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We're dealing with a client that wants more definitive anwers concerning overpressure protection on filters. His present criteria is:
PSV's NOT required for the following:
- The filter is a standard catalog item, having a catalog number which corresponds to a published design pressure and temperature, and whose volume is less than or equal to 15 cubic feet.
- The filter is constructed of seamless piping components in accordance with ASME B31.3, having a diameter less than or equal to a nominal 24 inches and a length less than or equal to 5 feet.
-The filter is constructed to ASME Section VIII Specifications, having a diameter less than or equal to 24 inches and a length less than or equal to 5 feet.
Spared filters shall be drained and vented when not in service.
Their thinking is the ASME Section VIII non-fired boilers guidelins have changed, but I'm not so sure. I do understand ASME Section VIII is rather loose when it comes to filters.
Obviously the catalogue filter has to be able to withstand the largest pressure the unit will see. In some cases this may require at least a PSV for hydraulic expansion.
What are people's thoughts about the above? Can you suggest some other things to add? Smaller dimensions on the maximum size of the filters?
Thanks for your help.
Gary F.
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Psv's
Started by johnnygeneric, May 03 2004 01:25 PM
2 replies to this topic
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#2
pleckner
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Posted 03 May 2004 - 05:03 PM
- Being a standard catalog item does not in of itself exclude it from being treated as a pressure vessel and one that requires a relief device. Volume does not enter the picture either. To not be considered part of Section VIII, Div 1 scope, this item would have to be a "vessel having an inside diameter, width, height, or cross section diagonal not exceeding 6 inches with no limitation on length of vessel or pressure". ASME Section VIII, Division, Scope, paragraph U-1 © (2) (i).
In other words, the filter would have to have a diameter of 6" or less!
To not be considered a pressure vessel, the design pressure would have to be no greater than 15.00000000 etc. psig [paragraph U-1 © (2) (h)].
ASME always undergoes change but this also has no affect on whether the filter is a pressure vessel or not.
The fact that the filter is constructed of seamless piping components in accordance with ASME B31.3 does not change the fact that this could be pressure vessel.
Get the latest copy of the code. You do not need all of ASME, just Section VIII, Div. 1 and show it to them.
I've had to put PSVs on small filters many times because they can most definitely be pressure vessels.
In other words, the filter would have to have a diameter of 6" or less!
To not be considered a pressure vessel, the design pressure would have to be no greater than 15.00000000 etc. psig [paragraph U-1 © (2) (h)].
ASME always undergoes change but this also has no affect on whether the filter is a pressure vessel or not.
The fact that the filter is constructed of seamless piping components in accordance with ASME B31.3 does not change the fact that this could be pressure vessel.
Get the latest copy of the code. You do not need all of ASME, just Section VIII, Div. 1 and show it to them.
I've had to put PSVs on small filters many times because they can most definitely be pressure vessels.
#3
Guest_Guest_ShaunHill_*
Guest_Guest_ShaunHill_*
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Posted 19 May 2004 - 12:04 AM
The basic question is whether you consider the filter as a pressure vessel or a part of the piping system.
I have seen many small filters that do not normally have separate PSVs on them. These are considered part of the piping and they are built to match or exceed the PSV on the process vessel that they are in the same system as. If anything, I might put a small differential pressure PSV that bypasses the filter to protect the filter element on these types of filters. These filters do not get classified as pressure vessels. Come to think of it though, I think these filters are smaller than 6" diameter.
On larger filters, or coalescing separators I would expect them to be classified as pressure vessels and would expect a fire case, or thermal expansion PSV as a minimum.
I have seen many small filters that do not normally have separate PSVs on them. These are considered part of the piping and they are built to match or exceed the PSV on the process vessel that they are in the same system as. If anything, I might put a small differential pressure PSV that bypasses the filter to protect the filter element on these types of filters. These filters do not get classified as pressure vessels. Come to think of it though, I think these filters are smaller than 6" diameter.
On larger filters, or coalescing separators I would expect them to be classified as pressure vessels and would expect a fire case, or thermal expansion PSV as a minimum.
