PFVO142/PFVO143 needs to be matched with PFVL 141 load cell

Description

Wall cabinet

A control unit can be installed in the dust- and hose-proof wall cabinet. The operator unit can be mounted on the inside of the door or through the door.

Matching unit PFVO 142/143

Each PFVL 141 load cell requires one matching unit, which is interchangeable between load cells. It can be located up to 25 m away from the relevant load cell (depending on the nominal load).

Matching device QIPZ 127

Each QGPR 104/102 load cell is delivered with an accompanying matching device. It should be located at a specific distance from the load cell.

DCS system fault diagnosis and handling methods: 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. But when a malfunction occurs, it can cause the device to shut down or even cause accidents. It is very important to detect and handle various faults as soon as possible. Our company’s synthetic ammonia process uses multiple sets of Zhejiang University Central Control JX-300XDCS for control, which is stable and reliable. Based on years of maintenance experience, we have summarized an effective set of fault identification and handling methods to address some of the existing problems.

1. View data from the monitoring screen
When the following situations occur, it indicates that there is a problem with the control system. The microcomputer maintenance personnel should be notified immediately for repair, and the operator should come to the site for treatment.
(1) Frequently changing data remains unchanged for a long time, and several or all data remains unchanged.
(2) In the control group screen, manual and automatic switching is not possible, or after manually inputting data, once confirmed, it returns to the original data and cannot be modified.
(3) In the trend graph screen, several trends remain unchanged as straight lines.
(4) In the monitoring screen, multiple data fluctuate significantly at the same time.
Determine whether the fluctuation data is a process related parameter. If it is a related parameter, notify the instrument and microcomputer personnel to check to see if a certain regulation system fluctuation has caused a change in the relevant parameters. At the same time, set the relevant regulation system to manual mode and adjust it on-site if necessary. In a water solution full circulation device, when the pressure of the urea synthesis tower is normal, it is l9.67MPa. If there is a sudden large-scale fluctuation, it will inevitably cause pressure fluctuations in the downstream medium and low pressure systems. This situation is due to the fluctuation of one of several related parameters causing changes in other parameters, not the failure of the control system itself.
If there is no direct impact on each other in terms of fluctuation data technology, it may be due to a malfunction of a certain card in the microcomputer. Immediately set the relevant automatic adjustment system to manual adjustment, and if necessary, go to the site for adjustment. At the same time, notify the microcomputer and instrument personnel to inspect.

2. Check the operation status of the operation station
When a certain operating station crashes, the monitoring screen data does not refresh, and the adjustment screen does not work. Check whether the upper right system alarm indicator light is normal, and check whether other operating stations are working properly. If it is normal, only that operating station has a problem. Notify the microcomputer maintenance personnel for repair. If the data from other operating stations remains unchanged, it indicates a malfunction in the system communication network. Immediately notify maintenance personnel to check the operation of the network equipment and repair it.

3. Observe the power outage of the operation station
If some operation stations suddenly do not display, it indicates that the UPS or mains power is off, and immediately notify the microcomputer maintenance worker for maintenance. If the operating station with electricity can monitor normally, it will not affect the normal adjustment of the control system at this time.

4. Pay attention to the situation where all control stations are powered off
Due to the dual power supply of all control station equipment, one UPS and one mains supply, the probability of this situation occurring is very low.
When the control station is completely powered off, the two system alarm red lights on the monitoring screen light up, communication is interrupted, and all data is not refreshed. All self regulating systems are completely out of control, and the regulating valve will return to its initial state, with the air opening valve fully closed and the air closing valve fully open. At this point, emergency handling or parking should be carried out immediately, and the operation should be carried out on site at the same time.

5. Pay attention to the situation where all operating stations are powered off
At this point, check if the power indicator light of the control station is normal, and if there is a fault with the card diagnosis indicator light. The red light and green light indicate that the card is working normally. If all of the above are normal, it can be determined that the control station is working normally and the self adjustment system is working normally. However, the operator cannot see the monitoring screen temporarily and cannot perform remote control operations on the site. Immediately notify the microcomputer maintenance personnel for maintenance and go to the site for monitoring.

6. The pressure of the instrument air source of the regulating valve is low or all instrument air is cut off
When multiple self regulating systems are found to be malfunctioning and the self regulating valve position on the monitoring screen is in the fully open or fully closed position, immediately check the instrument air source pressure. If the air source pressure is less than 0.4MPa, it is abnormal. Check the air source pipeline for blockage or leakage; If the gas source pressure is less than 0.2MPa, immediately perform an emergency shutdown. Turn all the self regulating systems on the monitoring screen to manual mode, adjust the valve position of the regulating valve to a safe position, notify the instrument technician to check the air source, and operate on site at the same time. Close the stop valves at both ends of the regulating valve and use a bypass valve for operation.
Conclusion
When DCS malfunctions, operators should master certain discrimination methods, identify problems early, and handle them appropriately to avoid or reduce the impact on process control.

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