The functions and troubleshooting of each component of the screw air compressor（2）

4. Several points for attention of screw air compressor

4.1   The screw air compressor rotor must not be reversed

        The rotor is the core component of the screw air compressor. The surfaces of the female and male screws do not touch, and there is a gap of 0.02-0.04mm between the male and female screws. The oil film acts as a protection and seal.  

        If the rotor is reversed, the pressure cannot be established in the pump head, the screw in the pump head has no lubricating oil, and the lubricating oil cannot be circulated. Heat is accumulated in the pump head instantly, resulting in high temperature, which deforms the inner screw and the shell of the pump head, and the female and male screws bite.  Locking, the end face of the rotor and the end cover stick together due to high temperature, resulting in serious wear of the end face of the rotor, and even component defects, resulting in damage to the gearbox and rotor.

         How to check the direction of rotation: Sometimes the phase sequence of the incoming line of the factory will change, or the incoming power supply of the screw air compressor will change, which will cause the phase sequence of the motor of the screw air compressor to change. Most air compressors have phase sequence protection, but  To be on the safe side, the following inspections should be made before the air compressor runs:

 ① Press and hold the cooling fan contactor with your hand to see if the fan wind direction is correct.

 ② If the power line of the fan has been moved, manually jog the main motor momentarily to see if the rotation direction of the motor coupling is correct.

4.2    Screw air compressor rotor can not deposit carbon

4.2.1  Causes of carbon deposition

 ①Use low-quality lubricating oil that is not genuine from the original manufacturer.

 ② Use a fake or damaged air filter.

 ③Long time high temperature operation.

 ④The amount of lubricating oil is small.

 ⑤ When replacing the lubricating oil, the old lubricating oil is not drained or the old and new lubricating oil are mixed.

 ⑥ Mixed use of different types of lubricating oil.

 4.2.2  Check the carbon deposition method of the rotor

 ①Remove the intake valve and observe whether there is carbon deposit on the inner wall of the pump head.

 ② Observe and analyze whether the lubricating oil contains carbon deposits from the surface of the oil filter and the inner wall of the lubricating oil pipeline.

4.2.3  When checking the pump head, it is required

          Non-professionals are not allowed to disassemble the screw air compressor pump head casing, and if there is carbon deposits in the pump head, only the professional and technical personnel of the manufacturer can repair it.  The gap between the female and male screws in the pump head of the screw air compressor is very small, so be careful not to enter any impurities in the pump head during maintenance.

4.3   Add motor bearing grease regularly

        Use a special oil gun to add, specific steps:

 ① On the opposite side of the oil nozzle, open the vent hole.

 ②The oil nozzle of the oil gun should be matched with the motor.

 ③Lubricating grease is divided into high-speed motor grease and low-speed motor grease, and the two cannot be mixed, otherwise the two will react chemically.

 ④ The amount of oil in the oil gun is 0.9g per press, and 20g is added each time, and it needs to be pressed several times.

 ⑤If the amount of grease is added less, the grease is on the oil pipeline and does not play a lubricating role; if it is added too much, the bearing will heat up, and the grease will become liquid, which will affect the lubrication quality of the bearing.

 ⑥ Add once every 2000 hours of operation of the air compressor.

4.4   Main motor coupling replacement

       The coupling must be replaced in the following situations:

 ① There are cracks on the surface of the coupling.

 ② The surface of the coupling is scorched.

 ③The coupling glue is broken.

5. Trouble Analysis and Elimination of Screw Air Compressor

5.1  A 40m³/min screw air compressor caught fire during operation in a company

         The screw generates high temperature during the compression process, and the lubricating oil is sprayed to take away the heat, thereby reducing the temperature of the machine head.  If there is no oil in the screw, the machine head will be locked instantly.  The oil injection point is different for each head design, so the oil products of various screw air compressor manufacturers are not the same.

          The screw air compressor in operation caught fire, and the machine was scrapped for the following reasons:

 5.1.1 The flash point of lubricating oil is around 230°C, and the ignition point is around 320°C.  Use inferior lubricating oil. After the lubricating oil is sprayed and atomized, the flash point and ignition point will be lowered.

5.1.2  The use of inferior wearing parts will cause the air compressor oil circuit and air circuit to be blocked, and the temperature of the air circuit and oil circuit components will be too high for a long time, which will easily generate carbon deposits.

5.1.3  The gasket of the oil-gas separator is not conductive, and the static electricity generated by the oil-gas separator cannot be exported.

5.1.4  There is an open flame inside the machine, and there are leaking fuel injection points in the oil circuit system.

5.1.5  Combustible gas is inhaled at the air inlet.

5.1.6  The residual oil is not drained, and the oil products are mixed and deteriorated.

          It was jointly confirmed by relevant experts and engineering technicians that the machine used poor-quality lubricating oil and poor-quality wearing parts during maintenance, and the static electricity generated by the oil-gas separator could not be exported, causing the machine to catch fire and be scrapped.

5.2  When the screw air compressor is unloaded, it vibrates violently and there is a fault of pouring oil smoke.

          The head of the screw air compressor shakes when it is unloaded during operation, and the air filter alarm occurs every 2 months, and cleaning the air filter with high-pressure air does not work.  Remove the air filter, oily fume is generated in the suction pipe, and the oily fume mixes with dust to seal the air filter tightly.  The intake valve was disassembled and the seal of the intake valve was found to be damaged. After replacing the intake valve maintenance kit, the screw air compressor operated normally.

5.3  The screw air compressor runs for about 30 minutes, and the new V-belt is broken.

          The pre-tightening force required by the V-belt of the screw compressor is set before leaving the factory. When replacing a damaged V-belt, the operator loosens the lock nut to reduce the automatic tension in order to save effort and facilitate the installation of the V-belt.  tight system tension.  After replacing the V-belts, the lock nuts were not returned to the original running position (at the corresponding color mark). Due to the looseness, wear and heat of the V-belts, the newly replaced 6 V-belts broke again.

6. Epilogue

         The operator of the screw air compressor should always pay attention to the precautions in the maintenance when maintaining, and it is very necessary to understand the functions of the main components of the air compressor.  Personnel in the equipment management and operation departments purchase the wearing parts of the original manufacturer to prevent the occurrence of inferior lubricating oil and inferior parts, and prevent unnecessary failures and incidents.