6 replies to this topic

[arkae]

hi everyone..

 

We have 2 x 100% configuration hrsg feed water pumps. And i have seen some of the reference P & ID's where the minimum recirculation lines are separate for each pump and each line is connected separately to the source.

 

Can't we combine the two minimum recirculation lines to a common header and then use a singl line to the source.

We are using Autorecirculation Valve at the Pump discharge. Hence in my opinion, even if individual minimum recirculation lines are combined together no problem will occur since Autorecirculation valve has a check valve.

 

Please comment if there are any technical problems with this.

[shan]

How do you set the rate for the recirculation valve open?  In the condition of the two pumps are identical, if you set at 2 x pump minimum flow, when single pump is in operating,  the valve will open at flow rate two times higher than the minimum flow.  If you set  at 1 x pump minimum flow, when two pumps is in operating, the valve will not open even the flow drops to the minimum. 

Also, a recirculation valve should be installed upstream of each individual pump block valve and check to protect the pump from dead head causing by closing of block valve.  It is impossible to protect two pumps by a single recirculation valve.

[arkae]

hi shan,

 

Please find attached the file where two cases are shown.

 

In all  the reference P & ID's i have seen case-I is shown.

 

Do you think is there any problem with Case_II.

 

And also at a time only one pump will be operating.

 

Thanks in advance

Attached Files

•  Min recir line.pdf   101.76KB   49 downloads

[breizh]

Possible ! 

What are the savings ? Make sure it will not generate trouble for operation , like manual valve forgotten .

 

Breizh

[shan]

I have no problem with Case_II.

[arkae]

hi Mr.breizh,

 

I didnt exactly calculate the savings but a 100 NB pipe of lengh nearly 50 m can be saved.

 

And also thankyou very much Mr.Shan

[fallah]

arkae,

 

Just take care the ARC in each discharge line to be installed upstream of the check valve in that line...Using common header for two minimum recirculation lines in your configuration will result in no operational problem and beside the saving you mentioned, eliminates one nozzle among all installed on suction drum...