Troubleshooting of common faults in oil-injected twin-screw air compressors

160KW Fixed Speed Screw Air Compressor

1. Exhaust high temperature

(1) False high temperature

——The temperature sensor is bad, or the wiring of the temperature sensor is wrong. For example: the temperature sensor used by a company’s electric mobile phone is PT100, and when wiring, pay attention to the positive and negative points of the wiring. The two red wires connected in parallel are negative, and connected to the marked end of the circuit diagram. The other white wire is connected positively.

——Check whether there is a disconnection fault in the middle of the temperature sensor, or whether there is a problem with the PT100. Under standard conditions (20°C), use an ohmmeter to measure the resistance of PT100 to about 100Ω. If it is too large or too small, it means it is broken.

(2) Really high temperature

——High ambient temperature: For example, a company’s air compressor is designed to use a maximum ambient temperature of 40°C. If the surrounding environment is high, there will be high exhaust gas temperature. At the same time, pay attention to whether the air inlet of the chassis is blocked, or whether the hot air from the radiator can be discharged smoothly or whether the hot air returns to the air inlet of the chassis.

——Whether the screw oil level is too low, the main oil return pipe of the oil and gas barrel cannot return to the oil due to the low liquid level. If the temperature drops significantly after adding some screw oil, this is the problem.

——Whether the fan is reversed or the air duct of the radiator is seriously blocked. The blockage of the air duct of the radiator is the most common problem. When purging the radiator, the air duct must be blown through. The fins can be seen on the other side.

——Whether the oil filter has not been replaced for a long time, resulting in blockage, which affects the reduction of the amount of screw oil injected into the machine head, resulting in high temperature. The solution is to replace the oil filter. If there is no oil filter on site, test and verify by poking a few short-circuit holes inside the old oil filter.

——Is the entire pipeline from the main oil return pipe of the oil and gas barrel to the main fuel injection port of the machine head and the components on the pipeline blocked? For example, after coking, the radiator oil passage is most likely to be blocked, and the main method can only be removed one by one for inspection.

——Screw oil coking (coking occurs due to long-term non-maintenance, mixed screw oil, long-term high-temperature screw oil hydride evaporation) blocking the main oil return pipeline or blocking the radiator oil passage. If the screw oil is mixed, the temperature will be high when loading.

——Temperature control valve failure, usually the paraffin bag of the temperature control valve is damaged, or the spool of the temperature control valve is stuck, causing the spool to fail to open normally, and the screw oil cannot be fully circulated. The solution is to temporarily pad the temperature control valve. The spool, and then replace the new spool for the customer.

——For air compressors with oil shut-off valves, failures will also occur if the oil shut-off valve has poor oil return.

——There is also a phenomenon of high temperature, which is a sudden increase in the temperature after starting up, and the temperature is normal after the pressure is established. One reason is that the oil is relatively thick in winter, and the pressure is not enough to quickly press the oil into the machine head when starting up. After several times of starting up, the screw oil temperature rises and the fluidity is good, and then the fault phenomenon disappears. It is good if the viscosity of the oil is reduced, but it should be noted that improper operation will lock the machine head. It is best to add screw oil to the machine head in advance. If the viscosity of the screw oil decreases after several inchings or the temperature is still high, check whether the relief valve has too much relief, which makes it impossible to build up the pressure and thus the temperature increases. The size of the discharge should be reasonable. If the discharge is too large, the pressure cannot be quickly established when the machine is started, and the temperature will be high. If the discharge is too small, the pressure of the oil and gas barrel will be too high when the machine is shut down. The air inlet will spray oil.

10) Some machine heads are designed at a high position. If the machine head does not have an oil shut-off valve and an exhaust check valve, when the machine stops for a period of time, the oil in the machine head will leak into the oil and gas barrel or pipeline, resulting in If there is a lack of oil, the temperature will rise too fast when starting.

2. What are the reasons for excessive oil content in the exhaust, and how to deal with it?

(1) The screw oil level is too high. If the oil level is too high, when the unit is running, the liquid level in the oil and gas barrel will fluctuate, and a large amount of oil will enter with the gas, resulting in an increase in the order of magnitude of the oil treatment, resulting in oil in the exhaust. Generally, after the shutdown is stable, the liquid level can be at 2/3 of the liquid level mirror.

