**Abstract:** This paper provides an overview of the key standards and testing procedures involved in the manufacturing and inspection of valves used in water supply and drainage systems. It outlines the different types of valves, such as shut-off, control, check, and air release valves, and explains the essential test items and methods required for each type. The document also highlights the importance of adhering to both domestic and international standards during valve production and quality assurance. Additionally, it discusses critical aspects like material properties, casting quality, pressure testing, sealing performance, and operational life, ensuring that valves meet safety, efficiency, and reliability requirements before being released for use.
**1. Overview**
Valves are essential components in pipeline systems, designed to regulate, control, or stop the flow of fluids. In water supply and drainage systems, they serve multiple functions such as isolation, pressure regulation, backflow prevention, and air venting. Valves can be broadly categorized into four main types: shut-off valves (e.g., gate, globe, butterfly, ball, and plug valves), control valves (e.g., pressure-reducing, throttle, and regulating valves), check valves (to prevent reverse flow), and air release valves (to expel air from pipelines). Before leaving the factory, all valves must undergo rigorous inspections, with some requiring type tests to confirm their compliance with performance and operational standards.
**2. Inspection and Test Items**
Common test items for valve type and factory testing are detailed in Tables 1 through 4. These include pressure tests, seal tests, and structural integrity checks. For example, the seal test is crucial for valves with sealing structures, and specific attention should be given to the sealing surfaces. Note that certain tests may be marked with symbols indicating their necessity, and special care must be taken to ensure that all relevant criteria are met.
**3. Standards for Valve Manufacturing and Testing**
A comprehensive list of domestic and international standards is provided in Table 5. These cover various aspects of valve design, materials, and testing. Domestic standards include GB/T series, while international standards such as ISO, BS, ANSI, and JIS are also referenced. Examples include GB/T 13927 for pressure testing, ISO 5208 for industrial valves, and AWWA C500 for water supply gate valves. Adherence to these standards ensures consistency, quality, and safety across different valve types and applications.
**4. Quality Requirements**
Valve quality is governed by several key factors:
- The chemical composition and mechanical properties of the valve body must meet material standards.
- Casting dimensions and shapes should conform to technical drawings.
- Non-machined surfaces should be smooth, free of defects like cracks, porosity, or sand inclusion.
- Connections between valve parts must be secure and not loose.
- Pressure and sealing tests must comply with standard requirements.
- Operation under nominal and specified pressures should be smooth and unobstructed.
- Valves must have a sufficient number of operations and service life.
- High flow capacity with minimal pressure loss is essential for efficiency.
**5. Inspection and Test Methods**
5.1 **Casting Quality**
Casting dimensions and shape must match technical specifications. If no size deviation is specified, JB/T 2580, GB/T 6414, and GB/T 2121 apply. Castings must be free of cracks, cold shuts, or sand inclusions. Surface defects like sand, sprues, and scale should be removed, and markings must be clear. The shell test, performed at 1.15 times the nominal pressure, must show no leakage or damage. Chemical and mechanical properties must meet GB/T 12225–12230 standards.
5.2 **Pressure Test**
The most fundamental test, pressure testing is conducted on every valve before it leaves the factory. According to GB/T 13927, the shell and seal tests are performed, with the latter focusing on the sealing structure. During the test, the valve must remain unaffected, and the packing must be properly maintained. Liquid media require air to be expelled, and valves must be closed as per design. Relevant standards include GB/T 13927, ISO 5208, API 598, and others.
5.3 **Operating Torque and Life Test**
Some foreign standards, such as BS 5163 and AWWA C509, specify maximum operating torque and minimum life cycles. While Chinese standards do not yet fully address these details, life test procedures for various valve types are established.
5.4 **Flow and Pressure Difference Coefficient**
Foreign manufacturers emphasize the flow-pressure difference and flow coefficient of valves. These parameters help users select valves that minimize pressure loss and maximize flow, leading to energy savings. China has also developed standards for measuring these values, enabling efficient system design.
**6. Conclusion**
Before leaving the factory, valves must be thoroughly tested and inspected according to relevant standards. This ensures their performance, reliability, and compatibility with the piping system, ultimately contributing to the safety and efficiency of water supply and drainage networks.
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