP 31.40.10.14- Pipeline Overpressure Protection)

i) well pressure; or ii) pressure from pressure boosting facilities such as pumps and

compressors; or iii) pressure from pressure controlled process vessels; or iv) operating pressure from a feeding pipeline; or v) hydrostatic head due to change in pipeline elevation; or vi) surges as a result of operational activities, e.g. valve closure, pump

start-up/shut-down; or vii) thermal expansion of blocked-in fluids; or viii) failure of the pressure control/ trip of pumps, compressors, pressure

controlled process vessels or feeding pipelines; or ix) incidental pressures from a feeding pipeline; or x) accumulation pressure during the activation of the overpressure

protection safety relief or isolation valves.


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As part of the safeguarding exercise all of above shall be evaluated for the systems under study. The PSV’s shall be installed on all pig traps and the sizing basis shall be arrived at by above study.

2.5 Pig Handling System

Pig handling systems depend on the type and weight of pig and the pipeline size. Each trap shall be provided with a suitable Pig handling system for either inserting the pig into the launcher, or extracting the pig from the receiver. For the purpose of lifting or lowering of the pig, a manual operated, floor mounted, jib-type crane shall be provided. The height of the jib crane shall be such that the lifting and transfer of the pig from the transporting vehicle are ensured. The pig handling facility shall consist of the following, as a minimum:

Perforated filtering basket-type tray mounted on wheels / rails or PTFE slides. Fabricated trolley support cradle frame for the perforated tray. Beam / manual winch to push / pull the basket for insertion and retrieval of

pigs. Jib crane with hand geared travelling chain hoist.

The height under the loading arm should be 4 meters, arm reach 3 meters and rotation angle 360°. The reach of jib crane shall be such that the lifting and transfer of the pig from the transporting vehicle to the steel bench is facilitated. The manual jib crane shall be supplied complete with foundation counter plates, anchor bolts and a manual hoist. Design load for this crane shall be at least 1.5 times the maximum weight of the heaviest applied pig for routine pigging. Sizing criteria of the pig handling facilities shall be based on tools maximum dimensions and weights. Receiver traps will be provided with a pig handling trolley assembly with pig extraction capability, railway mounted or equal (outside the trap) and launcher traps will be provided with a pig handling trolley assembly with pig insertion capability, railway mounted or equal (outside the trap). All handling equipment shall be suitable for longest cleaning pig plus 20% margin. However it is advisable to take feedback from Operations on the length of trolley required.


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2.6 Supports

Supports should permanently support and restrain the Pig Trap. They should be designed to carry the weight of the pig trap system filled with water, together with the weight of the associated heaviest intelligent pig. Supports under the barrel should normally be of the sliding type to compensate for expansion of the unrestrained part of the pipeline. Other supports may be fixed if the design calculations indicate that sufficient flexibility is incorporated in the pipe work to compensate for any axial and transverse movements. Where cathodic protection isolation joints are used, the supports should allow sufficient movement to avoid stressing of the joint above its design limits. Where isolation joints are not used the supports may need to be electrically isolated. Supports should be positioned such that the pig trap valves can be removed for maintenance or replacement without removal of the barrel.

2.7 Lifting Lugs

Lifting lugs shall be provided to facilitate the lifting of the complete trap or skid mounted trap during installation stage.

2.8 Earthing Lugs

Earthing Lugs shall be provided to help prevent the build-up of static electricity. The accumulated static charge if not earthed may suddenly discharge within a hazardous atmosphere. The resulting spark may easily act as the ignition source for an explosion.

2.9 Monolithic Isolation Joints

The purpose of isolating joints is to provide electrical separation between pipeline sections and adjoining/ neighbouring structures, pipelines, and other sections of the same pipeline system, thereby preventing detrimental electrochemical interaction and improving the effectiveness of the cathodic protection system. Isolating joints are used also to ensure effective current distribution for cathodic protection systems. Wherever practicable, the isolating joint is to be installed above ground, or in an inspection pit in dry conditions, in order to limit the possibility of electrical bridging across the joint. It is intended to be girth welded between two pipeline sections.


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The design of the isolating joint shall be compatible with the design code adopted for the pipeline in which it is installed. The isolating joint shall be suitable for operation under the environmental and operating conditions specified by the Company or Engineering consultant. The isolating joint shall be suitable for pigging operations. Requirements for isolating joints are given in DEP 31.40.21.31-Gen. A surge diverter connection shall also be provided across the isolation joint.

2.10 Hazardous Area Classification

The area around pig traps shall be classified in accordance with the IP Model code of Safe Practice latest edition IP 15. This shall be the basis for selection of electrical & instrument equipments.

3 LAY-OUT ANCILLIARY FACILITIES AND OTHER CONSIDER ATIONS

3.1 General

In determining the location of pig trap systems, account shall be taken of possible adverse environmental effects, which could result during construction and operations. Pig traps shall be located so that they are orientated with their end closures pointing away from personnel areas and critical items of equipment, i.e. those containing hydrocarbons and/or toxic material or in safety service. This is to minimize the risk of damage to adjacent facilities that might occur in the very unlikely event of a pig being ejected from the pig trap. Pig traps shall be oriented such that no equipment nor above grade piping are within a sectorial area, 15 m radius by 20 degrees, (10 degrees to each side of the centreline of the trap) from the closure door. Pig trap systems should generally be located adjacent to each other for ease of pigging operations. A minimum free space as indicated in Figure – 2A and 2B is required beyond the end closure door of the pig trap for pig handling. The clearance between the bottom of the trap and finished grade shall be 1 m to provide sufficient room to slope the drain lines as well as easy handling of the end closure and pigs. The varying pig trap heights make it difficult to standardize on accessories like trolley, Jib crane etc. Also lower or higher pig trap heights contribute to difficulty in loading / unloading the pig.


