Fuel gas system of gas production

FUEL GAS SYSTEM

11th Mar, 2013

Group 4

Thura Aung (Roland)

Phyo Wai Win(Melvin)

Thant Zin Kyaw (Richard)

Phyoe Maung Maung (Neon)

Thin Zar Soe (Tina)

Thu Zar Thinn (Angel)

Fuel Gas System

• To supply dry, filtered fuel gas for gas turbines,• Start-up seal gas for compressor, flare header purge and

blanket gas users.

Main Components

• Fuel Gas Scrubber (V-6200)• Fuel Gas filter Separators (V6220 A/B)• Fuel Gas Superheaters (E-6230 A/B)

Blanket Gas For Degassing Vessel

Blanket Gas For Sump Pile

Purge Gas For LP Flare Header

Purge Gas For HP Flare Header

Fuel Gas For Flare Ignition System and Pilot Burners

Fuel Gas For Turbo Generator

Fuel Gas For Gas Turbines

Fuel Gas For Glycol Regeneration Skid ( Reboiler, Stripping Gas )

Seal Gas For Compressor

To Condensate System

From Black STARTFuel Gas Supply

FUEL GAS DISTRIBUTION HEADER

From GLYCOL CONTRACTOR

To Flare

SOURCES :

• During normal operation, the gas is taken from the outlet of

Glycol Contactor.

• During start-up, the gas comes from Inlet Separator.

FUEL GAS SCRUBBER

Fig. Fuel Gas Scrubber

• It is a two-phase vertical separator fitted

with half open pipe, demister pad and

vortex breaker.

• The function of FG scrubber is to remove

99.5% of liquid and entrained liquid

droplets of 10 microns and larger.

FUEL GAS SCRUBBER

Fig. Fuel Gas Scrubber

• The half open pipe provides the initial separation of liquid and gas.

• The single demister pad is fitted to achieve required performance of 0.1 USgal/ MMscf. The purpose of demister pad is to coalesce small liquid droplets that do not settle out by gravity.

FUEL GAS SCRUBBER

Fig. Demister Pad

Fig. Half Open Pipe

INTERNAL DEVICES

Fuel Gas Scrubber

• The vortex breaker is located directly above the liquid outlet to prevent whirl pooling of liquid which would allow gas to flow out of the liquid outlet.

• Liquid is collected in the lower chamber of the scrubber and automatically drained to the condensate system.

Fig. Vortex Breaker

Protection of Fuel Gas Scrubber

• The Scrubber is protected from overpressure and under pressure by presetting high and low pressure trips that will automatically shutdown the FG system.

• High liquid level in the scrubber will also shutdown the system.

FG Filter Separator

• Receives the gas that is coming from Fuel Gas Scrubber

• Function-Remove particles that can’t be removed by Fuel Gas Scrubber

-Mist, fogs, and dust from gas streams

• Three Sections

Coalescing Section with filter element

Separation section with either a wire mesh or vane type mist extractor

A liquid accumulation section - to properly collect and discharge the liquid for further processing or disposal

FG Filter Separator

Coalescing Section or Filtration Section

Separation Section

Liquid Accumulating Section

Fig: Vertical Gas Filter Separator

Principle of operation

A. Incoming flow pass outside-in through the filter media where solids are removed and coalescing takes place.

B. The gas then carries the coalesced liquids through the standpipe/tubesheet.

Principle of operation

C. Remaining liquids are directed to the high efficiency vane mist extractor.

D. Liquids from the vane mist extractor are collected away from the gas stream.

In Zawtika Project

• 2 x 100% (Duty/Standby)

• Remove 99.98% of particles of size 0.3 micron and larger

• Removal of 99.98% aerosols of size 0.1 micron and larger before feed to the FG Superheater.

• Single stage coalescer which employs the use of filter coalescer cartridge type elements.

FG Filter Separator

FG Filter Separator

• Two (2) FG Filter Separators F-6220A/B are arranged in parallel

• To enable the online isolation of one filter separator for the replacement of blocked elements.

Fuel Gas Super heaters E-6230A/B

• 2 x 100% (Duty/Standby) FG Super heater E-6230A/B is required to provide 30°C of superheat to the FG in order to prevent liquids forming downstream as a result of pressure drop across the system.

• FG Super heaters E-6230A/B are designed with reduced active element length and a larger bundle diameter to ensure bundle removal for maintenance and inspection activities can be accommodated on the available skid footprint.

Fuel Gas Super Heaters E-6230A/B

• Heaters are also provided with high temperature shutdown devices to protect unit from overheating.

