The use and maintenance operation of screw unit
Description of parallel units:
Parallel unit: generally composed of the same type of compressor, but also can be composed of different types of compressors. It can be composed of the same type of compressor, or it can be composed of different types of compressors (such as piston machine + screw machine). As shown below:
2 The role of common components of screw compressors:
Oil drain valve: It is used to replace the compressor oil or drain the oil during maintenance.
Safety valve: used to discharge pressure exceeding the set "setting pressure".
Oil outlet connector: used for piping when installing the oil circuit blocking pin, connected to the inlet of the oil cooler.
Oil inlet connector: Used for piping when installing the oil circuit blocking pin, connected to the outlet of the oil cooler.
Oil path sight glass: Observe the oil flow when the compressor is running.
High oil level window: Observe the high oil level status.
Low oil level window: Observe the low oil level status.
Suction shut-off valve: used during compressor or system maintenance.
Exhaust shut-off valve: used during compressor or system maintenance.
Oil heater: used for heating refrigerating oil.
Economizer interface: used for evaporating temperature below -10°C, which can effectively improve compressor performance.
Oil blocking pin: Install the oil blocking pin when the compressor is connected to an oil cooler.
Low pressure detection valve: used to detect suction pressure and install a differential pressure switch.
Motor liquid spray angle valve: used to connect liquid refrigerant.
Medium pressure liquid injection joint: when the compressor is running at low temperature, it is used to cool the compression chamber piping.
start bypass solenoid valve: used to reduce the load when the compressor starts.
3 screw compressor cooling control:
Two solenoid valves are used to control the temperature of the motor. The solenoid valve 1 starts and closes simultaneously with the compressor.
The solenoid valve 2 is controlled according to the temperature of the motor embedded in the motor. When the temperature of the motor is higher than 80 °C, the solenoid valve 2 is opened, and when the temperature of the motor is lower than 50 °C, the solenoid valve 2 is closed to ensure that less liquid refrigerant can be used To achieve the effect of motor cooling.
4 screw engine lubricating oil system:
The application of oil cooling system can reduce the exhaust temperature and make the system reach higher efficiency. Oil cooling systems can be divided into three categories: refrigerant cooling, air cooling, and cooling water cooling.
icon symbol:
Schematic diagram of air cooling system: As shown in the figure below, this cooling method is indirect cooling, which cools the oil in the oil cooler through the ambient atmosphere.
Schematic diagram of refrigerant cooling system: The oil cooler uses liquid refrigerant as the cooling medium/substance. The basic system is shown below:
Schematic diagram of cooling water cooling system: This cooling method uses a shell and tube heat exchanger and a cold source from an external cooling tower or evaporative cooler. A water pump can be used to circulate the cooling medium water to release heat to the environment in the cooling tower or evaporative cooler. The basic cooling water cooling system is shown below:
The temperature of lubricating oil is an important factor affecting the life of compressor bearings. High lubricating oil temperature will reduce the viscosity of the oil, resulting in lower lubricating ability and heat absorption capacity of the lubricating oil. It is recommended to keep the lubricating oil viscosity above 15ram2/s.
The oil temperature should be kept above the condensation temperature of the system to avoid mixing of refrigerant into the lubricating oil. Equipped with an oil heater to heat the lubricating oil to increase the oil temperature to prevent the compressor from being insufficiently lubricated due to low temperature and excessive viscosity.
5 screw compressor refrigerating oil detection and replacement:
1. Main monitoring indicators:
1) PH value index: the acidification of lubricating oil will directly affect the life of compressor motor, so the acidity of lubricating oil should be checked regularly. Generally lubricating oil must be replaced if the acidity is lower than PH6. If the acidity cannot be checked, the system's filter drier should be replaced regularly to keep the system's dryness in a normal state.
2) Pollution degree index: If the pollutants in 100ml of refrigerating oil exceed 5mg, it is recommended to replace the refrigerating oil.
3) Water content: more than 100ppm, the refrigerating oil needs to be replaced.
2, replacement cycle:
Generally, the lubricating oil must be checked or changed every 10,000 hours of operation. After the first operation, it is recommended to change the lubricating oil and clean the oil filter every 2500 hours.
Note: The operating period is calculated based on 16 hours of operation per day.
3, the operation of replacing lubricating oil:
1.Recover the system refrigerant to the condenser side, remove the refrigerant in the compressor, and discharge the refrigerant oil from the oil drain valve of the compressor.
2.The lubricating oil of the compressor is discharged from the drain valve on the oil filter. When the lubricating oil is nearly exhausted, add a certain amount of nitrogen from the detection joint of the high-pressure end of the compressor, use the pressure to accelerate the lubricating oil discharge, and stop the injection Pressure, close the drain valve. Then remove the oil filter of the compressor, release all the lubricating oil in the oil tank, and then clean the oil filter and install it firmly.
3.Add lubricating oil according to the standard amount of the compressor. At the same time, pump down the system. It is recommended to select high (low) pressure side angle valve or other relatively high point for the contact of the vacuum pump to prevent pumping refrigerating oil from damaging the vacuum pump. When performing vacuum pressure holding or leak checking, observe whether the pressure rebounds.
4. Inject lubricating oil, connect it to the drain valve with a clean plastic pipe, and put the other end of the plastic pipe into the oil drum (the plastic pipe is placed at the bottom of the oil drum). The oil drum should be closed when filling oil to reduce air pollution to oil.
