Valve leakage testing is a crucial step in ensuring valve sealing. Sealing is one of the most critical performance characteristics of a valve, directly impacting the safety and stability of fluid control systems. Whether in the petroleum, chemical, power, or water supply industries, valve leakage testing plays a vital role in preventing accidents or losses caused by leaks. To ensure valve sealing and functionality, various international and national standards have clear regulations for valve leakage testing. This article will discuss valve leakage testing standards in detail, including test methods, leakage requirements, and applicable scope.

I. Importance of Valve Leakage Testing

As a key component of fluid control systems, the sealing performance of valves is paramount. Leakage testing helps determine whether a valve meets sealing requirements, thereby preventing fluid loss, environmental pollution, safety accidents, or equipment damage due to leakage. Valve leakage problems not only affect the normal operation of equipment but can also cause system pressure instability or inaccurate flow, ultimately impacting the reliability and efficiency of the entire production process.

II. Classification of Valve Leakage Testing

Standards Valve leakage testing standards are typically classified according to different valve types, operating environments, and leakage levels. According to the International Organization for Standardization (ISO) and national industry standards, the main standards for valve leakage testing are as follows:
1. ISO 5208 Standard
ISO 5208 is a general standard published by the International Organization for Standardization regarding valve leakage testing, applicable to the leakage testing of most valves. This standard specifies the classification, test methods, and leakage requirements for valve leakage testing. ISO 5208 classifies valve leakage levels into four categories: Sealed (A), Standard Sealed (B), Low Leakage (C), and High Leakage (D). These levels are applicable to different operating conditions based on the valve's sealing performance requirements.
Sealed (A): Highest sealing requirements, suitable for valves requiring extremely high sealing performance, suitable for applications with extremely high sealing requirements, such as high pressure, hazardous chemicals, or high temperature conditions.
Standard Sealed (B): Suitable for valves under general operating conditions, with low leakage, meeting routine operating requirements.
Low Leakage (C): Suitable for applications with lower sealing requirements, allowing a certain amount of leakage.
High-leakage type (Class D): Suitable for applications with low sealing requirements, allowing for a relatively large degree of leakage.
ISO 5208 defines the specific test methods and permissible leakage amounts for each leakage level to ensure the safety and effectiveness of valves during operation.
2. API 598 Standard
API 598 is a standard published by the Oil and Gas Industry Association (API), specifically for valve leakage testing in the oil, gas, and related industries. This standard specifies the test methods, test pressures, test media, and specific leakage requirements for valve leakage. API 598 particularly emphasizes valve testing requirements in high-temperature, high-pressure, and corrosive media environments.
According to API 598, valve leakage testing is divided into two categories:
Air tightness test:Applicable to valves operating under gaseous media, requiring the valve to undergo an air tightness test under high pressure to ensure it does not leak.
Liquid tightness test:Applicable to valves operating under liquid media, requiring the use of a suitable liquid media (such as water or oil) and testing at a specified pressure.
API 598 standard specifies leakage testing requirements for different types of valves, including ball valves, gate valves, and globe valves, and specifies the leakage rate for each valve at different pressure levels.
3. ASME B16.34 Standard
ASME B16.34 is a standard published by the American Society of Mechanical Engineers (ASME) that covers the design, materials, manufacturing, testing, and installation requirements for valves. The leakage testing requirements in this standard apply to various high-pressure valves, especially those used in high-risk environments such as oil, gas, and chemical industries. ASME B16.34 requires gas tightness and liquid tightness testing of valves and specifies the test pressure, medium, leakage rate, and measurement methods.
ASME B16.34 standard specifies leakage standards for common valve types, such as ball valves, gate valves, and butterfly valves, under different operating conditions, helping to ensure the reliability of valve performance under extreme conditions.
4. DIN 3230 Standard
DIN 3230 is a German industrial standard primarily used for valve leakage testing and quality control. This standard specifies the measurement methods and test conditions for valve leakage and is applicable to valve manufacturers in the European market. DIN 3230 standard specifies leakage requirements for different types of valves, including manual valves, automatic valves, and electric valves.
In DIN 3230, valve leakage is divided into multiple levels, from completely impermissible leakage to allowance of very small amounts of leakage, providing detailed test conditions and measurement methods for different working environments and media.
5. GB/T 13927 Standard
GB/T 13927 is a Chinese national standard applicable to leakage testing of most industrial valves. This standard requires comprehensive testing of the airtightness and liquid tightness of valves and specifies the specific test requirements, including test pressure, test time, and allowable leakage. GB/T 13927 standard particularly emphasizes the sealing performance of valves under high temperature and high pressure conditions, ensuring that they can meet the needs of complex operating conditions.

