Research On In-situ Monitoring Technology For Crosshead Bushing Of Reciprocating Compressor

Reciprocating compressor is one of the important production equipment in petrochemical production process.Its main function is to compress flammable and explosive gases such as hydrogen,which determines the working conditions to be quite harsh.Once there is malfunction,it will not only cause enormous economic loss,but may also endanger personal safety.The abrasion failure of the bushing is one of the important reasons for the malfunction of compressor.The abrasion of the bushing will cause the bushing temperature to rise,which will cause the compressor to run less efficiently and form a vicious cycle until the compressor cannot be used normally.Therefore,monitoring the temperature of the bushing is an important guarantee for the safe production of the compressor.In view of the limitations of non-explosion protection and electromagnetic interference existing in traditional sensors,a monitoring system based on Fiber Bragg Grating(FBG)technology is adopted to realize the in-situ measurement of the bushing temperature of the compressor.The main research contents and results of the paper are as follows:(1)Based on the installation environment of the petrochemical site,a single-ended fixed FBG temperature sensor was optimized and compared with the double-ended fixed FBG temperature sensor in terms of temperature,strain,and acceleration.The results showed that the former performed better in strain immunity and basically isolated the effect of strain on FBG.A temperature calibration experiment was performed on the sensor.The experimental results show that the temperature sensor has good temperature sensing performance and linearity of more than 99.97%,minimum repeatability error of 0.15%.(2)In order to solve the problem of fiber winding caused by in-situ measurement demodulator of temperature of crosshead bushing in reciprocating compressor,the optical signal space transmission scheme of fiber collimator was thoroughly studied.The collimation and coupling principle of optical fiber collimator are included,and the relationship between spatial transmission and coupling efficiency of optical signal is analyzed.(3)According to the motion model of the reciprocating compressor,the motion law of the equivalent crank slider mechanism is analyzed,and the relationship between the stroke,speed,acceleration of the bushing during the movement and the crank angle is determined.Based on the speed analysis of the bushing in the effective coupling space,the minimum sampling rate of the demodulator is derived.(4)For the problem of excessive center wavelength drift due to optical path loss during the movement,a method using the insertion loss threshold to extract the effective wavelength value in the U-shaped center wavelength was proposed,and the demodulated temperature error was changed from 5 ? control to within 0.1 ?,which greatly improves the accuracy of temperature demodulation.(5)The system was tested on the reciprocating compressor of Wuhan Sinopec Branch to verify the feasibility of the scheme.