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Problems to pay attention to when repairing pneumatic valves

2020-06-02
With the rapid development of China's industry, pneumatic valves have become more and more widely used in metallurgy, petrochemical and other fields. Their stability and reliability also become more and more important. The quality of their working conditions will directly affect the automatic control process. , Xiaobian will elaborate the use and maintenance of pneumatic valves.


Precautions for using the device


The control system of the new design and device, in order to ensure that the regulating valve can work normally when driving, and to make the system operate safely. Before the new valve is installed, it should first check whether the nameplate mark on the valve is consistent with the design requirements. The following items should also be debugged.

Basic error limit; full stroke deviation; return difference; dead zone; leakage (performed under strict requirements).

If the control valve in the original system has been overhauled, in addition to verifying the above items, the leak tightness of the stuffing box and connection of the old valve should also be checked. In the field use of control valves, many are often not caused by the quality of the control valve, but caused by the improper use of the control valve device, such as the device environment, the device location and direction is improper or the pipeline is not clean. Therefore, the pneumatic valve should pay attention to the following aspects when using the device:

(1) The regulating valve is a field instrument. It is required that the ambient temperature should be in the range of -25 ~ 60 ℃, and the relative humidity should be ≤95%. If the device is in the open air or high temperature, waterproof and cooling measures should be taken. Keep away from vibration sources or add anti-vibration measures where there is a vibration source.

(2) The regulating valve should generally be installed vertically. It can be tilted under special circumstances. For example, if the tilt angle is large or the valve itself is too heavy, support for the valve should be added to protect the valve.

(3) Generally, the pipeline of the regulating valve should not be too high above the ground or floor. When the pipeline height is greater than 2m, a platform should be installed as much as possible to facilitate the operation of the handwheel and facilitate maintenance.

(4) The pipeline should be cleaned before the regulating valve device to remove dirt and welding slag. After installation, in order to ensure that impurities do not remain in the valve body, the valve should be cleaned again, that is, all valves should be opened when the medium is passed in to prevent the impurities from getting stuck. After using the handwheel mechanism, it should be restored to its original neutral position.

(5) In order to enable the regulating valve to continue the production process in the event of failure or maintenance, the regulating valve should be added with a bypass line, as shown in Figure 1-1. At the same time, special attention should be paid to whether the device position of the regulating valve meets the requirements of the process.

(6) The electrical part of the pneumatic valve shall be installed in accordance with the relevant electrical equipment construction requirements. If it is an explosion-proof product, it shall be installed in accordance with the requirements of "Specifications for Electrical Equipment in Explosive Hazardous Areas". For example, the field wire adopts SBH type or other six-core or eight-core rubber device cable with an outer diameter of about 11.3mm. During use and maintenance, it is strictly forbidden to open the cover for maintenance and prying on the explosion-proof surface in explosive places. At the same time, do not scratch or scratch the flameproof surface during disassembly, and restore to the original flameproof required state after maintenance.

(7) After disassembling and repairing the reducer of the actuator, pay attention to oil lubrication. Generally, do not disassemble and wash oil for low-speed motors. After assembly, check that the valve position matches the valve position opening indication.