Common Causes and Solutions of Valve Faults - Problem Chain and Professional Answers

During the operation of valves, various faults often occur due to improper operation, inaccurate material selection or inadequate maintenance. The following provides professional answers to the most common types of questions raised by users one by one, helping you quickly identify the causes and take the right measures.

Q1: What causes air leakage in solenoid valves? How to handle it?

The most common cause of air leakage in solenoid valves is that the rubber ring inside the gasket between the solenoid valve and the actuator or mounting plate falls off during transportation or installation.

When handling, the connection between the solenoid valve and the actuator should be disassembled first to check whether the small rubber ring inside the gasket is in place. If missing, a rubber ring that meets the specifications should be replaced and tightened evenly with the specified torque to prevent deformation of the sealing surface due to excessive force on one side.

When purchasing valves, it is recommended to choose suppliers that have strict assembly standards and quality inspection procedures for actuator accessories. Before leaving the factory, W&T valves undergo a full-process assembly inspection of the actuator and accessories to ensure that the sealing rings, gaskets and other accessories are installed properly, reducing the risk of air leakage from the source.

Q2: How to determine internal leakage in valves? What's the reason?

Answer: The method to determine internal leakage in a valve is as follows: After the valve has been closed for 4 to 6 hours, measure the metal temperature of the valve stem (near the valve body) or 150mm downstream of the valve body with an infrared thermometer. If it is greater than 70℃, it is determined to be internal leakage.

This judgment method is applicable to most internal leakage valves. There are two reasons:

New valve: It might not be fully closed. A detailed investigation is needed

Old valve: It might be due to damage to the sealing surface. It needs to be disassembled for inspection, grinding or replacement

The Viti high-pressure differential steam trap regulating valve adopts a super-thick hard alloy surfacing sealing surface. When the valve is fully open, the valve core is completely protected by the pressure-reducing sleeve and is not eroded by the medium, fundamentally reducing the probability of sealing surface damage.

Q3: What are the reasons for the actuator not moving?

Answer: Whether the actuator does not act needs to be determined separately based on the type of actuator.

Diaphragm actuator: It might be that the diaphragm is perforated. It is necessary to determine whether it is due to temperature shock or the presence of corrosive gas in the air source. If the movement is very fast and exceeds the preset stroke, it indicates that the spring has been under long-term pressure, resulting in a decrease in its elasticity. The spring needs to be replaced.

Cylinder actuator: It is possible that the rubber ring on the piston inside the cylinder has aged due to long-term temperature shock, resulting in seal failure. If the movement is too fast, it is also caused by the decline of the spring's elastic force.

Rack and pinion actuator: If it still cannot be closed when turned to the maximum after ventilation, first observe the top indicator bar or limit switch. If it is not fully open, it indicates that the limit screw has not been adjusted properly and needs to be readjusted.

The Viti actuator is equipped with high-quality sealing materials and spring components. Before leaving the factory, it undergoes action tests and torque checks to ensure stable and reliable long-term operation.

Q4: What causes the valve stem to bend, the thread to be damaged or the rotation to get stuck?

Answer: There are mainly two types of reasons for valve stem bending, thread damage or rotational jamming.

Improper operation: Excessive force applied to the switch, malfunction of the limit device, and failure of the overtorque protection. The solution is not to apply excessive force and to check the limit device and the over-torque protection device.

2. Excessive operation frequency and long service life: Spare parts need to be replaced.

The main reasons for poor rotation or jamming include: the packing is pressed too tightly, the packing is not installed properly, the valve stem and the bushing are made of the same material or the gap is insufficient, the valve stem is bent, and the surface roughness of the thread does not meet the requirements.

The Viti valve stem adopts an integral high-strength design. The non-rotating valve stem structure minimizes the wear of the valve stem on the packing to the greatest extent. Combined with the butterfly spring compensation packing seal, it will not get stuck or leak internally during long-term operation.

Q5: How to deal with leakage at the sealing surface and packing of the control valve?

Answer: Leakage at the sealing surface is usually caused by scratches, wear on the sealing surface or changes in actuator parameters, resulting in an incomplete switch. Packing leakage is often caused by the gland not being tightened or pressed off-center, incorrect installation methods, or damage to the surface of the valve stem.

Sealing surface leakage treatment: Process and trim the sealing surface, or replace the valve seat and ball. Adjust or replace the actuator.

Packing leakage treatment

Check and adjust the packing gland to prevent it from being misaligned

Install the packing material in the correct way

Repair or replace the valve stem

The Viti control valve adopts a replaceable valve seat design. When the unit is under maintenance, the valve can be replaced and maintained online without being cut off from the pipeline. The sealing surface is surfacing with super-thick hard alloy to ensure compliance with the MSS-SP-61 sealing standard.

Summary

The core logic for handling valve faults is: first, determine the type of fault, then locate the root cause, and finally deal with the symptoms - adjust the actuator for operational issues, replace spare parts for material problems, and contact professional suppliers for selection issues.

W&T, based on German technology and supported by complete machine production in Russia, strictly adheres to international standards in the design, material selection and assembly of its valve products, providing long-life and highly reliable fluid control solutions for industries such as power, chemical engineering and metallurgy.