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SCHOOL OF CIVIL, ENVIRONMENTAL & CHEMICAL
ENGINEERING
PROC 2076 / Chemical Engineering
Design
Materials Selection and Design of Oil
and Gas Pipeline System
Group 20
27 September, 2015
Augustina Goh
Members :
Muhamad Syarifuddin Ab Aziz
Muhammad Shafeeq Ayub
Muhammad Syafiq Danial Dany
Mohd Afif Irfan Norazhar
Umar Faruq Zamanuri
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Executive Summary
This project requires us to select materials for piping design. Piping is an assembly of
pipes, flanges, gasket, valves, fitting and other components used to mix, distribute, control,
transfer fluid to a specific places. The better the material for the pipe, the longer the pipe
can last. Main threat in piping is corrosion that occurs due to present of oxygen, chloride
(in sea water), carbon dioxide (wet and dry) and others. Although there is no corrosive
element in kerosene, air still presents within the pipe even a small amount. That is for the
internal surface problem. For the external surface of pipes, the problem relies on the
environment. Our team decided to build pipes underground because of its advantage over
utilidor construction. There are approximately, 45% mineral, 20-30% water, 20-30% air
and 5% organic matter in the soil making external corrosion undeniable. Some criteria such
as corrosion resistant, cost, maintenance, availability, fracture toughness and fatigue
endurance are discussed and given rank. Then, material are selected and given ranked too
based on criteria and they were Titanium, Carbon Steel, Stainless Steel, Bronze and
Hasteloy C. We found that carbon steel is the most efficient material regarding its cheap
cost. Carbon steel then can be coated with Multi-component epoxy and polyurethane
coating (internal) and powder coating (external) to protect it from corrosion. More
information regarding cost of internal coating and external coating for carbon steel vs. cost
of stainless steel pipe is needed to make an absolute choice for best material. Criteria like
joining and density also should be focused more as joining of pipes involved considerable
amount of workforces and cost.
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Table of Contents
Executive Summary................................................................................................. 2
Table of Contents..................................................................................................... 3
List of Figures and Tables .......................................................................................4
Introduction / Scope................................................................................................. 5
Background / Literature Review.............................................................................. 6
Main Body of Report: Material Requirements and Selection .................................8
Pipe Coatings......................................................................................................... 15
Conclusions and Recommendations...................................................................... 16
References .............................................................................................................17
Appendix................................................................................................................19
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List of Figures and Tables
Figure.1 - Pipeline Typical Flow Scheme (Export Crude)
Table.1 – Criteria Definition
Table.2 – Criteria Comparison
Table.3 – List of Material and Their Resistant Against Each Fluid
Table.4 – Materials and Its Rank On Each Criteria
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Introduction / Scope
Piping is an assembly of pipes used to transfer fluid between places such as storage tank,
processing factory and other. Piping construction can be seen everywhere especially in oil
and gas industry. Food processing and transfer of gas to resident house also used pipes of
different materials. The objective of this report is to resolve the problem with chosen type
of piping and try to build new efficient pipes for transporting chosen fluid. There will be
some material that needs to be chose and how the pipe work and its principle are going to
be explained. Before choosing material, rank of criteria will be discussed and ranked
according to its definition. Material selection is the most important part because the
efficiency of one process in industry decided by the quality of the material chosen and the
selection of material will base on how well the material resists corrosion. For example,
stainless steel and carbon steel give different effect on pipes cause of its different
properties. The piping project will be conducted whether under the ground or utilidor
depends on their pros and cons, and of course their environment factor will be different.
Coating of pipes is necessary depends on the type of material and its environment.
