1.1 Introduction to the process system.
The process system of the exhaust gas compressor <1> used in the second plant of Kela can be divided into four parts: process gas system, cooling and water supply system, lubricating oil system and sealing system. It is the process system diagram of the exhaust gas compressor unit.
1.2 Introduction to the control system.
The control system of the exhaust gas compressor used by the second plant of Kela is from S7-300 type, S7-200 type PLC and its communication module, on-site PLC, frequency conversion controller, on-site instruments and on-site auxiliary equipment. composition.
2 Fault phenomenon and cause analysis.
2.1 The host cannot be loaded after booting.
During the process of starting the exhaust gas compressor, it is often the case that the compressor cannot be loaded. The main phenomenon is: after starting the compressor, the compressor main unit runs at a low frequency of 8~10Hz (the inverter output is 15Hz), and manually raises the host running frequency host. It has no effect, and the host still runs at a low frequency of 8~10Hz. load.
After discovering the above phenomenon, we organized technicians to investigate all possible causes of the on-site compressor unit. It is confirmed that due to the internal leakage of the automatic spray regulating valve of the unit, a large amount of spray liquid is accumulated in the compression chamber of the compressor before starting the machine (when the compressor is stopped, all the liquid in the compression chamber has been exhausted), resulting in The phenomenon that cannot be loaded when starting up.
2.2 The host is not properly uninstalled.
Two months after the operation of the exhaust gas compressor in the second plant of Kla, the compressor showed abnormal shutdown of the main engine more than 10 times without any warning. The main engine was changed from automatic frequency conversion operation to 15Hz manual operation.
After this phenomenon occurs, we initially judge whether the control system is faulty or the inverter is faulty. After the system control logic confirms, it is found that only after the inverter sends out the inverter abnormal signal to the S7-200PLC, the system automatically unloads and runs manually at 15Hz for self-protection. In fact, there is no abnormality in the inverter, so the reason for the judgment is that the inverter and the S7-200 data transmission error.
2.3 Exhaust gas temperature is too high.
After the compressor was put into operation, there were many cases where the exhaust gas temperature was extremely high. However, from the specific phenomenon, it can be divided into two types: 1 the automatic spray regulating valve opening degree is increased to 100%, the exhaust gas temperature continues to rise to the interlocking shutdown; 2 the automatic liquid discharging regulating valve suddenly closes automatically, and the central control room accepts Exceeding the relevant data of the host operation, the exhaust gas temperature continued to rise to an ultra-high level, and the on-duty personnel found ESD parking after the discovery.
The reason for the high exhaust gas temperature caused by the analysis of these two phenomena is as follows: the first case is caused by the blockage of the spray cooling water pipeline, and the U-shaped pipeline is blocked by the welding slag before the water filter is checked; The second case is caused by a fault in the control or communication system. The post-check is that the failure of the S7-200 communication module causes the control unit to lose communication connection with the on-site actuator, and the on-site unit is out of control.
The system uses AVR series low-power single-chip ATmega16L as the control chip, low-power chip nRF905 as the wireless transceiver module, designed and implemented the digital temperature and humidity sensor SHT11 temperature and humidity wireless measurement system, because SHT11 has digital output, free debugging It is free from calibration, free of peripheral circuits and full interchangeability. It not only saves the I/O port resources of the MCU, but also reduces the overall design cost of the system, and also improves the measurement accuracy, and greatly simplifies the programming of the MCU. The SHT11 also has superior signal quality, faster response time and more sensitive immunity to external interference, so the system has a much higher performance than traditional greenhouse measurement systems.
These low-power products make the system consume less power and are particularly suitable for miniaturization, intelligence, and instrumentation of the system. The wireless transmitting function replaces the cumbersome manual meter reading, which makes the system have broad application prospects.
2.4 Mechanical seal lubricating oil leakage is large.
After the operation of the vent gas compressor from the second plant of Kela, both compressors have a problem of large loss of lubricant <2>. After reviewing the compressor twice, it is found that the main causes of leakage of the mechanical seal of the compressor are: 1 mechanical seal sealing surface damage; most of the 2O-rings have gaps or fractures; 3 in the O-ring assembly During the process, distortion after assembly may result from improper assembly methods.
3 measures taken and their effects evaluation.
In order to solve the appeal problem of the exhaust gas compressor from March to August 2008, the following measures were taken: (1) In terms of operation, according to the actual situation of the site and some problems encountered, Detailed operating card and operating procedures for compressor start-stop, and strictly in accordance with the implementation; (2) can effectively improve the control alarm system, install pressure change at the compressor outlet, directly enter the DCS system of the second plant, When the compressor field PLC<3> and the power distribution control room communication are out of control, the alarm can be effectively issued and interlocked. (3) Improve and standardize the assembly method of the compressor mechanical seal, first before the O-ring assembly It is heated and assembled with hot water to prevent it from being distorted after assembly.
After the implementation of the relevant measures, the lubricating oil consumption of the exhaust gas compressor of the second plant of Kela No. 2 was only 0.2L/day, and the operating conditions were all normal.
4 conclusion.
With the gradual tension in the world's energy situation, the recovery of low-pressure natural gas produced in natural gas processing will become the trend of the times, and the most important equipment for recycling this part of natural gas is the screw compressor. After the compressor was put into operation, the corresponding improvement measures were formulated in accordance with the actual situation on the site, and good results were obtained, which ensured the safe and stable operation of the device, and adopted a new type of ball. Motion platform control system. The system can realize the movement of the ball along a given trajectory on the plate or positioning at any given position on the plate under PID control. The system joint debugging results show that the constructed small ball motion platform control system has fast response and high position control precision. It can be used in the laboratory control theory teaching experiment platform. The PID algorithm can be expanded as needed, or based on this. The platform studies other higher performance control algorithms.
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