Common causes of compressor failures and troubleshooting methods
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This post was last edited by *aoye613 on 2010-1-5 19:34. What are the reasons for compressor bearing burnout? The common reasons for tile burning are as follows: (1) Insufficient oil level in the oil pan (or crankcase) or blocked oil passages, resulting in poor lubrication. (2) Oil pressure is too low. The normal oil pressure should generally be between 1.5 and 3 kg/cm2. If the oil pressure drops below 0.8 kg/cm2, the machine should be stopped immediately for inspection; otherwise, bearing burnout can occur. (3) The mating contact surface between the bearing shell and the shaft journal does not meet the required standards. Generally, the contact area should be no less than 75%, with the contact points distributed evenly ； The fit clearance between the bearing shell and the shaft journal is either too large or too small, preventing the oil from forming a proper oil film during lubrication and resulting in poor lubrication. (4) If the ellipticity of the journal exceeds certain limits, it also prevents the formation of a proper oil film during lubrication, resulting in inadequate or poor lubrication. (5) Wear on the back of the large end of the connecting rod prevents the bearing shell from fitting tightly against the large end of the connecting rod, which leads to wear of the connecting rod bearings. (6) The quality of the bearing bush alloy is not up to standard; the alloy does not fit tightly against the backing bush. (7) The centers of the main bearing shells are not aligned, which causes the crankshaft to rotate within these bearings in such a way that the oil film is thick or thin in some areas, or friction occurs; in severe cases, this can lead to damage to the bearings.
This post was last edited by *aoye613 on 2009-12-23 19:54. What are the various lubrication methods used for compressors? Depending on the characteristics of the compressor’s structure, different methods can be used for lubrication. The following are the various approaches: 1. Pressure lubrication – In this method, mechanical devices such as oil pumps or injectors are used to apply lubricant under pressure to the relevant parts; it is also known as forced lubrication. This method is used in both large and medium-sized crosshead compressors. 2. Splashing lubrication method -- An oil injection rod mounted on the connecting rod sprays oil, causing it to splash onto various lubrication points; as a result, the cylinder and the moving mechanisms can only use the same type of lubricant. This method is commonly used in small compressors without crossheads. Its drawback is that the engine oil is difficult to filter, and the oil level must be strictly controlled. 3. Spray lubrication method–The oil mist sprayed is carried by gas to the lubrication locations such as cylinders; ultra-high pressure compressors, vane compressors, and screw compressors all use oil spray lubrication. 4. Oil drip lubrication method -- Using an oil cup and oil delivery pipes to supply lubricant to the components that need it, or adding lubricant regularly with an oil can. 5. Oil ring lubrication method -- A rotating shaft drives an oil ring that is fitted loosely around the shaft; this oil ring carries oil from the oil reservoir to the bearings, enabling circular lubrication.
After being used for a certain period of time, the quality of lubricating oil is affected by various factors, which requires it to be replaced regularly: 1. Metal shavings worn off from the friction surfaces due to wear and tear； 2. Dust and other hard particles brought in by air ； 3. Molding sand that was not carefully removed from the casting ； 4. The paint layer on the machinery has peeled off ； 5. Moisture is generated in the lubricant during the cooling process, causing the oil to deteriorate ； 6. The temperature of the lubricating oil and other factors in circulating lubrication cause its lubricating performance to gradually decline. The aforementioned debris easily forms an abrasive paste-like substance in the lubricant, contaminating it and drastically accelerating the wear of the machine’s friction surfaces. Therefore, if the lubricating oil in the machine deteriorates to the levels specified below over time, it should be replaced with fresh oil. If no testing equipment is available to conduct such checks, the oil should be replaced every 2000–3000 hours. And thoroughly clean the oil supply equipment and all lubrication points.
1. The clearance between the piston rod and the filler is too small； 2. Deflection occurs during the assembly of the piston rod and the packing ； 3. Rough surface of the piston rod ； 4. Dry friction caused by dirt in the lubricating oil for the piston rod and filler, or insufficient lubricating oil ； 5. Impurities mixed in the gas within the filler and in the oil ； 6. The metal disc seal in the stuffing box cannot be held in place and cannot move freely ； 7. The stuffing box equipped with a cooling device does not cool properly ； 8. When the stuffing box is assembled onto the machine body, the bolts are not tightened properly, causing the piston rod to tilt; this results in increased friction between the metal discs in the stuffing during operation, leading to heat generation. Exclusion methods: 1. Reassemble the packing and adjust its clearance appropriately ； 2. The piston rod must not be skewed when reassembled ； 3. Install the reground piston rod accurately ； 4. Clean and change the oil, adjust the oil supply volume ； 5. Clean the gas and oil ； 6. During installation, test it to ensure smooth movement and that a certain gap is maintained as specified ； 7. Check and adjust the cooling of the packing box ； 8. Recheck the packing box and correct its tilt.
