Operation guide for valve pressure testing

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First, let’s introduce the basic terms related to pressure testing: Sealing test – a test designed to evaluate the sealing performance of the seal between the valve stem and the valve cover; Shell test – a pressure test conducted on the entire valve housing, which consists of the valve body and the valve cover. The purpose is to test the tightness of the valve body and valve cover, as well as the pressure resistance of the entire housing, including the joint between the valve body and valve cover. Sealing test: A test to evaluate the sealing performance of the moving parts and the sealing surfaces of the valve body. Test pressure: The gauge pressure that must be applied inside the valve during the test. Test duration: The length of time the valve is subjected to the test pressure. The pressure tests described in this article are applicable to gate valves, globe valves, check valves, plug valves, ball valves, butterfly valves, diaphragm valves, etc. I. Test items: Items for pressure testing include 1) Housing test, 2) Upper sealing test (this test is required for valves with an upper sealing mechanism), 3) Sealing test. II. Test requirements: 1) Each valve must undergo a pressure test before leaving the factory. 2) Painting or applying other leak-proof coatings to the valve is not allowed until the housing test is completed; however, chemical rust prevention treatments that do not provide sealing effects, as well as lining the valve, are permitted. For painted inventory valves, if the user’s representative requests a repeat pressure test, it is not necessary to remove the coating. III. Before conducting the sealing test, oil stains from the sealing surfaces should be removed; however, a thin layer of protective agent with a viscosity not greater than that of kerosene may be applied. For valves sealed with grease, the grease specified in the design requirements may be used. IV. During the test, the valve should not be subjected to any external forces that could affect the test results. V. Unless otherwise specified, the temperature of the testing medium should be between 5 and 40°C. VI. The manufacturing factory shall choose the testing medium itself, provided that it complies with the specifications in Tables 1 and 2: 1. Liquids: water (rust inhibitors may be added), kerosene, or other suitable liquids with a viscosity not greater than that of water. 2. Gases: air or other suitable gases. VII. When using a liquid for testing, the gas present within the valve chamber must be removed. When using gas for testing, safety precautions must be taken. 8. When conducting sealing and leak-tightness tests, the components should be closed in the manner specified in the design. 9. The test pressure must comply with the regulations: 1. The test pressure for shell tests is as specified in Table 1. Note: The maximum allowable operating pressure at 20°C is determined in accordance with the relevant product standards. When the relevant standards do not provide specifications, these can be determined in accordance with Appendix A (Reference). 2. The test pressure for the sealing and upper-sealing tests shall be as specified in Table 2. 3. The test pressure must remain constant throughout the duration of the test. 10. The duration of the test shall comply with the specified requirements: 1. The duration of the shell test shall be no less than that specified in Table 3. 2. The duration of the sealing and upper-sealing tests shall be no less than that specified in Table 4. 3. In addition to complying with the requirements in Tables 3 and 4, the test duration must also meet the requirements set by the specific leak detection methods. 3. Test methods and procedures: The upper-sealing test and the shell test should be carried out first, followed by the sealing test. Upper-sealing test: Seal the inlet and outlet of the valve, loosen the packing gland (if the valve is equipped with an upper-sealing inspection device and the performance of the upper seal can be reliably checked without loosening the packing gland, then it is not necessary to loosen it). Keep the valve in the fully open position to close the upper seal, fill the chamber with the test medium, and gradually increase the pressure to the specified test pressure; thereafter, check the performance of the upper seal. Shell test: Seal the inlet and outlet of the valve, tighten the packing gland to maintain the test pressure, and keep the moving parts in a partially open position. Fill the cavity with the test medium and gradually increase the pressure to the test pressure (the check valve should be pressurized from the inlet side); thereafter, inspect the seal of the housing (including the stuffing box as well as the joints between the valve body and the valve cover). The method for applying pressure to main valves is specified in Table 5. However, for valves that specify the flow direction of the medium, pressure should be applied in accordance with the specified flow direction (except for check valves). During testing, pressure should be increased gradually to the specified test pressure, after which the sealing performance of the sealing pair should be checked. IV. Evaluation criteria: Shell testing – During shell testing, there should be no visible leaks at the pressure-bearing walls or at the joints where the valve body is connected to the valve cover; the shell (including the stuffing box and the joints between the valve body and the valve cover) should not suffer any structural damage. Unless otherwise specified, leakage at the packing is permitted at the shell test pressure; however, when the test pressure is reduced to the seal test pressure, there should be no visible leakage. During the duration of the seal test, no visible leakage is allowed. The maximum allowable leakage amount for the seal test is specified in Table 6. The leakage amounts in Table 6 apply only to emissions into the atmosphere. Class A is suitable for non-metallic elastomeric-sealed valves, while classes B, C, and D are suitable for metal-sealed valves. Among them: Grade B is suitable for relatively critical valves, while Grade D is suitable for ordinary valves. The maximum allowable leakage rate (grade) for various types of valves shall be in accordance with the provisions of relevant product standards. If the relevant standards do not specify otherwise, non-metallic elastic-sealed valves shall meet the requirements of Class A, while metal-sealed valves shall meet the requirements of Class D. If the customer requests compliance with Class B or Class C requirements, this shall be specified in the order contract