• The outlet line from FG Super heaters E-6230A/B are electric heat traced to maintain the FG temperature for gas turbines.

• Pressure relief valves are sized against check valve failure from compressor seal gas and vent to the HP flare header.

• Operating temperature is from 38 / 68°C.

Fuel Gas Super heaters E-6230A/B

Fuel Gas Super heaters E-6230A/B

• Each heater is provided with a dedicated thyristor control panel.• Heater is protected by a high element temperature shutdown device and a

high tube sheet temperature shutdown device.• Electrical power supply for fuel gas heaters E-6230A/B are from LSWG-

CPP-200 (LV Switchgear/MCC) at MSR (Main Switchgear Room).• Capacity of each heater is 186.5 kW and working voltage is 415V.

Maintenance of Fuel Gas Super heaters E-6230A/B

• In this test, a high potential AC voltage is applied between the heating element and the outer metal sheath (between the live parts and ground).

• This potential AC voltage is typically calculated by the following equation: - 2× E +1000 (Volts), - Where E is the line voltage rating of the heater

• The applied voltage is increased from zero to the test voltage and held for 1 minute.

High Potential (Hi-Pot) Test

• The insulation resistance test measures the resistance passing between the central element coil and terminal to the outer metal sheath.

• Any elements which are below 2MΩ should be dried out for about 12 hours in an oven at 250-300°C.

• To determine the insulation resistance, it is recommended that a 500 VDC or a 1000 VDC mega ohmmeter (Megger) can be used.

• Apply the leads from the megger to the heater terminals or circuits buss bars and the ground or heater chassis.

Insulation Resistance Test

• Leakage current tests on single elements for appliances are conducted by energizing the element using 120 or 240 volt power source and connecting a sensitive current meter between a line terminal and the sheath.

• UL standards limit the leakage current to 0.005 amps (5 mA) or less.

• Properly dried elements have passed leakage tests with as low as 30microamps (0.000030 amp) leakage current.

Leakage Current Test

• Element resistance test is measuring electrical resistance in ohms from terminal to terminal.

• If the heating elements are operational, the best way to check proper heater operation is to measure the current with a clamp on ammeter.

• If all circuits are drawing proper current, it can be assumed that all heater elements have continuity.

• If this test method is not possible, then it will be necessary to measure individual circuits or elements for continuity and proper resistance.

Continuity and Element Resistance Test

• Keep the equipment clean, particularly around the terminals, wiring enclosure, and heater itself through a regular maintenance program.

• While heating elements do have a long service life in most applications, the possibility of ultimate failure must be considered.

• Provisions should be made for ready replacement if the potential downtime will be expensive or critical to production or other operations.

• Replacement parts should be stocked as necessary so that a failed element can be replaced in a short period of time without completely stopping or disrupting the process.

Routine Service

Mechanical Maintenance of Fuel Gas System in Gas Plant

Maintenance of oil and gas industries is very important which means keeping the plant in good and safe operating condition.

Type of Inspection

In general, there are about eight types of inspection which are commonly done by the plant inspection personal,

1. Routine or periodic inspection2. Shutdown or Turnaround and Inspection 3. Equipment Inspection4. Fabrication Inspection5. Painting and Coating Inspection 6. Non-destructive Test (NDT)7. Corrosion Check8. Materials Check

The maintenance craftsman whose responsibility is the maintenance of piping systems, will be concerned:-

• Checking the pipe and flange connection leakage and corrosion. • Checking to be sure that valves are in working order. • Repacking valves, maintaining and replacing gaskets.• Checking insulation and possibly installing it as needed.• Checking hangers and pipe supports.• Reporting anything of an unusual nature.

Pipe and Flange Connection Part:

The Inspection of Scrubber Vertical Separator Vessel

• Leak at joint and flange• Corrosion/ Underside Corrosion• Weld cracks or defects• Condition of insulation or other covering• Condition of pipe supports and brackets• Thickness reading• Safety Valves setting and popping pressures• Insulation Resistance

• The inspection and test plan of PSV is based on API RP 527 and API STD 510 requirements.

• Inspection of inlet and outlet piping after pressure safety valve removal for any fouling

• Inspection of pressure safety valve charge and discharge nozzles for possible deposit and corrosion products

Pressure Safety Valve (PSV) Maintenance

FUEL GAS SYSTEM OVERVIEW

PRESSURE CONTROL

FG SEPARATOR AND HEATER

FG DISTRIBUTION HEADER

Q & A

Thank You

Group (4) ,POT Myanmar