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Pig trap systems shall be fenced (either separately or as part of adjoining facilities) and access should normally be provided for light trucks and lifting cranes, subject to hazardous area classification constraints. Within the pig trap system plot, where buried pipelines are less than 1 m below the surface, barriers or other protective measures should be used to prevent vehicles damaging the pipeline. A surface drainage system shall be provided to collect any spill from the trap and wash water. The pig trap area shall be paved with curbing all around to prevent spill-over to surroundings.

When a drain system is not available, a sump shall be provided. The volume of the sump should be twice that of the trap for liquid systems. For gas systems the volume should be determined on an individual basis. In addition, a catch pit or drip tray shall be constructed directly underneath the end closure with a volume equal to at least 5 per cent of that of the trap and of sufficient surface area to prevent any oil or debris contamination of the surrounding ground. This pit or tray may be connected to the sump but, if not, it should be designed such that it is safe and easy to empty. Local drain pit or sump near end closure of launcher/ receiver should be provided with removable cover to avoid sand accumulation. Special provisions shall be required for intelligent pigging. Depending on circumstances it may be appropriate to provide either temporary or permanent facilities for handling of these pigs based on Operations feedback. The requirements for pig handling depend on the type and weight of pig and the pipeline size. Normal pigs with a mass less than 30 kg may be manually loaded into or out of the pig traps. Typically this pig mass will occur in systems of 300 mm (12 inch) and below. Pig loading trolleys; cassettes or baskets enable heavier pigs to be properly loaded, aligned and retrieved in/from pig traps. The potential for errors during operations and maintenance can be greatly reduced with logical numbering system for equipment, valves and instruments. Particular care should be taken in numbering the new facility at a later date. Similarly particular care should be taken to provide a Nameplate for the pig trap. The name-plate should contain information about the pig trap like size, rating, length, tag no, fluid nature etc.


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A H2S, HC detection system shall be installed at pig trap sites as required per specific project philosophies. However these need not be provided on remote locations such as Mile Posts along MOL’s where the insistence shall be on operating procedures like carrying portable detectors, breathing apparatus etc. A windsock should be installed at the pig trap sites to indicate the direction of wind in the event of leak.

3.2 Pigging System Features

The general features of pig trap piping are: A minimum of one pig length of straight run pipe shall be installed between

bends, outlets, bends and outlets, check valves, and bends and check valves. Through conduit gate and full bore ball valves can be treated as straight runs of pipe.

The number of bends in piping shall be kept to a minimum. The maintenance of constant internal diameter is vital and demands close

attention. If internal diameter changes are unavoidable, the maximum deviation of internal diameter from nominal shall be kept below the figures given in the following table. All internal diameter changes shall be made with tapered transition of 1:5 minimum slopes.

Table – 6: Internal Pipe Diameter – Maximum Deviations

Nominal Pipe Diameter in

Inches Maximum Deviation in

mm 4 4 6 6

8 to 12 10 14 to 20 14 22 to 36 16

40 and over 20

• The bend internal diameter out-of-roundness shall be limited to 5 percent. A minimum of one pig length of straight run pipe shall be provided upstream and downstream of all bends. Pipeline bends shall not be less than the following minimum radii or the pig manufacturer’s requirement; whichever is greater.


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6”- 8” => Minimum Bend Radii 10 times diameter of pipe 10” and above => Minimum Bend Radii 5 times diameter of pipe

• The receiving line on pig receiver shall be located as near as possible

to the reducer. However the distance between the reducer weld on major barrel and receiving line outlet shall be sufficient to allow the pig’s back drive cup to clear the reducer. This will assure that the pig drive cups are inside the oversized pipe section, reducing the possibility of the pig getting stuck in the nominal pipe section.

• At all pig trap stations, the piping that connects the upstream and

downstream pipelines, and associated kicker and equalizer lines shall be constructed above grade.

• In the vicinity of Pig trap the buried pipes shall be minimum 4 m away from the pig trap vessel. Also the depth should not exceed 1.5 m from top of pipe.

• The piping around pig trap shall be free of dead legs i.e. stagnant liquid, which leads to corrosion.

A length of pipe equal to the length of a split tee shall be included on the pipeline side of the pig trap valve and on the pipeline side of the bypass line valve to facilitate future replacement by a hot-tap/stoppling operation.

3.2 Access Platforms

A platform shall be provided adjacent to any valve where the centre of the handwheel is more than 1500 mm above grade. Similarly, a platform shall be provided adjacent to any equipment (e.g. pig signallers, pressure gauge) which is more than 1500 mm above grade and which is used during pigging operations. Platforms shall be provided for easy access to valve actuators and closure operating mechanism. All valves shall be accessible from one side of the trap.

3.3 Closed Drain and Vent Systems

A closed drain and vent system as depicted in the P & ID’s, Appendix-2, 3 and 4 is recommended for the pig trap system for operating personnel’s Health, Safety and Environment protection.


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3.4 Pig Traps in Remote Areas

The remote areas are defined as a location:

a. Away from the main terminal (i.e. in the desert), b. Where electricity is not available (i.e. it is not economical to provide electricity

for small facility), c. Where there is no other facility/ equipment except one or maximum two pig

traps.

For such locations the pig trap system can be installed with some deviations as noted below:

a. The MOV’s shall be replaced with gear-operated valves or shall be provided with pneumatic power tool for valve operations.

b. Depending on the service and location the closed drain system could be avoided. Instead the drain/ vent can be routed to be burn pit away from the pig trap station. The burn pit shall be installed with automatic igniters panel to burn the gas. However it is recommended that for systems with H2S 500 ppm and above a closed drain/ vent system with flare shall be provided irrespective of the location.

c. For sweet service, the mechanical trapped key interlock for valves shall be simplified to incorporate only mainline valves, bypass valve, kicker valve along with trap QOEC.

d. The transfer of instrument signals to control room, audible pressure alarms etc can be excluded.

