what would be the effect of keeping the delivery valve closed during the working of the centrifugal pump ?
Dead heading (closing the delivery or exit valve) of a centrifugal pump will cause a few things to happen.
1. The pump speed will actually go up. This sounds counter intuitive until your realize that you are no longer accelerating or moving material so the energy absorbed by the system goes down.
2. The shearing on the material goes up and the liquid will heat up more than it would if the pump was allowed to operate normally. Also the fluid is not constantly replaced by fresh fluid.
Previous entry was correct. Also, this is sometimes done to provide initial prime to the pump. After the liquid enters the eye of the impeller, more liquid will get pulled in, providing prime.As a general rule, don’t shut the outlet valve all the way down, but it won’t hurt for short periods.
The centrifugal pump curve will move to the point of shut off head. Where at this point :
1. The capacity (Q) = 0
2. The head (H) = at max pressure
3. The Power consumption (kw) = at minimum
4. The impeller will be act same as the mixer to the fluid within the pump casing.
5. The electric energy will become kinetic and heat (the casing will be warm but not making damage to the pump.
6. The NPSH required by the pump is at minimum.
So the best way to operate the centrifugal pump is to shut the discharge valve (delivery valve) and then open it slowly until at the working pressure of the pumping system owned.
Indonesia, Nov 12, 2008
regard,
Haryono
