Reasons for vibration of inlet and outlet pipes of reciprocating compressor

Reasons for vibration of inlet and outlet pipes of reciprocating compressor

During the air load test of the carbon dioxide compressor, the pipeline between the third-stage outlet buffer and the third-stage cooler, the pipeline between the fourth-stage outlet buffer and the fourth-stage cooler, and the outlet pipeline of the fifth-stage outlet buffer occurred greatly. The vibration, especially the vibration of the outlet pipe of the five-stage outlet buffer is the most obvious. The reasons for the vibration of the inlet and outlet pipes of the reciprocating compressor are more complicated, including the following reasons.

　　1. The unbalance of compressor power causes vibration of the machine itself and its connected pipes.

　　The unit itself has problems such as poor dynamic balance performance, misalignment of installation, improper foundation and support, etc., all of which can cause vibration of the unit. Due to the transmission of vibration, the vibration of the machine body will cause the pipeline to vibrate, so the vibration of the machine body is strong, and the pipeline vibration is also strong.

　　2. The compressor intermittently sucks and discharges to cause air column vibration.

During the operation of the reciprocating compressor, the suction and discharge change intermittently and periodically, which will cause pressure pulsation of the gas. When the pulsating fluid is transported along the pipeline, it encounters elbows, reducers, valves, etc. After components, due to the instantaneous pressure, speed, and density changes, a time-varying excitation force will be generated, and the pipeline will receive a great impact. If the elbow lacks a fixed fulcrum or the fulcrum is not strong enough, severe vibration will occur. Generally speaking, pressure pulsation is the main cause of vibration in the outlet pipe of a reciprocating compressor.

　　3. The resonance generated when the frequency excited by the compressor is close to or equal to the natural frequency of the pipeline, including air column resonance and pipeline mechanical resonance.

When the frequency of the cylinder excitation force received by the airflow in the pipe is close to or equal to the natural frequency of the air column in the pipe, air column resonance will occur, which will cause strong vibration of the pipe and increase with the amplitude of the pressure pulsation, resulting in The air valve is damaged and the vibration of the entire unit and pipeline is aggravated. The pipeline system composed of pipelines, pipeline accessories, containers and supports, etc., will produce mechanical vibration response after being excited by the excitation force, which is commonly referred to as pipeline vibration. When the frequency of the exciting force is close to or equal to the natural frequency of the pipeline system, mechanical resonance will occur, and the amplitude of mechanical vibration is the largest. When the excitation frequency, the natural frequency of the air column, and the natural frequency of the pipeline system are close or equal, z* severe pipeline vibration will occur. In short, resonance will cause greater displacement and stress in the pipeline.