Constant flow pumps are fluid transfer devices widely used in laboratories, pharmaceuticals, chemicals, environmental protection, and other fields. They are highly trusted for their precise flow rate, stable operation, and low risk of contamination. To ensure long‑term stable operation, regular and standardised maintenance is essential. Based on common maintenance misconceptions and correct practices, this article provides a practical guide for pump care.
I. Lubrication System Maintenance
Correct practice: Replace the lubricating oil after the first 100 hours of operation, and thereafter every 500 hours. The oil level should always be kept at the centre line of the sight glass.
Common mistake – Adding oil without changing it: During use, the oil becomes contaminated with metal wear particles. Adding only fresh oil without replacing the old oil accelerates bearing wear.
Common mistake – Using the wrong oil type: Different lubricating oils have different properties; using an incorrect type can reduce lubrication effectiveness.
II. Priming and Inspection Before Start‑up
Correct practice: Fill the pump with priming water before starting, close the outlet gate valve, jog the motor to confirm the rotation direction, then start the pump formally.
Common mistake – Starting without priming: This can cause dry running, damaging the mechanical seal and the pump body.
Common mistake – Starting under load: Starting without closing the gate valve places a heavy load on the motor, which may burn it out or shorten its life.
III. Operate at the High‑Efficiency Point
Correct practice: Keep the pump operating as close as possible to its high‑efficiency point. This saves energy and extends equipment life.
Common mistake – Prolonged low‑flow operation: This not only reduces efficiency but may also increase internal temperature, leading to cavitation and vibration.
IV. Monitor Bearing Temperature
Correct practice: During operation, the bearing temperature should not exceed ambient temperature by more than 35 °C, and the maximum allowable temperature is 80 °C.
Common mistake – Ignoring abnormal temperature rise: Excessive temperature is often a sign of poor lubrication or improper assembly. Continuing to run the pump will lead to bearing failure.
V. Identify and Address Unusual Noises
Correct practice: If an abnormal sound is heard, stop the pump immediately and check for foreign matter, bearing damage, or loose components.
Common mistake – Ignoring early unusual noises: A small sound may be a warning of a major fault. Delaying action will worsen the damage.
VI. Standard Shutdown Procedure
Correct practice: When stopping the pump, first close the gate valve and the pressure gauge, then disconnect the power.
Common mistake – Directly cutting power without closing the valve: This may cause backflow of the medium and pressure surge, affecting the pump’s next start‑up.
VII. Adjusting the Packing Seal
Correct practice: The packing gland should be tightened moderately, allowing a small amount of leakage (preferably a drop‑wise seepage) from the packing chamber.
Common mistake – Overtightening to achieve “zero leakage”: This causes overheating and wear of the packing and the shaft sleeve, shortening their service life.
VIII. Regularly Inspect Wear Parts
Correct practice: The shaft sleeve is a wear part; inspect it regularly and replace it promptly when wear is severe.
Common mistake – Ignoring regular inspections: Failing to replace a worn shaft sleeve can increase leakage or damage other core components.
IX. Winter Freeze Protection
Correct practice: In low‑temperature environments, after stopping the pump, drain all liquid from the pump body to prevent freezing that could crack the pump casing.
Common mistake – Only cutting power without draining: Residual liquid freezing at low temperatures is the main cause of pump casing cracks.
X. Long‑Term Storage
Correct practice: If the pump will not be used for a long time, disassemble the pump body, wipe it dry, apply anti‑rust grease, reassemble, and store in a dry place.
Proper maintenance not only preserves the pumping accuracy and stability of constant flow pumps, but also effectively prevents unexpected failures and extends equipment service life. By comparing the “correct practices” and “common mistakes” mentioned in this article during actual operation, you can better implement maintenance procedures and ensure the smooth progress of research and production.
