304 Stainless Steel Pipe System using 316 SS instead 6

[newbeehere]

Sir/s:

Our project has mistakenly using 316 Stainless Steel instead of 304 Stainless Steel (Drawing BOM 304 SS).
Our client recommend to cut all joints and change to 304 SS Pipes.

As we know that 316L has higher corrosion resistant than 304.

What can we suggest to our client in terms of Code? We are hoping that, if ever they just can consider not to cut the joints
and continue using the 316 SS welded to 304 (even if not as per drawing).

Thanks,

John

 

[racookpe1978]

What is the design pressure, temperature, service fluid, Code, and jurisdiction?
What material was used as filler material?
Who was the inspector certifying the welds for?

 

[EdStainless]

Is the current system mixed materials?
And again what is the filler being used?
316 is only a little better than 304 in some environments, so knowing the application is critical.


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P.E. Metallurgy, Plymouth Tube

 

[BronYrAur]

Sorry i don't have anything to contribute, but i find this very interesting. I can understand that someone may want to remove 304 if it was supposed to be 316, but never the other way around. Since 316 is higher quality, what would be a reason to remove it?

 

[blacksmith37]

316 should be at least as corrosion resistant as 304 in any environment except in a very high temperature furnace .

 

[MickMc]

Does 316 meet the criteria for fluid and design conditions and if so present to client as suitable for service. I have typically in the past changed the requirement for 304 to 316 if suitable for service when 304 has been minor quantity in comparison and usually more economical in bulk order and logistically easier.

 

[mk3223]

Agreed with above if confirmed that the 316SS is suitable for the process as 304SS. Consider to add notes on P&IDs for the substituted material and the reason for the future O&M reference.

 

[EdStainless]

There are a lot of environments where 316 does not hold up as well as 304.
But the point of this issue is material control.
If they mixed 304 and 316 then how do I know what any of the material really is?
Is all of it even stainless?
If it were my system I would make them cut the whole thing out.

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P.E. Metallurgy, Plymouth Tube

 

[weldstan]

Agree with Ed. In the distant past, our Instrumentation Department would routinely replace 304 with 316 because manufacturers normally used 316 and without consulting our metallurgists. In more than one instance this was detrimental to the pipe system and we forced the change back. The USER may well be justified in demanding the replacement.

 

[DVWE]

There are a lot of environments where 316 does not hold up as well as 304.

Totally agree. One of the biggest misconceptions in industries is that 316 is carte blanche superior to 304. Not always the case.

The devil is in the details; she also wears prada.

 

[newbeehere]

Thank you for all the concern;
The Design pressure of the line is 7 kg/cm2g, temp 90 Deg celcius, Oil is the medium as, system Lube oil.

It was the material control who made the first mistake. then of course our Fabrication engineers who did not check also.
During the PMI, it was found out that the material is 304 instead of 316.
Since we cant represent any substantial documents for client that 316 can be used even if the line is 304,
we agreed to cut them all and fabricate new one.

Thanks,

John

 

[Chumpes]

hello
exception made for high temperature sulfiding environments (above which temperature ?? 400°C ??), i cannot figure even one of the numerous environments where 304 is superior to 316.
please EdStainless and DVWE, can you clarify 1 or 2 situations where 316 is worse than 304 ?
thanks

 

[LittleInch]

OP "Our project has mistakenly using 316 Stainless Steel instead of 304 Stainless Steel"

Post 7 Dec "During the PMI, it was found out that the material is 304 instead of 316."

Which one of these is true?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[newbeehere]

Sorry for the wrong typo.

(Re-written)

Thank you for all the concern;
The Design pressure of the line is 7 kg/cm2g, temp 90 Deg celcius, Oil is the medium as, system Lube oil.

It was the material control who made the first mistake. then of course our Fabrication engineers who did not check also.
During the PMI, it was found out that the material is 316 instead of 304 (drawing BOM).
Since we cant represent any substantial documents for client that 316 can be used even if the line is 304,
we agreed to cut them all and fabricate new one.

Thanks,

John

 

[moltenmetal]

There are in practice only a few corrosion services which are better resisted by 304 than by 316. A handful I can think of, but there are some.

As noted, 304 is a superior high temperature material to 316, but given the service is lube oil at 90 C, it's not relevant to the discussion.

It would be a shameful waste to rip out properly completed 316 piping in this service and replace it with 304 just because someone spec'd 304.

 

[fel3]

For my civil engineering applications, 316 is always (IIRC) better than 304, and if 304 is spec'd, 316 is always acceptable as a substitute.

However, for specific cases where a common substitution is NOT acceptable, I suggest stating this explicitly in the specs and/or in the drawings. For example, here you might say "SS 316 is not an acceptable substitute for SS 304 for this application." This type of statement is especially handy in my world where often the submittal reviewer is not the design engineer and the submittal reviewer sometimes neglects to discuss a substitution with the design engineer.

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[MJCronin]

i am still wondering about examples from EdStainless where 304SS piping is superior to 316SS .....

MJCronin
Sr. Process Engineer

 

[moltenmetal]

The specs practically overlap in Cr and Ni, so the real difference is the Mo- but of course the material you get is usually at the low end of the spec, and then 316 can be a little light in Cr. Any service where Mo is detrimental (i.e. high temperature) is another, although most 304 doesn't have a maximum Mo spec and since it contains some scrap 316, it always has a little Mo.

Nitric acid is the only service that immediately comes to mind where 304 is superior to 316 but EdStainless is the guru and will no doubt be able to list others.

https://www.bssa.org.uk/topics.php?article=31

 

[weldstan]

There is another case, again at high temp which involve CO CO2 in a near oxidizing/reducing environment in which 316 succumbs to metal dusting. 304 does not. Unfortunately I am not as clear as I used to be about the exact system since my last involvement with this was nearly 45 years ago.

 

[weldstan]

There are other environment as well in which 316 succumbs to metal dusting. Google 316 and metal dusting for additional info.

As moltenmetal stated in the lube oil environment, 316 is a most adequate replacement material for the 304. The customer should have accepted it as long as you could prove all the material in the system including weld metal.