11 replies to this topic

Hi,

Before getting into the question, let me intro myself, am arun working in oil & gas sector(Design area).
i have a clarification in the location of NRV in pump discharge, some FEED contractor put the NRV in the Upstream of minimum circulation line and some has put in the downstream of MCF.

what is the correct methodology to provide NRV?

[Qalander (Chem)]

Although not exactly recalled,but

most usually witnessed configuration by me have been 'as close as possible' to the discharge flange of centrifugal pump.

Leaving aside the existence of any minimum flow recirculation line provision.

The Minimum flow or warm-up(smaller) pipeline provision on multi-stage high pressure relatively viscous service pumps have the line initiating/re-joining the Main line at upstream/downstream side of main discharge valve.
Sometimes it is seen even initiating upstream of NRV.

[ankur2061]

jj23,

I would locate my MCF tap-off upstream of the check valve just in case that the check valve gets stuck closed & the pump gets dead headed. Also, please note that that the check valve is preferably located in a horizontal run of the discharge pipe. Essentially, this means that with a volute type pump where the pump discharge nozzle is in the vertical plane you have to provide a short vertical run, immediately succeded by a short horizontal run where you provide first your MCF tap-off then your local pressure gauge and then your check valve. If your discharge line is rising to a considerable elevation then after the horizontal run you may again provide a vertical run, and route your discharge line to the destination.

Hope this helps.

Regards,
Ankur.

[shan]

Hi,

Before getting into the question, let me intro myself, am arun working in oil & gas sector(Design area).
i have a clarification in the location of NRV in pump discharge, some FEED contractor put the NRV in the Upstream of minimum circulation line and some has put in the downstream of MCF.

what is the correct methodology to provide NRV?

If two pumps in parallel (one operating and one spare), NRV is installed for each pump and one MCF line is on the joint line (downstream of NRV).
If there is only one pump, MCF is installed upstream NRV.

[fallah]

If two pumps in parallel (one operating and one spare), NRV is installed for each pump and one MCF line is on the joint line (downstream of NRV).
If there is only one pump, MCF is installed upstream NRV.

Can you introduce valid reference(s) supporting your above statements?

[shan]

<!--quoteo(post=31619:date=Aug 10 2009, 09:00 AM:name=shan)--><div class='quotetop'>QUOTE (shan @ Aug 10 2009, 09:00 AM) <a href="index.php?act=findpost&pid=31619"><{POST_SNAPBACK}></a></div><div class='quotemain'><!--quotec-->If two pumps in parallel (one operating and one spare), NRV is installed for each pump and one MCF line is on the joint line (downstream of NRV).
If there is only one pump, MCF is installed upstream NRV.<!--QuoteEnd--></div><!--QuoteEEnd-->

Can you introduce valid reference(s) supporting your above statements?

The burden of proof is on the challenger side. It is correct unless you are able to point out something wrong with the configuration.

[Qalander (Chem)]

The usually witnessed Configuration

MCF pipeline(s)seen(Especially on critical service multiple pump(s)in cross country products pumping service)

initiating from the upstream side of installed NRV

terminating just downstream of Main discharge valve for each of the pump(s)

[fallah]

The burden of proof is on the challenger side. It is correct unless you are able to point out something wrong with the configuration.

Your proposed configuration for one pump is O.K.,but please specify the safeguard regarding inadvetent closing discharge valve of operating pump due to operator error,...., in your proposed configuration for two parallel pumps.

[Qalander (Chem)]

The burden of proof is on the challenger side. It is correct unless you are able to point out something wrong with the configuration.

Your proposed configuration for one pump is O.K.,but please specify the safeguard regarding inadvetent closing discharge valve of operating pump due to operator error,...., in your proposed configuration for two parallel pumps.

Dear fallah, If you kindly read my explanation alongwith shan's post then ;there does not seem any risk(s) indicated by you.as regards MCF line.
Do you agree or any comments?

[fallah]

Dear fallah, If you kindly read my explanation alongwith shan's post then ;there does not seem any risk(s) indicated by you.as regards MCF line.
Do you agree or any comments?

Dear Qalander,

Would you please submit a simple sketch?

Regards

[shan]

The burden of proof is on the challenger side. It is correct unless you are able to point out something wrong with the configuration.

Your proposed configuration for one pump is O.K.,but please specify the safeguard regarding inadvetent closing discharge valve of operating pump due to operator error,...., in your proposed configuration for two parallel pumps.

If you put minimum circulation line upstream the check valves in two parallel pump case, you have to install two minimum circulation lines (one for each individual pump), while single minimum circulation line is OK if it is on the common line (downstream of check valves).

If discharge valve is closed due to operator’s error, a high discharge pressure signal will trip the pump in both configurations. The minimum circulation line is designed for the “minimum” flow not the full flow.

[fallah]

If discharge valve is closed due to operator’s error, a high discharge pressure signal will trip the pump in both configurations.

FSLL as very low flow switch (set point near min flow) makes better sense and normally will stop the running pump and start automatically the spare one.

If after a few seconds flowrate would be still low,FSLL will trip both pumps.