pms

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PIPING MATERIAL SPECIFICATION

General:

It is important that proper materials are selected for pipes and pipe components, valves etc so that these items withstand the operating and design conditions of pressure and temperature under which they operate and also be suitable for the fluid flowing under the operating conditions.

They should give satisfactory service for the fluid it carries for the duration of the life of the plant.

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• Piping Materials• The various materials one encounters in piping are carbon

steels, low alloy steels, stainless steels and plastics. The applications of these materials are briefly explained in the following paragraphs. The selection is based on the following criteria:

• Design pressure,

• Design temperature,

• Compatibility with the process fluid (corrosion resistance),

• Special criteria such as hygiene (in food industry).

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Carbon Steels• Carbon steels are the most commonly used materials in piping

for the following reasons:• Easy availability,• Good corrosion resistance against many fluids,• Low cost,• Suitability for temperatures up to about 400-425 deg.C.• Ease of fabrication.• The following specifications are common for carbon steels:• IS 1239, IS 3589, ASTM A 106, API 5L for pipes,• ASTM A 234, ASTM A 105 for fittings and flanges,• ASTM A 216 grade WCB for castings and ASTM A105 for

forgings.

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Galvanized Carbon Steels• These are used for applications such as potable water,

instrument air etc. Galvanizing gives adequate protection against general corrosion for these services. IS1239 covers galvanized pipes and fittings.

• Cast iron and Bronze• Cast iron and bronze are generally used as valve body and trim

materials. Cast iron pipes are also used in fire protection piping.• IS 210 grades FG 200/260 for cast iron valves,• ASTM B62 or IS 318 for bronze valves.

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Low Alloy Steels

• At temperatures exceeding about 4250 C, carbon steels suffer a loss of strength at elevated temperatures due to a phenomenon called creep and low ferritic alloy steels are specified under such conditions.

• Two such alloys are 1¼ % chromium ½% molybdenum steels (ASTM A 335 Gr. P11) and 2¼ % chromium and 1% molybdenum steels (ASTM A335 Gr.P22).

• These are suitable approximately up to about 5100 C and 5450 C respectively.

• These find wide application in power plant steam piping.

• An alloy steel with 9% chromium is also being used for high temperature steam applications.

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Stainless Steels• When corrosion is a major problem or where contamination is

to be totally avoided, stainless steels find wide application. Normally used stainless steels are of the austenitic, “18-8” type. This refers to the percentages of chromium and nickel in these steels.

• Two common types are the 304 and 316 stainless steels. The latter contains molybdenum in addition to Cr and Ni. Type 316 is superior to 304 with in corrosion resistance and high temperature stability. It is also costlier.

• These two types have very wide application in chemical and process plant piping.

• Martensitic stainless steels (with 12 to 13% chromium) are widely used as valve trim materials.

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Piping Material SpecificationLow Temperature Applications

• Normal steels suffer a loss of ductility below a certain temperature and for low temperature applications, materials have to be chosen carefully. The following materials are generally recommended at the temperatures shown:

• Conventional carbon steels (IS 1239, ASTM A 106 Gr.B etc): up to (-) 290 C,

• Low temperature carbon steels ( ASTM A333 Gr.6) up to • (-) 450 C,

• Stainless steels for cryogenic applications.

• Materials for low temperature applications are characterized by good impact strength.

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Plastics• There are applications where plastics provide superior

corrosion resistance than carbon or stainless steels. The following are the types encountered in piping:

• PVC (polyvinyl chloride),

• HDPE (high density polyethylene),

• PP (polypropylene),

• PVDF (polyvinylidene fluoride),

• PFA (perfluoroalkoxy) and

• PTFE (polytetrafluoro ethylene).

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Piping Material Specification

• PFA and PTFE are known by the registered trade name “Teflon”.

• FRP ( fibre-reinforced plastic) pipes are used for sea water, effluents etc.

• Plastics are characterized by low mechanical strength, limited resistance to high temperatures and high coefficients of thermal expansion.

