2 replies to this topic

[Flyou]

Hi everybody,

 

I am working in the petroleum field and i have to specify on a project a gear or screw pump (rotary type API 676) on a viscous service. This pump operate also at high temperature (260°C).

 

Generally for centrifugal pump, we specify a warm up by pass so as to keep a small flowrate of hot liquid passing though the spare pump. The spare in this case is already hot and ready to start.

Nevertheless, this is not required on reciprocating pumps as this kind of pump does not let the flow pass though the pump.

 

What about rotary pump? Is it possible to specify a warm up by pass? Do anyone knows?

 

Thanks,

 

 

[Art Montemayor]

 

Flyou:

 

Contrary to what you state, a reciprocating, positive displacement pump WILL allow positive flow through its pumping chamber.  This all depends on the pump’s clearance volume and the position of the plunger while in the shut off position.  Usually, the PD pump will have enough clearance between the plunger and the head end that liquid (whether hot or cold) will flow through the suction valve, the end clearance, and out the discharge valve.  I know because I’ve had applications where this was done to prime the stand-by pump.

 

However, what I would design in your application is a PD pump with a heating jacket.  I would allow a slip stream of hot liquid to flow through the stand-by pump’s heating jacket and back to the source.  This would maintain the spare pump hot and ready to receive hot liquid immediately.  I believe that you can specify heating jackets on both gear (external or internal gears) and reciprocating pumps.

 

 

[Flyou]

Art, thanks a lot for your answer. I'll go for heating jacket and i'll remove the hot bypass line at the discharge of the pump.