The reasons why a bearing reaches temperatures above normal levels during operation may include: 1. Uneven fitting between the bearing and the shaft journal, or an insufficient contact surface (too small a fit clearance), resulting in excessive pressure per unit area; this situation occurs mostly during the trial run of a new machine or after replacing the bearing shells； 2. Bearing misalignment or crankshaft bending, warping ； 3. Poor quality of bearing shells, lubricant of inappropriate quality (low viscosity), or blocked oil passages. The supply pressure of the gear oil pump is too low, and there are interruptions in the oil supply, resulting in a lack of oil in the bearing shells and thus dry friction ； 4. The bearing contains debris, has too much lubricant, or the lubricant is too dirty ； 5. The bearing shells are unevenly over-worn ； 6. During compressor installation, the coupling between the main shaft and the main shaft of the motor (or diesel engine) was not aligned properly; the error was too large, resulting in the two shafts tilting. Exclusion method 1: Use the coloring method to scrape and polish the bearing shells so that their contact surfaces meet the required standards, thereby improving the specific pressure per unit area ； 2. Adjust its clearance appropriately, check for bending or twisting of the crankshaft, and replace it with a new one or repair it as necessary ； 3. Use shaft bearings of suitable quality, inspect the oil delivery pipes and gear oil pumps, employ lubricants that meet the required standards, and check and adjust the oil pumps to ensure that the pressure is at the desired level ； 4. Clean and replace with new engine oil, and adjust the oil pressure ； 5. Replace with new bearing shells ； 6. The concentricity between the two machines must be accurate, and the tolerance values for leveling must comply with those specified in the machine’s manual. Especially when a rigid connection is used to link the compressor and the motor, it is crucial to pay attention to alignment.
An increase in oil temperature during the lubrication of the compressor’s moving parts may be caused by the following reasons: 1. Poor quality or contamination of the lubricating oil； 2. The assembly clearance of the moving mechanism components (crosshead, connecting rod, bearings, crankshaft bearings, etc.) is too small, or there are hard metal particles trapped in between ； 3. Poor combined clearance at various lubrication points ； 4. The viscosity of the oil is not suitable for lubricating this machinery ； 5、There is too much dirt in the water pipes of the oil cooler, and this blockage prevents the lubricating oil from being cooled. Exclusion methods: 1. Replace with lubricant that meets the specifications ； 2. Readjust the clearance of the moving mechanisms to meet the specified fit standards; be careful not to let any small metal particles fall in during assembly. 3. Adjust the clearances at all lubrication points to the specified values ； 4. Clean the lubricating oil cooler; if the amount of cooling water is low, it can be increased.
