The ball valve serves as a crucial device for controlling, distributing, and altering the flow direction of fluids. Its operational mechanism involves the rotation of a spherical element by 90 degrees around the valve stem axis to facilitate opening and closing. Internal leakage within ball valves poses significant challenges during gas transmission pipeline operations, particularly affecting trunk pipeline shut-off valves. Various methods exist for the online detection of internal leakage in gas transmission ball valves, including valve cavity venting, process judgment, valve cavity pressure detection, instrument detection, etc. However, these methods come with their respective limitations. The approach outlined below offers a solution for intuitively displaying and accurately measuring the internal leakage of ball valves.

Online Detection of Internal Leakages in Ball Valves

Valve Cavity Venting

Valve cavity venting involves closing the valve and opening the drain port to vent gas from the valve cavity, allowing judgment on whether the valve is leaking internally. If the gas can be emptied to normal pressure immediately, it indicates no internal leakage. However, if gas discharge occurs after temporarily closing the valve cavity, it suggests slight internal leakage. In cases where the gas cannot be discharged continuously, it signals internal leakage or incorrect valve limits.

Process Judgment

For normally closed valves, internal leakage can be inferred from pressure changes in the processing system downstream of the valve. Conversely, for normally open valves, venting the upstream or downstream processing system post-valve closure aids in leakage assessment.

The internal leakage rate (Q) can be calculated using the differential pressure and volume of the connected processing system, considering factors such as initial and cavity pressures, volume, time, and nominal pipeline diameter.

Instrument Detection

Utilizing instruments such as ultrasonic detectors, acoustic emission detectors, infrared thermal imaging cameras, and ultrasonic phased array instruments allows qualitative or quantitative detection of internal leakages. However, these methods may not be suitable for buried globe valves and are relatively costly.

Pressure Detection of Valve

Chambers In ball valves with relief ports, pressure gauge installation enables observation of pressure variations or differences to assess internal leakage. The ideal gas state equation facilitates calculating the gas volume in the standard state, neglecting temperature effects.

Flowmeters

Installation of flow meters at discharge ports of ball valves facilitates internal leakage quantification by measuring gas flow rates. This method offers portable equipment and straightforward operation for accurate measurement.

In Conclusion

Effective detection of internal leakages in ball valves is essential for maintaining the integrity and efficiency of gas transmission systems. While various methods exist for online detection, each has its advantages and limitations. By combining multiple detection techniques and leveraging advancements in instrumentation and technology, operators can enhance their ability to identify and mitigate internal leakages promptly.