Selecting material standard for austenitic steel fitting (ASTM A 182 or ASTM A 403) 2

[Cruisnick]

First of all, thank you for reading my query and I will be hugely gratified for all the assistance and time that you will be providing. This problem has been nagging me from quite a time and I'll be truly glad if you can render me any help in sorting it out.

I have to select a material standard for stainless steel fittings complying with steel pipes as per ASTM A 312 TP304 (Welded). As per the tender specifications that I'm following, I have been given two choices namely ASTM A 182 (forged fittings) or ASTM A 403 (wrought fittings).

ASTM A 182 states :-

"Flanges of any type, elbows, return bends, tees, and header tees shall not be machined directly from bar stock"

So I'm guessing that in this case, rather than machining directly from bar stocks, the fittings will have to be manufactured by melting the austenitic steel and then forging it to shape by a forging machine such as a hammer, press, or ring rolling machine.

ASTM A 403 states :-

"The material for fittings shall consist of forgings, bars, plates, or seamless or welded tubular products"

and

"Forging or shaping operations may be performed by hammering, pressing, piercing, extruding, upsetting, rolling, bending, fusion welding, machining, or by a combination of two or more of these operations."

So again, I'm guessing that in this case in addition to manufacturing fittings by forging from molten steel and subsequently shaping them; there are other options of manufacturing fittings from plates or cold bending of seamless or welded tubular products which were not present in ASTM A 182.

So based on these observations I have two questions:-

1. What is the difference between both the standards in case of selecting austenitic steel fittings?

Other than that forgings are supposed to be manufactured from bar stocks and wrought fittings can be manufactured from forgings, bars, plates, or seamless or welded tubular products; is there any other difference?
F304 (as per ASTM A 182) and WP304 (as per ASTM A 403) both have the same chemical composition, mechanical properties and heat treatment requirements. So what is the difference between the forged and wrought fittings as denoted by these standards (for austenitic steel)?

2. Which standard should I select for fittings?

If both the forged and wrought products as per these standards have the same chemical composition, mechanical properties and heat treatment requirements, then which should I prefer and what should be the selection criteria? Is there any cost difference between these forged or wrought fittings? If so, then why?

Note:- The pipelines where the fittings will be used are for conveying demineralised water, alkali solution or scale inhibiting chemicals to CW forebay in a water treatment plant.
Design pressure - 8 kg/cm[sup]2[/sup]. Design temperature - 50 degree Celsius.

I'm quite new in this field so I will be glad if you can point out and clarify any misconception that I might have regarding these standards.

Thanks.

 

[metengr]

Lets take a closer look, first the titles

SA 182 SPECIFICATION FOR FORGED OR ROLLED ALLOY AND
STAINLESS STEEL PIPE FLANGES, FORGED FITTINGS,
AND VALVES AND PARTS FOR HIGH-TEMPERATURE
SERVICE



SA 403 SPECIFICATION FOR WROUGHT AUSTENITIC
STAINLESS STEEL PIPING FITTINGS

Scope: This specification covers wrought stainless steel
fittings for pressure piping applications.


Well, by the titles alone and even further review of scopes you can see you certainly don't need fitting material for elevated temperature service conditions and needing to be forged. So, given what you have stated, I would elect to use SA 403 material.

 

[EdStainless]

That is a concise answer, Well done

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P.E. Metallurgy, Plymouth Tube

 

[Cruisnick]

Thanks a lot metengr and EdStainless for taking the time out to read and reply to my query.

I would however like to point out that ASTM A 182 contains forged steel for normal conditions like F304, F316 etc. and also steels like F304H, F316H etc which are modifications of grade F304 and F316 and are intended for high temperature service. Hence as I understand all forged fittings provided in the standard are not meant for high temperature use.

The grade for the austenitic steel that I will have to select is either grade F304 as per A 182 or WP304 as per A 403. I won't be selecting F304H since as u have stated I don't need a high temperature sustaining material.
Hence as far as I can understand both F304 and WP304 are meant for normal temperature service.

So my question still lies that provided that both of them are meant for normal temperature, have same chemical composition and mechanical properties then which material should I go for and why?

As far as I can see I am unable to find any difference between F304 and WP304 with respect to steel fittings.

If I have made any discrepancy in comprehending the standard then I will be truly glad if anyone can rectify me.

Thanks.

 

[metengr]

Cruisnick

Hence as I understand all forged fittings provided in the standard are not meant for high temperature use

. This statement is incorrect. Also, when you make a comparison between material specifications, you review them side by side through each sections and don't simply use chemical composition and mechanical properties as the only means for review.

It would appear you are justifying using either material specification because you or somone else probably purchased the material and are looking for a response to justify using it. You asked for a difference between the two materials specifications, and I provided one.

 

[Cruisnick]

Hey metengr! Thanks again for your reply.

The material for the pipe has not been decided yet and certainly not purchased. I have been asked to prepare the material spec. for all pipe works in the water treatment plant and I am presently preparing the same. Moreover as you have stated I have compared both the standards side by side through each section. ASTM A 312 defines grades 304H for high temperature stating:-

Grades TP304H, TP309H, TP309HCb, TP310H, TP310HCb, TP316H, TP321H, TP347H, and TP348H are modifications of Grades TP304, TP309Cb, TP309S, TP310Cb, TP310S, TP316, TP321, TP347, and TP348, and are intended for high-temperature service.

Based on that I deduced that grade 304H must be for high temperature use and grade 304 can be used for normal conditions.

However, thank you very much for your explanation.

Regards.

 

[metengr]

Cruisnick;
Ok, thanks for the clarification. Both 304 and 304H can be used in elevated temperature service, which is why they are listed in SA 182. Second, one major difference is the SA 403 fittings can be supplied as seamless or seam welded, unlike SA 182. Some clients refer to use only seamless fittings at elevated temperature and pressure, hence the differences.

 

[Cruisnick]

Hey metengr!

You are certainly right. ASTM A 403 states :-

"The material for fittings shall consist of forgings, bars, plates, or seamless or welded tubular products"

However in case of ASTM A 182, the fittings will have to be manufactured by melting the austenitic steel and then forging it to shape by a forging machine such as a hammer, press, or ring rolling machine.

Hence in my case considering the low temperature and pressure I can certainly go with fittings manufactured from seam welded tubular products rather than forged fittings.

Hence in this regard I should be selecting A 403.

Well, thanks a lot for your patience. Your guidance has been truly enlightening. With your assistance I have been able to find a reasonable solution.

Thanks a lot again.

 

[MickMc]

A late comment as this is not a forum I usually visit as a piping engineer.

In piping specifications we would use the forged fittings in socket weld or threaded connections and wrought fittings for butt welding.