What are the possible causes and solutions for ball valve internal leakage?

Ball valves are widely used in various industries due to their reliability and efficient flow control. However, like all mechanical components, they can experience internal leakage over time. Internal leakage occurs when fluid passes through the valve despite it being in the closed position, which can pilot to operational issues, safety concerns, and increased maintenance costs.

One of the more frequent causes of internal leakage in ball valves is wear or damage to the valve seat. The valve seat is the sealing surface against which the ball rests to create a tight shutoff. Over time, if the fluid medium contains particles such as sand, rust, or other debris, these particles can cause abrasion or scratches on the seat. This wear compromises the sealing surface, allowing fluid to leak through even when the valve is closed.

Another possible cause of leakage is deformation of the ball itself. Ball valves are designed to operate under specific temperature and pressure ranges. Operating the valve beyond these limits, such as at excessively high temperatures or pressures, can cause the ball to warp or deform. This deformation prevents the ball from aligning properly with the seat, pilot to incomplete sealing and leakage.

Seal rings, often made of rubber, PTFE, or other polymer materials, play a crucial role in achieving a leak-tight closure. Over time, these materials can age, harden, or crack due to exposure to chemicals, heat, or mechanical stress. An aged or deteriorated seal ring loses its elasticity and sealing ability, which results in internal leakage.

When internal leakage is detected, the one step is to disassemble the valve and carefully inspect the valve seat and ball surfaces. Damaged or scratched parts should be replaced to restore the valve’s sealing capability. In some cases, light resurfacing or polishing of the ball and seat may be possible, but replacement is often the more reliable solution.

Selecting the appropriate sealing material based on the operating conditions can significantly reduce the risk of leakage. For high-temperature applications, metal seals are often preferred due to their resistance to thermal degradation. In contrast, soft seals like PTFE may be suitable for lower temperatures but may wear out faster under harsh conditions. Proper material selection ensures longer service life and improved sealing performance.

Preventive measures are equally important. One effective way to reduce internal leakage is to ensure that the pipeline and valve cavity are free from welding slag, dirt, and other foreign materials before installation. Contaminants inside the valve can cause damage to the sealing surfaces and pilot to leakage. Flushing or cleaning the pipeline prior to valve installation helps maintain valve integrity and prevents premature wear.

Routine inspection and maintenance can detect early signs of wear or seal aging. Scheduled checks allow for timely replacement of worn parts and small unplanned downtime. Lubrication of moving parts and verification of proper valve operation also contribute to reducing internal leakage.

Internal leakage in ball valves can arise from wear or damage to the valve seat, deformation of the ball, or aging of the seal ring. Addressing these issues involves inspecting and replacing damaged parts, selecting appropriate sealing materials for operating conditions, and maintaining clean pipelines. Through proactive maintenance and correct installation practices, the risk of internal leakage can be small, ensuring reliable valve performance and system safety.