Know all about self-priming pumps in this guide.
What is self-priming?A self-priming pump has an external surface casing that centrifuges the volute or pumps inside. Liquids have been added to the case, and the pump is now ready to operate. Self-priming pumps are similar to centrifugal pumps with extra features.
Fluid circulates inside the pump head of self-priming pumps, creating a vacuum. Air in the suction pipework is expelled, and the pump's impeller is filled with liquid. Since there is a separate chamber inside the pump head, self-priming pumps are less efficient.
Additionally, self-priming pumps handle a wide range of fluids and work well with solids, corrosive liquids, and slurries.
Types of self priming pumpBasic knowledge of pump technologies is necessary when choosing a self-priming pump.
Self priming centrifugal pumpA priming pump can pump gas, a liquid, or a mixture of both. If there is water inside the pump's body, it can use suction to generate a vacuum.
self priming water pumpFor both industrial and commercial uses, this pump primarily pumps clean water. Centrifugal pumps with a 40 liters per minute maximum flow rate are used for these pumps.
Seal-less self priming pumpThis pump moved a variety of fluids, slurries, solvents, salts, and acids. This pump is used for heavy work.
This pump works by being split into two parts: a stiff thermoplastic interior and a blendable outside wall.
Self priming chemical pumpThis self-priming pump enables the flow of oil, pigments, sewage, and water. The pump is quite similar to the self-priming centrifugal pump.
Vortex self priming pumpPure low-viscosity liquids devoid of any particles are pumped with this pump. A simple design and simple operation make up for the relatively modest capacity.
Liquid ring self priming pumpFoaming liquids are controlled with this pump. Water, black oil, and diesel fuel are also suitable for them. However, these pumps inexorably leak some of the working fluid transported outside the pump and the pushed media.
see also all about reciprocating pumps
How do self-priming pumps work?At the impeller, air enters the pump and combines with water. The impeller's centrifugal force causes water and air to be discharged into the reservoir simultaneously. As a result, water naturally tends to sink, but the air naturally rises.
Water without air, which is now heavier than water with air, flows downward by gravity into the impeller chamber, where it is ready to mix with additional air entering the suction line. The suction line becomes vacuumed when all air has been removed, and pumping starts due to atmospheric pressure forcing water up the suction line and toward the impeller.
When the pump starts to pump, the water no longer circulates inside. The pump will self-prime the following time it is turned on, which means it will be able to combine the water and air in the casing once more to produce a pumpable fluid until the pump is fully primed.
On the other hand, a standard centrifugal pump includes a built-in water reservoir that allows it to prime by recirculating water inside the pump, clearing the air from the pump and suction line. The location of this water reservoir can be either above or in front of the impeller.
Key points for operating self priming pump
Avoid dry start
Priming is done before pumping begins to prevent a dry start, possibly leading to a pump breakdown.
Avoid backpressure
Pay close attention to installing a bypass filling line to prevent back pressure in the discharge line, which could obstruct the priming procedure.
Airflow via the suction line is blocked by the backpressure that builds up in the discharge line due to air bubble accumulation.
Use a strainer
It is necessary to install a filter when using a pump in a dusty location to avoid solids building up in the filling compartment.
Use end seals
End seals are recommended for self-priming pumps. If the stuffing box seal fails, air may be trapped, making the filling more difficult and lowering the functional quality.
Suction line
Since the suction line is constantly below atmospheric pressure, air leakage is possible. Therefore, when the pump runs, the suction line should be at 0.5 meters (20 inches) of vacuum.
Uses of self priming pumps
Construction
Self-priming pumps can be used for numerous purposes in construction. These include groundwater drying and lowering, water supply from wells or channels, washing concrete surfaces, pumping out floodwaters, wastewater conveyance, firefighting, hazardous liquid collection, and water evacuation from pits or basins during excavation. In addition to being utilized to produce building materials, self-priming pumps are also used to maintain and repair utility networks and systems.
Agriculture
Self-priming pumps are used for agricultural needs such as surface irrigation and watering, pumping and spraying liquid fertilizers or manure, distributing liquid animal feed, and handling oil cake, brand-new wines, and fruit juice.
IndustrySelf-priming industrial pumps are utilized at various manufacturing facilities, in oil storage tanks, to clean up spills at chemical plants, and in the mining, metallurgical, pulp and paper, water supply, and drainage industries.
Advantages
Self-priming pumps, transmission hardware, and power machines are relatively less expensive than other pumping machines.
It is simple to maintain because the main component is above the water surface.
There is no need to transfer the power machine when dismantling since the lifting height is short, and the pump room is small.
Certain self-priming pumps are capable of handling particles up to 3 inches.
It is possible to pump fluid with a self-priming pump even when it is not submerged. This offers more flexibility than a submersible pump, which must be submerged to maintain prime and perform as intended.
Disadvantages
Although the term “self-priming” indicates that the pump does not require priming, manual priming may once in a while be required.
It frequently needs higher clearances to handle solids more effectively for its inefficiency. It also requires a larger volume to help with self-priming.
The liquid supply is farther distant from the pump. Therefore, a minimum pipe length is required to assist minimize air leakage and suction pressure loss.
The motor needs protection when the water level in the input tank is high. The self-priming pump's practical suction range is exceeded if the water level in the inlet tank is too low, making it unable to suction water.
FAQs Why are self-priming pumps not used in the houses?
The suction line has an air leak, which causes air to be forced out of the discharge when the pump circulates fluid to establish a low-pressure zone.
What happens if the pump isn’t primed?Without priming your pump, you risk mechanical seal failure and subsequent harm to other crucial pump parts.
Which kind of pump doesn’t ever need priming?Plunger pumps are self-priming when used above or below the fluid level. Therefore, they don't need to repeat the priming process each time.
What is a Compressed Air Self-Priming Pump?A compressed air self-priming pump is pushed through a jet into a tapered tube to produce a vacuum. It is pulled in and released with air from the pump casing and suction line.