Dual certified 304/304L and its pressure ratings

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13 years 5 months ago - 13 years 5 months ago #5957 by karthi090287
Replied by karthi090287 on topic Re: Dual certified 304/304L and its pressure ratings
Hi all,
im new to this forum,
i have 1 question ,due to lower carbon content in the ss304L(0.03%),is it restricted to use below 425 deg celcius or any other reason is behid this??
Can any one explain me wat is the Temperature range for SS304L ,SS304 ,SS304H???

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13 years 5 months ago - 13 years 5 months ago #5958 by HVN83

Hi all,
im new to this forum,
i have 1 question ,due to lower carbon content in the ss304L(0.03%),is it restricted to use below 425 deg celcius or any other reason is behid this??
Can any one explain me wat is the Temperature range for SS304L ,SS304 ,SS304H???


I think the reason behind this is the carbon content indeed.
I'm not quite sure, but I believe (please correct me if im wrong) that it has something to do with the resistance to high temperatures @ low carbon containing stainless steels.

Tip: just Google 'dual certified 304' and look for a thread going @ engtips.com (I think its the first Google result)

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13 years 5 months ago - 13 years 5 months ago #5916 by karthi090287
Replied by karthi090287 on topic Re: Dual certified 304/304L and its pressure ratings
hi HVN83,
i got ur question,dual certified 304/304L is used up to 537 degree celcius,because the carbon of this steel has the same percentage as normal ss304, if u refer ASME B16.5 ss304 materail and the temp range for the same is given,u will get better understanding

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13 years 5 months ago - 13 years 5 months ago #5926 by HVN83
I'm sorry but so far no one has really understood, nor answered, my question.
To put it in perspective again, here comes a new formulation of the same question:

If you use dual certified have 304/304L ASME B16.5 flanges, what is/are the max. temperature (limits) these flanges may be used to, and WHY?
B16.5 namely does not address any reasons why 304L flanges are limited to 425 deg C.
It only says 304 flanges may be used to 816 deg C, and 304L flanges up to 425 deg C.
Thus, what temperature limit should be used now for dual certified 304/304L?


PS: if Im making a mistake, i.e. my question has been answered, Im sorry if I understood the respective reply wrong. Just let me know where the answer is mentioned.

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13 years 3 months ago - 13 years 3 months ago #6109 by shrivallabha
Replied by shrivallabha on topic Re: Dual certified 304/304L and its pressure ratings
I tried to search as well but it all seemed to be going nowhere. Here is some explanation (and not all). We'll try to understand in step by step manner.

First, what defines the grade 304L, 304 and 304H?
The chemical composition i.e. Carbon content prominently. There is a grade comparison table on AZOM.com. If you have close look then 304L satisfies all criteria of 304 (chemical composition wise). This, probably, is the reason why the material is claimed in dual grade as it will reduce inventory.

What is the effect of Carbon on steel?
SS as it is also known as Austenitic steel allows more carbon solubility than many other steel grades. As you go on increasing carbon content it becomes harder and stronger (but less ductile). This explains as why the carbon content is increased for higher temperature ranges. The same is noted by ASME in ASME B 16.5, Table 2-2.1, Note(1).

What temperature range shall be used for dual certified steel?
This part still remains little gray. I tried to find some references which could pin it down. However, following excerpts from ASME might be useful.

At low or high temperatures, the designing person shall consider a possibility of leakage at joints due to forces and moments developed into the connected piping. When such joints are operating at creep range, the bolt loads will relax due to expansion. Such decreased bolt loads diminish the capacity to effectively sustain loads without leakage. These are]
So it indicates it is rather joint that flanges make (and not the Flanges themselves) act as restrictive parameter when we are looking at temperatures. However, the clear limit is 538°C. Above 538°C, you need Carbon content to be more than 0.04%. The moment Carbon %age is more than 0.04, it won't be 304L and you won't be able to claim 304L grade of the dual certified material. However range 425°C - 538°C still remains gray area

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13 years 3 months ago - 13 years 3 months ago #6156 by shrivallabha
Replied by shrivallabha on topic Re: Dual certified 304/304L and its pressure ratings
And some more points have come to light after talking to one experienced material engineer.

In ASME B 31.3 (Process Piping), the allowable values are provided for Pipe as well as fittings upto 1500°F (816°C approx) without any (bar) conditions.

It is NOT just the SS304 behaviour but also the fluid service will have bearing on the temperature restriction. If the fluid is corrosive then at higher temperatures such as 425°C, the material will be susceptible to intergranular corrosion. So you will have to first decide on the fluid properties and then look for restricting temperature range.

Hope this helps.

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