How to prevent the refrigeration compressor from reversing

How to prevent the refrigeration compressor from reversing

Reverse rotation is strictly prohibited after the refrigeration compressor is stopped. When the compressor rotor is stationary, there is still a large volume of process gas remaining in the pipeline and has a certain pressure, and the compressor rotor stops rotating at this time, and the pressure in the compressor is lower than the pipeline pressure. At this time, if there is no check valve installed on the compressor outlet pipe or if the check valve is far away from the compressor outlet, the gas in the pipe will flow back, causing the compressor to reverse, and it will also drive the steam turbine or electric motor and gear transmission. Wait for the rotor to reverse. The reverse rotation of the compressor unit rotor will destroy the normal lubrication of the bearing, change the force of the thrust bearing, and even cause the loss of the thrust bearing. The dry gas seal will also be damaged due to the reverse rotation of the compressor. In order to prevent the compressor from reversing, several issues should be paid attention to:

1. A check valve must be installed on the compressor outlet pipeline, and it should be installed as close to the outlet flange as possible to minimize the distance between the check valve and the compressor outlet, so as to reduce the gas capacity in this section of the pipeline , Will not cause reversal.

　　2. According to the conditions of each unit, install vent valves, exhaust valves or recirculation pipelines. These valves should be opened in time when shutting down to remove the high pressure gas from the compressor outlet to reduce the gas storage capacity in the pipeline.

　　3. The gas in the system may backflow when the compressor is stopped. High-pressure and high-temperature gas backflow into the compressor can not only cause the compressor to reverse, but also burn out the bearings and seals. It is worth noting that there are many accidents caused by gas backflow in China!

　　In order to effectively prevent the above accidents, the following two tasks must be done before speed reduction and shutdown:

　　 1. Open the vent valve or return valve to vent or return the gas.

　　2. Close the check valve of the system pipeline firmly.