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General material selection guidelines for oil and gas industry pipelines.

This article presents a few tips on pipeline material selection methodology based on a rational approach drawn from oil and gas industry practices and field experiences. There will be no dwelling dwelling

an abnormality of gait in a horse in which there is a momentary hesitation before the foot is placed on the ground.
 on any specific selections since the pipe material chosen purely depends on the operating envelope that includes such parameters as type of fluid, fluid compositions, flow, pressure and temperatures. The subject is vast and every selection is determined case by case. However, this is mainly a look at some general guidelines guidelines, a set of standards, criteria, or specifications to be used or followed in the performance of certain tasks.

Types Of Pipelines

The oil and gas industry normally deals with various types of pipelines depending on the functional application of the line like flow lines, transfer lines and export lines. General descriptions of the various pipelines are in Figure 1.
Figure 1: General descriptions of pipelines in the oil and gas

Injection lines: Pipelines injecting water / steam / polymer / gas into
the wells to improve the lift of the fluids from the wells.

Flow lines: Pipelines from the well head to the nearest processing
facility carrying the well Fluids.

Trunk lines / Inter field lines: Pipelines between two processing
facilities or from pig trap to pig trap or from block valve station to
block valve station.

Export lines / Loading lines: Pipelines carrying the hydrocarbons from
the processing facility to the loading or export point.

Transfer lines / Spur lines: Branch pipeline exiting into trunk line or
export line.

Gathering lines: One or more segment of pipelines forming a network and
connected from the well heads to processing facilities.

Disposal lines: Pipeline which disposes normally produced / separated
water into disposal wells shallow or deep well disposal).

Subsea pipelines: Pipelines connecting the offshore production
platforms to on- shore processing facilities.


A typical oil and gas facility showing some of the industry's pipelines is shown Figure 2.

Corrosion Threats

Corrosion phenomenon in the oil and gas industry--particularly in pipelines--is a major concern for many operators who normally want an uninterrupted flow of the export fluids. Some of the corrosion mechanisms which one comes across in the oil and gas industry are briefly described in Figure 3. However, the detailed information on these mechanisms can be obtained elsewhere in the published literature and case studies.
Figure 3: Some corrosion mechanisms encountered in the oil
and gas industry.

* C[O.sub.2] Corrosion (Sweet Corrosion)--General metal loss due to
the presence of C[O.sub.2] in the process fluid

* [H.sub.2]S Corrosion (Sour Corrosion)--Localized metal cracking and
corrosion due to presence of [H.sub.2]S in the process fluid

* Chlorides and Bicarbonates--Cracking in the metal due in the
presence of stress and chlorides in the process fluid

* Corrosion due to Oxygen--Oxidation and general metal loss due to
the contact of metal with dissolved oxygen in the process fluid

* Microbiologically induced corrosion--Corrosion induced by
reducing bacteria particularly in the presence of [H.sub.2]S

* Erosion (Abrasion) corrosion--Corrosion due to the fluid flow
and velocity within the pipe and suspended solids in the process

* Corrosion (External) Threats in the facilities--External
atmospheric corrosion on above ground lines and corrosion due to soil
contact for buried lines

* Corrosion Under Insulation--External corrosion of pipeline due to
water ingress under the insulating materials

Materials Selection Philosophy

The corrosion and material engineer is normally harassed by many and heckled by those in the industry who work in such functions as operations, process and maintenance. The corrosion engineer has the onerous on·er·ous  
1. Troublesome or oppressive; burdensome. See Synonyms at burdensome.

2. Law Entailing obligations that exceed advantages.
 task of selecting the appropriate materials without sacrificing the fitness of the materials for the service and at the same time not opting for exotic and expensive materials in the name of corrosion resistance. Some simple steps to follow in the selection process are listed as guidance and as a rule of thumb:

* Define the corrosion circuits or loops based on the corrosion environments.

* Identify corrosion threats addressing the corrosion mechanisms that can take place in the loop.

* Calculate the corrosion rate per year (mm per year).

* Calculate service life corrosion based on design life--total corrosion for the design life.

* Consider various materials options.

