5 replies to this topic

[eastorca]

Dear friends,

Could you please advise me what is the phylosophy of check valve selection. I am quite confused and could not understand the reason why people select swing sometime but piston another time....

Regards,
Eastorca

[fallah]

eastorca,

Attached may help you out on your query.

Fallah

Attached Files

•  Design and Selection Criteria of Check Valves.pdf   561.62KB   229 downloads

[Steve Hall]

That's an interesting article, Fallah. I wonder how many engineers actually apply such criteria, using a comparison of various types as suggested? I think many times the check valve specifications are pretty low on the list of priorities and may be rushed through. The selection may even be largely left to the piping contractor, depending on the size and value of the project and criticality of the valve. So I offer that in addition to a scientific approach to selection, the check valves are sometimes chosen for one of these reasons: persuasive valve salesman and/or advertising; availability; familiarity with the valve or valve type; cost. Other good selection criteria include having similar or the same valves already on the site (thus already having spare parts and maintenance procedures in place); reliability; and life cycle cost (including frequency and duration of preventative maintenance tasks).

In my industry (pharmaceutical manufacturing), check valves in process lines must comply with cGMP (current Good Manuacturing Practices). This usually means that they can be cleaned and steamed in place, having smooth surfaces and no dead spots. They are usually made of 316L stainless steel with a limited range of elastomers allowed. This greatly limits the selection with special "sanitary" swing, ball checks, and in some cases spring checks being most common. I also encounter situations where the cracking pressure is a critical parameter.

Final thought: in addition to the pressure drop through the valve (as discussed in the Selection Criteria paper), the sealing effectiveness should be considered. How tight must the seal be? This is application dependant, but if not understood and communicated an incorrect selection may result.

Edited by Steve Hall, 03 October 2012 - 06:19 AM.

[breizh]

Additional resource

http://www.apcovalve...assic/which.htm

Breizh

[kkala]

1. Useful attachement on check valves (post by fallah), also including a comparative selection chart.
2. Process in my workplace only notes the check valve on the PID, then specified by Piping Dept. Information from refinery says that check valves can be casually found dead or fatally corroded, even long time after the "event" (example: multiple condensate flash drums). What type of check valve is more reliable and maintenance free (for liquids or vapors)? Hopefully a member could clarify this question.
3, If two valves are to be placed in series, it is usual practice to specify different types, [url] http://www.cheresour...376-check-valve [url].

[eastorca]

Thanks so much for your all guideline.