Principle and troubleshooting of compressor oil pressure differential protection | Oil shortage, oil pump failure, and oil circuit blockage
The oil pressure differential protector is the last line of defense for the lubrication system, monitoring the difference between the outlet pressure of the oil pump and the return oil pressure of the crankcase. If the difference is insufficient, it indicates insufficient oil supply. After a delay, the machine will stop to protect the bearings.
Standard for oil pressure difference of semi closed piston machine: The normal operating oil pressure difference is 0.2-0.4MPa, and the oil pressure difference shutdown protection value is generally set at 0.1MPa, with a default delay of 60 seconds.
The Xiteluo piston engine relies on the main shaft to drive the built-in oil pump. Reverse rotation of the oil pump, clogged oil filter, and low oil level can all cause insufficient oil supply pressure difference and trigger an alarm.
There are two types of oil pressure difference alarms: an alarm at the moment of startup, mostly due to dirty and clogged oil filters, high oil viscosity, and poor low-temperature fluidity; Alarm during operation, mostly due to oil pump wear and lack of oil.
The low-temperature viscosity of POE refrigeration oil increases, and after long-term shutdown and cold start, the oil pressure difference is slowly established. The value of the crankcase heater is reflected here, preheating reduces oil viscosity.
Screw compressors have higher requirements for oil supply pressure difference, and the rotor bearing load is large. It is recommended to maintain a stable operating pressure difference of 0.3-0.5MPa, and the pressure difference protection logic is similar to that of piston engines.
Many maintenance personnel encounter oil pressure difference alarms and directly increase the pressure difference setting or extend the delay to cover up oil pump wear and tear faults, resulting in continuous low oil in bearings and cylinder locking in a short period of time.
Blockage of oil filter element is a common fault point for oil pressure difference. The filter element adsorbs metal powder and impurities, resulting in a smaller oil flow cross-section, a decrease in oil supply flow rate, and a drop in pressure difference.
Foreign trade low-temperature project, equipped with low pour point POE oil, to prevent the freezing of refrigeration oil in the machine room during low temperature, prevent the oil pump from being unable to pump oil, and continuously trigger oil pressure difference alarm.
After the oil pressure difference alarm stops, it is forbidden to start repeatedly. The bearings lack oil film lubrication, and each start will exacerbate the wear of the crankshaft and connecting rod bearings.
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FAQ
1. What is the normal range of oil pressure difference for piston engine operation? 0.2～0.4MPa。
2. How long does the delay of oil pressure differential protection usually last? Conventional 60 second delay.
3. What should be prioritized for troubleshooting oil pressure difference when starting up? The oil filter is clogged and the viscosity of the cold oil is too high.
4. Can the high voltage difference be adjusted to delay the forced startup? Not recommended, it may cause bearing cylinder pulling.
5. What is the normal range of oil pressure difference for screw machines? It is recommended to maintain a stable pressure of 0.3-0.5MPa.
What happens when the oil pump reverses? Unable to establish oil pressure, direct oil pressure difference alarm.
What are the consequences of repeatedly starting the oil pressure difference alarm? The bearing oil film is damaged, causing rapid wear and locking.
