If the working oil temperature of the oil-injected screw machine is too low, it will affect the decomposition of oil and water, causing oil emulsification and reducing the life of the lubricant; while too high oil temperature will reduce the gas transmission coefficient and increase power consumption, the viscosity of the lubricant will decrease, causing abnormal friction loss of the bearing, and even bearing loose beads. Excessive temperature will also cause the lubricant to thermally decompose under the catalysis of metal, generating free carbon, acids and moisture (carbon deposition) that are harmful to the work, and in severe cases, the screw will be stuck. There are many situations that cause high temperature of the air compressor. The correct analysis method can help to quickly find the cause of the high temperature failure.
A.9.1 Fault phenomenon
The exhaust temperature of the air compressor is high, the air compressor alarm signal appears, and the air compressor stops due to failure.
A.9.2 Cause Analysis
The oil circulation process can be divided into two processes, namely, engine head-oil and gas barrel-temperature control valve-oil filter-engine head. When the temperature exceeds the action value of the temperature control valve temperature sensing element (generally it will act at 71℃), the oil circuit circulation process is: engine head-oil and gas barrel-temperature control valve-oil cooler-temperature valve (merge)-oil filter-engine head.
Next, analyze the temperature difference of the connection pipes (A, B, C, D pipes) of the temperature control valve to determine the source of the high temperature. See Figure A.1 for the schematic diagram of the air compressor lubricating oil flow.
Figure A.1 Schematic diagram of air compressor lubricating oil flow
(1) When the temperature is high, first rule out whether the engine itself is faulty. The judgment method is: understand whether the engine has been overhauled recently, whether the lubricating oil is genuine, whether the unit lubricating oil is too little, turn the rotor by hand after shutting down, and feel whether it is stuck. After starting up, check whether the vibration of the whole machine is too high and whether there is any abnormal noise from the engine. If the high temperature is caused by the above reasons, the oil circuit should be normal, and the temperature values of points A and C of the oil pipe are close. Because the equipment is at high temperature, the temperature control valve is in full working state, and the temperature difference of points D and B is also close, and is significantly lower than that of points A and C (Note: points D and B are connected in any case. Some temperature control valves have only three interfaces, and point D is directly connected to pipe B with a tee).
Analysis: At this time, the temperature control valve is in normal state. The lubricating oil flows from the oil and gas barrel to points A and C, and flows to points D and B after being cooled by the cooler. After the oil meets at points D and B, it flows to the oil filter for oil purification and finally returns to the head. Therefore, the oil temperature difference at this time should be CA≈CC. Because the equipment is in a high temperature state, the temperature control valve is fully open, so CD≈CB,CA 、 CC ＞ CD、CB .
(2) At high temperature, if the temperature of points D and B is too low than that of points A and C, check whether the oil filter is blocked.
Analysis: The oil filter is blocked. The oil circuit is the same as described above, except that the oil filter is blocked, which reduces the flow of lubricating oil. At this time, the oil at points D and B stays in the cooler for a long time to cool. The temperature of points D and B is very different from that of points A and C. The high temperature is because there is too little oil to the head, which cannot meet the oil volume required for head cooling.
(3) At high temperature, the temperature of point D is slightly lower than that of point B, and the temperature of point B is only slightly lower than that of points A and C. The valve core of the temperature control valve cannot be fully opened. At this time, the temperature control valve should be checked.
Analysis: The above analysis shows the oil circuit in a normal state. If the temperature of point D is slightly lower than that of point B, and the temperature of point B is only slightly lower than that of points A and C, it proves that the valve core of the temperature control valve is not fully opened. At this time, the lubricating oil should flow from the oil and gas barrel to point A, part of the lubricating oil should flow to point C, and part of the lubricating oil should flow to point B. The oil at point C is cooled by the cooler and flows to point D and point B, and then flows to the engine head through the oil filter, so A≈CC＞CB＞C1 .
(4) At high temperatures, the temperatures of points D and B are slightly lower than those of points A and C. At this time, check the cooler cooling system.
Analysis: The cooler has poor heat dissipation effect. At this time, the lubricating oil should flow from the oil and gas separation tank to points A and C, flow to points D and B through the cooler, and then flow to the engine head through the oil filter. Because the cooler cannot fail 100%, there is still a slight temperature difference between A and C and D and B, so CA≈CC＞C1≈CB 。
(5) At high temperatures, if the temperatures of points A, B, and D are close, and the temperature of point C is significantly lower than that of points A, B, and D, it proves that the temperature control valve is not working.
Analysis: The temperature control valve is not working. At this time, the oil circuit flows from the oil-gas separation tank to point A. Because the temperature control valve is not working, the oil at point A flows directly to point B through the oil filter. Because the pipes of points B and D are connected, and points D and C are connected but there is a cooler in between, it is solid CA≈CB≈CD＞CC; the common reason why the temperature control valve does not work is carbon deposits and jams.
(6) At high temperatures, if the temperature values of points A, B, C, and D are close, there are many reasons, such as the radiator not working, the cooling fan not working, etc.
Analysis: The radiator is not working (such as serious fouling on the radiator wall). At this time, the lubricating oil flows from the oil-gas separation tank to points A and C, and then flows to points D and B through the cooler. After the oil merges at points D and B, it flows to the oil filter for oil purification and finally returns to the head. Because the cooler does not play a heat dissipation role, the solid CA≈CC≈CD≈CB .
