1 The meaning of oil-free lubrication The air compressor consumes a large amount of lubricating oil during operation. The lubricating oil enters the high-temperature cylinder and easily decomposes carbon. This is the basic condition for causing the air compressor to burn and explode during operation, especially in the fuel tank. The mechanical oil has a low flash point and is often easily pumped into the cylinder through the stuffing box, which is very dangerous. For some old, old and miscellaneous equipment, the quality of maintenance is not up to standard, the packing box is not well sealed, and many oil spills are caused, which is very uneconomical. Therefore, the lubrication of the air compressor must be completely modified.
Many mining bureaus in China have carried out research, testing and transformation of oil-free lubrication. Shanjiaoshu Mine has also been continuously reformed in its application and has achieved success. In the process of reform, the lubrication of the cylinder part of the air compressor was mainly modified. The piston ring made of PTFE synthetic material replaced the original metal piston ring and achieved good economic results. When the air compressor is in operation, the cylinder part is oil-free and can be used without compressor oil. In the aspect of saving fuel, saving the efficiency of the air compressor, reducing the exhaust temperature, and increasing the safety of the air compressor during operation, the superiority of oil-free lubrication is fully demonstrated.
2 Principle and characteristic principle of oil-free lubrication Oil-free lubrication, as its name implies, is made of a synthetic material with high wear resistance, high temperature resistance and low friction coefficient. Instead of metal fittings, it can be used without lubrication. The cylinder part of the air compressor is oil-free, and the piston ring is made of a polytetrafluoroethylene composite material. Polytetrafluoroethylene is a kind of plastic which has self-slip effect. Its working temperature is between 180 and 250e. It works for 1000 hours under 250e without significant change in mechanical properties. It has good chemical stability and does not interact with ordinary acids. Good insulation, no moisture absorption, friction coefficient is about 0105. It decreases with increasing temperature, speed, and pressure. Since the PTFE synthetic material is suitable for the working environment of the air compressor, the piston ring of the air compressor is made of this material, and the oil-free lubrication can achieve remarkable effects. Water reducing agent content) fly ash content) stone particle size.
4) The effect of the amount of water reducing agent and the ratio of water to cement on the impermeability is basically the same, followed by the amount of fly ash and the particle size of the stone.
5) The optimum ratio of undisturbed fly ash concrete is A. Characteristics of fly ash and fly ash concrete [M]. Beijing: Science in Beijing: China Building Industry Press, 1985.
The current building materials specification Daquan [S]. Beijing: China's construction industry publishing production experience Coal engineering features the use of Teflon piston rings to achieve oil-free lubrication has the following characteristics: 1 due to the reduction of lubricants, oil leakage is reduced, so easy Achieving a good standard o Because the lubricant is not used in the cylinder, the safety of the air compressor is increased. Due to the high wear resistance of the Teflon piston ring, the maintenance cycle can be extended?
No lubrication, reduced costs, good economics? Compared with metal, it is characterized by low strength, creep and thermal expansion.
3 Lubricating process without oil Because of the above characteristics of oil-free lubrication with PTFE, only oil-free lubrication is achieved on the air compressor in the air compressor, in the cross pin bushing material and the skateboard gasket, especially in The crankshaft lining has not been successfully reformed. The following is a brief description of the process of refining the oil-free lubrication with the cylinder part as follows: Mastering the original data In order to facilitate the comparison before and after the modification, some technical parameters must be collected for the original equipment, such as: cylinder diameter (including high and low pressure cylinders), piston stroke, speed, shaft power, voltage, capacity, load current, displacement, working pressure, fuel consumption, exhaust temperature, etc.
Work to be carried out during the modification process 1) Disassemble and inspect the cylinder: first remove the cylinder head when disassembling, then loosen the piston rod at the crosshead, and then take out the piston and remove the other parts. After the piston is taken out, first check the surface finish of the cylinder. (Because the surface finish of the cylinder has a great relationship to the wear of the Teflon piston ring), the air compressor cylinder with a long deactivation time is prone to rust and must be repaired. The ellipticity should be checked. If the value specified in the standard is exceeded, the cylinder treatment is performed.
