ASTM A335 pipe (with Grade P9, P11, P22, P91 pipes) has been widely used in
different industries for high temperature, high pressure services. According to
market data, it is one of the most consumption alloy pipes in boiler industry,
heat exchanger, power station, high and super high pressure vessels.
So why this pipe is required so large quantity in these special industries?
How much do you know about ASTM A335 pipe? And what is the most featured grades
in this standard?
Following article will tell you all the things you need to know about this
pipe.
Listed topics
What is ASTM A335 pipe
Standard specification
Featured Grades
Referred standards to manufacture this pipe
Raw steel material that used for the production
Tests involved
Things you need to notice when placing an order
What is ASTM A335 pipe?
We also call ASTM A335 pipe as ASME S/A335 Chrome-Moly pipe, it is a type of
seamless pipe could be used in high temperature environments of 540 – 750
°C.
The A335 pipes are generally called chrome moly pipe as they have a high
level of Chromium and Molybdenum presence in it. While Molybdenum increases the
overall strength, resistance, elasticity, hardenability and overall quality,
moly ensures that the material is more resistant to softening, restrains the
growth of grains and lessens the chances of embrittlement. It is the single
additive that is responsible for the increase in high temperature resistance and
it also improves the corrosion resistance to steel.
Key Elements Chromium for this pipe
Chromium is a key component that is used in the manufacture of stainless
steel. If the chromium levels are above 12%, it can be classified as stainless
steel. The oxidation resistance potential of chrome is irreplaceable even in
elevated temperatures. The hardness, tensile and yield strength is better at
standard temperatures. Due to the composition of the material, it is ideal to be
used in power plants, refineries, petro-chemical plants and other oil field
services when there is transportation under high temperatures and pressures
involved.
ASTM A335 Standard Specification and Scope
In ASTM international associates defines: “ASTM A335 is the standard
specification for seamless Ferritic Alloy-Steel Pipe for High Temperature
Service.” This specification covers nominal wall and minimum wall thickness pipe
that with alloy material and manufactured in seamless type. The pipe under this
specification shall be suitable for bending, flanging, and all the other similar
processing and formations. Although it shall be good for fusion welding.
Therefore, ASTM A335 pipe material also could be used to manufacture pipe
fittings like elbow, tee, reducers etc.
A335 Pipe Chemical Composition
ASTM A335 Mechanical Properties
Referred standards ASTM
a. ASTM A999/ A999M, Standard specification for common requirements for
stainless and alloy steel pipe
b. ASTM A92, Hardness test methods for steel materials
c. E213, Instructions and practice for ultra sonic testing of steel pipe and
tube
d. E309 Eddy-Current Examniation methods for steel pipe products
e, E381, Inspection methods for steel bars, beams, profiles, billets and
forgings.
f, E527, Numbering metals and alloys practices
g, E570, Instructions for flux leakage examniation of ferromagnetic steel
pipe products
Nominal Pipe Size
ASME B36.10M dimensions standard for welded and seamless steel pipe
Raw steel material that used for the production
Pipe material shall be either hot finished or cold drawn with the related
heat treatment required for different grades. For Grade P2 and P12 the steel
should be manufactured by coarsegrain melting procedures.
Featured Grades P9, P11, P22, P91 pipes
This chrome moly pipe featured grades are ASTM A335 P9, P11, P22, P91, so
also it could be called as P Grade pipe in some cases.
P11 pipe, P22 pipe and P91 pipes are used in power industry and
petro-chemical plants, meanwhile, P5 and P9 pipe generally find usage in
refineries.
ASTM A335 P91 pipes – High Pressure Boiler Pipes
It shall be noted that, ASTM A335 Grade P91 pipe is a good grade pipe applied
for high pressure boiler. And P91 pipe is ideal when it comes to bending,
flanging or when it is used in similar operations such as welding. The material
of steel should stick to the composition of chemicals, tensile property and the
requirements of hardness.
ASTM A335 P91 alloy steel pipe and high pressure boiler pipes are the two
variants available and the range is dependent based on the size, which is solely
based on the usage. The length of the pipe will be subject to hydrostatic test
and there will also be a non-destructive examination based on the
specifications.
As a result, The chrome moly pipe finds high usage in power generation
industry and petrochemical industry owing to its resistance to corrosion,
tensile strength, strength for high temperature owing to its
cost-effectiveness.
Tests involved
Some of the common tests that are done include transverse and longitudinal
tension tests, flattening tests, hardness test and bend test. In case of
material heat test that is done in a blast-furnace, it will be done on 5% of the
pipes manufactured from each lot.
In case of the diameter exceeding NPS 25, the diameter to wall thickness
ratio should typically be 7.0 or lesser than it. In case of NPS 10 and thicker
pipes, the flattening test is done only when the purchaser approves of it.
Things you need to notice when placing an order
When you send an inquiry of before place the order for ASTM A335 pipe, below
specifications shall be verified:
a. Length per piece and the quantity (Specified in feet, meters or
pieces)
b. Material Name (Seamless alloy steel pipe)
c. Grade (P5, P9, P11, P22, P91 pipe etc)
d. Manufacturing types (hot finished seamless or cold drawn seamless)
e. Size to described as below ways:
1. NPS and Schedule Number (According to ASME B36.10, for example NPS 7 inch
and Sch 40)
2. OD or ID and nominal or minimum wall thickness (inch or mm)