Caution : For remote areas it is to be ensured that Nitrogen and Water is available during pig launching and receiving operations.

4 DESIGN CONSIDERATIONS FOR SOUR SERVICE

4.1 Classification of Facility

The facilities shall be assigned to one of three categories, depending on the concentration of H2S in the gas phase, resulting from reducing the process fluid or process gas to atmospheric pressure:

• 0 to 49 ppm Sweet facility • 50 to 499 ppm Low Risk Sour facility • 500 and more ppm requires further assessment


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If Company regulations are more stringent then the same shall be applicable. Facilities shall be classified as High Risk Sour if both:

• the concentration of H2S in the gas phase, resulting from reducing the process liquid to atmospheric pressure, exceeds 500 ppm and

• an 1” diameter release can cause a 200 ppm or higher H2S in air concentration at a 2m distance from the point of release, with a wind velocity of 1 m/s.

4.2 Design Requirements

To minimize corrosion, piping should be designed and installed in such a way that dead ends and areas of intermittent flow are eliminated. Double block and bleed isolation shall be provided for High Risk Sour facilities. Screwed fittings shall not be used in Sour Service. Flanges on piping in Sour Service should be minimized wherever practical, to reduce the number of potential leak sources.

The location of sampling points shall be determined in consultation with Operations during design stage. Details of sample points shall be determined in consultation and agreement with Operations and Engineering teams, to ensure compatibility with local sample handling facilities. Closed system bomb sampling systems shall be used in High Risk Sour service. The use of bomb sampling in Low Risk Sour service should also be considered where there is a high Gas Oil Ratio. Sample return lines should be routed back into a lower pressure stream. Where this cannot be achieved the sample return line shall be flared or vented. Depressurising of equipment and process lines in Sour Service should be to a flare system. Where this is not possible, venting may be allowed but shall be designed such that personnel cannot be exposed to H2S concentrations above 10 ppm. All liquid in sour service shall be piped into a closed drains system. Vents and drains, which are for hydro testing, shall have their outlets blocked-off by blind flanges.

4.3 Site Selection

In remote areas the launcher/ receiver site selection shall be such that site access roads where possible shall be located upwind of prevailing winds to minimize exposure risk to personnel approaching the site.


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In selecting a facility site, consideration should be given to taking advantage of the prevailing wind direction, climatic conditions, terrain, transportation routes, and the proximity of populated or public areas. Clear entrance and exit routes should be maintained and confined areas within the facilities should be avoided. Location, spacing, and height of flares or vent stacks should be determined based on acceptable gas dispersion calculations.

4.4 Layout

Locations where operators make routine inspections for H2S release should be easily accessible when wearing a compressed air breathing apparatus. Elevated platforms shall use stairs only so that there is no hindrance when carrying breather sets or rescuing H2S affected personnel. A Fixed Detection system should be provided around all process plant facilities classified as High Risk Sour. Consideration should be given to installation on Low Risk facilities as part of the overall facility safeguarding philosophy. All fixed detectors shall have a range of 0 - 20 ppm, and shall alarm at 10 ppm.

4.5 Disposal Of Sour Gas

Sour gas that is to be disposed of in normal operation shall be flared. Flare systems shall be designed in accordance with DEP 80.45.10.10-Gen. The elevation of the flare stack and the fencing at the base shall fulfill the following criteria:

1) 50 ppm or less H2S at the stack base. 2) 10 ppm or less H2S at the fence. 3) 5 ppm or less SO2 at the fence.

Dispersion calculations shall be done to determine the stack height and fence location assuming that flare is not ignited for H2S and is ignited for SO2. Attempts shall be made in design to minimize sour gas release to environment. If no other solution is available, small volumes of sour gas may be allowed to vent locally to atmosphere subject to Company approval.


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5 OPERATING PROCEDURES

Appendix-2, Appendix-3 and Appendix-4 contains the recommended sequence of operations for the Pig launcher and Receiver in Oil, Gas and Multi phase flow fluids respectively. Prior to start of pigging operations the operations team shall calculate the required flowrate/ pressure to achieve the optimum pig velocity advised based on purpose of pigging, pig type and other parameters noted in paragraph 2.4.1.3 “ Pigging Speeds”. The estimated pig travel time shall also be calculated. The monitoring and control of pigging operation are carried out manually and local to the pig launcher/ receiver by appropriate positioning of valves. The most important locally- mounted instruments are pig signallers; which signal the safe arrival and departure of pigs. The pressure indicators give indication that the pig trap is pressurized or otherwise, as appropriate.

6 SAFEGUARDING SYSTEM AND PHILOSOPHY

6.1 General

Voluntary compliance of personnel operating the plant, pig traps and handling equipment. If these guidelines are contravened due to human error, or malicious malpractice, serious accidents will occur. Accordingly, the need for a safety system that positively controls the entire process, without dependence on human judgement, is MUST. The many separate operations involved when launching and receiving pigs must be made to follow a safe, predetermined path. This can be done by having an Interlock system between the end closure and various valves. The SHELL DEP suggests three types of Interlock system: Safety issues are always at the heart of pig trap design. Whilst pigging is a common procedure, typically carried out when a pipeline needs purging, cleaning or surveying, it can involve a high risk of human error, high enough to warrant pig traps being described as ‘primary grade sources of hazard’. Probably the greatest associated danger is when a trap is opened accidentally whilst still under pressure – usually to insert or remove a pig.


