What are the Protection Measures for the Compressor?

Why do Compressors Need to be Protected?

When the compressor is running, some abnormal conditions may occur, such as too high discharge pressure, too low suction pressure, insufficient oil pressure, overheating of the motor, excessive liquid into the cylinder, etc. When abnormal conditions occur, the compressor will be damaged if there are no protective measures.

The protection measures taken for the compressor can be divided into four categories.

1. to prevent liquid shock
2. Pressure protection
3. Protection of built-in motor
4. Temperature protection

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Prevention of Liquid Strikes

When the liquid into the cylinder is too much, too late to discharge from the exhaust valve, the cylinder will appear liquid strike, liquid strike when the very high pressure generated by the cylinder, piston, connecting rod ....... and other parts damage, so need to take a series of protective measures.

1. False cap

The valve assembly is pressed tightly with a spring at the end of the cylinder to form a false cap. When the pressure in the cylinder is too high, the exhaust valve will be jacked up, the liquid will be released and the pressure in the cylinder will be reduced rapidly.

2. Oil heater

The lubricating oil of the crankcase is dissolved with refrigerant, and the dissolved amount increases when the ambient temperature is low. When the compressor starts, the pressure in the crankcase suddenly decreases, a large amount of refrigerant vaporizes, the lubricating oil is foamy and is sucked into the cylinder, causing liquid strike. Using oil heater to heat up the lubricant before starting to reduce the amount of refrigerant dissolved in the lubricant is an effective measure to avoid liquid strike.

3. Gas-liquid separator

The gas-liquid separator shown is also called the reservoir. The gas-liquid mixture from the evaporator is separated in the gas-liquid separator, and the gas enters from the upper part of the outlet tube and exits from the lower part. The separated liquid accumulates at the bottom of the separator, where the liquid refrigerant is heated and vaporized into the upper part of the outlet tube, and the lubricant that cannot be vaporized flows into the outlet tube from the return hole and then into the compressor.

Pressure Protection

1. Suction and discharge pressure control

When the compressor is running, due to the system or the compressor itself, the exhaust pressure may be too high or suction pressure is too low, for this reason need to control the suction and exhaust pressure.

The common controller is not high and low pressure pressure controller, which consists of high pressure control part and low pressure control part.

When the exhaust pressure exceeds a given value, the high pressure control part of the action, cut off the compressor power to stop; suction pressure is lower than a given value, the low pressure control part of the action, cut off the compressor power to stop. Compressor shutdown; will also be issued at the same time the sound and light alarm signal.

2. Safety valve

In order to prevent the refrigerant from leaking to the atmosphere, a closed safety valve is adopted. The upper side of the valve disc bears the exhaust pressure, and the lower side bears the suction pressure and the spring force.

When the exhaust pressure is too high, the valve disc moves downward and opens the lateral hole in the lower part of the valve seat, and the high pressure gas flows into the suction chamber through this side hole and the lateral hole on the valve body.

When the exhaust pressure is lower than the specified value, the valve disc moves upward under the action of suction pressure and spring force to close the exhaust pipe. The opening pressure of the safety valve is adjusted by bolts.

3. Safety membrane

The safety diaphragm is installed between the suction and exhaust cavities. When the pressure difference between suction and exhaust exceeds the specified value, the diaphragm will break and the exhaust pressure will be reduced. The screen is used to catch the broken diaphragm to protect the compressor.

4. Lube oil differential pressure controller

The difference between the oil pressure at the outlet of the oil pump and the oil pressure in the crankcase of the lube oil pressure differential system. In order to protect the compressor moving parts of good lubrication, and to ensure that some compressor air delivery control mechanism (such as: hydraulic - tie rod control mechanism) of the normal action, must controller on the low pressure inlet and high pressure outlet connected.

When the pressure difference between the hydraulic pump inlet and outlet is too high or too low, the controller action, cut off the compressor power, the motor stops rotating.