Actuator Shut-Off Pressure

I think you're talking of a pneumatic actuator, perhaps membrane type, because of the "actuator pressure".

Unless it's a quarter turn valve, the actuator must supply the valve stem with thrust enough to overcome the maximum differential pressure across the valve, the packing friction and the stem rejection load (when you close a pressurized valve, you need to introduce some stem portion on a pressurized fluid, this load is stem cross section times the line pressure).

Flange rating has no influence on the required force.

Best regards

Given enough information about the process conditions, line size and utility availability, any good valve distributor will be able to offer a valve to do the job.

The presure required for an actuator of any valve is the force the actuator is able to provide to overcome sum of forces due to pressure differential across the valve, packing friction and the seat load required for attaining the leakage class( as per ANSI/FCI ) and unbalance area in the valve. This is for the actuator size and supply pressure to the actuator.

The actuator itself is sized on the shutoff pressure. So if you need to find the actuator shutoff pressure, fix the force the actuator can provide and then back calculate. However, the data for this calculation will be precisely available with any good valve manufacturer.

Hi,

Ideally you should consider the Differential Pressure for actuator Sizing as 1.5 X Max. Opearing Diff. Pressure across the Valve. But If the Valve is in the Downstream of Pump then the Actuator Sizing Pressure shall be "1.5 X the Pump Max. capacity pressure." Pump data you will get from pump vendor's document.

There is no point to consider the Line design Pressure because if u go for that then Your Actuator will be oversized.

Flange rating is nothing but line design pressure.

But some of the vendor provide the acruatorsized at flange rating/Body rating in order to make the case simple...but as i said actuator will be oversized.

Dear Frnds

Thanks for the Inputs

Regards

Jose