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Background / Literature Review
Piping is an assembly of pipes, fittings, flanges, bolting, gaskets, valves, strainers, pipe
supporting elements, expansion joints, and other components used to convey, distribute,
mix, separate, discharge, meter, control, or snub fluid flows. For example, the commonly
used types of pipeline in oil and gas industry are flow lines, injection lines, export lines,
subsea pipelines and etc. In this report, the type of pipeline used to transfer kerosene is
export lines which transfer fluid from processing facility to tankage or loading point. The
tankage or storage tank is a cylindrical, vertical, open or closed tank that has many sizes
and capacities for containing petroleum products within atmospheric pressure. The storage
tank normally has a maximum operating temperature of 260°C. The kerosene transferred to
tankage should be under flashpoint. Flashpoint is the minimum temperature for the liquid
to ignite in air by forming a mixture at the surface of the liquid. From the definition, we
can see the lower the temperature the more easily for the liquid to ignite.
Figure.1 Pipeline Typical Flow Scheme – Export Crude
The main problem with piping is the corrosion due to present of; oxygen, carbon dioxide,
chloride, H2S and others.
Kerosene is free from such corrosive elements. But, the present of air in the pipes cannot
be avoided. There will be corrosion due to Oxygen, Carbon Dioxide and erosion (abrasion,
corrosion due to the flow of the fluid and its velocity within the pipe). For external surface
of pipe, it is exposed to air even the pipe is buried under ground surface. The typical soil
consists of approximately 45% mineral, 5% organic matter, 20-30% water, and 20-30% air.
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Airs contain oxygen and carbon dioxide which induced corrosion where CO2 corrosion
(Sweet Corrosion) result in metal loss in the process fluid. Oxygen corrosion occurs when
metal is exposed to oxygen which leads to oxidation and metal loss. Acidity in soil also
can corrode a material such as steels. The greater the acidity, the higher the rate of
corrosion.
In this report the pipe will be buried instead of utilidor construction. From our research,
buried pipe is the recommended alternative, where possible. This is because buried pipes
do not disrupt roadways and lots, not subject to ambient temperature and vandalism. The
temperature below ground surface is around 20ºC, suitable for piping where temperature
(under flashpoint) of fluid low is a desirable. The buried pipes maintenance is cheaper than
utilidor type piping. Although it is hard to conduct maintenance, the pros still outperform
the cons.
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Main Body of Report: Material Requirements and
Selection
In this section, we are going to select appropriate materials for our piping design by using
suitable criteria. But first, ranking for the criteria must be made. The ranking is according
to the environment where the pipes will be installed and depends on the type of fluid used.
After that, using the criteria along with the ranking the selected materials are ranked
corresponding to its properties. Here is the list of criteria:
Table 1 - Criteria Definition
Criteria Definition.
Cost The price of the materials and substance
used to make those pipelines.
Availability The abundances of the material since the
less abundance it is the more expensive it
will be.
Maintenance Cost of maintenance activities such as
planned repairs, inspection, replacement and
equipment change.
Fracture Toughness The ability to withstand damage and not
fractured (cracked).
Fatigue Endurance The ability to withstand a long period of
cycle of the fluid during the life of piping
system.
Corrosion Resistant Affinity of a substance (usually a metal) to
withstand the damage caused by oxidization
or other chemical reaction.
Melting Point The max temperature where a material
melts.
Thermal Conductivity The tendency of the material to conduct
heat.
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From this point, criteria from the table above will be ranked in relation to our project.
Using properties of kerosene when transferring it to tankage, the component of soil and air,
we discussed the importance each criteria and give rank to it using comparison chart
below. The constant appearances of criteria in the table below depict its usefulness.
Table 2 - Criteria Comparison
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From the table above, the rank is as follows:
1) Corrosion Resistant
Our main concern in this project. Even though kerosene is not corrosive, air still
present leading to corrosion and there are external corrosion too due to exposure to
air. Corrosion damaged the pipe and can halt the process of transferring fluid within
the factory. That is why a material which resists corrosion is highly desirable.
2) Cost
Every company wants to save cost when constructing a facility. The cheaper the
material the better. But, it’s not just initial cost that need to be concern about, long
term cost should be consider as well such as the cost of repair, maintenance and etc.
3) Maintenance
The material must have good properties as it would long last. Material such as
stainless steel doesn’t need a future maintenance because of it high sustainability.
The less maintenance, the less the cost of maintenance. One of the reasons why
maintenance rank below cost.
