Self-priming pumps are a type of centrifugal pump that use an air-water mixture to reach a fully-primed pumping condition. It is used in many applications including sewage, construction dewatering and flood control.
A self-priming pump is able to overcome the problem of air binding by mixing air with water. After it gets rid of the air, the pump will continue to move water like a standard centrifugal pump.
It is important to note that self-priming pumps can’t operate without water
Self-priming pumps can handle a variety of fluids and they do well with slurries, corrosive fluids, and solids.
Solids handling is one of its most important advantages, as some self-priming pumps can handle solids up to 3 inches.
Another advantage, when compared to a submersible pump, is its ability to continue pumping fluid while pump is still situated out of the pit.
The disadvantage is its inefficiency, as clearances often need to be larger to allow for better solids handling, also a larger volute to assist with self priming.
ISSUES WITH SELF-PRIMING PUMPS
Like other types of pumps, self-priming pumps also come across various issues with continuous functioning. The main problem in a centrifugal pump occurs towards the pump’s suction side.
NEED OF RE-PRIMING
For a new self-primed pump, the process of priming has to be followed before it is being put into use. Always remember to refer to the manufacturer’s manual
Self-priming pumps need to be primed again following the initial priming. This is to ensure optimised operation due to multiple factors such as fluid evaporation during initial priming.
LEAKAGE IN THE SUCTION LINE
As the suction line of a self-priming pump is always below the atmospheric pressure, some air leakage might occurs. Ideally, one should have a suction line at 0.5 metres (20 inches) of vacuum when the pump is functioning.
THE PUMP IS TOO FAR FROM THE LIQUID SOURCE
It is ideal to place the pump as close as possible to the suction source. Usually 7.6 to 9 metre (25 to 30 feet) is the maximum recommended distance.
Prudent system design dictates that the suction pipe length be held to a minimum to promote long pump life. Every section of suction piping equates to a volume of air that must be removed when the pump starts. Best practice is to reduce priming time to a minimum.
For more than 13 years, Thai Khương Pumps has been distributing and supporting Industrial Pumps in a wide range of industries throughout VietNam for many years. Thai Khuong currently offers a number of genuine self-priming pumps from European and American brands meeting EU-G7 standards. Contact Us.