2) Turning piston: When modifying, firstly, we must master the dimensions of each part, determine the dressing according to the requirements, and strictly control the turning amount of the piston. Generally, the outer diameter of the piston is less than about 2mm of the cylinder diameter, because the metal ring is oil lubricated. In case of operation, the metal ring is 015 mm lower than the ring groove and the piston is allowed to run on the cylinder wall. Switch to the Teflon piston ring to achieve oil-free lubrication. If the piston bracket runs on the cylinder wall, it will generate high temperature by friction and burn the cylinder mirror surface, causing an accident. Therefore, in the modification of the various parts of the size, repair the piston, must be responsible, not thick and large leaves.
The value of the treatment of each part of the piston of the Shanjiaoshu Mine.
Cylinder cylinders measured size Piston diameter measured rolling turning volume cylinder and piston clearance primary cylinder secondary cylinder 3) secondary cylinder bearing ring groove treatment. After the piston ring is modified, because the piston and the cylinder wall cannot be in direct contact, the low pressure cylinder is vertical and vertical, and the running problem is not big, and the high pressure cylinder is not good, because it is the horizontal piston and the cylinder will sag when reciprocating. The bearing pressure in the lower part of the cylinder is increased. In order to overcome this phenomenon, a bearing ring is mounted on the secondary piston to bear the load. When the Shanli Tree Mine was rebuilt in the 4L20/8 air compressor, the handle bearing ring was expanded from the original 8mm to 18mm in the ring groove of the second cylinder piston near the taper. The car was 8mm near the taper and 2mm away from the other car. The distance between the seal ring and the support ring is only 9mm, and the car is very thin. At the same time, the center of gravity of the piston should be considered. The depth of the groove should be determined according to the thickness of the PTFE ring, because the specifications of the Teflon piston ring Sometimes it is different. If the ring groove depth can be padded at the bottom of the ring groove, it is better to adjust the copper skin.
When carrying the ring in front of the car, in order to ensure a smooth installation, the depth of the original piston ring groove and the thickness of the inter-carrier ring should be carefully measured.
4) The slit pattern and the slit gap of the Teflon piston ring. There are four types of slits in the piston ring: straight cuts, oblique cuts, tower cuts, and compensatory cuts.
Shanjiaoshu Mine adopts oblique incision. In order to overcome the shortcomings of leakage after piston ring incision, two piston rings are installed, the opening is staggered 180b, and two are installed on the left and right sides to increase the carrying capacity. The opening must have a certain The gap is extended to overcome wear and expansion. The gap is large, the leakage is large, the gap is too small, and the two mouths are easy to bite, causing accidents such as expansion of the cylinder. When the Shanjiaoshu Mine is being modified, the opening clearance of the ring is 615mm for the first-stage cylinder sealing ring, and the secondary cylinder sealing ring and the bearing ring are each 5mm.
5) The gap of the Teflon piston ring mainly refers to the backlash and backlash. Why should there be a gap? Because the metal ring and the tetrafluoroethylene ring act as a sealing ring to prevent the water in the cylinder from leaking from the high pressure side. On the low pressure side, it is not possible to straddle back and forth.
The sealing effect is mainly the degree of cooperation between the piston and the cylinder plug, the piston ring and the ring groove, and the opening clearance and opening position of the two piston rings. Because the metal ring has elastic force, and the PTFE ring has small elasticity, the sealing is achieved by the compressed air. The pressure of the backlash and the backlash makes the ring close to the cylinder wall and seals. Pay attention to maintaining the parallelism and concentricity of the sides of the PTFE ring. The size of the side gap should make the piston ring rotate freely.
Match the value.
Cylinder name Piston ring name Side gap Opening clearance Backlash Remarks Level 1 cylinder Upper ring Lower ring Second cylinder Seal ring Support ring 4 After the test run After assembling according to the required clearance size, first turn the car, if it can rotate, It can be put into trial operation. At the beginning of the operation, the lubricating oil was filled for 20 hours to promote the running-in process, and the transfer of the PTFE plastic powder to the cylinder wall was accelerated, thereby forming a gray PTFE film on the cylinder wall, and then the oil was shut down due to the cylinder. A layer of plastic film is attached to the wall surface, and the reciprocating motion between the piston and the cylinder wall is actually the relative motion between the molecules of the plastic itself. It has been proved that the operation is good for a period of time, and the working pressure is compared with that before the modification. The change is small, the exhaust gas temperature drops, and the noise decreases.
