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Case
Cause: The zero position of the actuator is inaccurately set, preventing the valve from fully closing. Especially during manual operation, the valve may not be completely shut off.
Solution:
Manually close the regulating valve globe valve and ensure it is fully shut;
Apply moderate force to tighten further, then turn it back half a turn (in the opening direction);
Adjust the limit switch to ensure the zero position is accurately set.
Cause: The actuator’s thrust is insufficient, particularly when the valve closes by pushing downwards. The actuator cannot overcome the upward force of the liquid when pressure is applied, resulting in incomplete closure. During pressure-free testing, the valve may seem to fully close, but it fails under pressure.
Solution:
Replace the actuator with a higher-thrust model;
Alternatively, switch to a balanced valve plug to reduce unbalanced forces from the medium.
Cause: During the manufacturing process, inadequate control over the regulating valve globe valve material, machining, and assembly may result in faulty sealing surfaces, porous surfaces, or pitting, leading to internal leakage.
Solution:
Reprocess and regrind the sealing surfaces of the valve;
Ensure strict quality control during manufacturing to eliminate defects.
Cause: Traditional electric control valves rely on mechanical control through limit switches and torque switches. These components are susceptible to environmental factors such as temperature, pressure, and humidity, leading to positioning inaccuracies, spring fatigue, and uneven thermal expansion, which cause internal leakage.
Solution:
Re-adjust the limit switches;
Regularly maintain and replace worn control components to ensure proper valve operation.
Cause: Improper adjustment during commissioning, such as incorrect settings of the torque switches or travel limits, can cause the valve to either not fully close or not fully open. Additionally, there may be cases where the valve is manually closed tightly but cannot be reopened electrically.
Solution:
Adjust the upper and lower limit switches accurately to ensure proper travel range for opening and closing;
Avoid setting the torque switch to overly high values to prevent damage to the valve and actuator.
Cause: Improper adjustment during commissioning, such as incorrect settings of the torque switches or travel limits, can cause the valve to either not fully close or not fully open. Additionally, there may be cases where the valve is manually closed tightly but cannot be reopened electrically.
Solution:
Adjust the upper and lower limit switches accurately to ensure proper travel range for opening and closing;
Avoid setting the torque switch to overly high values to prevent damage to the valve and actuator.
Cause: Cavitation occurs when the pressure difference across the valve exceeds the critical pressure difference, leading to the formation and collapse of bubbles. This process releases large amounts of energy, which severely damages the valve seat and plug, causing significant internal leakage. In cavitation conditions, a valve can experience serious damage in just a few months.
Solution:
Select the appropriate electric control valve based on process requirements;
Use multi-stage pressure-reducing or cage-type valves to mitigate cavitation.
Cause: Over time, the control valve may be eroded by the medium, causing cavitation and wear on the valve plug and seat. Aging of internal components can also contribute to internal leakage as the valve’s sealing performance deteriorates.
Solution:
Regularly inspect and adjust the actuator;
Replace aging components and perform periodic maintenance and calibration to ensure the valve operates properly.