Double pilot on POSV 2

[Eddwin]

Hello,

for a ship cargo tank, we have different operational cases with different settings for the safety valves (2 x 100% capacity required to be installed). I am considering to use pilot operated safety valves and install two pilots on each, with different set pressures. The iolation valve to the pilot with higher set pressure will remain allways open. The sensing line to the pilot with lower set pressure will have an isolation valve that can be closed.

Has anybody done this before and can they tell me what to be aware of?

Thank you,

Edwin

 

[The Obturator]

Speak with Emerson about their Anderson Greenwood Twin Pilot Operated PRV availability. I believe they made these designs precisely for sea going vessels.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[The Obturator]

Please find attached pictures of 2 earlier designs. In one 2 set pressures were possible by having a sort of pilot extension fitted to the pilot to obtain the higher set pressure. In the other example in the next post, 2 separate pilots are piped to one main valve. The company has had extensive experience in these designs for LNG service. The alternative method is to have a PRV inlet (and outlet?) Change Over Valve , but that would require 2 complete PRV's and use much more space and weight. Hope this helped.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[The Obturator]

Dual Pilot pic attached.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[Eddwin]

Great, thanks, will speak with Emerson. This is also LNG service. The pictures show exactly what I had in mind. On the extension on the pilot, it looks like two pilots were installed in series.

 

[The Obturator]

You're very welcome. Yes, for the first picture, the pilots were installed i series, though that was for the snap pop acting pilot design that vents to atmosphere - you may not be wanting that. I'm sure Emerson has a solution. Good luck.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***