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What are the common causes of failure for pumps and control valves in chemical manufacturing processes? How should control valves be maintained in actual production? Today, I will learn together with you the basic knowledge and essential skills in this area. 1 Regarding control valves, control valves are the terminal actuating devices in automatic control systems; they regulate the production process by receiving control signals. Regulating valves feature high performance stability, low cost, and fire and explosion protection capabilities; they can be used in conjunction with pneumatic and electric control instruments, offering a high degree of automation. The advantages of control valves during use are: 1. They respond quickly, enabling them to carry out various adjustment commands in a timely manner ； 2. Used in combination with a large cylinder, it provides a high torque thrust force ； 3. It maintains stable performance in harsh working conditions and can operate normally ； 4. High safety performance. The proper functioning and responsiveness of control valves have a direct impact on production quality and efficiency. Therefore, it is particularly important to analyze the factors affecting failures of control valves during use and to develop corresponding solutions. 2 Fault analysis of control valves 1. How to deal with a stuck control valve? When a sticking problem occurs in the control valve, it is necessary to quickly open and close the valve, using the fluid medium to flush out the blockage ； A pipe wrench can also be used to clamp the valve stem; under the action of an external signal pressure, the valve stem is moved back and forth to push the valve core past the jammed area. If the jamming issue cannot be resolved at this point, the external pressure and driving power can be increased appropriately to carry out repeated movements; if the device fails to resume operation, a professional must disassemble the control valve. 2. How should leaks in control valves be dealt with? After internal leakage occurs in the control valve, the length of the valve stem should be adjusted appropriately so that it is suitable and no further internal leakage takes place ； After the packing leaks, in order to facilitate handling of the packing, it is necessary to chamfer the top of the packing box, and to install a corrosion-resistant metal protective ring with a small gap at the bottom of the packing box. The contact surface between the metal protective ring and the packing should not be inclined, so as to prevent the packing from being pushed out by the pressure of the medium. The surface of the part of the stuffing box that comes into contact with the packing should be finely processed, which improves surface smoothness and reduces packing wear. Flexible graphite is the best choice for fillers, as it offers high gas sealing properties, low friction, minimal wear over time, is easy to maintain, and possesses high pressure and heat resistance. Leakage can occur due to deformation of the valve core and seat; therefore, it is essential to carefully select the materials for these components, choosing ones with high corrosion resistance. Products with defects such as pitting or sand holes should be excluded, so as to ensure a high level of sealing quality for the valve core and seat. When the valve core and seat are severely worn or damaged, it is necessary to replace them with new ones. 3. How to deal with oscillation in control valves? The control valve oscillates; when the oscillation is mild, the stiffness of the spring can be increased, for example by selecting a spring with greater stiffness for the control valve ； When the pipes and bases vibrate violently, additional supports should be added to eliminate the vibration interference ； If the frequency of the valve is the same as that of the system, the control valve needs to be replaced. 4. What to do if the control valve does not operate? When the control valve does not function, the pressure regulator must be adjusted to bring the pressure to the specified supply pressure ； Inspect the leakage points in the pipelines of the locator junction box, and tighten or replace the joints and pipelines ； Inspect the magnifying hole and throttle hole of the locator and carry out repairs. 5. How to deal with unstable operation of control valves? If the control valve does not operate stably, it is necessary to inspect the signal pipelines, connectors, sealing rings, etc., and eliminate any leaks ； Find a loose component and tighten it ； Apply lubricant to components with high friction. 6. How to deal with slow operation of control valves? The control valve responds slowly; check the components with high friction and reassemble them ； Adjust the packing gland and replace the packing again. 3 How should control valves be maintained? If a control valve fails during operation, it can cause significant harm to the normal and stable functioning of the system; therefore, it is necessary to maintain these control valves in order to reduce the incidence of failures. 1. Passive maintenance: When a control valve fails, it is necessary to inspect the valve, determine the cause of the failure, and carry out timely repairs. 2. Preventive maintenance: It is necessary to clean the control valves regularly to maintain their cleanliness and ensure the integrity and durability of all their components. Pipes should also be flushed on a regular basis, with attention paid to any blockages or debris inside them. The fixing fittings of the control valves should be inspected periodically to ensure good corrosion resistance and lubricity of the components. When installing control valves, minimize forced pulling and bending during installation to reduce pressure and deformation. Maintain a distance between the control valve and the compressor to reduce vibrations from the source. Regulating valves should be inspected regularly; close attention should be paid to their operation, and it is necessary to check for leaks in the packing, applying lubricant to it on a regular basis. 3. Predictive maintenance: Utilizes smart meters or other diagnostic devices to obtain operational data on control valves, thereby improving their control performance and diagnostic capabilities. Through diagnosis using smart meters or other diagnostic devices, issues with control valves can be detected in a timely manner, allowing for prompt identification of solutions and maintenance actions. Increase the development and use of intelligent valve positioners. As precision instruments, control valves benefit from regular maintenance and inspection, which can effectively extend their lifespan. This not only helps to ensure the normal operation of factories but also saves a great deal of resources. Now everyone should know what to pay attention to when using control valves and how to carry out maintenance checks!