5 replies to this topic

[Sherif Morsi]

Hi,

 

The attached sketch shows an atmospheric chemical tank with a double-head chemical injection pump, each head injects the chemical at a different location.

 

Head 1 discharge pressure is 40 bar and has a PSV set at 53 bar

Head 2 discharge pressure will be 11.5 bar and a new PSV will be installed and set at 20 bar.

 

The outlet lines from both PSVs will be routed back to the top of the tank.

 

For the new PSV, I need to calculate the backpressure (build up backpressure & superimposed back pressure). We are considering the case where both PSVs lift at the same time as both heads will be operating at the same.

Help is much appreciated.

 

Thanks

Sherif

Attached Files

•  20170114_141700.jpg   78.31KB   5 downloads

Edited by Sherif Morsi, 14 January 2017 - 12:47 PM.

[somayeh]

Dear Sir

 

Please clear the location of new PSV.

 

Thanks

[Sherif Morsi]

Each PSV is installed on the discharge line of the pump. 

 

The outlet line from the PSV is routed back to the atmospheric tank

[J_Leo]

To me, the superimposed backpressure is 0 (close to 0) psig, the pressure in the tank.

The buildup backpressure, is the pressure at the PSV discharge needed to send the relief low to the tank. Just do regular hydraulic calculation to get this number.

[Sherif Morsi]

Thanks for your feedback J_Leo. Appreciate it

[Dazzler]

Hi Sherif,

As the application is a liquid, if the RV's are lower than the tank, then they might routinely hold a liquid static head above the RV in the discharge line.   During relief this liquid head is always there and adding to the back pressure.  So you may need to add that static head to the discharge pressure.  The static head pressure is likely to be small and is unlikely to have any effect on the sizing or valve choice.

Dazzler