Centrifugal pump with self priming device

Centrifugal pump with self priming device
The core principle of converting a conventional centrifugal pump into a self-
priming pump is simply: It is to ensure the pump can retain water after shutdown
and automatically expel air from the suction pipe upon startup.The key to
modification liesThe not in altering the impeller, but in installing two essential
systems—the "water storage" and "gas-liquid separation" mechanisms—into the pump
body.
1. Maintain priming: For ordinary centrifugal pumps, water must be filled before
each start-up as the water in the pump casing and suction pipe will drain out.
During modification, install a check valve(non-return valve) at the inlet to allow
water to flow in but not out. After shutdown, water can remain in the pump body and
suction pipe, eliminating the need for refilling during the next startup
2. Air Removal: Simply retaining water is not enough—there is still air in the
suction pipe. Self-priming pumps rely on an air-water separation chamber: the
impeller mixes water and air into an air-water mixture and ejects it. When the
mixture enters a cavity with suddenly increased volume, the flow velocity drops
sharply, causing the air to rise and be discharged through the outlet while the
water falls back to continue the cycle. After several repetitions, the air in the
suction pipe is completely removed, and water rises
The core method for converting a centrifugal pump into a self-priming pump involves
installing a foot valve or check valve in the suction pipe, along with improvements
to the pump body sealing and priming system
Common modification methods
Install a foot valve or check valve: Install a foot valve at the bottom of the
suction pipe or inlet to prevent water backflow and ensure the suction pipe remains
fully filled with water.
Install an automatic suction device: Add a water collection pipe at the inlet and
an air-water separator at the outlet to achieve automatic air venting.
Set up the water suction tank: Install a negative pressure water tank or filling
chamber, ensuring sufficient liquid is retained for next startup
Key modification steps
Improve the shaft seal: Replace the cast iron bushing with a brass bushing and use
a mechanical seal kit (static ring, dynamic ring, spring, etc.) to ensure the
sealing performance of the rotating shaft.
Pump Body Modification: Install a stationary ring sleeve and rubber gasket in the
packing chamber, machine threads at the impeller shaft end to match the spring
seat, and sequentially install the sealing kit.
Pipeline Connection: All components must be tightly sealed, with no air leakage in
the suction and drainage pipelines
Precautions
Initial Water Filling: Before startup, fill the pump body with water, then close it
after expelling air through the vent valve.
Sealing Inspection: Regularly check the wear condition of the pump body and
impeller, and promptly replace worn components.
Installation Position: The pump should be installed as close as possible to the
liquid source, with the inlet pipe kept as short as possible to minimize flow
resistance

Minimum Order: 1 sets

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