A self-priming water pump is a type of pump also known as a self-priming wastewater pump, self-priming pump, or jet pump. Although self-priming pumps are not as commonly used as centrifugal or submersible pumps, they are among the most important pump types in terms of applications. Self-priming wastewater pumps are used to discharge water from both deep and shallow wells. As mentioned earlier, they are also called jet pumps or spray pumps. These pumps operate reliably, even in conditions where the water is muddy or aerated.
Working Principle of Self-Priming Pumps
Self-priming pumps are typically installed at ground level above the liquid source, requiring some infrastructure for setup. Being at ground level also makes maintenance and repairs easier. The correct pump type must be selected depending on the application, such as fuel pumps for fuel transfer or solids-handling pumps for wastewater applications.
A self-priming pump is filled with liquid, usually the same fluid it will pump. As the impeller rotates within the pump casing, a low-pressure area forms at the impeller eye. Since this pressure is lower than atmospheric, it pushes all the air from the suction line into the pump. The pump mixes the air with the recirculating liquid in the casing; the air separates from the fluid and is expelled. Once all air in the suction line is displaced, the pump operates dynamically like a regular centrifugal pump.
One major advantage of self-priming pumps is that they can prime without submersing the pump in water, allowing it to remain outside the fluid source. The UKMS series pumps can self-prime from up to 6 meters.
UKMS Series Self-Priming Wastewater Pumps
The UKMS series are self-priming, centrifugal pumps with valves. Only the suction pipe needs to be in the well. They can be driven by diesel or electric motors using an elastic coupling. The series includes six different sizes: 2”, 3”, 4”, 6”, 8”, and 10”. The impellers are open and two-bladed. Depending on the pump size, they can handle solid particles up to 76 mm (3”), and clearing clogs is easy. The front suction cover allows easy access to the impeller, stuffing box, and mechanical seal without modifying the suction or discharge piping.
Key features include:
- The valve in the suction flange is specially designed.
- The valve can be removed and replaced without altering the suction piping.
- The bearing housing is supported by the pump casing, preventing alignment issues.
- Being self-priming, these pumps are easy to use.
- Once the suction pipe is submerged, the pump starts within about one minute depending on the suction height.
Advantages and Disadvantages
Advantages:
- Can handle solids up to 3 inches in diameter, allowing transportation of solid-containing liquids.
- Can continue pumping while remaining outside the fluid source, unlike submersible pumps.
Disadvantages:
- Susceptible to air leaks since the suction line is always below atmospheric pressure.
- After the first priming, the pump may need to be refilled before restarting.
Tips for Using Self-Priming Wastewater Pumps
- Before use, check for leaks at connectors, suction lines, or pump seals. Any leaks can reduce pump efficiency.
- The length and diameter of the suction hose or pipe are important; longer hoses can reduce suction efficiency.
- Keep the pump close to the water source to minimize friction losses.
- Prime the pump before first use.
- In cold environments, prevent freezing as expanding ice can damage the pump casing.