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To overcome this danger it is vital that a system is incorporated which ensures that the trap is fully vented before the door can be opened. Venting depressurises the trap and removes the force necessary to propel the pig. Pig trap systems also involve other more complex, procedures. Even in a basic system, safe operation of the closure require it to be correctly sequenced with certain valves which are incorporated into the trap – these being the pig trap valves, drain and kicker valves. The pig trap line valve governs the piping connection between the pig trap and the main pipeline whilst the kicker valve is on a secondary piping connection used to move the pig into and out of the trap. Both valves must be closed, isolating the trap from the main pipeline, before the trap is drained. By establishing safety guidelines, a certain level of control over pig trap operations can be imposed but these usually rely on the

Relay based; that is thought of as monitoring device instead of safety device and hence will not be considered;

Micro-processor based; and Mechanical Key transfer Interlocking

6.2 Safety and Interlock Systems

The microprocessor based safety interlock and mechanical key transfer safety interlock systems have the following advantages and disadvantages that are discussed in the following sections.

6.2.1 Micro-processor based Interlock System

Advantages: • Soft logic. • No mechanical parts and hence no wear, tear and maintenance problems. • Changes in the logic is possible i.e. operator intervention possible. • Addition of future logic possible.

Disadvantages: • Expensive. • Hazardous area protection needs to be considered. • Valve needs to be automated. • Temperature control for panel is required and hence in remote areas were

electricity is not available a passive cooled shelter to maintain temperature suitable for instruments shall be required.


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6.2.2 Mechanical Key Transfer Interlock

Advantages:

• Forces the operator to carry out tasks in the correct sequence and hence eliminates the possibility of human error.

• No electric power required. • Unauthorized by-passing of sequential activities is not possible. • Simple mechanical device.

Disadvantages: • Corrosion problems with the key. • Sand and dust particles clog the grooves of the key. • Damage to groove / key or loss of key leads to procedural delays. • Loss of flexibility. • Frequent vendor intervention would be required for maintaining the key

transfer interlocks. • Operation becomes cumbersome when key transfer interlocking is

incorporated between lots of valves.

6.2.3 Selection of Interlocking System

The ‘Sequential Mechanical Key Transfer Interlock system’ is selected. Mechanical key transfer interlocking is developed from the principle that actions performed in the correct sequence are safe but potentially lethal if performed out of sequence. Therefore, the use of trapped key interlocks in pig trap operations will limit the sequence of valve and end closure operations to a single, unchanging path. By fitting interlocks to all relevant valves, as well as to the end closures, it becomes impossible to load or retrieve a pig without first depressurising the pig trap. In a typical system, the key can only be retrieved to open the end closure when the vent valve is opened, thereby reducing the pressure within the vessel. This is the simplest form of trapped key interlock. This system can be extended to include interlocks on all isolating valves like pig trap valve, bypass valve, kicker valve, drain and vent valves. It is decided to select the sequential mechanical trapped key interlock between various valves for the pig trap systems.


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In addition the pig trap Quick Opening Closure (QOEC) shall be provided with a safety lock device that will not permit the closure to be opened before the internal pressure has been fully released, and that prevents pressurizing the trap before the closure is in the properly locked position, in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, Paragraph UG-35.

6.2.4 Interlock Logic

The mechanical interlock system shall be designed to prevent opening of the scraper trap Quick Opening Closure (QOEC) when the kicker/by-pass and main line isolation valves are open. The valves installed in the main line at the launcher/receiver outlet/inlet and in the kicker/by-pass line shall be mechanically interlocked so that the valves cannot be opened if the launcher/receiver closure is open and the trap closure cannot be opened if the isolation valves are in open position. A typical mechanical key interlock logic between various valves & end closure of pig trap is depicted in the Appendix-9 P & ID 30.78.08.607. The following Figure – 5 represents a generic logic in graphical format for more clarity.


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PREMISSIVE TO OPEN DOOR

KICKERLINE, PURGE & PRESSURING VAVE(S)

& PIP TRAP ISOLATION VALVE(S) CLOSED

DRAIN VALVE

CLOSED

VENT (TO FLARE)

CLOSED

NOTE - 2

OR

AND

AND

PIG TRAP ISOLATION VALVE(S) CLOSED

(INTERLOCK)

KICKERLINE & PRESSURISING VALVE(S)

CLOSED (INTERLOCK)

PURGE VALVE(S) CLOSED (INTERLOCK)

BARREL DEPRESSURISED(NOTE-1)

VENT (TO FLARE) CLOSED

PREMISSIVE TO OPEN DOOR

CLOSURE DOOR OPEN (AND CLOSURE DOOR

INTERLOCK)

DARIN VAVE(S) OPEN

PERMISSIVE TO OPEN DRAIN VALVE(S) ‘D’

INHIBIT KICKERLINE PURGE & PRESSURISING VALVE(S) PIG TRAP ISOLATION VALVE(S) & VENT (TO FLARE) VALVES(S)

FROM REOPENING

INHIBIT DRAIN VALVE(S)FROM OPENING IF

CONNECTED TO CLOSED DRAIN SYSTEM

Figure 5: PIG Launcher / Receiver Logic Diagram Notes: 1. Barrel Pressure alarm is energised when PIG Trap is depressurized. This signal together

with permissive signals from all valve interlocks permit unlocking of closure door. 2. Only required when Drain is connected to the closed drain system


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7 SUGGESTED PIGGING SCHEDULING

Date Activity Responsibility

Minimum of 1 week prior to launch.

Pigging sequence schedule prepared and distributed to the relevant parties/authorities.

ADCO to define

Minimum of 2 days prior to launch.

Pig checked: refurbished, replaced as necessary. Locator and transmitter checked, batteries charged.

ADCO to define

One day before Launch

Confirm launch event to the relevant parties/authorities. Advice expected travel time of pig.

ADCO to define

Pre-launch Line up the pipeline and the receiver.

ADCO to define

8 SAFETY PRECAUTIONS

General When opening the door of a launcher or receiver, NEVER stand in front of

the door or at the side where the hinge is fitted. Ensure that NOBODY stands directly in line with the door.