1. Large clearance in the main shaft bearing shells； 2. Large clearance between the big end bearings of the connecting rod ； 3. Large inner circular clearance in the connecting rod cap bearing shells. 4. Loosening due to hot fitting of the crosshead bearing shells and connecting rod cap bearing shells ； 5. Loose double-headed bolts ； 6. Loose piston rod nut ； 7. Loose piston nut ； 8. Loose crankshaft and coupling ； 9. Large clearance between the crosshead bearing and the crosshead slide ； 10. Arc wear of the crosshead slider. Exclusion methods: 1. Replace the spindle bearings to ensure that their clearance meets the values specified in the machine’s manual ； 2. Replace the big end bearings of the connecting rod so that the clearance meets the values specified in the machine’s manual. 3. Replace the small end bearings of the connecting rod so that the clearance meets the values specified in the manual ； 4. Crosshead bearings, rod end bearings ； Sufficient allowance for interference is provided for the outer diameter tolerance ； 5. Tighten the double-headed bolts to prevent loosening ； 6. Tighten the piston rod nut and secure the washer firmly ； 7. Tighten the piston nut appropriately ； 8. Electroplated crankshaft, with sufficient interference fit left ； 9. Bushing adjustment clearance ； 10 Redress the slider’s curved surface and adjust the clearance
Knocking sounds inside the cylinder can be caused by: 1. Wear of the piston or piston rings； 2. Piston ring stuck or piston ring broken ； 3. Mechanical debris has fallen into the cylinder ； 4. Wear of the cylinder or cylinder liner ； 5. The crankshaft-conrod mechanism is not aligned with the centerline of the cylinder ； 6. The piston rod is bent or the piston rod nut is loose ； 7. The clearance volume of the cylinder is too large ； 8. Excessive lubricating oil or high water content in the gas leads to water hammer phenomenon ； 9. Poor cooling, lubricant coking ； 10. Water from the cylinder water jacket leaks into the cylinder ； 11. Noise is generated due to faulty operation of the intake valve and exhaust valve ； 12. The piston or pin of the valve forcing device is loose ； 13. Damaged filler. Exclusion methods: 1. Repair the piston or replace the piston rings; 2. Remove mechanical impurities and accumulated oil and water from the cylinder ； 3. Adjust the lubrication of the cylinder; enhance cooling if necessary ； 4. Check and adjust the concentricity of the crankshaft-conrod mechanism and the cylinders ； 5. Adjust the piston rod, and tighten the piston rod nut and piston nut ； 6. Adjust the clearance volume of the cylinder appropriately ； 7. Inspect and repair the water jackets of the cylinders and cylinder heads, and replace the gaskets. 8. Repair or replace the valve seats. 9. Inspect and repair the valve lifting mechanism ； 10. Replace the packing.
The reasons for the gradual decrease in oil pressure in the oil pump are as follows: 1. The temperature of the oil keeps rising； 2. The oil filter is gradually clogging ； 3. The oil suction pipe is leaking or clogged ； 4. Air enters the oil pump ； 5. Reduced oil pump speed (belt-driven) ； 6. Oil pump oil sump plug ； 7. Gear wear in the oil pump ； 8. Excessive moisture mixed in with the oil ； 9. Decrease in lubricant viscosity (oil is too thin) 10. Malfunctions in the oil safety valve, oil suction valve, and oil return valve ； 11. Oil pipeline rupture ； 12. Excessive wear of the shaft bushing due to press-fitted lubrication ； 13. The oil pressure gauge connection pipe is blocked or the gauge is malfunctioning ； 14. The fuel level in the tank is low. Exclusion method: 1. Cool the oil temperature appropriately to normal levels ； 2. Clean the oil filter, oil suction pipe, and oil suction valve ； 3. Check all connections to eliminate oil leakage ； 4. Inspect and repair the oil pump, replace worn gears, and adjust the speed ； 5. Check the oil safety valve and return valve and make appropriate adjustments ； 6. Maintain the tightness of the oil pump and oil pipes ； 7. Remove water accumulated in the oil or replace it with lubricating oil of appropriate viscosity ； 8. Clear the oil pipe connected to the pressure gauge, and check whether the oil pressure gauge is malfunctioning ； 9. Check whether the bearing shells are over-worn ； 10. Add fuel if the tank level is low.
The main reasons why the oil pump does not deliver oil are as follows: 1. Improper assembly of the oil pump or it running in reverse； 2. Air enters due to an imperfect seal in the oil pump housing ； 3. Air leakage caused by an imperfect oil suction pipe system ； 4. The oil suction pipeline is blocked ； 5. The packing gland of the oil pump is not airtight ； 6. The oil filter is clogged or the oil suction check valve is malfunctioning ； 7. The fuel level in the tank is too low. Exclusion methods: 1. Check and repair the oil pump ； 2. Clean and repair the oil filter, oil suction valve, and oil suction pipeline ； 3. Eliminate any leaks to prevent air leakage ； 4. Remove air from the oil suction pipe and oil pump using the oil filling method ； 5. Maintain a certain oil level in the tank.
The reasons for oil leakage from the packing are as follows: 1. The springs that hold each section of the packing are broken； 2. Piston rod wear ； 3. Scratches and abrasions on the piston rod and sealing ring. 4. Wear of the sealing ring and no clearance at the ring wall. Solutions: 1. Replace the spring ； 2. Replace or chrome-plate the piston rod for repair. 3. Replace the piston rod and packing rings. 4. Replace the sealing ring.