1 PROC 2076: Chemical Engineering Design Assignment 2: Oil & Gas Pipeline Material Selection Group 3 17 September 2015 Dr. Liam Ward Group Members: Farihin Afini Abdul Muthalib Fatin Hanisah Mohd Anuwi Sharifah Nurfasha Syed Idris Shuhada Atika Idrus Saidi Wan Lily Aisyah Mazlan SCHOOL OF CIVIL, ENVIRONMENTAL & CHEMICAL ENGINEERING
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
PROC 2076: Chemical Engineering Design
Assignment 2: Oil & Gas Pipeline Material Selection
Group 3
17 September 2015
Dr. Liam Ward
Group Members:
Farihin Afini Abdul Muthalib
Fatin Hanisah Mohd Anuwi
Sharifah Nurfasha Syed Idris
Shuhada Atika Idrus Saidi
Wan Lily Aisyah Mazlan
SCHOOL OF CIVIL,
ENVIRONMENTAL & CHEMICAL
ENGINEERING
2
1 EXECUTIVE SUMMARY
The main idea and the scope of this report is on the process of material selection and designing
an oil and gas pipeline system for distribution purposes. Out of a few different types of oil and gas
pipeline exist, natural gas distribution pipeline is chosen. Natural gas is delivered via distribution
pipelines domestically, industrially, or even agriculturally.
Different types of corrosion in underground environment exists where underground pipelines are
installed including general corrosion, pitting corrosion, stress-corrosion cracking (SCC), and
differential corrosion cells. Meanwhile, differential aeration cell and galvanic corrosion are another
two types different corrosion classified under the differential corrosion cells where oxidation and
reduction occur separately.
The specific function and a few functional requirements are listed first before introducing the
design concept of natural gas distribution pipeline. A shortlist of suitable materials for use as
construction of the pipeline based upon the major requirements is provided. The materials
involved are steel, copper, polyethylene, and fiberglass while the discounted material are cast
and wrought iron. The four materials are ranked according to a few factors affecting the choice of
materials which are corrosion-resistant, maximum service temperature, toughness and cost of
materials. From the rank and index mentioned before, the best materials are then selected based
upon the degree of resistance to corrosion required for the design. A critical analysis is done
based upon the materials ability to meet the requirements for the system. The focus is on
combating exterior corrosion since there is not much issue with internal corrosion due to the
contents of the natural gas passing through. Polyethylene is finally chosen as the most suitable
material to resist corrosion from the surrounding underground environment while carbon steel is
selected as the type of interior pipe. Other factors affecting the choice of materials for the
construction of pipelines that could be taken into account are weldability and joining,
environmental factor, availability of materials, maintenance, and miscellaneous shock factors.
Several possible improvements that will allow the distribution line to work at its optimum efficiency
are suggested such as consideration for internal coating, materials’ grades, and accuracy in
calculation.
Conclusively, carbon steel and polyethylene are chosen to construct the interior and exterior of
natural gas distribution pipeline respectively as they match well with the five main operating
15.2 Material selection charts .............................................................................................19
4
3 LIST OF FIGURES AND TABLES
Figure 1: Simple design concept where 1 – internal surface, 2 – external surface Page 7 Table 1: Corrosion-resistant classification for considered materials Table 2: Range of maximum service temperature for considered materials Table 3: Toughness for the considered materials
Page 9
Table 4: Cost for considered materials per kilogram Page 10
5
4 INTRODUCTION
Oil and gas pipelines are needed for safe and efficient transportation of large quantity of oil and
gas for instance crude oil and natural gas. The delivery network for this transportation consists of
many types of pipelines, each serving its purposes. In general, pipelines can be considered as
cost-effective alternative options apart from using tanker truck loads and rail cars. Pipelines need
impressively less energy to function than operating trucks or rail. This is due to the fact that
pipelines have much lower carbon footprints count. Underground pipelines are one of the many
safer way for oil and gas transport.
From the numerous types of pipelines, this report will mainly be focusing on the natural gas
distribution pipelines. Natural gas is a hydrocarbon compound which consists of hydrogen and
carbon atoms. The simplest form of natural gas is methane gas which is made up of one carbon
atom bonded to four hydrogen atoms. Gaseous hydrocarbon includes compounds with lesser
amount of natural gas liquids, and other gas such as nitrogen, carbon dioxide, hydrogen sulfide,
or even water. These trace compounds will be discarded at gas processing facilities once they
are produced. The natural gas which flows along the pipelines will be distributed domestically,
industrially, and agriculturally. The outer diameter of pipeline can be as small as ½ inch to 24 inch
while the length depends on how far the natural gas will be distributed to.
The natural gas delivery network starts at the producing wellheads, where products will go through
a gathering lines to a compressor station. From this compressor station, the unrefined natural gas
will either go to the underground storage through transmission lines, or to a processing plant,
where the gas is further refined and compressed before getting delivered to city gates or local
distribution companies. Through distribution lines, refined gas is then supplied to commercial or
residential customers.
