Always Pneumatic Shutdown valve actuators are sized for minimum pressure 5.5 BARG,(80 psig).

Why can't be actuator sized for pneumatic pressure for minimum 6 BarG (or) 7barG, as-long air compressor capable to deliver the required air pressure slightly below the normal pressure.?

Does any international standard asks for 5.5 barg (80psig)?
Does the actuator manufacturer have difficulties to design and fabricate the actuators anything above 5.5 Barg?

 

I'm having trouble understanding the problem.

Minimum pressure doesn't mean it always has to be supplied with that pressure, it just means that the lower limit of the range of acceptable supply pressure is "x" (5.5 barg; 80 psig). And most instrument/plant air compressors I've encountered run at pressures 1.25-1.5 times this minimum pressure, and have very large receivers (accumulators) so that in the event of a loss of compression or a leak they can still provide at least 5.5 barg/80 psig for some period of time.

I believe the actuators are sized for operation at pressures above 5.5 barg/80 psig--again, that's just the minimum pressure required for operation, and anything above that (up to the maximum allowable pressure rating) will result in satisfactory operation.

Actuator force is a function of pressure times area (speed is a function of flow-rate). It seems to me that it would require a larger actuator to operate with a minimum pressure of 5.5 barg than one to operate at 6 or 7 barg.... And size can quite often be an issue when it comes to some applications.

So, what am I missing?

Perhaps if you can explain the problem you're having sourcing an actuator for an application we can help?