Hello!
I need to share a personal opinion about SDV fail position.
Many times, I read or hear something like that:
“A shutdown valve actuator shall pneumatic/hydraulic fail-safe spring-return type. Generally a shutdown valve failed to close (FC).”
I guess this comes from the possibility that you could have a problem with your instrument gas supply.
But….in cases where I have a completely reliable system to generate instrument gas (in this case air), provided by:
· Two twin compressors (one is back up).
· 10m3 recipient for 24 hours consume.
· Pressure transmitter to indicate and alarm of low-pressure air.
· Independent pressure transmitter to generate emergency shut down in case of low low-pressure air (usually 4 bar).
Can I choose to install doble- action actuator? Especially for big ASME #600 valves (> 12in)?.
Thera are:
· Less expensive
· Much more smaller
· Less maintenance need
· Easy re-open or operate in start up/shut down operation. An operator can open/close de valve from a control panel beside the valve.
In advance, thanks for your expert opinions!
Ariel