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PF_Technical_instr
Active Contributor

Join Date: May 2010
Posts: 18

Trunnion Vs Floating Ball Valves

06/07/2010 2:33 AM

I read a few discussions related ball valves here & the conclusion is that trunnion mounted ball valves are gnerally used for sizes 6" & above. And trunnion mounted ball valves provide block & bleed feature which is not available in floating ball valve designs.

But what if I need block & bleed feature in ESD valve sizes 2" or less. I saw a lot of manufacturers offering trunnion mounted ball valve design for as small as 1/2" size.

I would invite a discussion on related experiences for use in oil & gas/Petrochemical industry.
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Tornado
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Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21017
Good Answers: 795
#1

Re: Trunnion Vs Floating Ball Valves

06/07/2010 3:27 AM

I think two separate issues are being confused here. As ball valves become larger, the pressure difference (proportional to pipe/valve area) is imposed on the seal area (proportional to diameter). This will compress or even crush the seal unless some other bearing method such as trunnion mounting is used.

Block-and-bleed refers to configurations such as two valves in series, with a bleed-off branch valve between. This should not depend on trunnion mounting or otherwise, so long as the valves' construction is suited to their size and ΔP.

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