List of Problems and Solutions for Screw Compressors

Screw compressor is another type of commonly used compressor. We’ve listed the following 11 problems and solutions for reference of anyone or business in need.

1. List of Problems and Solutions for Screw Compressors

No.	Problem	Reason	Solution
1	Compressor Unable to Start	The fuse is burnt.	Replace the fuse and restart the compressor.
		Under phase or poor contact of power button.	Check whether the sensor ring and the sensor wire are connected reversely.
		Setting error of exhaust pressure	Reset the pressure value.
		Motor overload protection trip or damage	* Screw compressor is equipped with motor overload protection device. If the discharge pressure is higher than the set value, the compressor will trip automatically and it cannot be started again. * The pressure should be reset. * If there are damaged parts, you should replace them.
		AC contactor failure	Examine if the AC contactor line is broken.
		The compressor is not reset after a failure shutdown.	Wait for 2 minutes to restart.
		Main motor failure	Press the emergency stop button to reset it. Check the main motor and turn it on.
2	Unable to Build up Pressure	Intake valve is stuck in closed position, and the hole is blocked.	* There's too much water in the control pipe. You should maintain the control pipe every day. * Check intake valve, cylinder, valve sleeve, shaft and other parts, and replace them if necessary. * Inspect and replace the inlet valve spring. * Check and solve the wiring problem of solenoid valve. * Check and replace the reciprocating valve.
		Solenoid valve failure	Check the components in the solenoid valve or circuit to solve the problems.
		Serious blockage of air filter	Clean the air filter. If the blockage is serious and cannot be cleaned, it needs to be replaced.
		Air leakage of minimum pressure maintaining valve	Adjust the pressure maintaining valve or replace it.
3	High exhaust temperature or over temperature protection	Insufficient lubricating oil and low oil level	Add lubricating oil properly.
		High environment temperature	* High environment temperature can also cause high exhaust temperature. Especially in summer, when the environment temperature is too high, you should take appropriate cooling measures for the compressor. * If you can't avoid the high temperature with several trials, and it's difficult to change the environment temperature, you can open a new mesh vent with a diameter of 600mm on the door panel at the end of the motor of the equipment to enhance the heat dissipation. Of course you should do this after communication and with the consent of the manufacturer.
		The surface of oil cooler is too dirty.	Clean the oil cooler regularly.
		Poor heat dissipation due to Fan or fan motor failure.	Check the fan or fan motor.
		Oil filter blocked	According to the requirements of operation, you should replace the oil filter after a new compressor has run for 500h. After that, it should be replaced every 3000h under normal conditions.
		Temperature control valve failure	* The temperature control valve automatically controls the oil circuit with the oil temperature rising in the lubrication system. * The alarm temperature set by the compressor manufacturer is 105 ℃, and it will be automatically turned off if the temperature exceeds 110 ℃. There will be an over temperature shutdown prompt on the monitor. * Here you should examine whether the lubricating oil is cooled by the oil cooler. If not, remove and check the temperature control valve. * In addition, if the temperature display control is in problem, you should reset the display.
4	Frequent switch between full load and non-load	PLC breakdown	According to the electrical schematic diagram, make sure the PLC input and output indicator is correct.
		Leakage of air pipe	Fix air pipe.
		Small pressure difference between working pressure and unloading pressure	Readjust the working pressure and unloading pressure.
		Poor sealing of minimum pressure valve	Check the minimum pressure valve and fix the sealing surface to ensure there’s no air leakage.
		Unstable fuel consumption	* Increase the capacity of the air tank. * Discharge the water in the air tank regularly, and keep the pressure of the air tank above 0.6MPa.
5	Unable to stay in non-load status or unable to maintain pressure or safety valve action when the compressor stays as non-load.	Malfunction of intake valve	Fix the intake valve and solenoid valve.
		Solenoid valve failure	* If the connector of solenoid valve is loose or falling, you can solve the problem by fastening the connector. * Air leakage of solenoid valve - replace sealing gasket or slide valve. * Solenoid valve coil burned - replace solenoid valve coil. At the same time, you should avoid letting water enter the solenoid valve. Also, you should avoid the spring to bend too hard. * In case of emergency, you can turn the manual button on the coil from the normal operation of "0" to "1" to turn over the valve.
		Filter of oil gas separator blocked	Check if the temperature control valve works normally. When the indicator light of differential pressure of oil-gas separator is active or the oil pressure is higher than gas pressure, the oil-gas separator must be replaced.
		The value of the safety valve changes or goes wrong.	* The discharge pressure of safety valve should be set as 1.1 times of rated exhaust pressure. Usually the compressor has been set before leaving the factory. * If the safety valve does not work, you can adjust the discharge pressure of the safety valve again.
6	Discharge volume or discharge pressure lower than normal value	Blockage of air filter	Clean the air filter. If the blockage is serious and cannot be cleaned, replace the air filter.
		There is oil and air leakage in the system.	Check the connection of control pipeline with the compressor.
		The air consumption exceeds the exhaust volume of the compressor, and the intake valve fails to operate.	Inspect the intake valve and check whether the valve plate and valve seat are worn.
		Failure or leakage of solenoid valve	Fix or replace solenoid valve.
7	Excess oil in exhaust gas and large oil consumption	The oil return pipe or oil return nozzle is blocked.	Dismantle and clean the oil return pipe and oil return nozzle.
		Filter of oil gas separator blocked	Replace the filter of oil gas separator.
		Loose minimum pressure valve spring	Adjust or replace the minimum pressure valve spring.
		Oil leakage of oil pipeline or oil seal	Eliminate the leakage part in the oil pipeline.
8	Oil leakage	It is usually caused by aging of the sealing rings of relevant parts and poorly sealed joints.	Replace the sealing rings.
9	Abnormal noise	Wear of main motor bearing, fan motor bearing or main motor bearing	* Generally speaking, a quality screw compressor rarely has the problem of head bearing damage within the warranty period. * If there's damage, do not ignore it or try to continue to use the compressor, otherwise it is easy to damage the whole machine. * In case of damage on the bearing of the main motor, you should have professional technicians to check and repair in time and replace the damaged parts.
9	Abnormal noise	Collision between fan and windshield	Adjust the positions of fan and windshield.
10	Overload protection	Low voltage	Try to use the compressor with desired voltage.
		High exhaust pressure resulted by inaccurate sensor	Replace the sensor for testing.
		Main motor thermal protector failure	Inspect and eliminate the problem of thermal protector.
		Main motor bearing wear	* If the main motor bearing of the compressor is damaged, do not ignore it and try to continue to use, otherwise it is easy to damage the whole machine. * In case of damage on the bearing of the main motor, you should have professional technicians to check and repair in time, and replace the damaged parts.
		Screw failure of main motor
11	Repeated overload and blocked rotation during start up; frequent movements of main contactor	The start time of the motor is less than the star angle delay time.	Reset motor startup time.
11		The emergency stop button is loose.	Fasten the emergency stop button.

