When the Hitachi screw compressor is running, some abnormal conditions may occur, such as the exhaust pressure is too high, the suction pressure is too low, the oil pressure is insufficient, the motor is overheated, excessive liquid enters the cylinder, etc. When abnormal conditions occur, the compressor will be damaged without protective measures. The protection measures taken for the compressor can be divided into four categories: 1. Liquid shock prevention 2. Pressure protection 3. Built-in motor protection 4. Temperature protection.
1. Prevent liquid slugging
When too much liquid enters the cylinder of a Hitachi screw compressor and cannot be discharged from the exhaust valve in time, liquid slugging will occur in the cylinder. The high pressure generated during liquid slugging will cause The cylinder, piston, connecting rod and other parts are damaged, so a series of protective measures need to be taken.
False cover
The lift limiter of the strip exhaust reed valve of Hitachi screw compressor is pressed against the valve plate with a pressure relief spring. When the pressure in the cylinder increases due to liquid slugging, the lift limiter is lifted up, causing the pressure in the cylinder to drop. After the liquid shock disappears, the pressure relief spring presses the lift limiter against the valve plate, and the compressor continues to operate.
Oil heater
The lubricating oil of the crankcase contains refrigerant, and the amount dissolved increases when the ambient temperature is low. When the compressor starts, the pressure in the crankcase suddenly drops, a large amount of refrigerant vaporizes, the lubricating oil becomes foamy and is sucked into the cylinder, causing liquid shock. The oil heater is used to heat the lubricating oil before starting, and reducing the amount of refrigerant dissolved in the lubricating oil is an effective measure to avoid liquid hammering.
, Gas-liquid separator
The gas-liquid mixture from the evaporator is separated in the gas-liquid separator. The gas enters from the upper part of the outlet pipe and flows out from the lower part. The separated liquid is stored at the bottom of the separator. The liquid refrigerant is heated and vaporizes into the upper part of the outlet pipe. The lubricating oil that cannot be vaporized flows from the return hole into the outlet pipe and then enters the compressor.
2. Hitachi screw compressor pressure protection
Control of suction and discharge pressure
When the compressor is running, discharge may occur due to system reasons or the compressor itself. The air pressure is too high or the suction pressure is too low. For this reason, the suction and exhaust pressures need to be controlled. Common controllers are high and low pressure pressure controllers, which consist of a high-pressure control part and a low-pressure control part. When the exhaust pressure exceeds the given value, the high-pressure control part acts to cut off the power of the compressor and shut down the compressor. When the suction pressure is lower than the given value, the low-pressure control part acts to cut off the power of the compressor and shut down the compressor. When the compressor stops, it will also send out an audible and visual alarm signal at the same time.
Safety Diaphragm for Hitachi Screw Compressor
When the suction and exhaust pressure difference exceeds the specified value, the diaphragm will rupture and the exhaust pressure will decrease. The filter is used to capture broken diaphragms to protect the compressor.
Lubricating oil differential pressure controller
The difference between the oil pressure at the oil pump outlet of the Hitachi screw compressor lubricating oil differential pressure system and the oil pressure in the crankcase. In order to protect the good lubrication of the moving parts of the compressor and ensure the normal operation of some compressor gas delivery control mechanisms (such as hydraulic pull rod control mechanisms), the low-pressure inlet and high-pressure outlet on the controller must be connected. When the pressure difference between the inlet and outlet of the hydraulic pump is too high or too low, the controller acts to cut off the power of the compressor and the motor stops rotating.
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Contact Luo Lifeng
Hitachi screw compressor 100ASCCW-Z