6 replies to this topic

[sattarsajid]

Dear All,

 

I hope you are fine.

 

I need your help regarding bypass line (Valve) across SDV for depressurization and repressurization of system.

 

I briefly explain the system:

 

we have:

 

Lp/MP two stage compressors with 1st stage suction scrubber, 1st stage discharge and 2nd stage suction common scrubber and a discharge scrubber for 2nd stage.

 

LP gas enters at suction scrubber of first stage and MP Gas meets LP gas just before common scrubber and compressed in 2nd stage.

 

This gas will further be compressed in three stage Injection gas compressor.

 

Q: How many bypass lines we need across the SDVs?

 

The gas from the first stage of injection gas compressor goes to dehydration unit. This gas enters glycol contactor filter.

 

Q: Do we need bypass line across SDV before Glycol contactor filter?

 

One stream of gas from the first stage of injection gas compressor goes to gas sweetening unit. The first equipment to which gas enters is K.O drum.

 

Q. Do we need bypass line across SDV at the inlet of K.O drum?

 

Hot Oil System:

 

we are using WHRUs to heat the oil and supply to heat exchangers.

 

Do we need by pass line across SDVs to avoid thermal shock?

 

I will be thankful to you for kindness.

 

Best Regards 

[fallah]

Hi,

 

Please upload sketch of the system you described...

[sattarsajid]

Hot oil system is not included but heat exchangers are there where heat oil is being used.

 

 

Thank you for prompt reply.

 

Best Regards

Attached Files

•  Block Flow 14-01-03...pdf   165.55KB   45 downloads

[fallah]

_Hi,

 

Other than ESDV of shutdown level 1, you are authorized to consider a by pass line across all SDVs in your plant. But applying the by pass line depends on the maximum delta P to which the SDV might be exposed during all conditions such as start up, repressurization, depressurization,.....

If the maximum delta P will result in high torque leading to a large actuator, then it's better to consider by pass line for mitigation of delta P across the SDV, if not no need to by pass line...

Edited by fallah, 20 January 2014 - 03:46 AM.

[sattarsajid]

Dear fallah could you help me about relations for delta P torque and actuator size???

You mean finding actuator size by delta P and comparing with actuator size of ESD valve??

If yes please help me to know relations or equations for finding torque and actuator size.


And for hot oil system do we need bypass line across ESDV??? During start up during commissioning when hot oil system is already in service and we are going to introduce hot oil to new unit. Do we need bypass line across SDV at battery limit to avoid thermal shock??

Thank you

[sattarsajid]

Is there any guidelines or standard procedure for requirement evaluation of bypass line across SDVs?

[fallah]

Dear fallah could you help me about relations for delta P torque and actuator size???

You mean finding actuator size by delta P and comparing with actuator size of ESD valve??

If yes please help me to know relations or equations for finding torque and actuator size.

 

 

Hi,

 

Actuator sizing is normally performed by ESD valve manufacturers...

 

Anyway, valve torque is a function of its maximum shut off differential pressure. Then the actuator would be sized based on maximum differential pressure across the valve. On the other hand, actuator torque values are always calculated at the minimum/maximum available of the supply air.