5 replies to this topic

[anuraggupta76]

Hi Everyone,

 

I am a Control system Engineer and working on a Detail Engineering project . Currently I am given the task of purchasing shutdown valves. Process is specifying the Maximum Shutoff differential pressure as the design pressure of that line, which is making shutdown valve actuator very huge as compared to the valve. Moreover I donot see that pressure will reach to that value of design pressure. Kindly advise what should be the optimum method of specifying the maximum shutoff differential pressure

 

Anurag

[fallah]

 

I am a Control system Engineer and working on a Detail Engineering project . Currently I am given the task of purchasing shutdown valves. Process is specifying the Maximum Shutoff differential pressure as the design pressure of that line, which is making shutdown valve actuator very huge as compared to the valve. Moreover I donot see that pressure will reach to that value of design pressure. Kindly advise what should be the optimum method of specifying the maximum shutoff differential pressure

 

 

Anurag,

 

Please let's know about the type of the selected actuator....

 

Anyway, you cannot reduce the differential pressure and have to go to use an actuator with smallest dimensions and minimum required footprint...

[anuraggupta76]

It is a spring return actuator

[fallah]

It is a spring return actuator

 

I meant electric, hydraulic or pneumatic type?...

[shan]

The possible largest differential pressure of a shutdown valve occurs at the startup, when the valve upstream pressure is at the design pressure and the valve downstream piping section pressure is at 0 psig. 

 

You may consider a small bypass line controlled by a manual valve to equalize the pressure between the upstream and downstream of valve piping sections prior to opening the shutdown valve for elimination or reduction of differential pressure at the startup.  

Edited by shan, 18 October 2018 - 10:00 AM.

[Technical Bard]

Agree with shan - you cannot arbitrarily choose a lower differential pressure unless you KNOW that you could never have a scenario of design pressure on one side (or at least maximum operating pressure) and zero (or vacuum) on the other.   A small bypass valve to pressurize the downstream side is often used to help reduce the size of actuators on large valves with very high shutoff pressures.