Troubleshooting and Handling of Common Faults in Oil Injection Twin Screw Machines

A. False high temperature
1) The temperature sensor is damaged, or the temperature sensor wiring is incorrect. For example, the temperature sensor used by a company for electromigration and electromigration is PT100, and attention should be paid to the difference between positive and negative wiring during wiring. The two red lines are connected in parallel as negative and connected to the symbolic end of the circuit diagram. Connect the other white wire correctly.
2) Check whether there is a broken wire fault in the middle of the temperature sensor or whether there is a problem with the PT100. Use an ohmmeter to measure the resistance of PT100 under standard conditions (20 ℃), which is about 100 Ω. If it is too large or too small, it indicates that it is broken.
B. True high temperature
1) High ambient temperature: For example, a company has designed a maximum operating ambient temperature of 40 ℃. High exhaust temperatures may occur if the surrounding environment is high. At the same time, on-site attention should be paid to whether the air inlet of the chassis is blocked, whether the hot air from the radiator can be smoothly discharged, or whether the hot air returns to the air inlet of the chassis.
2) Check whether the screw oil level is too low, which results in the main oil return pipe of the oil and gas drum not being able to fully return oil. If the temperature drops significantly after adding some screw oil, this is the problem.
3) Whether the fan is reversing or the radiator air duct is severely blocked. Blockage of the radiator air duct is the most common problem. When purging the radiator, it is necessary to blow through the air duct. The judgment method is to see the other side through the air duct fins from one side of the radiator.
4) 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, leading to high temperatures. Solution: Replace the oil filter. If there is no oil filter on site, it can be verified by poking several short circuit holes inside the old oil filter.
5) Is there any blockage in the entire pipeline and components on the pipeline from the main oil return pipe of the oil and gas tank to the main oil injection port of the machine head? For example, the radiator oil ducts are most likely to become clogged after coking, and the main method is to remove them one by one for treatment and inspection.
6) The main oil return pipeline is blocked or the oil passage of the radiator is blocked due to coking of screw oil (long-term non maintenance, mixing of screw oil, long-term high-temperature screw oil hydride evaporation). If screw oil is mixed, the temperature is high during loading.
7) The failure of the temperature control valve is usually caused by the damage of the paraffin package of the temperature control valve, or the sticking of the valve core, resulting in the valve core not being able to open normally, resulting in the inability of the screw oil to undergo a comprehensive large circulation. The treatment method is to temporarily cushion the temperature control valve core, and then replace the valve core with a new one for the customer.
8) A screw air compressor with an oil shutoff valve may also have a malfunction if the oil shutoff valve does not return oil smoothly.
9) Another high temperature phenomenon is a sudden increase in temperature at startup, and the temperature becomes normal after the pressure is established. One reason is that the oil is relatively thick in winter, and the pressure is insufficient during startup to quickly press the oil into the machine head. After several times of startup, the temperature of the screw oil rises and the fluidity is good, and the fault phenomenon disappears. The solution is to start the unit multiple times to reduce the viscosity of the screw oil, but it is important to note that improper operation can lock the machine head. It is best to add the screw oil into the machine head in advance. If the viscosity of the screw oil is reduced or at high temperature after multiple inching operations, check whether the relief valve has too much pressure to establish, resulting in an increase in temperature. The discharge size should be reasonable. If the discharge is too large, the pressure cannot be quickly established during startup, and the temperature will be high. If the discharge is too small, the pressure of the oil and gas tank will be too high during shutdown, and the air inlet will inject oil.
10) In some designs where the machine head is at a high position, if the machine head does not have an oil shutoff valve and an exhaust one-way valve, the oil in the machine head will leak into the oil and gas barrel or pipeline after the machine is stopped for a period of time, resulting in a lack of oil inside the machine head. During startup, the temperature will also rise too fast.
2、 What are the reasons for excessive oil content in exhaust gas and how to handle it?
1) The oil level is too high. If the oil level is too high, the fluctuation of the liquid level in the oil and gas barrel during unit operation will cause a large amount of gas to enter the oil content, leading to an increase in the magnitude of the oil content processing capacity, resulting in oil content in the exhaust gas. Generally, after the shutdown is stable, the liquid level can be at 2/3 of the liquid level mirror.
2) The oil subdivisions have not been replaced for a long time or are damaged. The oil is subdivided into a glass fiber winding structure that uses glass fibers to capture small oil droplets. If the oil separator is not replaced for a long time, it will become saturated and reduce the oil separation effect. In addition, when the oil separator is opened, obvious short circuit cracks, etc., indicate that the oil separator is invalid. When the oil component is damaged, there will be significant oil content in the exhaust gas from the exhaust port.
3) The exhaust pressure is too low. If the exhaust pressure is too low, the oil content treatment capacity will become relatively large, increasing the oil content burden, and the phenomenon of exhaust oil containing will occur. The pressure maintaining valve can be adjusted higher or the ball valve can be closed to suppress pressure for improvement.
