The air compressor online analysis system includes two technologies: online monitoring and online fault diagnosis. On-line monitoring consists of a signal sensor and a data acquisition box installed at each monitoring unit of each air compressor unit for collecting various on-site signals such as vibration signals, shaft displacement, key phase (and speed measurement), and slow variable signals ( Such as temperature, pressure, etc.; the data acquisition box will convert the above signals into 4~20mA standard analog signals and send them to the computer for online display. Through the display screen, the fan on-site operation status can be clearly seen, such as front and rear bearings, shifting The vibration value of the tile seat, the measured value of the rotation speed and the change of the shaft displacement.
Online troubleshooting consists of an application software system installed in the computer. The software comprehensively extracts the diagnostic information from the vibration signal, and provides powerful and rich map analysis and diagnosis functions including waveform spectrum map, axis trajectory map, vibration trend graph, process vibration trend graph, polar graph, and axial position map. The types of data that can be analyzed include real-time data, five trend data (hours, days, weeks, months, years), historical data, and data such as start-stop.
2 system structure and function
2.1 Distribution of signal monitoring points
The signal monitored by the system is divided into vibration signal and non-vibration signal. The non-vibration signal has exhaust temperature and pressure, tile temperature, lubricating oil pressure, fuel tank oil level, negative pressure, oil temperature after cooling, new water pressure and temperature, and circulation. A large number of signals such as water pressure and temperature, motor tile temperature, motor stator temperature, motor voltage and current. A common feature of these signals is that the amplitude of the signal is slowly varying relative to the vibration signal and is therefore referred to as a "slow variable" in the system.
The vibration signal mainly includes the X and Y axis vibrations, wattage vibration, shaft displacement and other signals of the speed increase box and the air compressor rotor. The common feature is that the output amplitude of the sensor is zero when the equipment is in normal operation; In the case of an anomaly, the amplitude will change sharply in a very short time (milliseconds), so it is also called "transient variable" in the system.
2.2 part of the signal
2.2.1 key phase signal
The key phase signal is used to accurately describe the vibration phase angle, while the phase angle measurement can be used to describe the position of the machine rotor at a particular time. The phase angle measurement system is capable of determining the position of the "high point" of the corresponding machine rotor on each sensor signal relative to a fixed point on the rotor. By determining the position of the "high point" on the rotor of the machine, it is possible to determine the equilibrium state of the machine and The position of the unbalanced weight remaining on the rotor of the machine. A change in the balance state of the machine rotor will cause a change in the high point, which is indicated by a change in the phase angle.
2.2.2 Axis displacement signal
The shaft displacement signal is used to accurately describe the relative position between the compressor rotor thrust ring flange and the thrust bearing. In the high-speed operation of the compressor rotor, the rotor moves in the axial direction due to various factors such as load, temperature, and the like. The main purpose of axial position monitoring is to ensure that the axial friction between the rotor and the stator is eliminated. The failure of the axial thrust bearing may be the most serious fault of the compressor.
2.2.3 Temperature signal
The temperature of the bar alloy linings for radial and axial bearings is now becoming more and more important, and their air compressors must not exceed 80 ° C when they are operated. Finding the relationship between temperature data and vibration measurements, as well as temperature data and position measurements, helps to identify possible machine failures in a timely manner.
2.3 System device configuration
1~4#PLC is responsible for the collection and processing of mechanical vibration signals of 1~4# air compressor units, and 5#PLC is responsible for all slow variable signals of 4 air compressor units (such as temperature, pressure, flow and current, etc.) ) Collection and processing.
The central server is the core of the entire system. Based on the client/server architecture model, the server uses the standard TCP/IP communication protocol to provide internal LAN functionality to the system. It has a complete signal analysis function, which quickly and accurately performs various analysis and data processing on dynamic signals of different units at different times and in different states, and displays them on various interfaces with various maps. The fault diagnosis expert system configured on the server has the functions of symptom acquisition, automatic diagnosis, dialogue diagnosis and storage of diagnosis results, which ensures the advanced nature of the system and the reliability of the diagnosis results.