The receiver should always be lined up prior to launching a pig. Erection of suitable barriers and warning signs, drawing attention to a

possible serious accident should be performed. Use of either open flames or other ignition sources (i.e. lighted cigarettes

etc.) shall be forbidden. All persons involved with handling of pig trap operations shall wear personal

H2S monitors. Ensure that pressure gauges are lined up and reading correctly. Ensure that TSV’s lined up and routine maintenance carried out to ascertain

the reliability. Pyrophoric scale may accumulate in the debris collected by pig. The debris

must be kept wet and disposed of in a suitable area by burning. Ensure that the internal walls of the pig trap in H2S service are wetted. As a rule allow


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minimum 10 minutes water soaking time in the trap to damp the pyrophoric dust.

Always take gas test for H2S at vent valve before opening the trap door. If the test reading shows more than 10 PPM H2S then breathing apparatus must be worn whilst opening the door.

For closed drain tank without automatic recycle, check that the drain tank has sufficient space for atleast 2 launcher draining volumes. If not arrange to empty the drain.

Before starting the pigging operation the personnel in-charge shall make available on site the necessary safety equipment like breathing apparatus, nitrogen cylinders, sufficient water, fire extinguishers, gas detectors, escape units etc and ensure that they are working.

Care shall be taken to reset the pig signallers. Spark free tools shall be used. Spark arrestor fitted vehicles shall only be allowed. Suitable emergency arrangements shall be ready in the unlikely event of HC

spill.

9 EMERGENCY SHUTDOWN (OPTIONAL)

Emergency shutdown valve shall be provided on the pipeline if an ESD cause from the station side safeguarding logic is required to isolate the pipeline and the pig trap system from related facilities. The ESD valve can be provided on the mainline or on the bypass line. If decided to provide on the bypass line the conversion of isolation valve on the bypass line to ESD valve shall be considered. The provision of ESD valve on the pipeline or bypass line is not a mandatory requirement. This requirement shall be discussed during detail design Safety Audits and Hazop reviews for each project.

10 SHARED (TEMPORARY) PIG TRAPS

Common Pig Traps between various locations would require considerable preparation and maintenance due to the following problems:

1) Increased wear and tear of the units particularly the seals due to continuous

assembly and disassembly 2) Additional requirements of spare parts like gaskets, bolts etc and their

availability.


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3) Pig Trap Handling difficulties and possibility of damaging during loading / unloading and transporting

4) Physical difficulties of man handling hot metal in desert conditions. 5) Physical difficulty to handle pigs when there is no permanent provision of

trolleys, lifting beams etc. 6) Difficulty in providing proper supports for pig traps 7) Additional skilled manpower and supervision required

In principal; no two pipeline installations can be completely identical and hence the sharing of pig traps will result in compromise in most cases. Also there is no possibility of installing safety systems like trap door – valve interlocks leading to an increased risk during pigging operation. Hence the decision of sharing the pig trap between various locations may be attractive from CAPEX point of view but it is not an attractive proposition from operating point view. On the other hand the frequency of pigging operation is very less for such installations. Therefore it is recommended to review installation of dedicated pig traps in view of the above facts against the frequency of pigging operation on case-to-case basis.

11 PIG TRAP DATA SHEET

The Appendix – 1 contains a Typical Data Sheet for Pig Trap system. Also attached are the Launcher & Receiver sketches showing the relative orientation of the nozzles along with general design data, nozzle-schedule. These data sheets shall be utilized either by ADCO or its contractors for specifying new pig traps or pig traps that will replace existing systems.

12 TYPICAL PIG LAUNCHER/ RECEIVER SYSTEM ARRANGEMENT

Typical arrangements of Pig Launcher and Receiver Systems including piping and valves are shown on the template P & ID’s attached as Appendix – 2, 3 and 4. Three types of systems are indicated for:

1) Oil service (such as MOL’s, Oil transfer lines operating above bubble pressure) 2) Gas service (such as gas injection, gas lift pipelines and lean gas pipelines) 3) Multi phase service (such as oil transfer lines, gas trunk lines etc)

The template P & ID’s are intended as supplement to the information provided in the document.


ADCO DOC. NO. 30-99-00-0103-1



13 MECHANICAL INTERLOCK SEQUENCE – A CASE EXAMPLE

A typical mechanical key interlock sequence for pig trap operation as a case example is attached in Appendix - 9. The actual interlock sequence shall be developed for each pig trap system during detail design based on the guidelines in paragraph 6.2.4.

ATTACHMENTS APPENDIX - 1 : Data Sheets – Launcher & Receiver

APPENDIX - 2 : Template PID and Operating Sequence for Oil PIG Traps

APPENDIX - 3 : Template P&ID and Operating Sequence for Gas PIG

Traps

APPENDIX - 4 : Template P&ID and Operating Sequence for Multi Phase

Flow PIG Traps

APPENDIX - 5 : Pipeline Pigging Requirements

APPENDIX - 6 : Intrusive and non-intrusive PIG Signaller Vendor Ketches

APPENDIX - 7 : Flow Rae Vs Velocity Graph – Liquid & Gas

APPENDIX - 8 : Barred TEE

APPENDIX - 9 : PIG Trap Interlock System - Case Example

DOCUMENT TITLE: APPENDIX – 1 PROJECT No. MASTER

ADCO DOC. No. 30-99-00-0103-1

REV. 2 DATE: March 07


Page 1 of 6

PIG TRAP DATA SHEET 1. GENERAL

PROJECT DATA SHEET UNIT SPEC P.O. TAG ITEM DWG CONTRACT SERVICE

*MFR. SERIAL PIECES No ITEM SELECTION

1 Trap Type Launcher Receiver Launch + Receive 2 Design Code ANSI B31.4 ANSI B31.8 3 Tag Number(s)

150 300 600 4 ASME Pressure Class 900 1500 2500 5 Design Pressure barg 6 Design Factor 7 Applicable Piping Class (see Note 3)

