Do positive-displacement pumps such as screw pumps require a foot valve when drawing in water?
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As the title suggests, there is a project that uses horizontal screw pumps to draw in leachate and fuel – is it possible to omit the bottom valve?
Positive displacement pumps all have strong self-priming capabilities.
It’s not necessary; the liquid can be drawn directly, and a self-priming pump is also not required.
Don’t any of these pumps require priming? Is it because they have a built-in check valve, or because they don’t need the pump chamber to be filled with water?
It should be pumped up before the first start-up (for self-priming pumps)
No. Without a bottom valve, the pump is prone to dry running when started, which is harmful to the pump screw.
It depends on the type of screw pump you are using. In the case of single-screw pumps, the rubber components of the stator tend to wear out easily. For multi-screw pumps installed in a horizontal position, residual fluid usually remains in the pump chamber after initial use. If it is a fuel tank or if the distance from the pump inlet to the liquid surface is not too great, and is within the range allowed by the net positive suction head, the fluid can be drawn in quickly; in such cases, there is generally no need to install a bottom valve. If it is not to be used for an extended period of time, it is recommended to prime the pump, and to manually turn the shaft at regular intervals to prevent rusting inside the screw, among other issues.
We have a horizontal-type percolate pump; its suction lift is probably around three meters. It runs for several hours each day, I guess. What do you think? And what is the function of the barring gear?
Does a screw pump also need to be primed? If it stops suddenly, will the water drain away? Do I need to pump it again next time?