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| 1. Inability to rotate |
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When galling occurs due to a foreign object in the piping |
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When galling occurs because the temperature of the pumped liquid rises and the side clearance disappears |
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When idled or grazing operation is performed for a long time |
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When galling occurs because the
temperature of the liquid rises due to extended operation with the
built-in safety valve working, and the side clearance disappears |
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When galling occurs because the side clearance disappears due to distortion of cast products |
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When a problem such as shaft breakage occurs |
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When galling occurs because the gears come
in contact with the side plate due to misalignment of the pump or too
much tension of the V belt |
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When galling occurs due to operation with the discharge pipeline closed, or operation exceeding the specified pressure |
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When galling occurs due to wear of the
parts inside the pump, and especially when wear of the shaft bearing
(metal)/bearing has progressed |
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Due to failure of the power engine or motor, etc. |
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Due to defect of electric wiring, switch, etc. |
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When scratching occurs
due to such causes as idling, in some cases the inability to rotate
does not occur immediately after the accident, but after a while the
scratching will lead to the inability to rotate. Scratching leading to
this trouble is often caused during commissioning immediately after
installation of the pump. |
| 2. Leakage |
| (1) |
Leakage from seal |
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When the pumped liquid and packing/seal material do not match |
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When there is pushing pressure on the suction side |
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When negative rotation occurs |
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When the shaft is worn out |
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When the viscosity of pumped liquid becomes lower than the specified viscosity |
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When the seal surface is flawed |
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When foreign objects such as slurry have entered the sealing liquid or pumped liquid of the mechanical seal |
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When the seal surface of the mechanical seal is worn out |
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Due to defective assembly, or uneven contact of the seal surface |
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When the pumped liquid hardens due to sliding heat of the mechanical seal |
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When the sealing liquid of the mechanical seal undergoes thermal expansion |
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When pressure is placed while the pump is stopping, causing deformation/damage of the mechanical seal parts |
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Structurally, it is
impossible to completely stop liquid leakage of gland packings, oil
seals, or mechanical seals. If you need to completely prevent liquid
leakage, please use a seal-less gear pump. |
| (2) |
Leakage from other places |
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Defective assembly such as foreign objects in juncture of the case and cover |
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When abnormally high pressure is applied compared with the specified conditions |
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When electromagnetic valves are suddenly closed or pressure does not escape due to narrow bypass piping |
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Damage to the gaskets, defective or uneven application of packing agent |
| 3. Insufficient capacity |
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When the safety valve is working (the pressure indicator swings) |
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When there are foreign objects on the seat surface of the safety valve |
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When there is air leakage from the suction pipeline, or pump seal section |
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When excessive resistance (cavitation) occurs on the suction side |
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When the viscosity of the pumped liquid becomes high |
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When the valve on the suction side is turned down too much |
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When the head of fluid on the suction side lessens |
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When the strainer is clogged |
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When the piping is small for the viscosity/flow rate of the pumped liquid |
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When the rotation speed is excessive for the viscosity of the pumped liquid |
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When the specified pressure is exceeded |
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When the viscosity of the pumped liquid becomes significantly lower than the specification |
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When regular rotation speed is not obtained due to slipping, etc. of the belt |
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When the clearance in the pump becomes large due to wear |
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When the flowmeter is malfunctioning |
| 4. Insufficient discharge pressure |
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When the capacity is insufficient |
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When the safety valve is working (the pressure indicator swings) |
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When there are foreign objects on the seat surface of the safety valve |
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When excessive resistance (cavitation) occurs on the suction side |
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When the viscosity of the pumped liquid becomes high |
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When the valve on the suction side is turned down too much |
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When the head of fluid on the suction side lessens |
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When the strainer is clogged |
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When the piping is small for the viscosity/flow rate of the pumped liquid |
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When the rotation speed is excessive for the viscosity of the pumped liquid |
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When the resistance of the discharge pipeline becomes excessively small |
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When the resistance of the nozzle due to wear of the nozzle. |