Among the components listed above, the main motor bearing is the core of a screw compressor. As the working time increases, the wear of the motor bearing is inevitable, which may gradually result in axial and radial movements of the screw.
The movements will change the clearance between one screw and another, between the screw and the main motor shell and between the front and rear end faces.

The clearance change is normal and allowed during the life of the bearing, so are the aftereffects of gas production attenuation and increased load of transmission motor. When the bearing wear and main motor clearance exceeds the allowable limit, serious consequences may occur.

First of all, there will be friction between the internal screw and the front and rear end faces of the main motor, and friction between the screw and the main motor shell, resulting in a sharp increase in the motor load. The most serious consequence is that the screw locks up and the main motor is scrapped. If the motor protection response is not sensitive enough or fails, the motor may be burned.

Secondly, there will be attenuation of the gas production, which may affect the ideal use of compressor users.

2. When a screw compressor needs an overhaul

Accurately speaking, when the motor of a screw compressor needs an overhaul should be determined by the service life of the bearing.

However, it is difficult to have accurate indicators to judge whether the service life of the bearing is about to expire or has expired.

With nearly 100 years of practical experience, some internationally renowned air compressor manufacturers say the standard is that most motors of compressors need an overhaul after 20,000 hours or 4 years of operation.

In addition to the above standard, we can also make a more accurate judgment on the condition of the main motor from the following aspects according to our experience:

* When the main motor is running, check if there's abnormal sound, especially the bearing.
* Inspect whether there's a difference between the running current value of the compressor, especially the non-load value and the standard current value.
* Check if there's vibration on each part of the bearing.

It is necessary to have complete testing tools, which can compare the testing results with the technical data to effectively judge whether the main motor needs to be overhauled.　

3. Work Details of Main Motor Overhaul

* Remove and pull out the corresponding gears, including belt pulley and other transmission device, and bearing.
* Clean screw, shaft and clearance adjusting gasket. Grind and repair damaged surfaces of shaft, screw and stator.
* Press the bearing, adjust the clearance and test it.
* Run the compressor as trial, and readjust.

For oil free screw compressor, users are not suggested to maintain it themselves. You need to find professional and technical personnel for maintenance.

Regarding the motor of oil injection screw compressor, you should pay attention to the following aspects:
* The bearing must be replaced completely.
* Check the rotor surfaces and see if correction is needed.
* Check the inlet and outlet bearing seats to see if they need to be corrected.
* Understand the motor assembly requirements, in case you don't know whether you should open the main motor or not.
* Generally speaking, the clearance at the inlet end is 0.35-0.50mm, and that at the exhaust end is 0.08-0.15mm. If it is a repair, the clearance should be as large as possible within the allowable range.

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