Min °C 8 Ambient Temperature Max °C 9 Fluid Type Liquid only Gas only Liquid + Gas

toxic corrosive sour 10 Fluid Nature Non-toxic Non-corrosive Non-sour 11 Trap Orientation Horizontal Vertical 12 Reversible Use Yes No 13 Pipeline Diameter inch 14 Pipeline Thickness mm

Major barrel Inch 15 Trap Diameter Minor barrel inch Major barrel m 16 Trap length Minor barrel m

17 Corrosion Allowance mm 18 Support Type sliding fixed 19 Chosen Valve Type Gate Ball 20 Double Block & Bleed Valves Yes No 21 Valve connections to mainline Parts Weld end flanged 22 Power Actuated Valves Yes No 23 End Closure Type 24 Vacuum suitability of End Closure Yes No

25 Non-metallic seals resistant to explosive decompression Yes No

26 Interlock Systems Yes No 27 Coating

Normal Spheres Other (state below) 28 Type of Pigs Intelligent Foam

29 Intended Pig Frequency By Operations 30 Chemical Injection Yes No 31 Thermowell Installation Yes No 32 Pre-commissioning Drying Method Vacuum Methanol N.A.

Materials 33 Minor barrel 34 Reducer 35 Major barrel 36 Flanges and Forged Fittings 37 End Closure

In shaded boxes, use “ Check mark” to indicate selection * Information supplied by manufacturer unless already specified

NOTES 1. This is a Standard Data Sheet for Launcher and Receiver 2. Pig trap system shall comply with DEP 31.40.10.13- Gen. 3. This is project specific pipe class number.

ADDITIONAL DATA

``


ADCO DOC. No. 30.99.90.xxxx


PIPELINES LAUNCHER & RECEIVER SYSTEMS Page 2 of 6

INFORMATION TO BE SUBMITTED WITH THE TENDER

``





2. PIG LAUNCHER (SIZE & TAG NO.)

PID Ref. No. :

PIG LAUNCHER

Dimensions

Minor barrel length (L1) mm :

Reducer length (L2) ) mm :

Major barrel length (L3) ) mm :

Scraper Launcher Total Length (L ) mm :

Minor barrel CL elevation (Z) ) mm :

``





2.1 Nozzle Schedule

MAIN COMPONENTS

Mark No. Name Size/Rating/Facing

A1 1 Minor Barrel (Pipeline Connection)

A2 1 Reducer

A3 1 Major Barrel

A4 1 Quick Opening end Closure

A5 1 Filtering Basket

A6 1 Lifting Arrangement

NOZZLE DATA

Mark No. Name Size/Rating/Facing N1 1 Kicker line N2 1 Balance Line

N3 1 Drain (Minor barrel)

N4 1 Drain (Major barrel)

N5 1 Vent (Minor barrel)

N6 1 Vent (Major barrel)

N7 1 Relief

N8 1 Purge

N9 1 Pig Signaller

N10 1 Water Inlet Nozzle

(Optional)

K1 1 Pressure Indicator (Major

barrel)

K2 1 Pressure Indicator (Minor

barrel)

NOTES

1. Orientation of all Nozzles shall be confirmed during detail design drawing approval stage.

2. Thickness of body and neck shall be designed based on pipeline design parameters and

manufacturing requirements. Necessary calculations shall be submitted to company for approval.

``





3. PIG RECEIVER (SIZE & TAG NO.)

PID Ref. No. :

PIG RECEIVER

Dimensions Minor barrel length (L1) mm :

Reducer length (L2) ) mm :

Major barrel length (L3) ) mm :

Scraper Launcher Total Length (L ) mm :

Minor barrel CL elevation (Z) ) mm :

``





3.1 Nozzle Schedule

MAIN COMPONENTS

Mark No. Name Size/Rating/Facing

A1 1 Minor Barrel (Pipeline Connection)

A2 1 Reducer A3 1 Major Barrel

A4 1 Quick Opening end Closure

A5 1 Filtering Basket A6 1 Lifting Arrangement

NOZZLE DATA

Mark No. Name Size/Rating/Facing N1 1 Kicker line N2 1 Balance Line N3 1 Drain (Minor barrel) N4 1 Drain (Major barrel) N5 1 Vent (Minor barrel) N6 1 Vent (Major barrel) N7 1 Relief N8 1 Purge N9 1 Pig Signaller N10 1 Water Inlet Nozzle

(Optional)

K1 1 Pressure Indicator (Major

barrel)

K2 1 Pressure Indicator (Minor

barrel)

NOTES

1. Orientation of all Nozzles shall be confirmed during detail design drawing approval stage.

2. Thickness of body and neck shall be designed based on pipeline design parameters and

manufacturing requirements. Necessary calculations shall be submitted to company for approval.

DOCUMENT TITLE: APPENDIX - 2 PROJECT No. MASTER

ADCO DOC. No. 30-99-00-0103-1



Note: 1) Refer Appendix-9 for an example of typical sequential key interlock logic developed

based on the above.

Operating Sequence for Pig Trap System (Oil) (Note1)

A. Pig Trap Depressurised

Step Yes No

• Check the pressure on the pig launcher

• Check that the pig launcher isolation valves (M1 and M2) are closed.

• Check that all the vents (V1, V2 & V3)) / drains (D1, D2 & D3) valves are closed.

• Check the purge connection valve (N1) is closed.

• If the pressure is not atmospheric following is necessary:

• Open the Vent valves to release the pressure. Ensure that the pressure is reduced to atmospheric pressure.

• Open purge valve N1 and purge the trap for adequate time

• Close purge valve N1

• Check vent valves V1, V2 and V3 for close position

• Open drain valves D1, D2 and D3 and release any liquid entrapped to the drain system.

• Ensure the pressure inside the pig trap is completely released.

