Common faults, phenomena, causes and brief solutions of screw pump operation
A、 Insufficient flow/pressure (most common)
1. Blockages in import and export pipelines, filters, and bottom valves
The medium contains impurities, crystals, and viscous substances, resulting in poor suction, pump idling, and sudden drop in output.
2. Screw and liner/stator wear and clearance increase
Long term transportation of granular media, dry grinding, insufficient lubrication, decreased volumetric efficiency, inability to increase pressure, and decreased flow rate.
3. Low suction liquid level and air leakage in the suction pipeline
Air enters and forms an air trap, causing the pump to fail to apply pressure and experience significant pulsation.
4. Low speed, motor malfunction, belt slippage/coupling slippage
The actual speed cannot reach the rated value, and the displacement decreases synchronously.
B、 Abnormal heating of the pump body
1. Dry operation (no medium idle)
The medium is both a conveying material and a cooling lubricant. After a few seconds of dry grinding, the stator rubber will melt, the screw will lock, and the pump body will rapidly heat up.
2. The outlet valve is closed and operated under pressure
The medium repeatedly shears and rubs inside the pump, and heat accumulates and heats up.
3. Bearing and shaft sleeve wear, increased friction and heating
4. The viscosity of the medium far exceeds the design value, resulting in a significant increase in internal friction.
C、 High vibration and abnormal noise
1. Cavitation, gas binding, medium with a large number of bubbles
Make intermittent explosions and buzzing sounds.
2. Screw eccentricity, rotor wear, bearing damage, aging and cracking of elastic coupling rubber blocks.
3. Loose anchor bolts, insufficient rigidity of pump foundation, and pulling of pump body due to hard connections in pipelines.
4. Scratching occurs between the screw and the stator, resulting in sharp friction sounds.
D、 Leakage issues (shaft seals, inlet and outlet flanges, pump body interface)
1. Wear and aging of mechanical seals/packing seals, spring failure: dripping, oil spraying, and material leakage at the shaft end.
2. Aging of gaskets and inconsistent tightness of bolts: flange surface leakage.
3. The medium corrodes the sealing components (incorrect selection of rubber and fluorine rubber), resulting in direct failure of the short-term seal.
E、 Motor overload, high current, tripping
1. The medium viscosity exceeds the standard, crystal agglomeration occurs, and the load suddenly increases.
2. The outlet is blocked, the valve is fully opened to hold pressure, and the load exceeds the limit.
3. The screw stator is locked, the bearing is stuck, and the motor stalling protection trips.
4. Three phase voltage imbalance, phase loss, motor overload protection action.
F、 The pump is stuck and cannot rotate completely
1. Core: Long term idle dry grinding, stator rubber melted and wrapped around the screw.
2. Crystallization, solidification, and agglomeration of the medium can cause the rotor gap to become stuck.
3. Foreign hard particles enter the pump chamber and get stuck on the screw.
G、 Large pulsation and fluctuating flow rate during medium transportation
1. Air intake and restraint;
2. Mismatch of import and export pipe diameters, and failure of buffer tanks;
3. The wear clearance of the screw is uneven, and the volume change is inconsistent with each rotation.
H、 Corrosion and rapid loss of components
1. Corrosion of screws, shells, and stator rubber by media acidity, alkalinity, and solvents;
2. The selected materials (cast iron, 304, 316, duplex steel, corrosion-resistant rubber) do not match.
F、 Reverse Backflow Shutdown Reverse
The failure of the outlet check valve can cause the pump to reverse due to the backflow of the pipeline medium after shutdown, which can easily damage the bearings, couplings, and screws.
The above:
Working principle of screw pump 
Pressure switch
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