Coal engineering production experience air volume / pressure / current / low pressure cylinder temperature / e high pressure cylinder temperature / e cooling water temperature / e first modified before 1818 modified 1915 second modified before 1818 modified 2013 1987 April, mountain foot tree The mine has modified the cylinder part of the 5 air compressor in the Nanjing pressure fan room. After one year of observation, the measured data of the high and low pressure cylinder seal and the thickness and wear of the support ring before and after the modification are shown in Table 4.
Low-pressure cylinder seal ring high-pressure cylinder seal ring support ring before the thickness of the operation of the 12-month measured wear amount of practice: the wear and tear of all parts are normal. According to the measured data of this wear condition, it is estimated that the sealing ring of the high and low pressure cylinder can run for more than 20,000 hours, and the high pressure cylinder support ring can run for 7200 hours. (According to the operation of 18 hours per day, 300 days per year calculation) Teflon The piston ring can run for at least 15 months.
5 Comparison of economic effects before and after modification 511 Saving oil consumption Before the conversion, not only the fuel consumption was much, but also the oil leakage was very serious. After the modification, each machine saved 375g per hour, calculated by 18 hours per day, except for the micro-oil lubrication with 60g. It can also save 61 7kg per day, and it can save fuel by 2010kg for 300 days per year. Each year, each air compressor can save 13065 yuan.
512 to reduce power consumption in the same pressure, air volume and voltage, the average current before modification is 135A, 128A after modification, preliminary calculation, energy saving 120 degrees per day, each year can save electricity million degrees, per degree is calculated according to 0137 yuan It can save 13 yuan in electricity costs a year.
513 parts consumption situation The metal ring used before the modification is 56 yuan per set, the running time is one year, the cost of each set is 106 yuan after switching to the PTFE piston ring, the running time is 15 months, except for the multi-purpose parts 50 yuan. Each year, each company can save 26,335 yuan.
514 Reduces the maintenance workload. In addition to the simple assembly and disassembly, the PTFE piston ring has low friction coefficient, self-slip property, good sealing effect, less air leakage, and greatly reduces the wear on the mirror surface of the cylinder. The maintenance workload is greatly reduced, and the equipment life and maintenance cycle are extended.
The 515 air compressor with modified operation has no oil, and the compressed gas is cleaned, which improves the air supply quality. It is also beneficial to the air compressor pipe and the air moving tool, avoiding the explosion and fire accident caused by the low flash point of the lubricating oil. It will not burn the cylinder due to lack of oil, ensuring safe production.
Machine noise is significantly reduced, improving the working environment and contributing to the health of workers.
6 modified oil-free lubrication should pay attention to several aspects of the 611 before the modification of the relevant data collection before the modification, must be measured on the exhaust volume, exhaust temperature, motor operating current and fuel consumption and other relevant data, the only way In order to identify the modification effect.
612 Carefully handle the matching clearance between the cylinder and the piston. Before the modification, the ellipticity and piston size of the cylinder should be measured. Pay attention to the clearance. After the modification, pay attention to the sound of each part of the machine and the cylinder temperature and the working current of the motor. Is it appropriate to make timely changes?
613 Handling the gap gap problem The opening gap must be reasonable. Since the expansion coefficient of the Teflon piston ring is large, the opening gap must not be too small.
Solution to the 614 sealing problem The sealing of the piston ring and the cylinder is mainly achieved by the assembly gap between the ring and the ring groove. Without these gaps, the proper sealing effect is lost. Therefore, the size of the backlash and backlash should be noted. Can not be ignored.
The 615 Teflon piston ring's micro-oil-lubricated PTFE piston ring can achieve oil-free lubrication, but the micro-oil lubrication can greatly improve the service life of the Teflon piston ring. The so-called micro-oil lubrication is before starting the operation. Or add a few minutes of lubrication before stopping, it has been proved that the implementation of micro-oil lubrication is very beneficial.
616 Checking the test run phase After the modified test run phase, it is necessary to make a good operation record, pay attention to the operation of each department, sum up the experience in time, and adjust it properly to ensure normal operation.
After the 617 modified maintenance work, the high and low valves should be cleaned once in the first month after the modification, to avoid the impact of the powder in the running-in stage.
7 Conclusion Oil-free lubrication with PTFE piston ring not only reduces the cost, but also reduces the probability of safety accidents. It also reduces noise pollution, improves the working environment of workers, and reduces the workload. The production has played a major role.
Production experience coal engineering
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