``

DOCUMENT TITLE : APPENDIX – 2 PROJECT No. P30168

Engineering Specification for Pig Trap System ADCO DOC. No. 30.99.90.601

REV. 1 DATE: 29.09.04

INTEGRITY EVALUATION OF ADCO PIPELINES LAUNCHER & RECEIVER SYSTEMS

Page 2 of 6


B. Pig Loading

Step Yes No

The Pig Launcher Quick Opening Closure (QOC) provided with a safety lock device will not permit the closure to be opened before the internal pressure has been fully released, The same locking device also prevents pressurizing the trap before the closure is in the properly locked position.

• Open the Pig Launcher End Closure in accordance with manufacturers instructions.

• Insert the pig ensuring its position correctly in the reduced bore section of the launcher.

• Check the door seal and close the End Closure.

``



REV. 1 DATE: 29.09.04


Page 3 of 6


C. Launcher Line Up

Step Yes No

• Check that isolation valves on the drain and vent are closed.

• Open the balance valve BV1.

• Open the Vent valves V1, V2 and V3.

• Ensure that Purge Valve N1 is closed.

• Open the main line valve M2

• Open Kicker line valve K1

• Open Pressurizing valve P1

• Open slowly pressurizing throttling valve P2.

• Close all vent valves

• Allow the pressure to reach the main line pressure

• Close P1 and P2



• Close Balance valve BV1

``



REV. 1 DATE: 29.09.04


Page 4 of 6


D. Receiver Line Up

Step Yes No

• Check that the pig receiver is fully depressurised


• Check that all the vents (V11, V12 & V13) / drains (D11, D12 & D13) valves are closed.


• Open pig trap isolation valve M12

• Open Kicker Line valve K11

• Open Balance line valve BV11

• Open vent valves V11, V12 and V13

• Open pressurizing valve P11

• Open slowly the pressurizing valve P12

• Close all vent valves V11, V12 and V13

• Allow the pressure inside the pig trap to reach the main line pressure

• Close pressurizing valves P11 and P12


• Open pig trap isolation valve M11.

• Close Balance Line valve BV11

``



REV. 1 DATE: 29.09.04


Page 5 of 6


E. Pig Launching

Step Yes No

• Confirm that the receiver is lined up to receive the pig.

• Slowly close the bypass valve BP1 until the pig starts moving as can be detected by the pig signallers.

• Open fully the bypass valve BP1

• Close Main line valve M1

• Close kicker line valve K2

• Open vent valves V1, V2 and V3 to ensure depressurising up to atmospheric pressure.



• Open drain valves D1, D2 and D3

• Close drain valves D1, D2 and D3

• Open purge valve N1 and allow purging

• Close vent valves V1, V2 and V3

• Close purge valve N1.

``



REV. 1 DATE: 29.09.04


Page 6 of 6


F. Pig Receiving

Step Yes No

• Arrival of pig is indicated by the pig signallers

• Slowly close the Bypass Valve BP11 till the pig is into the pig receiver as indicated by the pig signallers located upstream of the pig trap.

• Fully open the bypass valve BP11

• Close main line valve M12



• Open Pig trap vent valves V11, V12 & V13 till pressure is atmospheric



• Close balance line valve BV11

• Open drain valves D11, D12 & D13 drain the liquid and then close the valves.

• Open Purge connection valve N11

• Allow purging then close vent valves V11, V12 & V13

• Also close purge valve N11

• Ensuring that the trap is depressurised open the trap door and unload the pig

• Close the door

DOCUMENT TITLE: APPENDIX – 3 PROJECT No. Master

ADCO DOC. No. 30-99-00-0103-1



Operating Sequence for Pig Trap System (Gas) (Note 1)


Step Yes No



• Check that all the vents (V1, V2 & V3)) / drains (D1, D2 & D3) valves are closed.


• If the pressure is not atmospheric following is necessary:




• Recheck for vent valves V1, V2 and V3 closure position.

• Open drain valves D1, D2 & D3 and release any liquid entrapped to the drain system.

• Close drain valves D1, D2 & D3.

• Fill the trap with water through water-in connection to soak any pyrophoric dust on the pipe internals and to displace any flammable/ toxic gas. Keep the atmospheric vent valve open during filling.

• After soaking for sufficient time drain the water.

• Once the pig trap is fully drained close the atmospheric vent and drain valve.



based on the above.

`` DOCUMENT TITLE: APPENDIX – 3 PROJECT No. P30168


REV. 1 DATE: 29.09.04


Page 2 of 6


B. Pig Loading

Step Yes No


• Open the Pig Launcher End Closure in accordance with manufacturers instructions



• The pig is now loaded but there is air in the Pig launcher. This has to be dispelled by Nitrogen or combination of Water and Nitrogen before launching can commence.

• Open the atmospheric vent valve and purge the trap.

• Purge for at least 10 minutes and then close the atmospheric vent valve.

• Close the purge valve and leave the pig trap under small positive nitrogen pressure.

• The pig is now ready for launch.



REV. 1 DATE: 29.09.04


Page 3 of 6


C. Launcher Line Up

Step Yes No


• Open the balance valve BV1



• Open the main line valve M2.






• Close P1 and P2


• Open the main line valve M1.




REV. 1 DATE: 29.09.04


Page 4 of 6


D. Receiver Line Up

Step Yes No



• Check that all the vents (V11, V12 & V13)) / drains (D11, D12 & D13) valves are closed
















REV. 1 DATE: 29.09.04


Page 5 of 6


E. Pig Launching

Step Yes No





• Close kicker line valve K2.

• Open vent valves V1, V2 and V3 to ensure controlled depressurising to atmospheric pressure



• Open drain valves D1, D2 & D3.

• Close drain valves D1, D2 & D3.



• Pressurise with Nitrogen to leave a small positive pressure in the Pig Launcher.




REV. 1 DATE: 29.09.04


Page 6 of 6


F. Pig Receiving

Step Yes No







• Open Pig trap vent valves V11, V12 & V13 till pressure is atmospheric.


• Close main line valve M11.