(2) The oil subdivision has not been replaced for a long time or the oil subdivision is damaged. The oil is finely divided into glass fiber winding structures, and the glass fibers are used to capture fine oil droplets. If the oil is not replaced for a long time, it will be saturated, which will reduce the oil separation effect. In addition, when the oil is opened, there are obvious short-circuit cracks, etc., which indicate that the oil has failed. When the oil component is damaged, there will be obvious oily phenomenon in the self-exhaust port.

(3) Exhaust pressure is too low. If the exhaust pressure is too low, the oil treatment capacity will be relatively large, increasing the oil burden, and the exhaust oil will appear. The pressure maintenance valve can be increased or the ball valve can be closed to improve the pressure.

(4) There is blockage in the oil subdivision oil return pipeline. The oil that is subdivided and separated returns to the machine head through the oil return pipe. If the pipeline is blocked or the oil return check valve in the middle and the oil return port of the machine head are blocked, the exhaust gas will contain oil (the oil return check valve has also occurred. opposite phenomenon). You can check the pipeline or add another oil return pipeline to the counterweight (or one-way valve) of the intake valve.

(5) For the external oil, if the O-ring of the center pipe is damaged or installed poorly, the oil and gas will be remixed, and the exhaust gas will also contain oil. The solution is to remove the central tube and check the installation of the O-ring and whether it is damaged.

(6) There are trachoma in the combination valve so that oil and gas are mixed. If all are resolved by exclusion method, replace the combined valve experiment.

(7) There are manufacturing defects in oil and gas barrels, and the primary separation is poor. The performance is that the secondary oil return is very large.

(8) The oil quality is poor, the volatility is high, and the exhaust temperature is high.

3. What are the reasons for oil return from the air filter port and how to deal with it?

(1) Mainly due to abnormal shutdown, the unit shuts down under pressure so that the intake valve is too late to close, and high-pressure oil and gas are ejected from the intake valve (such as power failure shutdown, emergency shutdown shutdown)

(2) The counterweight of the intake valve or the sealing surface of the one-way valve is dirty, and the sealing surface is damaged or stuck, which will also cause the air filter to return oil.

(3) The exhaust gas has a high oil content. Some models that are discharged to the air filter have oil in the air entering the air filter from the dump valve, resulting in oil in the air filter. At this time, it is often accompanied by oil in the exhaust gas.

(4) If the oil level of the AIV-40B air intake valve is too high, when the temperature of the unit is too high and the discharge valve discharges too quickly when the shutdown is too fast, due to the high temperature and rapid pressure change during high-pressure emergency stop, if the screw oil Poor foaming will cause a large number of air bubbles to pour into the oil, resulting in more oil in the discharge pipe, and it is easy to form the phenomenon of oil return from the air filter port. At the same time, it is accompanied by a large oil content in the exhaust gas.

4. What are the reasons for insufficient displacement?

(1) The relief valve is discharged when it should not be discharged. Check that each bleed valve is not stuck and keeps blowing air.

(2) The clogging of the air filter results in less air intake. Take off the air filter element for a short test run to see if the pressure has increased (the unit without a safety filter element should pay attention to ensure that debris does not enter the machine head)

(3) The speed decreases. (shaft broken, belt loses rotation and slips, inverter rated frequency is low, diesel engine throttle is not in place)

(4) Advance action of capacity adjustment.

(5) The intake valve is stuck and cannot be opened or cannot be fully opened.

(6) The oil is subdivided and blocked.

(7) Insufficient false gas volume: The gas consumption of subsequent equipment increases, or the pipeline leaks. There may be ground fissures with drilling rigs. The treatment method is to check the air compressor part to prevent the problem of the air compressor part, and close the ball valve to see that the rated pressure can be reached. For electric-driven units, check whether the current under the rated pressure is consistent with the current under normal conditions, so as to judge whether there is a large change in the gas volume.

(8) Measure the gas volume to rule out air compressor problems.

