Preventive maintenance is a planned maintenance before the failure of the regulating valve. It can be understood as a routine maintenance and usually includes the following tasks.
1.1 Stress relief
The pipeline may generate various stresses due to improper combination or installation, such as thermal stress generated by high temperature medium, stress caused by unbalanced tightening force during installation, stress caused by some human collisions to the regulating valve and its piping. These stresses act on the regulating valve and its pipelines, which can easily affect the performance of the regulating valve. In severe cases, it will affect the regulating system itself, causing the stem and the guide to deform and not centered with the valve seat; for the split valve The body's regulating valve may cause the valve body flange to disengage; the stress may also cause the valve seat to leak. Therefore, at all times, it is necessary to ensure that stress is avoided or eliminated, and the stress is directed away from the regulating valve.
1.2 Check support situation
The optimum position for the installation of the regulating valve is such that the stroke direction of the valve stem is in a vertical plane with the actuator above the valve body. If the regulating valve must be installed at a position where the valve stem is moved horizontally, or if the direction of movement of the valve stem is at a certain angle to the horizontal plane, the actuator should be supported so that the various components of the regulating valve are in a natural state. If the support is not added or the support is improperly installed, the valve stem and the valve seat may be different from each other, which may cause a fault or a leak of the filler. Even if the regulating valve has fixing and supporting measures, it must be inspected regularly, usually once every 2 to 3 months.
1.3 remove or prevent foreign matter from entering
Always check the presence or absence of rust, welding slag, dirt, etc. in the connecting pipe of the regulating valve, and remove it in time. If it is easy to accumulate foreign matter in the regulating valve and piping, consider installing a simple filtering device on the upstream side of the regulating valve. Where it is easy to penetrate hard materials in the process medium, it is necessary to install a permanent filter device. Because the control valve is closed, a small piece of rust or welding slag is enough to damage the well-welded seat sealing surface, and these dirt can also cause wear on the regulating valve spool and seat, affecting its normal operation.
1.4 Regularly check the gas source and power supply
The gas source is one of the key energy sources for driving the regulating valve. Although the membrane chamber of the pneumatic control valve does not consume air, if the air source system contains impurities such as moisture and oil, the valve positioner, the relay and other accessories may be blocked and malfunction. Therefore, the gas source and power source must be inspected regularly to ensure that the gas source is clean and dry, and the power supply is reliable.
1.5 regular maintenance and refueling
Fillers and oilers need to be re-adjusted after a short period of use. In the case of dust, the packing box and the guiding part should be protected by a plastic sleeve or a rubber sleeve around the valve stem. When there is corrosive gas or liquid droplets, special protective measures should be adopted. Generally, the control valve is wrapped with an anti-corrosion bag, but Note that it does not affect its operation. In the case of fire resistance requirements, special refractory coatings, fireproof bags, etc. may be used. The material of the fireproof bag contains multiple layers of ceramic fibers or glass fibers.
1.6 Transportation and storage
After the adjustment valve is assembled and painted and attached to the actuator, handwheel, positioner and other accessories as required, in order to prevent foreign matter from entering the regulating valve, all air ports connecting the regulating valve should be blocked, and the connecting flange is equipped with a protective cover. Pay attention to the connection points, such as the position of the valve positioner intake pipe and the actuator interface. Any protruding accessories that are easily damaged, such as oil gauges and potentiometer pressure gauges, should be removed from the joint and packaged separately with the regulator valve. The adjustment valve is fixed by a special bracket to prevent looseness and to ensure the overall vertical position or horizontal position. If transported over long distances, it is best to ship in a solid wooden case.
When storing the regulating valve, do not support the regulating valve in sensitive parts such as valve positioners, valve stems, etc. Environmental conditions for transportation and storage should meet the requirements of the product specification. It is best not to carry out other work in the storage area. If it is unavoidable, care must be taken not to touch the regulating valve. The site should also be protected from harsh conditions such as sand, dust, rain, etc. If there is no suitable place, the regulator valve must be placed in a moisture-proof bag or placed in a similar container before storage.
1.7 Inspection of safe operation
Regulators and related accessories used in explosive hazardous areas should be checked for safe operation, such as whether the sealing cover is tightened, the operation of the safety barrier, the power supply, etc., to ensure that the regulating valve and related accessories can operate safely.
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Label: regulating valve preventive maintenance
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