Scientific start - up and shutdown operations, along with proper long - term shutdown maintenance, play a vital role in prolonging the service life of refrigeration compressors and ensuring the steady operation of industrial refrigeration systems. Component wear, refrigerant leakage and other faults are often caused by improper operation and insufficient maintenance during shutdown, which raises maintenance costs and impacts the normal functioning of cold storage and industrial cooling projects.

Before start - up, one must check the following:

• The power supply voltage (ensuring it is within ±5% of the rated voltage) and the firmness of electrical connections to prevent poor contact.
• The oil level of the compressor (keeping it between the upper and lower marks of the oil sight glass).
• The refrigerant pressure (suction pressure should be 0.3 - 0.5MPa, discharge pressure should be 1.2 - 1.5MPa).

After confirming that all parameters are normal, start the compressor without load, and gradually adjust the load to the rated value within 5 - 10 minutes to avoid impact damage to the motor and mechanical parts.

For normal shutdown, first reduce the compressor load to the minimum, then cut off the power supply after the unit runs idle for 3 - 5 minutes to ensure that the refrigerant is fully recovered to the condenser.

In the case of emergency shutdown due to faults, immediately cut off the power supply, record the fault phenomenon, and carry out a comprehensive inspection before restarting to avoid secondary damage.

It should be noted that frequent start - up and shutdown (more than 3 times per hour) should be avoided, as this will greatly shorten the service life of the compressor.

For long - term shutdown (more than 1 month), overall maintenance measures are crucial:

1. Completely recover the refrigerant in the system to the condenser and close the suction and discharge valves to prevent refrigerant leakage.
2. Drain the lubricating oil in the compressor, clean the oil tank and filter, and refill with new lubricating oil that meets the specifications (selecting oil with viscosity grade ISO VG 46 under normal temperature conditions).
3. Clean the surface of the compressor, condenser, and evaporator, and cover the unit with a dust cover to prevent dust and moisture from entering, which may lead to corrosion of metal components.

Regular inspection during long - term shutdown is also indispensable:

• Check the tightness of valves and pipe connections every 2 weeks.
• Start the compressor for idle operation for 10 - 15 minutes every month to ensure the flexibility of mechanical parts and avoid rusting.

These maintenance measures can effectively decrease the failure rate of refrigeration compressors after restart and ensure their stable operation in industrial refrigeration situations.