3 replies to this topic

[Abdullah_28]

Dear 

Iam working on small project where I need to change ON/OFF valves on the suction line of pumps ( to have same rating of discharge line) in different units of refinery .

 

Question:

 

As per I know the Shut of pressure (closure delta P -used for actuator sizing)  is specified as following :

 

                     Shut of pressure=Max Upstream pressure- Downstream Pressure  

 

In case the suction line of pump, I used the following:

 

                      Shut of pressure=Max Suc. pressure (Set press.) - Downstream Pressure  (0 brag)

 

 

However ,one friend told me if there is a leak in check valve, there will be  back pressure on the downstream of suction block valve. so the worst case is to specify two Shut of pressures  as following:

               

               Forward Shut of pressure:

               Shut of pressure=Max Suc. pressure (Set press.) - Downstream Pressure  (0 brag)

 

               Reverse Shut of pressure:

               Shut of pressure=Normal Suc. pressure  - Discharge pressure Pressure  

 

Is this make sense?  

​I need your Valuable input on this subject.

 

 

Thanks a lot  

Edited by Abdullah_28, 26 September 2018 - 03:33 AM.

[fallah]

Dear 

Iam working on small project where I need to change ON/OFF valves on the suction line of pumps ( to have same rating of discharge line) in different units of refinery .

 

Question:

 

As per I know the Shut of pressure (closure delta P -used for actuator sizing)  is specified as following :

 

                     Shut of pressure=Max Upstream pressure- Downstream Pressure  

 

In case the suction line of pump, I used the following:

 

                      Shut of pressure=Max Suc. pressure (Set press.) - Downstream Pressure  (0 brag)

 

 

However ,one friend told me if there is a leak in check valve, there will be  back pressure on the downstream of suction block valve. so the worst case is to specify two Shut of pressures  as following:

               

               Forward Shut of pressure:

               Shut of pressure=Max Suc. pressure (Set press.) - Downstream Pressure  (0 brag)

 

               Reverse Shut of pressure:

               Shut of pressure=Normal Suc. pressure  - Discharge pressure Pressure  

 

Is this make sense?  

​I need your Valuable input on this subject.

 to 

 

Abdullah,

 

If the pump is conducting the fluid to a pressurized system and the relevant check valve is susceptible to leak, the reverse flow can be occurred in pump trip case and the suction on/off valve (if existed) can be subject to discharge pressure at downstream while there is normal suction pressure at upstream. 

[Abdullah_28]

Dear Fallah, 

Does this mean  we have to consider both cases in data sheet ? (  Forward and Reverse)

[fallah]

 

Does this mean  we have to consider both cases in data sheet ? (  Forward and Reverse)

 

Abdullah,

 

You haven't to do so; you can specify the worst case and reflect it to the valve data sheet...

 

If you have a problem to specify the worst case you can reflect both cases in data sheet...