4) The oil subdivision return line is blocked. The oil separated by oil subdivision returns to the machine head through the return pipe. If the pipe is blocked or the intermediate return check valve or the machine head return port is blocked, it can cause oil in the exhaust gas (reverse installation of the return check valve has also occurred). Check the pipeline or add another return line to the underside of the intake valve counterweight (or one-way valve).
5) For external oil separators, if the O-ring of the center pipe is damaged or poorly installed, the oil and gas will be remixed, and oil in the exhaust gas will also occur. The treatment method is to remove the center pipe and check the installation and damage of the O-ring.
6) The combination valve has sand holes that allow oil and gas to mix. If the elimination method fails, replace the combined valve for experiment.
7) The oil and gas drum has manufacturing defects and poor primary separation. The secondary oil return volume is very large.
8) The oil is poor, volatile, and the exhaust temperature is high.
3、 What are the reasons for the oil return from the air filter port and how to handle it?
1) The main reason is abnormal shutdown. The shutdown under pressure in the unit causes the intake valve to be closed too late, and high-pressure oil and gas spurts out from the intake valve (such as power failure shutdown and emergency shutdown)
2) Dirt on the sealing surface of the intake valve counterweight or one-way valve, and damage or seizure of the sealing surface can also cause oil return from the air filter.
3) The oil content in the exhaust gas is high. Some models that are discharged to the air filter have oil in the air filter gas from the discharge valve, resulting in oil in the air filter. At this time, there is often oil in the exhaust gas.
4) If the oil level in the oil and gas barrel of the AIV-40B intake valve is too high, when the unit temperature is too high, and the shutdown relief valve discharges too quickly, due to the high temperature and rapid pressure change during the high-pressure emergency stop, if the screw oil has a poor foaming property, a large number of bubbles will flow into the oil, resulting in more oil in the discharge pipe, and it is also easy to form the appearance of oil return at the air filter port. At the same time, there is a large oil content in the exhaust gas.
4、 What are the reasons for insufficient exhaust?
1) The relief valve is discharged when it should not be discharged. Check whether each drain valve is stuck and deflates all the time.
2) Blockage of the air filter leads to low intake air. Remove the air filter element and conduct a short test run to see if the pressure has increased (for units without safety filter elements, please ensure that debris does not enter the machine head)
3) The rotational speed decreases. (Shaft breakage, belt loss of rotation and slipping, low rated frequency of frequency converter, diesel engine throttle not in place)
4) Capacity adjustment advance action.
5) The intake valve is stuck and cannot be opened or fully opened.
6) Oil subdivision clogged.
7) Inadequate false gas volume: The subsequent equipment gas consumption increases, or the pipeline leaks. There may be geological cracks in the area with drilling rigs. The treatment method is to check the screw air compressor part to prevent problems with the screw air compressor part, and close the ball valve to see if the rated pressure can be reached. For electrically driven units, check whether the current at rated pressure is consistent with the current under normal conditions to determine whether there is a significant change in air volume.
8) Measure the air volume and eliminate the problem of screw air compressor.
5、 What are the simple methods for measuring gas volume? How to operate and calculate
However, for on-site conditions that cannot meet the test requirements, the more direct method is to use the tank filling method to roughly measure the exhaust volume, as follows:
1) Ensure that there are no longer pipes or other equipment pipes that affect the volume from the screw air compressor to the air storage tank. If any, calculate the volume.
2) There is no air leakage between the gas storage tanks, and the gas storage tanks have closed valves to hold the pressure, while ensuring that the valves do not leak internally. The pressure gauge on the air reservoir is in good condition.
3) The screw air compressor capacity adjustment should preferably fail to prevent the capacity adjustment from functioning during testing and affecting the measured value.
4) The frequency conversion or belt conveyor shall ensure that during the testing process, at the rated rotational speed of the machine head, there shall be no reduction in the rotational speed due to the frequency conversion action or the belt slipping affecting the rotational speed.
5) The initial pressure should preferably be above the opening pressure of the pressure maintaining valve in order to prevent the pressure maintaining valve from not opening from affecting the calculation, and also avoid the impact on the gas volume calculation during the startup loading process.
6) After meeting the above conditions, close the vent ball valve of the air storage tank, open the screw air compressor, and hold the stopwatch. For example, the opening pressure of the machine pressure maintenance valve is 4 kgf, and the rated pressure is 10 kgf. It is best to calculate the time consumed by the air storage tank from P1=4.5 kgf to P2=9.5 kgf, T=0.5 (min), and the volume of the air storage tank is V=2m ³， The formula for the displacement of the screw air compressor is Q=V (P2-P1-1)/T=2 × （9.5-4.5-1）/0.5=16m ³/ min。 The above formula ignores the temperature effect. If there is a significant difference in gas temperature before and after tank filling, the temperature should also be taken into account in the calculation.

The above content is organized by Superb heater Company, super heater. Mainly professional production: industrial heating elements, temperature measuring elements, production equipment, accessories, and raw materials such as tubular heaters, tubular heaters, belt heaters, ceramic heaters, silicone rubber heaters, thermocouples, etc.

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