Common Faults, Reasons of Faults, and Solutions of Vacuum Pump

1. Common Faults

Figure 1: The disassembly and inspection of broken vacuum pump.

Falling vacuum degree;
Abnormal operation, even being jammed;
Large noises during the operation;
Oil leakage resulting from not well-sealed pump body;
When starting, large amount of oil drops and oil mist are sprayed, causing environmental pollution;
Difficult start.

2. Failure Reasons and Solutions

2.1 Reasons of Low Vacuum Degree

1.Insufficient oil.
Solution：Refuel.
2.Dirty or emulsified oil.
Solution：Replace oil.
3.The pump oil brand does not match or the oil is mixed, or use oil with too low viscosity in summer.
Solution：Replace oil.

Figure 2: Different types and specifications of vacuum pump oil.

4.Air leakage.
Solution: Check the following parts such as shaft seals, exhaust valves, end caps, air inlets, etc.
5.There is big fit clearance or abrasion and scratches.
Solution: Check the sealing condition of each part, and repair the sealing ring, check the matching clearance among the pump chamber, rotor, rotary vane and end cap plate, remove junks and impurities, and regrind in accordance with the required accuracy.

6.The oil pipeline is blocked, and the appropriate amount of oil is not maintained in the pump chamber.
Solution: Adjust the oil intake of the oil pipeline, blow through the oil hole with high-pressure air during cleaning, and clean the deposits.

7.The temperature during the pump operation is too high, which makes the pump oil concentration thinner, the sealing performance deteriorates, and the oil vapor pressure increases.
Solution: Put in cooling water to cool down, check the matching clearance and repair it in accordance with the required accuracy.
8.When the partition plate in the pump is pressed in, the magnitude of interference is too large, causing the pump chamber bulge and deformation and air leakage.
Solution: Repair the pump chamber or replace the pump, or discard it.

9.Exhaust valve is damaged or poorly sealed.
Solution: Repair or replace valve.
10.Improper assembly, different tightness of end cap screws, and displacement of rotor axis.
Solution: Reassemble.
11.Poor activity of rotary vane.
Solution: Grind the fit of the rotor and the rotary vane, and replace the spring.

Figure 3: Different types and specifications of rotary vane.

12.The temperature of the pumped gas is too high.
Solution: Add into the cooling device before the hot gas is pumped into the pump.
13.The filter net of inlet pipe is blocked.
Solution: Take out the air inlet filter net, clean and dry it.
14.Gas ballast valve washer is damaged or not tightened.
Solution: Replace the washer or tighten gas ballast valve.

2.2 Reasons of Jammed Vacuum Pump

Figure 4: The appearance and design model of vacuum pump motor.

Vacuum pump motor is overloaded, or even cannot turn, resulting jammed situation.

1.Damaged spring causes uneven force on rotary vane.
Solution: Replace spring.
2.Improper assembly causes force on a certain part.
Solution: Reassemble.
3.External pollutants such as metal filings, particles, etc. fall into the pump chamber, due to damaged filter net.
Solution: Disassemble the pump to check, clean and replace the filter net.
4.The end face clearance is so small that pump temperature rises too high.
Solution: Grind the rotor vanes and adjust the clearance.

5.Pump oil deterioration or scaling, or inappropriate oil viscosity.
Solution: Relace oil.
6.Rotor suffers from damage.
Solution: Replace the new rotor.
7.Shaft and shaft sleeve are too tight, lack of oil lubricant.
Solution: Enhance oil pipelines lubrication.
8.The middle air passage is not smooth.
Solution: Clean the middle air passage or replace with a thinner rubber pad.
9.Cross joint in shaft suffers from damage.
Solution: Repair or replace rotor shaft or cross joint.

2.3 Noises During the Vacuum Pump’s Operation

There Are Noises During the Vacuum Pump’s Operation.

1.The spring is broken, and the impact sound of the rotary vane is emitted during operation.
Solution: Replace the spring.
2.Improper assembly and loose parts cause abnormal running sound.
Solution: Reassemble.
3.There is dirt in the pump chamber and burr or deformation on the parts, which spell faults in operation.
Solution: Disassembly, cleaning, inspection, grinding.

Figure 5: The appearance and model of vacuum pump chamber.

4.Poor lubrication of the oil in the pump chamber.
Solution: Dredging and adjusting the oil passage.
5.The harmful space in the pump cavity is too large.
Solution: It belongs to the fault of the pump, the middle partition can be offset by a few centimeters to reduce the harmful space.
6.Motor suffers from faults.
Solution: Repair and replace the motor.

2.4 Oil Leakage in Vacuum Pump

1.The sealing parts such as bearing, end cover, oil window, oil drain hole, oil tank, etc. are damaged or not pressed flat or tightly.
Solution: Replace the new sealing parts, pay attention to the correct position during assembly, tighten the screws, and make the pressure even and appropriate.

2.There are leaks on the pump chamber.
Solution: Stop the leakage.

2.5 Oil Spraying in Vacuum Pump

Figure 6: The appearance and model of hydraulic pump oil tank.

1.Too much oil.
Solution: Drain excessive oil.
2.Sudden exposure to the atmosphere.
Solution: When starting the pump, attention should be paid to intermittently starting the motor. If the system is exposed to the atmosphere due to damage, attention should be paid to closing the low vacuum valve or clipping.

3.The original design of the pump oil tank is too small.
Solution: Add oil and gas separation device at the exhaust port, and connect a rubber tube to the exhaust port to lead away from the working scene.
4.The pump rotor runs in reverse.
Solution: Reconnect the power supply, and reverse the direction.

2.6 Difficulty in Starting the Vacuum Pump

1.The oil temperature is too low.
Solution: Heat the oil to above 15°C and ensure that the room temperature of the workplace is above 15°C.
2.Poor lubrication in the pump.
Solution: Adjust the oil passage to enhance lubrication and replace the appropriate mechanical pump oil.

3.Oil has deteriorated or mixed diffusion pump oil.
Solution: Replace oil.
4.When the pump is stopped, the atmosphere is not put into the pump chamber, and a large amount of pump oil enters the pump chamber.
Solution: Pay attention to deflation when the pump is stopped, and check whether the differential pressure valve is working normally.
5.There are faults in power distribution room.
Solution: Contact the electrician to address.

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