U-STAMPED VESSEL VENTED TO ATMOSPHERE

[767]

A steam condensate system has a condensate collection vessel U-stamped design pressure 5 barg open to atmosphere through a 8" line.
According to ASME should I install PSVa set at 5 barg?
Thanks

 

[rzrbk]

I would think that as long as the existing 8" vent to atmosphere is large enough to prevent overpressure from any of the various scenarios, then a PSV is not needed.

The vent would probably need to be treated as a relief line with supporting calcs for overpressure protection capacity. Also, line should probably not have any restrictions/valves.

 

[MJCronin]

767,

Typically, this kind of a condensate collection tank has a generously sized vent (with no shutoff valves)open to atmosphere.

The fact that your tank has been designed to 5 barg (~73 psig) means to me that it was probably originally used in another service. Even deaerators that are slightlt pressurized are only designed to a MAWP of 30 or 50 psig.

Usually this type of tank has corrosion problems and is replaced every 4-7 years. Stainless steel and heavy wall cast iron models are available.

http://www.eng-tips.com/viewthread.cfm?qid=18507&page=74

-MJC

 

[unclesyd]

We have numerous condensate collection vessels and all are designed and code stamped for the maximum direct steam pressure, 175# steam, and the atmospheric vent sized for the maximum flow that they could see if everything in system failed at the same time. Even if the vent was closed off by some means the vessel would hold until the vent and drain could be reestablished. If these vessels start to pressure up an alarm is trigger by a pressure switch.

Initially the added shell thickness from design definitely helped with the corrosion/erosion aspect. When repairs are necessary the top section is changed to SS. In the later years several of the vessels were easily converted to flash tanks to generate low pressure steam and the appropriate CIDs’ generated and PSVs'aded to cover the change in service.

All these vessels are on the Vessel Inspection Schedule.