4) Fatigue Endurance
The stronger the material, the higher the fatigue endurance. When the material has
high fatigue endurance, the higher the number of cycle of the fluid the pipe can
withstand. Thus, the gap of future maintenance increases, nonetheless saving cost.
5) Availability
After considering above criteria, then we have to consider its availability. Even if
the material has outstanding performance, if it’s a rare material (not abundance
within that area or country) it would be expensive. It’s number 5 in ranking because
although the material might be expensive, a long term benefit might beat the cons.
6) Fracture Toughness
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The maximum temperature when transferring kerosene is 38°C and below. Unseen
problem such as temperature drop might happen probably because of cold winter
although the pipe is buried. When temperature drops, pressure also drop and the
material have to withstand such changes or cracked is imminent.
Next, we selected materials from the most important aspect which is corrosion resistant.
Then we go slowly through criteria above from top 1 to number 6 and add other criteria if
necessary.
Corrosion Resistance 1)
Excellent 2)
Good 3)
Poor
Fluid
Metal
Carbon
Steel
Cast
Iron
302 and
304
Stainless
Steel
316
Stainless
Steel
Bronze Durimet Monel
Hasteloy
B
Hasteloy
C
Titanium
Carbon dioxide, dry 1 1 1 1 1 1 1 1 1 1
Carbon dioxide, wet 3 3 1 1 2 1 1 1 1 1
Oxygen 1 1 1 1 1 1 1 1 1 1
Petroleum oils 1 1 1 1 1 1 1 1 1 1
Water, sea 2 2 2 2 1 1 1 1 1 1
Calcium Chloride (alkaline) 2 2 3 2 3 1 1 1 1 1
Magnesium ions 1 1 1 1 2 1 1 1 1 1
Sulfuric acid, air free 3 3 3 3 2 1 2 1 1 2
Table 3 – Material resistant against corrosion rating
Table above shows metals with it corrosive resistant against specific type of fluid. From
the table above, we can see that titanium, nickel alloy and stainless steel have excellent
resistant against almost all of the fluid listed. The highlighted row means the fluid is
present as a threat in our project. Sea water containing NaCl is considered present because
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of condensate seawater. Carbon and bronze has medium corrosion against the highlighted
fluid.
Next, we bring the chosen materials from table above to the next stage. The following is
the material we could discuss further.
1. Titanium
2. Stainless steel
3. Hasteloy C (Nickel Alloy)
4. Carbon Steel
5. Bronze
Unselected material is due to:
Monel: Too expensive although it is resistant to salt which is highly desirable.
302 and 304 Stainless Steel, 316 Stainless Steel : There are many types of stainless steel,
thus a general stainless steel is chosen to simplify things. While for Durimet (stainless
steel), it is hard to cut and require many workforces for cutting.
Cast Iron : Cast iron is vulnerable to rust when exposed to moisture
The table below shows the top 6 criteria with the chosen materials. Each material has their
advantages and disadvantages. The materials will be ranked according to the respective criteria.
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The rank of criteria decreases from left to right.
Citeria Corrosion
Resistant
Cost Maintenance Fatigue
endurance
Availability Fracture
toughness
score
Titanium 1 3 1 2 2 2 11
Stainless
Steel
1 3 1 1 2 1 9
Hasteloy
C(nickel)
1 3 1 1 2 2 10
Carbon
Steel
3 1 2 1 1 1 9
Bronze 1 3 2 3 1 1 11
Table 4 - Materials and Its Rank on Each Criteria
From the table above, the rank is as follow:-
1. Stainless Steel and Carbon Steel
2. Hasteloy C
3. Bronze
4. Titanium
Although stainless steel and carbon steel has the same scores, carbon steel fall in our 1st
rank while carbon 2nd
.
