Are Oil-Free Vacuum Pumps Really Oil-Free and How to Maintain It?

Brief introduction of oil-free vacuum pump

The oil-free vacuum pump is a mechanical vacuum pump that can run without any oil for lubrication. It has the advantages of easy operation, good durability, convenient maintenance, simple structure, and no pollution to the environment. It is a compression, vacuum, dual-purpose vacuum pump. For obtaining vacuum, it is widely applied and taking as basic equipment in many places. Hawach has Standard Diaphragm Vacuum Pumps and Anti-Corrosion Diaphragm Vacuum Pumps for your choice.

The working principle of an oil-free vacuum pump is the same as that of a general positive displacement pump. It consists of main parts such as a stator, a rotor, a rotary vane, a cylinder, and a motor. The rotor with rotary vanes is installed eccentrically in the fixed cylinder. When the rotor rotates at high speed, four radially sliding rotary vanes in the rotor slot divide the pump cavity into four working rooms. Due to the centrifugal force, the rotary vane is tightly attached to the cylinder wall, separating the inlet and outlet of the stator, and it rotates again and again to change the volume, and the inhaled gas is discharged from the exhaust port to achieve the purpose of air extraction.

Oil-free vacuum pumps can be widely used in pharmacy, chemical industry, food packaging, medical equipment, milk processing industry, printing, lighting, air conditioning, extensive fields such as blister forming and laboratories. To be more specific, it can be used for the repair of air conditioning and refrigeration equipment, suction devices for medical instruments, printing machinery, vacuum packaging, vacuum blister, physical and chemical experiments, and small devices that require a vacuum environment for various vacuum operations. It can also be used as a backing pump for small oil booster pumps, oil diffusion pumps, and molecular pumps. Oil-free vacuum pumps are not suitable for pumping out gases that are corrosive to ferrous metals, chemically react to pump oil, and contain particulate dust, as well as explosive toxic gases. Also, it’s unsuitable to pump from one container to another. That is, it can not be taken as a transfer pump.

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Are oil-free vacuum pumps really oil-free?

When purchasing an oil-free vacuum pump, you must first determine the vacuum required to work, otherwise, the vacuuming requirements will not be met, and the work requirements will not be met. Under its working pressure, the vacuum pump should be able to exhaust all the gas generated during the process of the vacuum equipment. Combine the vacuum pump correctly. Sometimes one type of pump can not meet the extraction requirements because of the vacuum pump selective extraction, and it is necessary to use a combination of multiple pumps, complement each other.

Secondly, we need to consider the pumping rate. The pumping rate should be slightly greater than the required pumping rate when selecting the model. If the demand is high, the vacuum pump selected should be higher than the required vacuum, so that it can better meet the requirements. The different pump has different working pressure ranges. Finally, look at whether the extracted gas is corrosive, corrosive gas will corrode the pump, and special materials must be used to meet the demand. We need to consider installing auxiliary equipment on the inlet pipe, for instance, dust collectors or condensers and so on, if there are particles, steam, and corrosive gases in the.

According to the definition of an oil-free vacuum pump, in order to meet a good environment, its suction chamber is oil-free. But the mechanical transmission part also needs oil lubrication, such as multi-stage oil-free vacuum pumps and screw-type dry pumps. The bearings of the transmission gears all need to be lubricated. The labyrinth seal structure is used to isolate the pump cavity and gearbox. The simpler method is to fill dry inert gas between the pump cavity and the part that needs lubrication or install a sealing ring.

There must be good measures to prevent backflow. Most oil-free vacuum pumps are used at low pressure, and the labyrinth structure can prevent lubricating oil from entering the pump cavity, but it may allow gas to pass because the gas pressure in the gearbox is not affected. The limitation is that if the gas pressure in the gearbox is greater than the pressure in the pump cavity, there will be a pressure gradient that will cause the oil vapor in the gearbox to diffuse into the pump cavity.

Therefore, the structural design of the oil-free vacuum pump should be carefully considered. The oil sump in the gearbox is decompressed and pre-pumped to control the gas pressure in the gearbox and isolate the oil sump from the pump cavity through a lip seal to avoid contamination of the pumped gas.

Maintenance of oil-free vacuum pump

1. Check the oil-free vacuum pump pipeline and joints for looseness. Turn the oil-free vacuum pump by hand to see if the oil-free vacuum pump is flexible.
2. Unscrew the water diversion screw plug of the oil-free vacuum pump body, and pour water diversion or slurry diversion.
3. Close the gate valve of the outlet pipe, the outlet pressure gauge, and the inlet vacuum gauge.
4. Turn on the motor. When the oil-free vacuum pump is running normally, open the outlet pressure gauge and the inlet oil-free vacuum pump. Open the gate valve slowly and check the motor load, after proper pressure is shown.
5. Try to control the flow and head of the oil-free vacuum pump within the range indicated on the label to ensure that the oil-free vacuum pump runs at the rate point to achieve great energy-saving effects.
6. During the operation of the oil-free vacuum pump, the bearing temperature should not exceed the ambient temperature of 35℃, and the temperature should not exceed 80℃.
7. If an abnormal sound is found in the oil-free vacuum pump, stop immediately and check the cause.
8. To stop using the oil-free vacuum pump, first close the gate valve and pressure gauge, and then stop the motor.