* Carry out the Life Cycle Costing (LCC (Leadless Chip Carrier, Leaded Chip Carrier) See leadless chip carrier, CLCC and PLCC.

1. LCC - Language for Conversational Computing. Written at CMU in the 1960's.
)--Capex, Opex, installation cost, maintenance costs.

* Review materials selection with regard to design, operating, welding welding, process for joining separate pieces of metal in a continuous metallic bond. Cold-pressure welding is accomplished by the application of high pressure at room temperature; forge welding (forging) is done by means of hammering, with the addition of heat. , constructability.

* Finally, select the choice materials.

Materials Options

The biggest challenge faced by corrosion and materials engineers This is a list of materials engineers, people who were trained in Materials Engineering. For other disciplines, see list of engineers.
  • Leonid Brezhnev - Metallurgical engineering
  • Bonnie Dunbar - Ceramic engineering, astronaut
  • F.B.
 is to select the proper materials which are just optimum and "fit for service" without going in for costly materials to ensure longer service life for the application. There are many options available for the corrosion and materials engineer who is obliged to analyze an·a·lyze
1. To examine methodically by separating into parts and studying their interrelations.

2. To separate a chemical substance into its constituent elements to determine their nature or proportions.

 each option on a case-by-case basis before finally zeroing in on the choice material of construction. Some of the options at present within the oil and gas industry are mentioned in Figure 4 for reference.

Advantages And Limitations

While considering various material options, it should be borne in mind that every materials option will have advantages, disadvantages and some limitations. The corrosion engineer should exercise restraint RESTRAINT. Something which prevents us from doing what we would desire to do.
     2. Restraint is lawful and unlawful. It is lawful when its object is to prevent the violation of the law, or the rights of others.
 in selecting the proper and optimum material for the application without any over-rating.

Also, it is imperative imperative: see mood.

imperative - imperative language
 to verify (1) To prove the correctness of data.

(2) In data entry operations, to compare the keystrokes of a second operator with the data entered by the first operator to ensure that the data were typed in accurately. See validate.
 the environmental conditions imposed by NICE/ISO 15156 if the process fluid conditions indicate sour applications. The advantages and limitations of material options are listed in Figure 5 for guidance.


Though the pipeline material selected purely depends on the corrosion threats based on the fluid conditions and operating parameters as indicated earlier, some typical examples of materials used for the pipelines in the oil and gas industry in the Middle East are indicated in Figure 6.


It should be clearly understood that no single material is a cure for all the ills of corrosion. Corrosion is a complex activity and a judicious ju·di·cious  
Having or exhibiting sound judgment; prudent.

[From French judicieux, from Latin i
 approach is necessary when addressing the issue of material selection. It is equally important to note that an expensive and exotic material may not necessarily be the best choice for corrosion resistance. There may be a cheaper material that provides a more economically ec·o·nom·i·cal  
1. Prudent and thrifty in management; not wasteful or extravagant. See Synonyms at sparing.

2. Intended to save money, as by efficient operation or elimination of unnecessary features; economic:
 attractive solution for the corrosion problem.

By K. Nalli Nalli is a last name for some people living in Vizianagaram district which is in the northern region of Andhrapradesh stata, India. The name can also be found in families of central Italy, specifically within the Lazio province. , Mott MacDonald The Mott MacDonald Group was formed in 1989 when Mott, Hay and Anderson, renowned for its contribution to transportation engineering, merged with Sir M MacDonald & Partners, distinguished by a long tradition of water-related projects.  & Co LLC (Logical Link Control) See "LANs" under data link protocol.

LLC - Logical Link Control
, Muscat Muscat, Maskat, or Masqat (all: mŭs`kăt, mŭs`kət), city (1993 pop. 533,774), capital of Oman, SE Arabia, on the Gulf of Oman. It is flanked by rugged mountains. , Sultanate of Oman Oman (ōmän`), officially Sultanate of Oman, independent sultanate (2005 est. pop. 3,002,000), c.82,000 sq mi (212,380 sq km), SE Arabian peninsula, on the Gulf of Oman and the Arabian Sea. It was formerly known as Muscat and Oman.  

