1.1 System working principle There are 7 air compressors (one to be installed) in a mine of Pingmei Group, of which 3 are BLT screw-type pressure fans and 3 are LGD screw-type pressure fans.
Start process of the pressure fan: first turn on the water pump to input cooling water, then open the exhaust valve to open the main motor; open the intake valve to start the empty load; after running for about 3 minutes, close the exhaust valve and load into the load.
Parking process: first close the intake valve, then open the exhaust valve to unload, then close the main motor and cooling water pump, and finally close the exhaust valve.
1.2 system control strategy
(1) Set up the pump control system site, and integrate the existing 6 pressure fan system substations to form a centralized control system for the air compressor.
(2) Realize two kinds of control methods: remote control and near control. In the remote control mode, the remote control of the main control room is automatically started and stopped, the parameter fault is automatically stopped, and the standby air blower is activated. The device can automatically adjust the running state according to the monitoring parameter change; in the near control mode, the local control room can be realized. Ground control, remote computer control fails, the fan is controlled by the local operation screen, and the water pump is controlled by the local control cabinet.
1.3 System Energy Saving Measures In the actual operation of the pressure fan group, the following measures can be taken to achieve energy saving:
1 Reasonably configure the gas pipeline to reduce the pressure loss and air leakage of the pipeline;
2 Reasonable lubrication, use low-viscosity, lubricating oil with good lubricating performance to reduce the frictional power consumption, and set the low pressure of the exhaust fan as much as possible while ensuring the actual air volume, because the lower the exhaust pressure is set, The less shaft power is consumed;
3 Regularly perform maintenance on the pressure fan to maximize the performance of the machine. In addition, energy efficient can be achieved by selecting an efficient motor.
However, relying on the above measures, the energy saving potential of the pressure fan group cannot be fully explored. The method of frequency conversion adjustment for the pressure fan group can greatly improve the working efficiency during light load operation, reduce the energy consumption of the pressure fan, and create better economic benefits, which is of great significance to the economic operation of coal mining enterprises.
2 control system structure and monitoring function
2.1 The structure of the control system
It is proposed to design the structure of the compressor control system into a three-level network architecture. According to the vertical control level, it can be divided into equipment layer, control layer and information management level. The control layer collects device parameters and executes control commands. The master station and the substation communicate through the 485 mode, and the master station communicates with the monitoring computer through the fiber optic Ethernet.
The equipment layer is the bottom layer of the 3-level network architecture, which mainly includes the oil-injected screw pressure fan, the screw-type pressure fan and the circulating water pump, and the sensor; the control layer is the middle layer of the 3-level network architecture, mainly including the PLC controller. , touch screen and UPS power supply and other equipment; information management is the highest level of the three-level network architecture, is the management and scheduling of the control system, mainly including monitoring servers, workstations, engineering stations, Ethernet switches, printers, UPS power supply and other equipment . Monitoring and protecting the parameters and faults of the air compressor group through the 3-layer network architecture can make the system run more perfect, and each part runs independently and coordinates with each other.
2.2 system monitoring function
Real-time monitoring of the status of the fan motor, voltage, current, exhaust gas temperature, intake air temperature, exhaust pressure, oil (oil pressure), inlet pressure, drainage pressure, inlet water temperature, drainage temperature, oil level, front bearing Temperature, hydration pressure, rear bearing temperature, cooling water temperature, pump status, valve status, pump current, pool temperature, pressure, tank temperature and room temperature of the blower room are displayed in a curve form in the host computer, and history is recorded. Data, easy for staff to make inquiries. The simulation diagram of the monitoring state of the pressure fan operating state is shown in Figure 3. It mainly includes 6 air compressors, 3 water tanks, 6 water pumps, 6 gas storage tanks and related valves.
3 pressure fan common faults and FTA research
3.1 Common faults of the pressure fan system
According to various related literatures and practical experience of engineers and technicians, the common faults of the pressure fan system in the actual operation process, the causes of the faults and the solutions are summarized.
3.2FTA algorithm research
Fault Tree Analysis (FTA) is an analytical method that reduces the cause of system failure from the whole to the partial densification. It is reliable for complex dynamic system design, factory test or field failure mode. An effective tool for sexual analysis, the purpose of which is to identify the basic faults, determine the cause, impact and probability of occurrence of the fault.
With the "air compressor system failure" as the top node event, five sub-system nodes are set, that is, the bearing temperature is too high, the air compressor unit vibrates greatly, the exhaust volume is insufficient, the air compressor oil system system fails and the air filter The resistance is large, which constitutes the secondary node fault tree of the air compressor system, and then the system fault tree is expanded into a three-level node fault tree according to the faults contained in the secondary nodes.
The solution process of fault analysis is mainly the process of reasoning and control. The so-called reasoning refers to the thinking process of deriving other possible faults according to a certain type of fault. The control refers to a set of control methods that control how the diagnostic process proceeds and under what circumstances. That is, the control of the direction of reasoning and the selection strategy of the inference rule, that is, planning and distinguishing the faults that occur, and then selecting the corresponding solution in the fault tree for fault diagnosis. The system uses the forward-backward hybrid inference control strategy to model the fault diagnosis model of the air compressor unit energy-saving system. According to the important symptoms, the hypothesis is initially obtained through forward reasoning, and then the backward reasoning is used to further verify whether the hypothesis is correct. Until the final conclusion of the fault is indicated.
There are two types of fault search methods: width priority and depth priority. Depth-first is relatively easy to implement. It goes along the direction of an inference rule, and then goes deeper into the more detailed part of the problem. It asks all the related questions in depth while the width-first search generally jumps from a "topic". Go to another "topic" and ask at random. In view of the simultaneity of the failure of the pressure fan system, and the degree of action of various specific faults on the unit, the task of fault diagnosis of the pressure fan system is to find out and distinguish the various specific faults at the same time. So the system chose a breadth-first search strategy.
4 Conclusion
The automatic control system of the air compressor unit is a continuous air supply system composed of multiple screw air compressor equipment. In view of the problems of high energy consumption and insufficient fault protection during the operation of the air compressor unit, the original unit control strategy and system structure are analyzed for energy saving measures. The control mode of frequency conversion regulation is proposed, and the pressure fan group is designed. The 3-layer network architecture enables automatic control and remote management of the entire system. Based on the fault diagnosis and expert system knowledge, the types and solutions of faults that may occur in the compressor group are analyzed. The application of FTA algorithm in unit fault maintenance is discussed. The width-first fault search strategy and forward and reverse are determined. The hybrid inference control model realizes the fault diagnosis of the control system of the compressor group.
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