• Close balance line valve BV11.

• Open drain valves D11, D12 & D13, drain the liquid and then close the valves.




• Ensuring that the trap is depressurised open the trap door and unload the pig.

• Close the door.

DOCUMENT TITLE: APPENDIX - 4 PROJECT No.MASTER

ADCO DOC. No. 30-99-00-0103-1



Operating Sequence for Pig Trap System (Multi Phase) (Note 1)


Step Yes No



• Check that all the vents (V1, V2 & V3)) / drains (D1, D2 and D3) valves are closed.


• If the pressure is not atmospheric following is necessary




• Recheck vent valves V1, V2 and V3 for closure position.

• Open drain valves D1, D2 and D3 and release any liquid entrapped to the drain system.






based on the above.

``



REV. 1 DATE: 29.09.04


Page 2 of 6


B. Pig Loading

Step Yes No


• Open the Pig Launcher End Closure in accordance with manufacturers instructions



• The pig is now loaded but there is air in the Pig launcher. This has to be dispelled by Nitrogen or combination of Water and Nitrogen before launching can commence.

• Open the atmospheric vent valve and purge the trap.

• Purge for atleast 10 minutes and then close the atmospheric vent valve.

• Close the purge valve and leave the pig trap under small positive nitrogen pressure.

• The pig is now ready for launch.

``



REV. 1 DATE: 29.09.04


Page 3 of 6


C. Launcher Line Up

Step Yes No


• Open the balance valve BV1




• Open Kicker line valve K1.





• Close P1 and P2

• Open Kicker line valve K2.



``



REV. 1 DATE: 29.09.04


Page 4 of 6


D. Receiver Line Up

Step Yes No



• Check that all the vents (V11, V12 & V13)) / drains (D11, D12 and D13) valves are closed.



• Open Kicker Line valve K11.








• Open Kicker Line valve K12.



``



REV. 1 DATE: 29.09.04


Page 5 of 6


E. Pig Launching

Step Yes No






• Open vent valves V1, V2 and V3 to ensure controlled depressurizing up to atmospheric pressure.



• Open drain valves D1, D2 and D3

• Close drain valves D1, D2 and D3



• Pressurise with Nitrogen to leave a small positive pressure in the Pig Launcher.


``



REV. 1 DATE: 29.09.04


Page 6 of 6


F. Pig Receiving

Step Yes No







• Open Pig trap vent valves V11, V12 and V13 till pressure is atmospheric.



• Close balance line valve BV11

• Open drain valves D11, D12 and D13, drain the liquid and then close the valves




• Ensuring that the trap is depressurised open the trap door and unload the pig.

• Close the door.

DOCUMENT TITLE: Appendix - 5 PROJECT No. MASTER

ADCO DOC. No. 30-99-00-0103-1



Appendix - 5

PIPELINE PIGGING REQUIREMENTS

PIPELINE SERVICE

REASON FOR PIGGING TYPE OF PIG FREQUENCY OF PIGGING AND

RELATED FACTORS

CRUDE OIL Monitoring of pipeline condition

Intelligent type The frequency of intelligent pigging is likely to be not less than yearly and is dictated by the results of pipeline corrosion monitoring

To remove deposits from the internal surface of pipelines.

Cleaning type Approximately on a weekly basis. Pigging frequency set by the amount of wax, sand, debris, etc. which can be handled or by the pipeline pressure drop.

WET GAS (Free water or hydrocarbon condensate)

Control of liquid hold-up.

Batching type Frequency of pigging is dependent upon the capacity of the downstream liquid handling facility and the amount of liquid hold-up in the pipeline under various operating modes. Actual pigging frequency may vary between daily and yearly operations.

Control of Corrosion.

Batching type Corrosion inhibitor solutions can be applied to the internal surfaces of the pipeline between two batching pigs. The frequency of this may vary between weekly and monthly dependent on the type of inhibitor used.

In controlling pipeline corrosion, the pigging frequency may be less important than other considerations such as disruption to pipeline operations.

Monitoring of pipeline condition.

Intelligent type As for crude oil lines.

DRY GAS (No free water or hydrocarbon condensate)

Monitoring of pipeline condition

Intelligent type As for crude oil lines.

There is no requirement for routine pigging, provided the dry gas line remains free of liquids and solids.

Space is required for temporary pigging facilities, if pipeline monitoring not required.

Appendix 7 - DOCUMENT TITLE : PROJECT No. MASTER

ADCO DOC. No. 30-99-00-0103-1



Page 1 of 4

Liquid Flowrate/Velocity Graph

0

1

2

3

4

5

6

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Flowrate [m³/h]

Velo

city

6" 8" 10 12" 14 16 18 20"

24"

26"

28"

30"32"

36"40"42"48"

Graph – 1


ADCO DOC. No. 30-99-00-0103-1



Page 2 of 4

Gas Flowrate/Velocity Graph

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 200,000

Flowrate [Sm³/h]

Velo

city

@ 10 bara /

6" 8" 12"10" 20"18"16"14" 28"26"24"

40"

36"

32"

30"

48"

42"

Graph – 2


ADCO DOC. No. 30-99-00-0103-1



Page 3 of 4


0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000

Flowrate [Sm³/h]

Velo

city

@ 50 bara / 20°C

8"6" 12"10" 14" 16" 18" 20 24"

26"

28"

30"

32"

36"

40"42"48"

Graph – 3


ADCO DOC. No. 30-99-00-0103-1



Page 4 of 4


0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 400,000 800,000 1,200,000 1,600,000 2,000,000

Flowrate [Sm³/h]

Velo

city

[m/s

]

@ 100 bara /

8"6" 12"10" 14 16" 18" 20 24" 26

28

30

32

36

4042

48

Graph - 4

DOCUMENT TITLE : APPENDIX – 8 PROJECT No. MASTER ADCO DOC. No. 30-99-00-0103-1



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