K. Nalli is a mechanical engineer with the post-graduate qualification of M.Tech in production technology from the Indian Institute of Technology in Kharagpur, India India, officially Republic of India, republic (2005 est pop. 1,080,264,000), 1,261,810 sq mi (3,268,090 sq km), S Asia. The second most populous country in the world, it is also sometimes called Bharat, its ancient name. India's land frontier (c. . He has 28 years of experience as a metallurgist, welding, materials, and corrosion engineer in India and abroad. At present he is working as a corrosion and materials engineer with Mott MacDonald & Co LLC, a consultant in oil and gas industry in Muscat, Sultanate of Oman. He can be reached at
Figure 4: Materials options for pipelines.

Metals                Non Metals     Metals + Lining

Carbon Steel with     Glass          Carbon Steel with
or without            Reinforced     internally coated
corrosion allowance   Epoxy (GRE)    FBE

Stainless Steel       Polyethylene   Carbon Steel with
                      (HDPE)         internal PE lining

Duplex Stainless                     Corrosion Resistant
Steel                                Alloy clad/lined

Figure 5: Materials advantages and disadvantages.

Material         Advantages         Disadvantages

* Carbon Steel   Cheapest option    Corrosion rates
  (CS)           Possibility of     are high Opex
                 Intelligent        involves inspection
                 Lowest Capex       pigging and external
                 pigging            painting or coating
                 Internal           Additional opex
                 corrosion          thru inhibition
                 control thru

* Carbon Steel   Capex slightly     Susceptible for
  with FBE       more Low Opex      corrosion if FBE
                 Internal           coating is damaged
                 corrosion          Coating gets
                 protection         damaged if fluid
                 through lining     contains suspended

* Carbon Steel   Capex is           Not advisable for
  with PE        slightly more      gas lines lining
  lining         than CS+FBE        collapse due to
                 Internal           depressurization
                 corrosion          Operating
                 protection         Temperature limited
                 through lining     to 65 Deg C max

* Stainless      No corrosion       External corrosion
  Steel          Opex is low        protection
                                    thru coating
                                    Not suitable for
                                    fluid where
                                    chlorides are
                                    present Long lead
                                    time for procurement

* Duplex         No corrosion       Susceptible to
  Stainless      Opex is low        stress cracking
  Steel                             in the operating
                                    range of 80 to 120
                                    Deg C High Capex
                                    Long lead time
                                    for procurement

* GRE            No corrosion       Limitation use due
                 No operating       to temperature
                 Expenses           /pressure.
                 Medium Capex       Line to be buried
                                    only No pigging

* CS + CRA       No corrosion       High capex
  internal       Can tolerate       Materials
  clad           highly wet sour    Sourcing problems

Material         Limitations

* Carbon Steel   High corrosion rate

* Carbon Steel   Coating holidays
  with FBE       during coating /
                 and operation

* Carbon Steel   Operating temp of 65
  with PE        Deg C maximum

* Stainless      Chlorides in fluid

* Duplex         Operating temp
  Stainless      Controlled
  Steel          welding -heat
                 input during

* GRE            Temp & Pressure
                 Inspection limitation
                 Aboveground lines
                 Susceptible to damage

* CS + CRA       Welding difficulties

Figure 6: Examples of pipeline materials used in the
Middle East.

Pipeline Description       Materials of Construction

Injection Water lines      CS with CA or CS with
                             internal FBE lining
Steam Injection lines      CS with CA
Polymer Injection lines    CS with internal PE lining
Lift Gas lines             DSS lines (Sour conditions)
Produced Water Disposal    CS with internal FBE or
  lines lining               CS with internal PE
Well Fluid lines           Multiphase (Crude +
  (Flow lines/Bulk           Gas + Water) - Wet Sour
  Headers/Manifolds)         Conditions--CS with internal
Main Oil lines/Trunk
  lines/ Crude Export      CRA lining
Lines/Dehydrated Crude     CS with CA or GRE
Export Gas lines           Dry gas-Sweet gas--CS
                           Wet gas-Sour gas-
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Comment:General material selection guidelines for oil and gas industry pipelines.
Author:Nalli, K.
Publication:Pipeline & Gas Journal
Geographic Code:1USA
Date:Mar 1, 2009
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