5. What are the simple methods to measure gas volume? How to operate and calculate?

However, if the on-site conditions cannot meet the test requirements, the more direct method is to use the tank filling method to roughly measure the exhaust volume. The specific method is as follows:

(1) Make sure that there are no long pipelines from the air compressor to the air storage tank or other equipment pipelines that affect the volume. If there is, the volume will be included in the calculation.

(2) There is no air leakage between the air compressor and the air storage tank. The air storage tank has a closing valve to hold the pressure, and at the same time ensure that the valve does not leak. The pressure gauge on the gas tank is good.

(3) It is best to adjust the capacity adjustment of the air compressor to fail, so as to prevent the capacity adjustment from working during the test and affect the measured value.

(4) For frequency conversion or belt conveyors, it is necessary to ensure that during the test, under the rated speed of the machine head, there should be no speed drop due to frequency conversion or belt slippage affecting the speed.

(5) The initial pressure should preferably be above the opening pressure of the pressure maintaining valve, in order to prevent the calculation from being affected by the pressure maintaining valve not being opened, and also to avoid the influence on the gas volume calculation during the start-up loading process.

(6) After meeting the above conditions, close the exhaust ball valve of the air storage tank, turn on the air compressor, and take a stopwatch. For example, the opening pressure of the machine pressure maintenance valve is 4kgf, and the rated pressure is 10kgf. We’d better calculate the air storage tank from P1= The time consumed between 4.5kgf rising to P2=9.5kgf is T=0.5(min), and the volume of the air storage tank is V=2m³, then the displacement formula of the air compressor is Q=V(P2-P1-1) /T=2×(9.5-4.5-1)/0.5=16m³/min. The above formula ignores the influence of temperature. If the gas temperature difference before and after filling the tank is large, the temperature should be taken into consideration in the calculation.

6. What are the manifestations and causes of loss of magnetism in permanent magnet motors?

(1) Demagnetization judgment: After the permanent magnet motor loses magnetism, the most direct and accurate judgment is that the back EMF of the measured motor will decrease a lot (for example, the normal back EMF is 350V, and it will drop below 300V after demagnetization, and the reverse direction is determined according to the magnitude of the demagnetization electromotive force size). It can also be judged according to the input voltage on the display screen, the input voltage value will decrease after demagnetization (generally about 20V lower than the standard). Because the current is large after demagnetization, if the frequency converter is equipped with self-protection, it will work at reduced frequency.

(2) Reasons for loss of magnetism: first of all, high temperature. The permanent magnet of the motor is most afraid of high temperature. If there is a high temperature above 150°C, there may be loss of magnetism. Another reason is that if the carrier frequency of the inverter is very low, the sine wave waveform will also be bad, resulting in a larger negative value of the ID current, resulting in demagnetization. At this time, the above-mentioned demagnetization performance is manifested, and at the same time, the noise and vibration of the motor increase.

(3) Treatment method: First, prevent the occurrence of high temperature. When setting the carrier frequency, according to experience, a sine wave requires at least 20 points of control, so the setting of the carrier frequency = 20 × working frequency. For example, the maximum 200Hz unit, its carrier frequency should be set at least 20×200=4000Hz. The carrier frequency should not be too high, otherwise the IGBT will heat up and shut down the inverter. Different manufacturers have different standards, and the general module temperature limit is set to 85°C. When setting, you can ask the inverter manufacturer for reference settings.

7. What are the reasons for the speed reduction of the diesel engine when it is working?

(1) The main reason for the decrease in diesel engine speed is insufficient power, and subdivision is nothing more than insufficient air intake and insufficient oil intake leading to a decrease in speed.

Insufficient air intake can be checked:

A. Whether the intake air filter of the diesel engine is clogged

B. With intercooler, whether there is air leakage in the intercooler pipe, resulting in insufficient air intake

C. With turbocharger, whether there is a problem with the turbocharger.

Insufficient oil intake can be checked:

A. Whether the diesel oil level is full, and whether the variety is suitable (for example, lower grade diesel oil should be used in winter in Northeast China to prevent cold diesel oil crust from clogging the oil pipe and oil filter)

B. Whether the diesel filter is clogged

C. Whether there is air mixed in the oil pipeline (use the hand oil pump to empty the air, pay attention to the high-pressure common rail pump and do not dismantle the high-pressure oil pipe part, if it is removed, the high-pressure fluid may cause personal injury).