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When the resistance of the discharge pipeline becomes lower due to decrease of the viscosity of the pumped liquid. |
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When the clearance in the pump becomes large due to wear |
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When the pressure indicator is malfunctioning |
| 5. Inability to suction (Although the pump rotates, liquid is not drawn) |
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When the safety valve is working (the pressure indicator swings) |
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When there are foreign objects on the seat surface of the safety valve
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When excessive resistance (cavitation) occurs on the suction side |
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When the viscosity of the pumped liquid becomes high |
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When the valve on the suction side is turned down too much |
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When the head of fluid on the suction side lessens |
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When the strainer is clogged |
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When the piping is small for the viscosity/flow rate of the pumped liquid |
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When the rotation speed is excessive for the viscosity of the pumped liquid |
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When there is air leakage on the suction side |
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When the suction pipe is not dipped (immersed) in the liquid (e.g. the tank is empty) |
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During suction from an
underground tank, for example, if the viscosity of the pumped liquid is
low and there are no check valves (non-return valves) in the suction
piping, or even if there are check valves, they do not function
properly, and all the liquid falls down when the pump stops. |
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When the inside of the pump is dry, and the required pressure cannot be generated on the suction side |
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When the flow rate of the suction pipe is excessively small |
| 6. Heating of pump |
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When the temperature of the liquid itself is abnormally high because the tank capacity is excessively small in a closed circuit |
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When the built-in safety valve of the pump is frequently activated, or remains activated |
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When the gland packing is closed too tightly |
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When the shaft bearing, shaft seal, etc. of the pump generate heat due to wear of parts, for example |
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When there is misalignment or the V belt is too tight |
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Due to warp, etc. of the base |
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When installation of the pump is poor |
| 7. Swing of pressure indicator |
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When the safety valve is working (chattering, etc.) |
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When air is sucked in from the suction piping |
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When the pumped liquid is partially vaporizing in the suction piping (vapor lock) |
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When excessive resistance (cavitation) occurs on the suction side |
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When there is an air pocket in the piping |
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When the pressure indicator is malfunctioning |
| * |
Depending on the cause, in addition to swinging of the gauge, there may also be vibration, noise or decrease of capacity.
Please also check the situation around the pump. |
| 8. Overload of motor |
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When the discharge pressure is
higher than the specification due to operation with the discharge
pipeline blocked or closed, etc. |
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When the rotation speed is higher than the specification |
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When the viscosity of pumped liquid increases due to a temperature change, for example |
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When the inside of the pump is worn |
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When "galling" of the gear or "burning" of the shaft bearing (metal) is about to occur |
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When foreign objects are caught |
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When the gland packing is closed too tightly |
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When the pump is misaligned or the V belt is too tight |
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Due to warp, etc. of the base |
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When installation of the pump is poor |
9. Abnormal noise/vibration  |
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When the safety valve is working (the pressure indicator swings) |
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When excessive resistance (cavitation) occurs on the suction side |
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When the viscosity of the pumped liquid becomes high |
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When the valve on the suction side is turned down too much |
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When the head of fluid on the suction side lessens |
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When the strainer is clogged |
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When the piping is small for the viscosity/flow rate of the pumped liquid |
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When the rotation speed is excessive for the viscosity of the pumped liquid |
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When the flow rate is excessive and turbulent flow is occurring in the piping |
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When there is air suction in the suction pipeline |
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When the pump is idling |
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Engagement of the gears is defective, backlash is inappropriate, or containment phenomenon occurs |
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When the piping before and after the pump is resonating/sympathizing |
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When the coupling is misaligned |
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When the inside of the pump is worn |
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When noise is generated from the motor or geared motor |
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Wear of coupling or coupling pin, rubber |
| Although the overview of
problems of gear pumps is itemized above, there are many cases where
causes of problems are hard to be identified. Also, when some causes
overlap, identifying the causes becomes even more difficult. In order
to prevent problems, please read the Instruction manual and operate
accordingly. |
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