NRV Required

I would have preferred a bit different question

Whether butterfly valve is required for this line or else the Non-Return Valve is enough.

Normally in this type of configuration in the discharge line we always put the NRV with a series isolation valve (we are at higher pressure and lower flow so we go for Ball valves)

I have to open/close the valve. Is it possible in NRV?.

No.

But then why do you have to close the valve ?

The active pump will be any way working with the valve open.

To avoid the recirculation through the standby pump you must isolate it, preferably on the discharge side. The NRV exactly serves this purpose.

The secondary valve (butterfly/ball/gate/plug) is used to isolate the main discharge header (where all the pumps are connected) from the NRV - it helps to service the pump as well as the NRV.

Hi Guest, you answer is appropriate, You should identify yourselves to receive an appreciation,GA.

Too much missing information from the OP about the situation.

What configuration are the pumps, are these (Vertical on the deck or Horizontal drawing from the side of the basin or drawing suction with a dip Pipe)?

What is the Line size of the Suction?

What is the line size of the Discharge from each pump?

What is the size of the Common Cooling Water Supply Line?

NRV is must on such situations, which meant for automatic stoppage of backflow to the non-running pump. Any system designer you consult, will opt for it. Butterfly valve is for isolation and it can not do the job of NRV. In case of auto-start system where stand-by pump starts automatically when one of the running pump trips you can not think of without NRV. One more thing I must say that NRV also stands for safety, and you should not avoid it. Many accidents in piping system are occuring just because of non-functioning of NRV or non-provision of NRV at right point. The point you have described is very right for NRV.