The gathering of raw natural gas is done by the small diameter pipes from producing well. It is
then transferred to a gas processing facility. This can also be applied to water, impurities, and
other gases. Natural gas is said to be moving at speeds up to 40 km/h through these pipelines
(Canadian Energy Pipeline Association, 2015).
Back in the days, pipelines were made from hollowed-out logs, lead and copper. Now as the
technology improves, they are made from high quality steel.
The scope of this report is to design an improvised version of line-pipe system for distribution
purposes. The main objective is to provide justification for the groups or classifications of materials
that are selected based upon the line-pipe design requirements and the ability of the materials to
meet these requirements. The specific function and functional requirements for natural gas
distribution lines are listed thus a simple design concept is outlined. A few suitable materials for
use as construction of the pipeline based upon the major requirements are shortlisted. The
materials are next ranked in terms of suitability and meeting the operating requirements. Three
materials that have been shortlisted are then selected based upon the degree of resistance to
corrosion required for the design. A detailed analysis is also provided based upon the materials
ability to meet the corrosion requirements for the system under consideration and importance of
corrosion resistance compared with other requirements for final selection of material for
construction. Other factors affecting choice of material such as cost, availability of materials,
processing, welding, joining, etc. are discussed thoroughly. Some possible improvements that
can be made to the pipeline design are suggested.
6
5 LITERATURE REVIEW
The main aspect of material selection for this assignment is on corrosion, thus this literature
review will cover the different types of corrosion in underground environment where underground
pipelines are installed. In United States, from 1994 until 1999, it was recorded that many accidents
happened under the case of natural gas transmission pipeline and natural gas distribution pipeline
due to the hazardous liquid in the pipelines which the main factors of its existence are caused by
corrosion, internal and external (US Department of Transportation, 2015).
According to American Society of Metals International (2002), the types of corrosions in the
underground environment for pipeline installation are general corrosion, pitting corrosion, and
stress-corrosion cracking (SCC). Another type of corrosion that is most affect the underground
pipelines is the differential corrosion cells. The most common morphology of the differential
corrosion cells is uneven metal loss over localized areas covering a few to several hundred square
inches.
The basic mechanism in corrosion is redox reaction, where they occur physically at or near the
same location on a metal. Oxidation and reduction reaction always occur at the same moment.
However, as its name, differential corrosion cells, the oxidation and reduction reaction occur
separately on the metal surface, where the oxidation occur at one side and reduction occur at the
other side of the metal.
In addition, under differential corrosion cell, a variety of different types exist. They are differential
aeration cell and galvanic corrosion. Differential aeration cell happens when different parts of a
pipe are exposed to different concentration of oxygen in soil, and cells created by differences in
the nature of the pipe surface or the soil quality. Meanwhile, galvanic corrosion occurs when
potential difference in the flow of electrical current is created by the presence of different metals.
This is because different metals have a different corrosion potential in a given environment.
In the ASM Handbook (2006), prevention of corrosion can be done through various methods such
as coatings, cathodic protection and surface preparation. The Canadian Energy Pipeline
Association (CEPA) member companies suggests that surface preparation for new constructions
of pipelines can be done, such as fusion-bonded epoxy (FBE), liquid epoxy, urethane, extruded
polyethylene, and multilayer or composite coatings (Beavers & Thompson, 2006). Fusion-bonded
epoxy (FBE) coatings are integrated in pipeline construction by CEPA for natural gas distribution
pipeline. CEPA has a performance of 99% safety with this approach (Canadian Energy Pipeline
Association, 2015).
7
6 SPECIFIC FUNCTION AND FUNCTIONAL REQUIREMENTS
Natural gas distribution lines serves a specific purpose of distributing refined natural gas directly
to residential areas and commercial customers. The operating parameters for natural gas
pipelines consists of gas composition, pressure, temperature, and ambient conditions. The type
of distribution pipeline chosen is underground distribution pipelines.
The functional requirements for distribution pipelines rely heavily on the operating parameters.
1. Corrosion-resistant: Depending on gas composition, distribution pipelines need to be
manufactured suitable with the type of substance that passes through it. Thus, materials
used in production of distribution pipelines should be corrosion-resistant to the substance
it carries. If the pipeline carries toxic chemical substance, the materials should be
unreactive to the substance.
2. Able to withstand operating pressure: Determining the pressure plays an important role in
meeting the functional requirements. Materials that make up the distribution pipeline
should be able to withstand operating pressure, making strength of the material to be a
vital factor. Most distribution pipelines operates at low to intermediate pressure.
3. Able to withstand operating temperature: Temperature of the operating conditions would
also determine the type of materials used in manufacture of pipeline. The material should
be able to withstand extreme temperatures if needed without getting damaged, such as
cracking when it is too cold.
4. Long-lasting in ambient condition: For underground pipelines, one ambient condition that
should be considered is the soil humidity or acidity, to determine what material would be
able to hold out against these conditions.
5. Cost-effective: Distribution pipeline network is extensive and requires a large production.
Getting the right materials would also mean that cost factor has been weighed in to prevent
a high expense both to the manufacturers and buyers.