Abstract: This paper introduces how to choose refrigerating machine lubricating oil, and analyzes and explains the fault and maintenance of refrigerating machine.
Key words: refrigerating machine; Lubrication system; maintenance
First, the selection of refrigerant oil
The special working nature of refrigerating machine also puts forward the corresponding requirements for its lubrication, so the special refrigerating machine lubricating oil is developed.
When choosing lubricating oil, it should be analyzed comprehensively according to the type of refrigerating machine, the type of refrigerant, its evaporation temperature and working conditions (speed, load, environment, etc.) to determine the specification or brand of lubricating oil.
Small low speed (average linear speed is less than 2m/s) two-cylinder piston freezer can choose N15 or N22 freezing oil; Large, medium high speed (average speed is greater than 3m/s) multi-cylinder piston freezer can choose N32 or N46 freezing oil; N68 freezer oil can be selected for piston type chillers with high exhaust temperature, large load and particularly bad service conditions; N32 or N46 freezer oil can be used for screw type refrigerator with oil injection lubrication; Small dry type (non-injection lubrication) screw freezer and centrifugal freezer, because the lubricating oil may not contact with the refrigerant, according to the load of the gearbox and main bearing can choose N32 or N46 frozen oil, also can choose the viscosity pole equivalent to L-TSA32 or L-TSA46 gasoline oil.
Two, refrigeration machine lubrication system failure and maintenance
The main signs of normal operation of refrigerator lubrication system are:
1. The indication of oil pressure gauge is stable. The indication pressure is 0.05-0.3MPa higher than the suction pressure for piston type refrigerator, and 0.2-0.3MPa higher than the condensing pressure for screw type refrigerator.
2. The oil temperature in the crankcase should be kept between 10-65℃, and the most suitable working temperature is 35-55℃.
3. The oil level in the crankcase should be high enough and stable for a long time.
4. The filter element of the oil filter should not be blocked, and the fine oil filter with differential pressure should have a blocked message indication.
The most common faults of lubrication system are oil pump no pressure, pressure regulation failure and pressure gauge pointer violent swing. The main reasons are:
1. The oil temperature in the crankcase is too low, the refrigerant oil is too large, the filter screen of the pump inlet is too dense, the filter element is blocked and the oil level is too low, the oil pump suction is difficult, resulting in the suction phenomenon.
2. The oil pump works for a long time, the wear of the pump is serious, the internal leakage is too large, and the volume effect is significantly reduced.
3. The regulating valve spool is stuck in the open position or the regulating valve spring fails.
4. Serious leakage of the system.
The fault of the lubrication part of the refrigerator does not belong to the problem of the lubrication system itself, but it can also lead to the failure of the system. Such as cylinder piston ring structure selection and processing and assembly can cause a large number of oil running phenomenon; Abnormal leakage at the shaft seal will also make the crankcase oil level decreased significantly, resulting in the suction of the oil pump; Connecting rod size head bearing and front and rear main bearing assembly clearance is too small, lubricating oil is too dirty and lubricating oil deterioration will increase the friction and wear of moving parts; When the cylinder wear is serious, there will be high and low pressure gas channeling, leading to crankcase heating, oil temperature rise, lubricating oil clearance reduction, resulting in a vicious cycle of lubrication conditions and lubrication system failure. Therefore, the fault analysis of the lubrication system should be comprehensive, that is, in addition to the problems of the lubrication system itself should also be checked, analyzed and judged from the operating condition of the refrigerator.
Maintenance of lubrication system should pay attention to the following points:
1. Check the oil quality regularly according to the oil change index specified in the frozen lubricating oil, and replace or supplement the filtered new oil.
2. Replace or clean filter element, pipe and crankcase regularly.
3. Pay attention to observe whether the oil level, oil temperature and oil pressure are normal in daily spot inspection.
4. In the middle and overhaul, attention should be paid to check and adjust the end clearance of the oil pump, and the pump should be changed if necessary. The end clearance of the pump is about 0.03-0.08mm depending on the size and specifications. The specific value can be referred to the assembly technical requirements and factory regulations of the pump.
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