3 replies to this topic

[chem2013]

Dear All,

 

I want to know whether reverse flow scenario will be applicable for PSV sizing for the following scenario:

 

There is a MEG storage tank having working volume 2900 m3.

 

This tank will be filled during start up from a  pump source ( 22.8 m3/h). This is let say source 1 start up line.

 

There are two different drain drum pump discharge line which gets joined together with the start up line and finally one common line will enter into the storage tank. At high high level, XV located on the common inlet line will get closed.

 

Each line from drain drum pump discharge is having normally closed valves and each of this is provided with dissimilar check valves.

 

Each drain drum is provided with a PSV, set pressure of which is less than maximum discharge pressure of pump from source 1.

 

Is reverse flow scenario applicable for each PSV of drain drum ?

 

As per I am concern, we should analyze reverse flow for PSV without considering any procedural control in place since PSVs are for ultimate protection.

 

Let me know what is your opinion.

 

Thanks.

Regards.

 

 

 

[Bobby Strain]

How about a sketch?

[fallah]

chem2013,

Please submit a simple sketch of the system you described...

[mhs]

As I understood from your explaination of system above, reverse flow scenario for RV sizing is applicable only if design pressure of drain vessel is lower than the max. shut off head of pump at souurce 1.

 

There is possibility of XV on common line being closed & inadvertant open valves in drain pump discharge line with flow from Source 1 to drain vessel. Liquid level in drain vessel will build and eventually causing overpressurization.

 

The relief load should not take any credit for 1 check valve whereas relief load reduces to flow correspond to 10% of dia. if 2 dissimilar check valves have been provided.

 

 

In addition if time required to fill drain vessel is more than 30min, operator action can be considered to avoid relief scenario (client to agree upon same).

 

BR
Mahesh