3.3 spool, valve leakage deformation
Valve core, valve leakage was mainly caused by the production process control valve in the casting or forging defects can lead to corrosion strengthened. The corrosive medium through the fluid medium can also result in erosion control valve leakage. Erosion or corrosion mainly exists in the form of cavitation. When the corrosive medium through the valve, it will give rise to spool, valve seat materials, erosion and impact so that valve core, valve seat into an oval or other shape, as time goes on, leading to valve core, valve seat is not matching, there is clearance, Guan lax leak. | MechNet | more knowledge, please visit the China National Machinery and network of experts, http://www.mechnet.com.cn/
Solution: The key to a good valve core, valve seat material selection customs, quality. Select corrosion-resistant materials, Ma points, trachoma and other defective products and resolutely removed. If the valve core, valve seat deformation is not serious, can grind through the fine sandpaper to remove traces, improve sealing finish to improve sealing performance. If serious damage, it should be re-replaced with new valves. | MechNet | more knowledge, please visit the China National Machinery and network of experts, http://www.mechnet.com.cn/
4, oscillation
Control valve spring stiffness of inadequate control valve output signal instability could easily cause a drastic change in valve oscillation. Also that the election of the frequency of the system valve or pipe the same frequency, base severe vibration, so that control valve resulting vibrations. Selection of improper valve working in a small opening there is a violent flow resistance, velocity, pressure changes, when more than valve stiffness, stability deteriorated, severe oscillation.
Solutions: As the oscillation are many reasons, so the concrete analysis of specific problems. A slight vibration vibration, can increase the stiffness to eliminate. Chooses to use the large stiffness of spring, use piston implementation structures. Pipeline, the base support by increasing the elimination of severe shock vibration interference; selected valve the same as the frequency and system frequency, then switch to a different structure of the valve; work in the small openings caused by the oscillation, it is improper selection of flow capacity of C values of selected large, Selection of capacity C must be re-circulation of the value of the smaller or using sub-process control valves, or Picture-regulating valve in order to overcome the work of a small opening.
5, valve positioner faults
5.1 Common locator using mechanical force balance principle, namely nozzle baffle technology, mainly in the following fault types:
1) the use of mechanical force balance principle of work and its moving parts are more susceptible to temperature, vibration, resulting in control valve fluctuations;
2) The nozzle shield technology, due to the nozzle hole is very small, prone to dust or clean gas source block is the locator does not work;
3) Use of force balance principle, elasticity of the spring occurs in adverse changes in the scene, resulting in non-linear lead to the control valve decline in the quality.
5.2 Smart Positioning is controlled by the microprocessor (cpu), A / D, D / A converter and other components, whose working principle and common Locator different. For a given value and actual value comparison of purely electric signal, is no longer a force balance. Therefore, to overcome the conventional force balance locator shortcomings. However, for emergency parking lot timely, such as emergency shut-off valves, emergency venting valve. These valves require stationary at a certain location, only an emergency occurs, it requires good movement. Prolonged stay in a location easy for the electric converter small-signal does not cause uncontrolled movements of hazardous situations. In addition, the valve position sensor for the potentiometer as a result of on-site, easy to change in resistance value caused by the small-signal non-action, large-signal full-hazards. Therefore, in order to ensure the reliability and intelligent positioning device availability, they must be frequently tested.
6, Conclusion
By regulating valve failure cause analysis and take appropriate treatment, improved methods will greatly enhance the utilization of regulating valve to reduce instrument failure rate, the process technology to improve production efficiency and cost-effective and energy consumption all have an important role in reducing can effectively improve the quality of conditioning systems, thereby ensuring long-cycle production plants running.
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