1. Carbon Steel: Among the threat, carbon steel is weak against sea water and wet
carbon dioxide where stainless steel is much better. But this problem can be solved
by coating both internal and external surfaces of carbon steel pipe. The price of
carbon steel is almost 10 times cheaper compared to stainless steel. The good
fracture toughness increases its fatigue endurance (life span) and reduces the needs
for maintenance and repairs. Carbon steel does not rot and can withstand natural
disaster such as earthquake and tornado. It is also highly resistant to vibration and
shock. What makes carbon steel interesting is it can be recycled without losing any
strength and makes it environmentally friendly.
2. Stainless Steel: It has good corrosion resistant against all fluid especially chlorides
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which are present in sea water, but its cost make people reject this option. Stainless
steel doesn’t need to be coated like carbon steel and that fact reduce the
maintenance cost. Thus, no need for repainting and nonetheless further reducing the
cost. But, if maintenance is made, it will cost 3 times the amount to construct the
stainless pipe. Still, long term investment can be considered.
3. Hasteloy C: Hasteloy C is an excellent corrosion resistant and salt which supposed
to be a good material for piping. But, the fact it is the most expensive in the list
turns decreases its rank. If the cost for the material is expensive the maintenance
must be expensive too. Maintenance at least needs to be done 1-10 times a year for
Hasteloy pipes. Its fracture toughness is not as good as carbon steel and bronze.
4. Bronze : Copper is corrosion resistant and strong. Making it long lasting and
require less maintenance. However, the downside is that the price of copper is
expensive due to its low availability. Its fracture toughness exceeds the 5 materials
and sadly the rate of wear surpasses those 5 materials too.
5. Titanium: Also a good corrosion resistant. Once again, the high price is one of the
downside. It also has poor wear resistant. Maintenance needs to be done every 6-12
months. Its availability is still good but there’s a limit when buying it. The fracture
toughness is the lowest among the 5 materials. Higher risk of cracked. Cracking of
pipe during sudden pressure drop especially during start-up is not a trivial thing.
After ranking materials for their ability to resist corrosion and other criteria, we found out
carbon steel is the best material for piping. Cheap, strong, wear resistant and its availability
are the best fit for the pipe, but only when an internal and external coating is applied.
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Pipe Coatings
The coating used for carbon steel pipe surface is as follow:-
Internal Coating (Multi-component epoxy and polyurethane coating)
Epoxy coating can be either double layer or thin film. Epoxy is the anti-corrosion agent. As
mention, although kerosene is free of corrosive element, oxygen and carbon dioxide (wet)
still exist within the solution. Corrosion due to oxygen and carbon dioxide still occur. The
coating limits the contact of oxygen and carbon dioxide. Kerosene might have sand in it.
These particulates become aggressively corrosive projectiles when travelling in pipes.
Such coating is able to withstand high impact created by these fast moving particulates.
External Coating (Powder Coating)
Powder coating is a passive barrier protection besides paint that physically isolating the
steel from external threat such as carbon dioxide, water, oxygen and condensate sea water)
making the carbon steel invincible to corrosion .This method is the most widely used when
protecting against corrosion. The powder coat emits zero volatile organic compounds.
Moreover, the waste powder can be collected and reused after sprayed giving it almost
96% efficiency in usage. The coating also is flexible and yields with the material it is
spread to. Thus, it is ideal when involved in transportation industry as they moved down
the road with less vibration and twisting leading to low risk of damaged material.
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Conclusions and Recommendations
Having an appropriate design of piping nonetheless will save cost even in long-term
period. However, in order to build a better pipe, a suitable material is a must. Getting the
right material require a great knowledge on the purpose of the piping. Buried and utilidor
piping had different impact on the external surface of pipe. A comparison should be made
in future to distinguish their advantages and disadvantages. Although many recommend
buried piping, more info is needed to get the picture of how it works. The type of fluid and
any unnecessary threat within internal surface of pipe must be known too. Certain material
like carbon steel require coating while stainless steel not. More information regarding cost
of internal coating and external coating for carbon steel vs. cost of stainless steel pipe is
needed to see a bigger picture when selecting best material. Criteria like joining and
density also should be focused more as joining of pipes involved considerable amount of
workforces and cost. Same goes for density of material, the higher the density, the higher
the cost of transportation.
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