• Steel pipes lined with plastics are used in some application where the mechanical strength of steel taken advantage of.

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Piping Material Specifications

Plastics• The temperature limitations of the above plastics are:• PVC: 450 C,• HDPE: 55 to 600 C,• PP: 600 C• PVDF: 1350 C,• PTFE: 200 to 2250 C• PFA: 2600 C.• FRP piping: depending on the resin used, these pipes may be

used up to about 1200 C.• PVC and HDPE are used for water pipes and plumbing.• Reference should be made to manufacturer’s recommendations

for any application.• Rubber-lined pipes are used in DM water plants.

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Specifications for pipes and fittings for steel materials

ITEM PIPES BUTT WELDING FITTINGS

SOCKET WELDING/ FLANGES

CASTINGS

Carbon steel IS 1239, ASTM A 53 Gr.B, A 106 Gr.B

ASTM A234 Gr. WPB

ASTM A 105 ASTM A216

Gr. WCB

Low alloy steels

ASTM A335,

Gr.P11/P22 ASTM A234

Gr.WP11/22 ASTM A182 Gr. F11/22

ASTM A 217Gr.WC6/

WC9

Stainless

steels ASTM A 312, Gr. TP 304/316

ASTM A 403

Gr.304/316 ASTM A 182 Gr. F304/316

ASTM A 351Gr.CF8/

CF8M

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• Gaskets• Gaskets are used to effect a leak-tight joint between flanges

and are made of a flexible material or a combination of materials:

• Resilient material inserted between flanges compressed by bolts to create a leak-tight joint.

• Commonly used types• Sheet, asbestos, rubber, PTFE etc• Spiral wound, combination of stainless and asbestos or others• Solid metal ring of soft iron or other material.

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• Bolts, studs and nuts:• These are used for bolting up the flange joints.• ASTM A307 Gr.B for machine bolts and nuts (limited to 150

class).• ASTM A193 Gr. B7 for stud bolts and ASTM A194 Gr. H for

nuts• Stainless steel bolting materials are also available.

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Piping Material Specification data Sheet

• A typical piping material specification (PMS) data sheet contains the following information:

• Piping identifying grade such as CA, CB, CC etc,• Services for which the PMS is applicable such as air, water or

steam etc,• Applicable pipe sizes with wall thicknesses, corrosion

allowance,• Pipe connection details whether butt welding, socket welding or

threaded etc with size ranges as applicable,• Material specifications for pipes, fittings, flanges, flange

bolts/studs and nuts, flange gaskets,• Dimensional standards for pipes, fittings, flanges, gaskets etc,

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Piping Material Specification• Wall thicknesses of fittings or ratings, type of flanges,• Ratings of flanges,• Types of branch connections and branch fittings with a branch

connection chart,• Types of valves used,• Ratings of valves,• Valve and speciality body materials and trim materials,• Valve rating and end connection details and• Any special requirements such as IBR, special testing or

fabrication etc.• In the case pipes with internal liners, all details shall be

specified.• PMS is a very important document for both the design engineer

as well as the fabricator.• A typical TCEL PMS is shown.

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• General Materials for Valves• Cast iron body with bronze trim for water service, ≥ 50 mm,• Bronze body with bronze trim for water and air service,≤40mm• Forged carbon steel body with 13% chromium steel trim for

general steam, condensate etc, ≤40mm,• Cast carbon steel body with 13% chromium steel trim for

general steam, condensate etc, ≥ 50 mm,• Low alloy forged and cast bodies and stellite trim for high

temperature steam etc.• Stainless steel body and trim for process applications.• Plastic valves in plastic piping.

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• Pipes are identified on PIDs by a line number. • It has the format, for example:• AST-150-CC-176• AST represents the fluid, in this case, auxiliary steam,• 150 represents the nominal pipe size, 150mm here,• CC refers to the pipe class, here, 150 class IBR,• 176 is the unique line number for the project.

pms

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