Choosing between a positive displacement pump and a centrifugal pump can be tricky. They act very...
At Professional Pump, we know the frustration of a self-priming pump that won’t prime. These pumps are designed to lift fluid from below, making them easier and safer to maintain than submerged alternatives. However, when conditions aren’t ideal, they can struggle to function properly. Let’s explore why this happens and how to get your pump back on track.
How a Self-Priming Pump Works
While self-priming pumps can evacuate air and establish suction, they must have liquid in the casing to start. Running dry, even briefly, can cause severe mechanical seal damage and pump failure.
Here’s the process:
- The impeller spins, moving the initial prime fluid into the discharge chamber.
- Air separates from the fluid and exits through the air release line.
- Recirculated fluid creates low pressure at the impeller’s eye, allowing atmospheric pressure to push fluid up the suction line.
- This cycle continues until the pump is fully primed and running normally.
But what if your pump isn’t priming?
5 Common Causes of Self-Priming Failure
If there’s a leak in the suction line, air will continuously enter the system, preventing proper pressure buildup.
Debris Blocking the Impeller:
Clogs at the impeller eye reduce its ability to generate suction. Regular maintenance can prevent this issue.
Pump is Air-Bound:
- Trapped air in the pump prevents priming. This can happen if:
- There’s no air release line, trapping air inside.
- The discharge valve is closed, giving air nowhere to escape.
- Excessive impeller clearance reduces priming efficiency due to wear or improper assembly.
If the recirculation port is blocked, the pump cannot create the low-pressure zone needed for suction.
Lift is Too High for the Pump’s Capacity
An undersized pump won’t generate enough suction lift. Proper selection based on NPSH requirements is critical.
Need Expert Pump Support?
Professional Pump specializes in diagnosing and resolving self-priming pump issues. Our team provides expert guidance, repairs, and customized solutions for industrial pumps, valves, and skid systems. Contact us today for a consultation and keep your operations running smoothly!
