How to select the Vacuum for priming the centrifugal pump?
How to select the Vacuum for priming the centrifugal pump?
(OP)
Recently, I am involved with a sewage pump station, which are centrigugal pump and is applied for transporting the sewage from one pond to other area.
With regard to centrifugal pump, it is well know that,the inlet pipe of centrifugal pump must be primed, in ordet to avoid the air bind and cause that the water can not be drawn from the lower water level than the inlet of pump. As usual, at the view of cost, installation a foot valve at the inlet pipe is a way to keep the water with the inlet pipe for next start-up, and at the same time, a water tank can be put into the pump station to fulfill the inlet pipe and drive the air out of inlet pipe.
However, the Owner of this project requests to add the vacuum pump to draw water and prime the inlet pipe. Can anybody can enlighten me which plan is better and reliable? Foot valve with priming water tank or vacuum pump? and if vacuum pump, how to select it? which standard or code can be referenced?
Thank you very much at advanced.
With regard to centrifugal pump, it is well know that,the inlet pipe of centrifugal pump must be primed, in ordet to avoid the air bind and cause that the water can not be drawn from the lower water level than the inlet of pump. As usual, at the view of cost, installation a foot valve at the inlet pipe is a way to keep the water with the inlet pipe for next start-up, and at the same time, a water tank can be put into the pump station to fulfill the inlet pipe and drive the air out of inlet pipe.
However, the Owner of this project requests to add the vacuum pump to draw water and prime the inlet pipe. Can anybody can enlighten me which plan is better and reliable? Foot valve with priming water tank or vacuum pump? and if vacuum pump, how to select it? which standard or code can be referenced?
Thank you very much at advanced.





RE: How to select the Vacuum for priming the centrifugal pump?
Doug
RE: How to select the Vacuum for priming the centrifugal pump?
RE: How to select the Vacuum for priming the centrifugal pump?
You may also want to look at a Self Priming Pump. These are used alot in packaged lift stations for pumping sewage. The foot value will work however if a solid keeps the valve from seating you will loose your suction leg.
RE: How to select the Vacuum for priming the centrifugal pump?
Depending on your pump size and duty I can offer further suggestions later.
RE: How to select the Vacuum for priming the centrifugal pump?
RE: How to select the Vacuum for priming the centrifugal pump?
RE: How to select the Vacuum for priming the centrifugal pump?
RE: How to select the Vacuum for priming the centrifugal pump?
RE: How to select the Vacuum for priming the centrifugal pump?
RE: How to select the Vacuum for priming the centrifugal pump?
However, as you started out with saying you have options 1) using a priming tank and 2) using a vacuum pump arrangement to prime the pumps.
Priming tanks have 2 configurations – the first is simply a tank with an inlet connected to the inlet pipework with a foot valve attached to of the tank connected to the pump inlet, usually the inlet and outlet are inline giving a straight thru arrangement to the flow. This is not an option I prefer for your duty as the foot valve is prone to being jammed open from material in the pumped liquor. The second is similar but the inlet to the tank is at a level higher than the pump inlet (again no footvalve) so that pump remains full and the pump primed when it is shut down. Again not a good option in my opinion – as the flow into the pump is very disturbed and can cause problems on the pump inlet side, any incoming air can collect in the top of the tank and gradually displace the incoming product and put the pump off-prime - you possibly need a non return valve on the discharge side depending on the discharge pipe arrangement so as not to drain the back from the discharge point.
My preferred option is a vacuum primed unit/s for a number of reasons –
1. they will self prime from dry
2. any air leakage or air coming in with the pumped flow can be removed
3. the pumps can “snore" and reprime if you have fluctuating inflow
4. the vacuum pump only needs to be sized sufficient to prime the pump initially within a reasonable time and to handle any incoming air in the product to ensure the pump remains fully primed.
The disadvantage is there is higher maintenance on the vacuum primed unit – ie lubrication for the vacuum pump and the air / water separation valve arrangement but overall is a better option than priming tanks .
There are a number of companies making vacuum self priming pumps and will usually supply the equipment as a package to fit your units.
Companies I know are
Andrew-Sykes and Godwin pumps in England
Sykes Pumps and Multiflow in Australia
Possibly Gorman Rupp in the USA
RE: How to select the Vacuum for priming the centrifugal pump?
John Nabors
Never try to teach a pig to sing. It wastes your time and annoys the pig.
RE: How to select the Vacuum for priming the centrifugal pump?
I put a vacuum priming system on their two pumps and they never had any problems after that. They loved the system. They were one happy client. I wish all my projects had worked out that well.
rmw
RE: How to select the Vacuum for priming the centrifugal pump?