Tackling Internal Leakage in Electric Control Valves

Internal leakage in DN50 electric control valves is a common issue in industrial pipeline control. It can affect system performance and lead to energy waste or production losses. This article analyzes several common causes of internal leakage in WEIZIDOM electric control valves and provides corresponding solutions.

1.Inaccurate Zero Position Setting of the Actuator

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.

2.Insufficient Actuator Thrust

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.

3.Poor Valve Manufacturing Quality

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.

4.Control Components Affecting Valve Leakage

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: 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.

Conclusion:

Internal leakage in electric control valves can result from various factors, including actuator settings, insufficient thrust, valve manufacturing quality, commissioning errors, and improper sizing. Regular maintenance, accurate limit adjustment, and selecting the appropriate valve type are crucial to preventing leakage. Proper valve selection and process improvement can enhance valve lifespan and system reliability.