On the system LAN, according to the specific use requirements and the division of labor of the post operator, multiple browsing stations can be configured. The industrial configuration method can be used to edit the data and expressions to be monitored online (such as structure diagram, bar graph, Tables and numbers, etc., as well as various data and analysis graphs for calling any unit.
3 example of fault diagnosis
Before the 3# machine stopped for a certain time, the system has captured a large amount of fault information. 3# machine (ZD3) 11X measuring point vibration trend map and waveform spectrum map, around May 8th, the vibration has been obviously abnormal, the waveform analysis of the waveform, found that the vibration waveform has obvious shock pulse, showing fault .
Then the unit waveform spectrum diagram shows the dynamic and static collision friction. The system solution sign (the waveform appears in the vibration waveform), and other vibration points have similar phenomena. As the fault deteriorated further, it eventually had to stop.
The cause of the accident of the rotor friction equipment of the centrifugal compressor: the secondary diaphragm of the stator part of the compressor has manufacturing defects, obvious blisters and cracks. After long-term vibration, the upper partition of the casing breaks and falls, resulting in the rotor. The slight friction with the stator seal, at this time the radial vibration of the compressor changes, there is a shock pulse, as the friction is further aggravated, the thrust bearing is damaged, the axial displacement of the rotor, and then the friction of the rotor and the stator throughout the circumference The thermal deformation caused by the friction causes the rotor to bend, and the eccentricity of the rotor is increased, and finally the compressor vibration suddenly becomes large, causing damage to the compressor bush, the rotor and the diaphragm.
4 system application effects
(1) Dynamic management of the operating state of the device is achieved. The system can continuously monitor the vibration data of each measuring point of the field unit and the process parameters such as temperature, pressure, shaft displacement, flow and current, and display it dynamically through various forms, graphs and data tables. The storage and classification management of the relevant data realizes the reproduction of historical data such as the shift, the day, the current month, and the current year, and further forms various trend analysis results.
(2) Provides a comprehensive protection function. Especially in the start-stop phase, it is very intuitive to provide relevant trends and trends over time between various signal parameters throughout the process. When the unit is running abnormally, it also has sound, light over-limit alarm and gradient alarm function. Various monitoring results can be printed at any time. At the same time, real-time communication with the management machine can be completed, so that the higher authorities can grasp the running status of the unit in time.
(3) It provides the possibility for scientific and accurate online fault analysis and diagnosis of equipment. The intelligent fault diagnosis system configured by the system can identify the changes of various characteristic parameters of the operating unit provided by the online monitoring system, and use the fault diagnosis expert system to comprehensively analyze these changes, accurately determine various fault points and severity, and maintain the equipment. Managers make reliable decisions based on reasonable decisions.
(4) The equipment operation rate is improved, the labor intensity of the post operator is reduced, the service life of the equipment is prolonged, and the workload is reduced. When an abnormality is found in an individual part of the unit, some abnormal phenomena are analyzed and judged according to the online data, and many unnecessary shutdowns can be avoided. In this way, the maintenance workload is greatly reduced compared with the previous one, and the frequent start and stop times and losses of the equipment are correspondingly reduced.
(5) Provide a basis for determining the optimal inspection timing and formulating a reasonable maintenance plan. Using online monitoring data combined with fault diagnosis technology, under the condition that the equipment load is running without stopping, monitor and analyze various state parameters of the equipment to determine whether there are abnormalities or faults, the location, cause and severity of the fault, and avoid In the past, the inspection after the shutdown can find the exact cause of the failure, which not only saves time for maintenance, but also makes the development of the maintenance plan more scientific and reasonable, and improves the quality of maintenance of the equipment.
(6) The system has powerful data management, high-speed transmission and sharing functions, which lays a foundation for enterprises to realize remote centralized management and monitoring of large-scale equipment in the future.
5 Conclusion
The online analysis system was put into use in early 2006, and after continuous summarization and exploration, it achieved good results. On this basis, the online analysis system of 6 CO2 compressors of CO2 compression station was transformed, and the two systems were connected through the network to form a complete "Chengzhou branch compressor online analysis system". The device online analysis technology has been promoted and applied.
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