Check Valve

Dear Sir,

Thanks for your valuable reply, Now I am facing one problem that I have 2 pumps. P2A/B. There is a new by pass line starting from the discharge line of P2A to Discharge line of P2B. the starting point is in between the check valve and Isolation valve of the discharge line P2A and end point is after the isolation valve of the discharge line P2B. I want to prevent the reverse flow or pumping flow of P2B to P2A discharge line. where I will put the check valve and new isolation valve for this new line

Thanks and Regards

Vani

That is a problem you apparently have a lead and lag set up where pumps alternate on an hour timer set up to give equal hours of service to both pumps with your existing set up you can't take one of the pumps out of service in the event of motor/pump failure.

The "Starting Point" of the "new Bypass line" should be down stream of the isolation valve on the existing pump.

Wait for it, I am sure another poster will provide a sketch, or you can Google Bell and Gossette for recommended pump piping arrangements and applications.

Dear Vani

For each pump P2A and P2B, the recommended sequence should be pump, check valve, isolation valve and then bypass. The bypass should have isolation valve.

Sabri Ahmad

Well, place check valve first in discharge line of both the pumps. Isolation valve in bypass line is necessary in addition to the isolation valves in the discharge line of both pumps (installed after by pass line connection).

You have not mentioned the liquid. In fact for liquids with very low boiling point, check valve is installed after isolation valve.

Dear Vani

For centrifugal pump in parallel, the recommended practice is to install the check valve before (upstream) the isolation valve (each pump) so that the check valve can be isolated when the need arises to do maintenance on stream.

Similarly for other locations, but you need to use your judgement whether one more isolation is required for maintenance on stream. For example, if the upstream line is too long and draining the fluid is wasteful, then upstream isolation valve would be appropriate.

Hope the above helps.

Sabri Ahmad

I am new in this profession. I wish to know the positon of check valve in a system, It will be before or after the Isolation valve

Since you did not state what the system it is I will only assume that it is a hot water system. The position of the checkvalve is before the Isolation valve on the supply line. The checkvalve should have valves on both sides with a union inbetween when repairs to the checkvalve become neccessary. This configuration is applied in most Hvac systems.

Gerald Eagy Jr.
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Dear Sir,

The system is Caustic soda pumping. Temp 170 F pressure 622 psig. As per the others comment I dont have access to put the by pass line after the isolation valve of P2A discharge pump. I prefer in between the Check valve and Isolation valve. Is it right ?..

Thanks and Regards

Vani.

Yes, it is right only if check valve is before the new pipe connection.

Check any pump installation Schematic/ P & I Drawing and it will tell you where.