D. Increase the total oil supply of the oil pump. (Hengyang pump can disassemble the bottom cover plate on the right side of the pump, and turn it clockwise for about 1 turn, so as to increase the total oil supply of the pump. This measure is generally not used, and it should be used with caution! It may cause excessive fuel injection and cause combustion Incomplete combustion in the exhaust manifold causes the exhaust manifold to turn red)

E. Check whether the flameout solenoid valve is in place?

F. The flameout during the capacity adjustment process is mainly due to the difference between closing the throttle cylinder and closing the intake valve cylinder.

(2) There is a problem with the oil pump of the diesel engine itself. Only the service station can be notified for maintenance.

(3) Other issues

A. The breathing tube is stuck

B. Poor oil lubrication leads to increased friction power and insufficient total power

8. What are the reasons for the high water temperature of the diesel engine and how to deal with it?

(1) The unit is overloaded, and the work of the diesel engine itself becomes larger. Solution Adjust the diesel engine to the rated working state (is the rated pressure of the air compressor set high, and the rated speed of the diesel engine set high?)

(2) Whether the fan belt is slipping, resulting in insufficient fan speed and insufficient cooling air volume.

(3) The air duct of the water tank is blocked. If the blockage is serious, the water tank can be removed and cleaned with a high-pressure water gun.

(4) The water channel inside the water tank is blocked. (If no good antifreeze is used, there may be scaling inside the water tank, which will affect the circulation of the coolant, and a special descaling agent should be used for water cleaning and descaling)

(5) The structure of the head of the water tank is damaged.

9. What are the factors of motor overcurrent?

(1) Whether the customer voltage is low.

(2) Whether the customer is under excessive pressure. (If the rated pressure of 8kgf is set to 8.5kgf, or the pressure sensor is defective, it should be 8.5kgf but it shows 8kgf, it needs to be checked with the pressure gauge)

(3) Whether the customer’s exhaust volume has increased (if the pulley has been replaced, the air volume has become too large)

(4) Is the load on the machine head increased (whether the manual cranking feels obviously stuck)

(5) The load on the oil circuit such as screw oil coking is large.

(6) Oil clogging.

(7) Misreporting by the current transformer or the main control (judged by pinching the current with the current clamp meter, if the main control test is not accurate, it can be corrected in the column of plotter coefficient correction.)

10. Reasons for frequent loading and unloading of the unit

(1) The pressure sensor is installed before the pressure maintenance valve

(2) The pipeline behind the pressure maintenance valve is frozen or blocked, resulting in small volume and rapid pressure change.

(3) The loading solenoid valve is damaged.

11. What are the reasons why the electric stationary machine unit does not load? How to check and deal with it in general?

(1) No loading is mainly due to the fact that the intake valve cylinder is not open. The judgment method is: after the display shows “loading”, for a normally closed valve, disassemble the nylon tube leading to the cylinder to see if there is air passing through it. If it is enough, the loading pipeline is normal, then check whether the intake valve cylinder is damaged or whether the valve plate is stuck; if there is no air in the nylon tube of the cylinder, check where there is a problem in the entire loading pipeline, the most likely problem is the loading solenoid valve, the display After “loading”, first check whether there is 220V electricity at the coil of the solenoid valve. If you do not check the main control, if there is no 220V at the main control, the possibility of damage to the main control is high. If there is 220V electricity at the solenoid valve and there is no gas, the electromagnetic There is a high possibility of damage inside the valve body (confirm that the pipeline from the oil and gas barrel to the solenoid valve is not blocked). For normally open valves, the check is the opposite of the above.

(2) For normally closed valves, if there is air in the cylinder of the intake valve but cannot be loaded, and the cylinder can be loaded normally after pushing the cylinder by hand, the internal pressure may not be established enough or the valve plate of the intake valve may be stuck. The treatment method is to extend the ball head of the cylinder with a thread. The purpose is to allow the valve plate to have a pre-opening amount, so as to speed up the establishment of internal pressure and prevent the possibility of the valve plate being stuck. If the cylinder leaks, replace the cylinder.


Sollant Group-Professional Compressed Gas Solutions Provider