9 replies to this topic

[shantanu.ghag]

Dear all,

 

I came across in one of the project document, where vessel is feed from the outlet stream(#1) of centrifugal pump. PRD set pressure at pump outlet piping is 70 kg/cm2g(other stream #2).

Vessel design pressure is 35 kg/cm2g and protected by PRD set by 35 kg/cm2g. 

As per the client standard, vessel design pressure at pump discharge should be based on shut-off pressure of the pump.

I believe that there will not be any safety concern if vessel PRD is sized for inlet feed rate, however, it does not comply with standard. 

 

I would like to know your comments on vessel design pressure/PRD set pressure considered in the design, is it correct, any concerns?

(please refer the attached sketch)

 

Thanks, 

Shantanu Ghag. 

 

Attached Files

•  DOC090220-09022020074644.pdf   353.46KB   28 downloads

Edited by shantanu.ghag, 02 September 2020 - 05:12 AM.

[Chemitofreak]

It is not necessary that the destination vessel /tank should be designed for SOP of the pump. If that was the case then all the ATM/LP storage tanks would be designed for higher pressure.

 

If the vessel is liquid filled then it makes sense to apply that fundamental or else relief valve can be designed to take care of the same

 

This is not the first instance that you will see this philosophy.

 

Revert in case of any query.   

[fallah]

Dear all,

 

I came across in one of the project document, where vessel is feed from the outlet stream(#1) of centrifugal pump. PRD set pressure at pump outlet piping is 70 kg/cm2g(other stream #2).

Vessel design pressure is 35 kg/cm2g and protected by PRD set by 35 kg/cm2g. 

As per the client standard, vessel design pressure at pump discharge should be based on shut-off pressure of the pump.

I believe that there will not be any safety concern if vessel PRD is sized for inlet feed rate, however, it does not comply with standard. 

 

I would like to know your comments on vessel design pressure/PRD set pressure considered in the design, is it correct, any concerns?

(please refer the attached sketch)

 

Thanks, 

Shantanu Ghag. 

 

Nothing attached...!

[fallah]

 

I came across in one of the project document, where vessel is feed from the outlet stream(#1) of centrifugal pump. PRD set pressure at pump outlet piping is 70 kg/cm2g(other stream #2).

Vessel design pressure is 35 kg/cm2g and protected by PRD set by 35 kg/cm2g. 

As per the client standard, vessel design pressure at pump discharge should be based on shut-off pressure of the pump.

I believe that there will not be any safety concern if vessel PRD is sized for inlet feed rate, however, it does not comply with standard. 

 

I would like to know your comments on vessel design pressure/PRD set pressure considered in the design, is it correct, any concerns?

(please refer the attached sketch)

 

 

In general, downstream vessel's design pressure could be lower than pump shut off pressure, provided that the PRD on the vessel which is set at vessel design pressure can handle the relief load at least equal to pump minimum flow...

[shantanu.ghag]

 

 

I came across in one of the project document, where vessel is feed from the outlet stream(#1) of centrifugal pump. PRD set pressure at pump outlet piping is 70 kg/cm2g(other stream #2).

Vessel design pressure is 35 kg/cm2g and protected by PRD set by 35 kg/cm2g. 

As per the client standard, vessel design pressure at pump discharge should be based on shut-off pressure of the pump.

I believe that there will not be any safety concern if vessel PRD is sized for inlet feed rate, however, it does not comply with standard. 

 

I would like to know your comments on vessel design pressure/PRD set pressure considered in the design, is it correct, any concerns?

(please refer the attached sketch)

 

 

In general, downstream vessel's design pressure could be lower than pump shut off pressure, provided that the PRD on the vessel which is set at vessel design pressure can handle the relief load at least equal to pump minimum flow...

 

Thank you sir for response. sketch attached now.

[shantanu.ghag]

It is not necessary that the destination vessel /tank should be designed for SOP of the pump. If that was the case then all the ATM/LP storage tanks would be designed for higher pressure.

 

If the vessel is liquid filled then it makes sense to apply that fundamental or else relief valve can be designed to take care of the same

 

This is not the first instance that you will see this philosophy.

 

Revert in case of any query.   

Yes for storage tanks, we consider PSV sizing based on breath out at pump rated flow. but for pressure vessel i am little confused because of standard requirement. so i want to verify with cheresources community. Thank you, sir.

[Bobby Strain]

Your sketch implies that the vessel is liquid filled. The liquid composition and/or the relief discharge disposal should be safe. If disposal creates a hazard, the vessel should be designed for the pump shutoff pressure.

 

Bobby

[Chemitofreak]

 

It is not necessary that the destination vessel /tank should be designed for SOP of the pump. If that was the case then all the ATM/LP storage tanks would be designed for higher pressure.

 

If the vessel is liquid filled then it makes sense to apply that fundamental or else relief valve can be designed to take care of the same

 

This is not the first instance that you will see this philosophy.

 

Revert in case of any query.   

Yes for storage tanks, we consider PSV sizing based on breath out at pump rated flow. but for pressure vessel i am little confused because of standard requirement. so i want to verify with cheresources community. Thank you, sir.

 

 

A PVSV is only designed for protection from over/under pressure due to gas/air. For liquid overfill case we need instrumentation protection.

 

Anyway, I gave the example of a storage tank for ease of understanding, even distillation columns and other equipment do not follow the criteria you have specified.

 

What is the purpose of the vessel in your system ? Is it liquid filled?

[Chemitofreak]

Sorry, I missed your diagram.

 

What I comprehend from your sketch is that the you are adding a vessel in an existing system. This vessel is liquid filled as it has one inlet and one outlet. The existing system has a pump which has a discharge pressure more than the pressure required in the new system hence you kill the same with a control valve. The design pressure of the downstream vessel is less and has a relief valve.

 

In case of blocked outlet in the downstream of the new system the new system will be exposed to the SOP of the pump and the relief valve on the new vessel will help in not letting the pressure reach the SOP of the pump.

 

Hope that is clear. Revert in case of any query.

[Sharma Varun]

Sorry, I missed your diagram.

 

What I comprehend from your sketch is that the you are adding a vessel in an existing system. This vessel is liquid filled as it has one inlet and one outlet. The existing system has a pump which has a discharge pressure more than the pressure required in the new system hence you kill the same with a control valve. The design pressure of the downstream vessel is less and has a relief valve.

 

In case of blocked outlet in the downstream of the new system the new system will be exposed to the SOP of the pump and the relief valve on the new vessel will help in not letting the pressure reach the SOP of the pump.

 

Hope that is clear. Revert in case of any que

Yes relief valve at the new vessel will make the new system safe. 

You have informed about shut of pressure what is pump normal discharge pressure for the existing ckt.

You need to study the effect of 35 kg/cm2g on existing system also as once the new PSV at 35 kg/cm2g pops the existing system will also get disturbed,

 

If your budget allows put a HIPPS valve in new ckt. to isolate same from pump discharge in case pressure rises above 34.5 kg/cm2 g i.e. before popping the new PSV.