Boiler Feed Recirculation Valve 1

[poppeye]

Any recommendations for a Boiler Feed Recirculation Valve. Will need to Recirculate back to the DA through a 2" pipe. Boiler Max Load 30,000 lbs per hr. Min Load 6000 Lbs per hr. Customer wants to maintain 450psi at boiler inlet control. Drum pressure 340psi. Estimated recirculation would be 44gpm. Customer having problems with spiking feed pressure wants to stabilize.

 

[rmw]

For a flow that small, why not just size an orifice instead of using a valve?

I used to buy a lot of Goulds pumps for BFW service, and Goulds would supply an orifice sized appropriately to protect the pump based on the pump conditions.

At the conditions you give, you are taking a 110 psi pressure drop across your control valve which seems to me to be a high delta P for a BFW control valve. I would expect it to be "goosey" and that would explain your spikes.

You need to check and see what the sizing delta P was for the BFW control valve. And then, if necessary put a differential pressure valve in the circuit that would maintain a constant differential pressure (at the sizing delta P for the valve) across the valve.

rmw

 

[poppeye]

RMW: Customer will be installing an orifice for pump protection, but this will only protect the pump. It will not maintain constant feed pressure like the customer wants. As the feed inlet opens and closes the system pressure spikes or dips. Thanks for the information though.

 

[JimCasey]

Before you can size a valve for that you will need to know the pressure upstream of the BFW pump, or at wherever the BFW valve discharges.

I can almost guarantee that there will be cavitation in this application, just because there is a high pressure drop. However, it's not like the BFW Recurc valve in a supercritical fossil plant, which would require many stages of pressure reduction.

For this kind of pressure drop, cavitation containment trim is adequate. I'd use a 1 1/2" Valtek Mark 1 with single-stage cav-control trim, flow over the seat. Cv=4 (calculated Cv required is 2.1) The Cav-Control trim is a cage with drilled holes, so the cavitation bubbles meet and cancel in the center of the outlet. Fisher, Masoneilan, Leslie, etc. all have similar trims.

 

[rmw]

So does Copes Vulcan.

They used to make a self contained constant differential pressure valve, but I haven't looked at their catalog in a long time.

rmw

 

[BSQUAREDBUCKEYE]

The other condition to be aware of is the boiler start-up condition. Until the boiler is up to pressure a valve has to take the full boiler feed pump pressure to almost atmosphere. The location of the valve can have a signifcant impact on it's performance. These valve are best located in the basement of a power house to increase the P1 and P2 valves.