Valves - MAWP
Valves - MAWP
(OP)
A fundamental question (the 1st question):
- Take for example I have a 150# line class and I need a valve in there. Will I be correct in assuming that a 150# class valve will automatically be suitable for it?
The reason I am asking is valves have their own MAWPs I believe (which is slightly less then the flange P&T)and therefore won't it then be appropriate to look at the line process design conditions and review the suitability of the valve MAMP for the application. However, the valve casing maybe suitable for the full P&T.
Second question:
I have cladded valve (CS + 316L) in a Duplex Stainless Steel (DSS) 300# class. Naturally, the full P&T of the corresponding clad valve will be somewhat lower that the 300# DSS. Is this Ok as long as the process design conditions are met? But please note that the valve casing will not be able to withstand the full P&T of the DSS class.
Any help/input/insight will be much appreciated. Thanks in advance.
- Take for example I have a 150# line class and I need a valve in there. Will I be correct in assuming that a 150# class valve will automatically be suitable for it?
The reason I am asking is valves have their own MAWPs I believe (which is slightly less then the flange P&T)and therefore won't it then be appropriate to look at the line process design conditions and review the suitability of the valve MAMP for the application. However, the valve casing maybe suitable for the full P&T.
Second question:
I have cladded valve (CS + 316L) in a Duplex Stainless Steel (DSS) 300# class. Naturally, the full P&T of the corresponding clad valve will be somewhat lower that the 300# DSS. Is this Ok as long as the process design conditions are met? But please note that the valve casing will not be able to withstand the full P&T of the DSS class.
Any help/input/insight will be much appreciated. Thanks in advance.





RE: Valves - MAWP
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Valves - MAWP
RE: Valves - MAWP
Here are two articles written by Greg Johnson, president of United Valve that underscore the information posted by BigInch and JLSeagull.
http://www.unitedvalve.com/art-valve_standards.htm
http://www.unitedvalve.com/art-valve_testing.htm
Here is need to know list to specify a valve even if you think a plain vanilla will do.
http://www.vma.org/?SpecifyingChecklist
Also you might want to contact United Valve for information on old valves.
http://www.unitedvalve.com/valve_res_library.htm
For pressure temperature values here is a starting point from Forged Components.
Go to the technical information section on the home page
http://www.forgedcomponents.com/
All the information laying around doesn't absolve one the need to have a copy of the applicable codes and standards that cover one's specific applications.
RE: Valves - MAWP
in other words, the normal valve ratings published in B16.34 which are based on the flanges may not apply to a soft seated valve; in these valves the manufacturer is allowed to design them and stamp them for less than the flange rating.
RE: Valves - MAWP
Thanks, almost close to the answer I was looking for. I'll try to rephrase the question again for better clarity this time:
I have 300# piping class in Duplex Stainless Steel. The design conditions for this piping class is based on the P&T of the duplex flange in accodrance with B16.5. For economic reasons, I would like to use clad (cs+316L cladding) material for a 10" valve in the above piping class. But I am also aware for 300# CS Flange Pressure Temperature ratings per B16.5 will be somewhat slightly lower compared to a duplex material. So:
1. Is it OK to use this clad valve in the duplex 300# class
- OR -
2. Is there an absolute necessity to de-rate the entire duplex stainless steel 300# design conditions (flange P&T) to match the corresponding carbon steel class in order to meet uniform design conditions throught the piping system?
Any input will be appreciated.
Thanks.
RE: Valves - MAWP
The same is true with pipe schedules. If you have a system where Sch 5 SS pipe is adequate for design conditions you might want to use Sch 10 to alleviate fabrication, handling and support problems with the Sch 5 pipe.
We have a very large process area where we use Class 300 SS flanges in lieu of Class 150 SS flanges that are OK as far as process design conditions are concern. This change was made due to concerns with gasket leaks that were evident on startup with the as built Class 150 flanges.
RE: Valves - MAWP
However, once you use a component with a lower rating, the system must be derated. The system rating can not be higher than the lowest rated component used within it. This means that any pressure relief devices that might be in use to protect this system, would need to be set based upon this lower rating and you would list this lower rating as the design condition in your documentation (e.g., project line lists).