Surface pump
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Surface pump
How does one prime a surface pump?
In order to prime a surface pump, you have to fill the suction line with water. There is a place for this purpose on the pump; it is either a plug or a bolt that can be unscrewed.
Make sure you have a foot valve; otherwise, it will take a long while to fill up.
First of all, it should be noted that there are surface pumps that, due to the installation configuration, are in effect self-priming. In other words, the pump has the suction permanently flooded because the water level in the tank is higher than the pump. However, for pumps with a suction pipe and a foot valve at the bottom, priming means a charge of liquid is required to begin pumping action, usually by opening a priming valve on the pump itself. It goes without saying that if the foot valve is defective this can cause priming problems if the valve is not watertight, the suction pipe will have trouble filling and thereby prevent the pump from priming.
To ensure proper priming of any pump the suction must be 100% sealed to avoid a loss of suction between the eye of the impeller and the water surface. The best suction line will be one free of any joints and of suitable material and construction as to not collapse under suction. A foot valve at the suction line inlet or a one way valve in the pump suction casing is imperative. there should be a way of manually introducing pumpage ( water ) to the pump casing and if all other conditions are met, the pump will prime. A closed discharge valve will trap air so having the discharge throttled slightly will assist in building a strong flow from the pump gradually up to full flow.
A flooded suction pump will start on its own. But this requires that the casing be free of air; on vertical centrifugal pumps, a bleeding valve is provided for this purpose. If the pump is in suction mode, the upstream water column must be pre-filled.
Can you tell us what type of pump is being used? Brand, model, etc. Not all surface pumps are self-priming; some require a specific installation of the suction line in order to achieve this.
