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

 

[EdStainless]

The applications that I had in mind are some acid environments where Cr is all that really helps and not the Mo. The 2% difference in Cr can be a big deal. I have come across a few of these in working with 'personal care products' (shampoo).
In Cl environments the Mo does help a lot, the 2.0% Mo is worth about 6.5% Cr.
One thing that I have found in practice is that the welds (autogneous TIG) that are used for fabrication can have a lot of impact.
In 316L with the Mo you get more serious weld segregation than you do in 304L.
The end result is that the pitting resistance of 316L welds in no better than the welds in 304L, and in some cases actually worse.
As far as the piping and other components are concerned in virtually all applications there is no discernible difference between 304 and 316.

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P.E. Metallurgy, Plymouth Tube

 

[hacksaw]

don't forget metal strenth at temperature, 316 is not always better

 

[cap1a79]

In this time, I would suggest to focus on the technical issue as what will happen if using SS 316 instead of SS 304 for "lube oil" service.
(definitely it should have been accepted by client on normal work flow though.....)

I fully agree with that SS 316 is not always superior to SS 304. Based on my experience, I realized that SS 304 can be superior grade at the specific range of temperature in nitric acid service.

However, if the service fluid is just "lube oil", is that really different? Is there any solid reason that SS 304 is acceptable while SS 316 is not?

Referring to google reference as below(kind of a category in common sence), the property of lube oil has some basic functions to reduce friction force and of corrosion prevention "by forming stable and protective bond on metal surface". As it were, lube oil has a role of "preventing corrosion" NOT inducing corrosion. (This gives me a great benefit of not having to go to the garage often to repair my car that uses lubricant a lot.)

https://en.wikipedia.org/wiki/Lubricant

Now back to the subject, in lube oil service which is "to contribute to the prevention of corrosion", is there any basis to use ONLY SS 304, NOT SS316? No, I do not think so.......Definitely, the use of SS 316 shall be / must be suitable option in lube oil service.














Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[EdStainless]

My biggest concern in this case isn't the use of 316 in place of 304.
It is the mix up.
If they mixed that what else is miss identified?
I have seen carbon steel fittings mistakenly put into all SS systems. It isn't pretty.

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P.E. Metallurgy, Plymouth Tube