III. Basic Requirements for Valve Leakage Testing
The basic requirements for valve leakage testing are as follows:
1. Test Medium
Valve leakage testing usually requires the use of a specific test medium. Common media include gases (such as air or nitrogen) and liquids (such as water, oil, etc.). 1. **Gas Media Testing:** Testing gaseous media is generally used for valves in low-pressure or high-pressure gas pipelines, while testing liquid media is used for valves in liquid pipelines. For valves handling corrosive media, a suitable chemical medium must be selected to ensure that the testing process does not damage the valve material.
2.Test Pressure:Test pressure is a crucial parameter in leak testing and is typically determined according to the valve's operating pressure rating. Different standards and industry requirements may dictate different test pressures. Generally, the leak test pressure is 1.1 to 1.5 times the design pressure, depending on the specific application requirements.
3.Leakage Quantity Requirements:Leakage quantity is a key indicator for evaluating valve sealing performance. Different standards have different leakage quantity requirements for different valve classes. For example, ISO 5208 specifies the permissible leakage quantity for each leakage class. Generally, the lower the leakage quantity, the better the valve's sealing performance, suitable for applications requiring strict control of fluid leakage. Standards have specific leakage quantity requirements for different types of valves to ensure that the valve maintains efficient sealing performance during use.
4.Test Time:The test time is another critical factor. The test time should generally be long enough to ensure that the leakage quantity can be accurately measured. Generally, the test time ranges from 10 minutes to 1 hour, with the specific time varying depending on the valve's size, type, and test standards.
5. Test Environment The temperature and humidity of the test environment have a certain impact on the leakage test results. In some standards, the test environment temperature should generally be controlled at room temperature (around 20°C) to avoid temperature changes affecting the performance of the sealing materials and valve body. In special cases, if the test requires the valve to operate at high or low temperatures, adjustments must be made according to the corresponding test standards.

IV. Implementation Process of Leakage Testing

The implementation process of valve leakage testing typically includes the following steps:
1. Preparation Before conducting the leakage test, a visual inspection of the valve is required to confirm that the valve's model, specifications, and operating pressure meet the requirements. Simultaneously, the valve's installation location and operating environment should be checked to ensure that the test process is not interfered with by external factors.
2. Pressure Application According to standard requirements, the test medium is applied to the valve's inlet and outlet, and the test pressure is gradually increased. The test pressure should be set according to the valve's design pressure and standard specifications. Once the required test pressure is achieved, the leakage test begins.
3. Leakage Monitoring
After applying pressure, monitor the valve's leakage rate. If the leakage rate is within the standard's allowable range, the valve passes the test; if it exceeds the standard's specified leakage rate, the valve is considered unqualified and requires repair or replacement.
4. Result Recording
After the test, record data such as leakage rate, test pressure, and time, and determine whether the valve meets the leakage standards based on the test results.

V. Summary
Valve leakage testing is a crucial step in ensuring the normal operation of valves. Standards cover multiple aspects, including test methods, test pressure, leakage rate, and media requirements. Different valve types and application areas require different test standards and methods. Common standards include ISO 5208, API 598, and ASME B16.34. In practice, leakage testing should adhere to strict standard requirements to ensure the valve's sealing performance meets application requirements and guarantees the safe and stable operation of the system.