The Vibration Characteristics Analysis And Improvement Measures Of Platform Compressor Unit Deck Structure

The vibration of a reciprocating compressor in power machine is special and more complex. When a reciprocating compressor is running, if the frequency is close to the natural frequency of the system, there will be a resonance state. In the resonance condition, the vibration amplitude of the compressor will be strengthen continually. When the frequency, magnitude and application points of the exciting force are combined with the modal and natural frequency of the system in the worst way together, there will be violent vibration. Violent vibration of reciprocating compressor will cause many problems, such as the fracture of connecting bolt, cracking of the pipe, the damage of main bearing, and even the crack of compressor foundation and so on. Therefore, research on the vibration characteristics of the compressor system, and taking effective measures to eliminate the harmful vibration and making the vibration of the reciprocating compressor system is restricted in allowable range, which are important for security of service of the compressor system.Skidded reciprocating natural gas compressor, which the compressor and other equipment are mounted on skid, is usually applied on the platform. Thus, the vibration of compressor system is consist of compressor vibration, motor vibration skid vibration and deck vibration. In this paper, one compressor system applied on the platform is set as an example. The vibration characteristic of the compressor system is researched. The main research contents are followed:(1) The finite element model is modelled with ANSYS WorkBench and then the modal analysis is conducted. With this analysis, the natural frequency, displacement and vibration diagram are received from the first twenty-four step modal. With the result, a conclusion is obtained: the violent vibration of the compressor system is caused by deficient stiffness, because the natural frequency of the compressor system is low and far away from the working frequency of the compressor. So the compressor is mounted on the flexible beam structure and is easy to deform and vibrate under external loads because of deficient stiffness of deck. (2) The response values and aberration nephogram of the compressor system are obtained by harmonic response analysis when the system is under excitation force and the longitudinal deficient stiffness is considered as the contribution to the violent vibration of the system. So increasing the number of longitudinal beams and strengthening the longitudinal stiffness are considered as the measurement to reduce vibration. And then the harmonic response analysis is carried out once again after the structure modification. Compared to results before modification, the response of the compressor system is reduced obviously.(3) In order to validate the finite element calculation results, acceleration sensor is applied to measure the vibration of the compressor system before and after modification. In order to obtain the peak value of the response, the acceleration signal is transformed into speed signal. And when compare the results of finite element calculation to measured values, the strong consistency is confirmed and thus the correctness of the finite element analysis is verified.In this paper, the example is an offshore platform compressor system, in order to receive the vibration response, the finite element analysis method is applied. Then the accuracy of the calculation results is confirmed by comparing to the measured data. And at last, the improving measures is put forward. This paper takes on certain guidance to engineering practice.