Two-component polyurethane adhesive (PU Adhesive) is an adhesive containing urethane group (-NHCOO-) or isocyanate group (-NCO) in the molecular chain. It is composed of isocyanate and hydroxyl-containing compounds such as polyester, polyether, castor oil or Other polyols are obtained by reaction. It has excellent performance, strong molecular designability, wide physical properties, and wide application range of bonding. It is one of the important varieties of synthetic adhesives. Two-component polyurethane adhesive is the product with the largest variety, the largest amount and the most widely used in PU. The two components of the product are packaged separately, easy to store, adjustable performance, high adhesive strength, wide application range, good weather resistance and other characteristics, showing unique advantages in the application field.
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Talking about the Preventive Maintenance of Control Valve
Control valve repair in general there are two: First, preventive maintenance, mainly refers to the regulator valve to ensure the reliable operation, and in the absence of failure to take preventive maintenance measures, including the installation and use of regulating valve in the field when a Series of preventive measures; the second is the failure of maintenance, that is, the control valve in the case of failure can not meet the operational requirements of a series of overhaul work, under normal circumstances in the production workshop to complete, under special circumstances may also be directly on the pipeline maintenance . Preventive maintenance Preventive maintenance is planned maintenance before the regulator fails, can be understood as routine maintenance, usually including the following work. 1. Elimination of stress lines due to combination or improper installation will produce a variety of stress, such as heat stress caused by high temperature medium, the installation of the fastening force is not balanced due to stress, some man-made impact to the control valve and its pipeline caused by stress . The stress on the regulating valve and its pipeline, it is easy to affect the performance of the regulating valve, will seriously affect the regulation system itself, resulting in deformation of the stem and the guide and the valve seat can not be aligned; for the split valve The body of the control valve, valve body flange may cause disengagement; stress may also cause seat leakage and so on. Therefore, at all times ensure that stress is avoided or relieved, directing the stress away from the regulating valve. 2. Inspection of Safe Operation The control valve and related accessories used in explosive hazardous area should be checked for safe operation, such as tightening of sealing cap, operation of safety barrier, power supply, etc. to ensure that the control valve and related accessories can safe operation. 3 Check the support situation The best position to install the control valve is the valve stem stroke direction and the actuator above the body in a vertical plane. If the control valve must be installed in a position where the valve stem moves horizontally or the valve stem moves in a certain inclination to the horizontal plane, the actuator should be supported so that the various parts of the control valve are in a natural state. If you do not add support or improper support improper installation may cause valve stem and valve seat of the different heart, easily lead to poor change or filler leakage and other failures. Even if the control valve has a fixed and support measures, but also must be regularly checked, usually 2 to 3 months to check. 4 to remove or prevent foreign objects to enter Check the valve regularly to connect the pipeline without rust, welding slag, dirt, etc., should be promptly removed after the discovery. If the control valve and piping easy to accumulate foreign matter, it is necessary to consider the upstream side of the control valve to install a simple filter device. In the process medium easy to infiltrate hard debris occasions, be sure to install a permanent filter device. Because the valve is closed, a small piece of rust or welding slag is sufficient to destroy the well-worn seat sealing surface, Moreover, these dirt will also cause valve spool and seat wear, affecting its normal operation. 5 Regular Maintenance and Refueling Fillers and lubricators need to be readjusted after a short period of use. Dusty occasions to around the stem with a plastic sleeve or rubber sleeve to protect the stuffing box and the guide parts, corrosive gases or droplets in the presence of special protection measures should be used, the general use of anti-corrosion bag wrapped around the control valve, but to Attention can not affect its operation. In the fire resistance requirements of the occasion, you can use special refractory coatings, sets of fire bags and other methods, fire bag material containing multi-layer ceramic fiber or glass fiber. 6 transport and storage control valve assembly and paint and installed on the actuator, handwheel, locator and other accessories later, in order to prevent foreign substances into the control valve, connecting all the air control valve interface must be plugged, connect the flange Install the protective cover, pay attention to the various connection parts, such as the valve positioner intake pipe, the actuator interface state. Any protruding attachments that are easily damaged, such as pressure gauges for oiler and potentiometer, should be removed from the fitting, packaged separately from the regulator, and shipped together. Control valve dedicated bracket fixed to prevent loosening, to ensure the overall vertical position or horizontal position. If the long-distance transport, it is best to use a solid wooden shipping. When storing the control valve, do not support the control valve in sensitive areas such as valve positioners, stems and the like. Environmental conditions for transport and storage shall meet the requirements of the product specification. Storage area is best not to carry out other operations, can not be avoided, we must be careful not to touch the control valve. Locations should also be protected from harsh conditions such as wind, dust, rain and the like. In the absence of a suitable site, the regulator must be installed in a damp-proof bag prior to storage or in a similar container. 7 Regular inspection of the gas source and the power source is one of the key energy sources driving the control valve. Pneumatic valve diaphragm chamber does not consume air, but if the gas source system contains moisture, oil and other impurities, it will plug the valve positioner, the relay and other clogging and failure. Therefore, we must regularly check the gas source and power supply to ensure that the gas source clean, dry, reliable power supply.