DCS system maintenance and repair methods
DCS is the short for Distributed Control System (Distributed Control System), and it is commonly called distributed control system in China. It is a multilevel Computer system composed of process Control level and process monitoring level with Communication network as the link, integrating computer (Computer), communication (Communication), display (CRT) and control (Control) etc. The basic idea is decentralized control, centralized operation, hierarchical management, flexible configuration and convenient configuration. DCS has the following characteristics:
(1) High reliability Because the DCS system control function is dispersed in each computer, the system structure is fault-tolerant design, so the failure of a computer will not lead to the loss of other functions of the system. In addition, since the tasks undertaken by each computer in the system are relatively simple, special computers with specific structures and software can be used for the functions that need to be realized, so that the reliability of each computer in the system is also improved.
(2) Open DCS adopts open, standardized, modular and serialized design, each computer in the system adopts local area network communication to achieve information transmission, and when it is necessary to change or expand the system function, the new computer can be easily connected to the system communication network or removed from the network, almost without affecting the work of other computers in the system.
(3) Flexibility The software and hardware configuration is performed according to different process application objects through the configuration software, that is, to determine the measurement and control signals and the connection relationship between them, select the applicable control law from the control algorithm library, and call various monitoring and alarm screens required by the basic graphics from the graphics library, so as to facilitate the formation of the required control system.
(4) Easy to maintain a single function of the small or micro special computer, with the characteristics of simple and convenient maintenance, when a local or a computer failure, can be replaced online without affecting the operation of the entire system, quickly eliminate the fault.
(5) Coordination between workstations through the communication network to transmit a variety of data, the entire system information sharing, coordination work to complete the overall function of the control system and optimize processing.
(6) Complete control functions Rich control algorithms, set continuous control, sequence control and batch control in one, can achieve cascade, feedforward, decoupling, adaptive and predictive control and other advanced control, and can easily add the required special control algorithms. The composition of DCS is very flexible, can be composed of a dedicated management computer station, operator station, engineer station, recording station, field control station and data acquisition station, etc., can also be composed of a general server, industrial control computer and programmable controller. The process control level at the bottom is generally realized by decentralized field control stations, data acquisition stations and other local data acquisition and control, and transmitted to the production monitoring computer through the data communication network. The production monitoring level carries out centralized operation management of the data from the process control level, such as various optimization calculations, statistical reports, fault diagnosis, display alarm, etc. With the development of computer technology, DCS can be connected with higher performance computer equipment through the network to achieve more advanced centralized management functions, such as planning and scheduling, storage management, energy management, and so on.
Process industry CIMS is a complex integrated automation system, dealing with all the production activities of the whole enterprise, DCS as an effective tool and implementation means, in the process industry CIMS to complete important basic control and real-time production data acquisition, dynamic monitoring and other functions. Compared with the management computer, DCS can provide more reliable production process data, so that the optimization decision made by the CIMS system is more reliable.
From the functional point of view, the production automation system, dynamic monitoring system and online quality control in the process industry CIMS can be realized by DCS. From the perspective of CIMS hierarchy of process industry, DCS is mainly responsible for process control and process optimization tasks, and some production scheduling and production management work can also be completed on DCS.
DCS system fault identification and treatment method: With the improvement of automation level, DCS control system (distributed control system) has gradually replaced conventional instruments, and its superiority has been accepted by the majority of operators. However, when the fault occurs, it will cause the device to stop and even accidents, so how to find and deal with various faults as early as possible is very important. The synthetic ammonia process of our company uses several sets of Zhejiang University Central control JX-300XDCS for control, which is stable and reliable. In view of some existing problems, according to years of maintenance experience, we have summarized a set of effective fault identification and treatment methods.
1, view the data of the monitoring screen
When the following situations occur, it indicates that the control system has a problem, should immediately notify the computer maintenance personnel to repair, while the operator to the scene for processing.
(1) Frequently changing data is unchanged for a long time, and several or all data are unchanged.
(2) In the control group screen, the manual automatically cannot be switched, or after manually entering the data, once confirmed, it is restored to the original data, and can not be modified.
(3) In the trend chart screen, several trends are unchanged as straight lines.
(4) In the monitoring screen, multiple data fluctuate greatly at the same time.
Determine whether the fluctuation data is related to the process parameters, if it is relevant parameters, notify the instrument and computer personnel to check whether the fluctuation of a regulation system causes the change of relevant parameters, and at the same time, the relevant regulation system is played to the manual state, and the field is adjusted when necessary. For example, in the aqueous solution full cycle device, the normal pressure of the urea converter is l9.67MPa, and if the sudden wide fluctuation, it is bound to cause the pressure wave of the downstream medium pressure system and low pressure system. This situation is due to the fluctuation of one parameter in several relevant parameters causing other parameters to change, not the fault of the control system itself.
If the fluctuation data process does not directly affect each other, it may be a microcomputer card failure, immediately the relevant self-adjusting system to manual adjustment, if necessary to the scene for adjustment, at the same time, notify the microcomputer and instrument personnel to check.
2, check the operation of the station
When it is found that an operation station crashes, the monitoring screen data is not refreshed, the adjustment screen does not work, check whether the system alarm light on the upper right is normal, and check whether other operation stations are working normally, if normal, only the operation station has a problem, notify the computer maintenance personnel to repair. If the data of other operating stations are also unchanged, the system communication network fails, and the maintenance personnel are immediately notified to check the operation of the network equipment and repair it.
3. Observe the power failure of the operation station
If part of the operation station suddenly does not show, it indicates that the UPS or the mains power failure, immediately notify the microcomputer maintenance worker for maintenance. If the operating station with power can be monitored normally, the normal adjustment of the control system will not be affected at this time.
4, pay attention to the control station all power off
Since all the control station devices are dual power supply, one UPS, one mains, so the probability of this situation is very small.
When the control station is all powered off, the two systems on the monitoring screen are red, the communication is interrupted, the data is not refreshed, all the self-adjusting systems are completely out of control, the regulating valve will return to the initial state, the gas opening valve is fully closed, and the gas closing valve is fully opened. At this time, you should immediately deal with the emergency or stop, and at the same time go to the scene for operation.
5. Pay attention to the power failure of all operating stations
At this time, check whether the control station power light is normal, the card diagnostic light has no fault red light, the green light indicates that the card works normally, if the above are normal, you can determine that the control station works normally, the self-adjusting system works normally, but the operator temporarily can not see the monitoring screen, and can not remotely operate the scene, immediately notify the computer maintenance personnel to repair, And to the scene for monitoring.
6, the control valve instrument air source pressure is low or the instrument air is completely out of gas
When multiple self-regulating systems are found to fail, the self-regulating valve position on the monitoring screen is fully open or fully closed, immediately check the instrument air pressure, if the air pressure is less than 0.4MPa, it is abnormal, check whether the air supply pipeline is blocked or leaky; If the air source pressure is less than 0.2 MPa, stop the vehicle immediately. All the self-regulating system on the monitoring screen is set to manual, the valve position of the regulator is adjusted to a safe position, the instrument worker is notified to check the air source, and at the same time, the operation is carried out on the site, the globe valve at both ends of the regulator is closed, and the bypass valve is used to operate.
Concluding discussion
When DCS fails, the operator should master a certain discrimination method, find the problem early, and deal with it appropriately, which can avoid or reduce the impact on process control.