[Ocean Chemical Valve Management] series of stickers - pressure testing methods for various valves, all masters are reading!

2. Pressure test methods for various industrial valves 2.1 Ball valves (including pneumatic ball valves) The ball valve pressure test is divided into strength test and sealing test. Floating, fixed, and three-way ball valves have different structures and different test procedures. The entire process follows the GB/T 13927-2022 standard. 2.1.1 Strength test The test is carried out with the ball in a half-open state. Both ends of the valve are closed, the test medium is filled into the valve cavity and clean air is discharged. The pressure is increased to 1.5 times the cold working pressure of the valve, and the pressure is maintained according to the nominal diameter.: DN≤50mm maintains pressure for 15s, 50＜DN≤150mm maintains pressure for 60s, 150＜DN＜350mm maintains pressure for 120s, DN≥350mm maintains pressure for 300s ； Check the valve body, valve cover, packing and gasket. If there is no visible leakage or structural damage, the valve is qualified. 2.1.2 Sealing test floating ball valve: The valve is half open, one end introduces medium, and the other end is closed ； After the ball rotates several times, it closes. Open the closed end to check the sealing surface and check that there is no leakage in the packing and gasket. ； Then introduce the medium in the reverse direction and repeat the test. If there is no leakage at both ends, it is qualified. Fixed ball valve: Before the test, rotate the ball several times without load, close the ball, and introduce medium at one end to the specified test pressure (1.1 times the cold working pressure). If there is no pressure drop during the pressure maintenance period, it is qualified. ； After repeating the test in reverse direction, the half-open valve is closed at both ends, the valve cavity is filled with medium, and the sealing performance of the packing and gasket is checked. Three-way ball valve: The sealing test needs to be carried out at each on-off working position to ensure that there is no leakage on the sealing surface of each flow channel. 2.2 Check valve The check valve test must be in a fixed standard posture, and it is strictly prohibited to place it randomly to affect the test results.: Lift check valve disc axis maintains vertical and horizontal position ； The axis of the swing check valve channel and the disc axis are approximately parallel to the horizontal line. (1) Strength test: Introduce the medium from the inlet end to the specified pressure, seal the outlet end, and the valve body and valve cover are qualified if there is no leakage or deformation during the pressure maintaining period. ； (2) Sealing test: Introduce the medium from the outlet end in the reverse direction, and check the sealing surface, packing and gasket at the inlet end. If there is no visible leakage, it is qualified. 2.3 Pressure reducing valve The pressure reducing valve test is divided into strength test and sealing test, taking into account both unit and assembly tests. The bellows welded components require additional special pressure tests. (1) Strength test: It can be assembled as a single piece after pressure test, or it can be assembled as a whole and then pressure test. ； The holding time is divided according to the nominal diameter.: DN＜50mm maintains pressure for 1min, DN65～150mm maintains pressure ≥2min, DN＞150mm maintains pressure ≥3min ； After the bellows and components are welded, conduct a strength test using air at 1.5 times the maximum pressure after the pressure reducing valve. If there is no leakage, it is qualified. (2) Sealing test: Carry out according to the actual working medium, the air/water medium test pressure is 1.1 times the nominal pressure, the steam medium is tested according to the maximum allowable working pressure at the working temperature, the inlet and outlet pressure difference ≥ 0.2MPa ； During debugging, the outlet pressure can be adjusted sensitively and continuously within the range without stagnation or jamming. ； The steam pressure reducing valve shuts off the valve and then cuts off the valve. The outlet pressure rises within 2 minutes and meets the regulatory requirements. ； The water/air pressure reducing valve is closed after the outlet pressure returns to zero. If there is no leakage within 2 minutes, it is qualified. 2.4 Butterfly valves (including pneumatic butterfly valves) (1) Strength test: Consistent with the stop valve strength test method, pressurize to 1.5 times the cold working pressure, maintain the pressure and check that there is no leakage in the shell. ； (2) Sealing test: Introduce the medium from the medium inflow end, open the butterfly plate, close the other end, and pressurize it to the specified value. After checking that there is no leakage in the packing seal, close the butterfly plate and open the closed end. If there is no leakage on the sealing surface of the butterfly plate, it is qualified. ； Butterfly valves used only for flow regulation do not need to undergo sealing performance testing. 2.5 Plug valve (1) strength test: The medium is introduced from one end, the remaining channels are closed, and the plugs are rotated to each fully open working position in sequence. The valve body is qualified if there is no leakage during the pressure maintaining period. ； It is allowed to apply non-acidic thin lubricating oil on the sealing surface before the test. It is strictly forbidden to apply grease on the gas plug valve. (2) Sealing test: The straight-through cock keeps the pressure in the chamber equal to that of the passage. Rotate the plug to the closed position. Check that there is no leakage at the other end. Rotate 180° and repeat the test. ； Three-way/four-way cocks are rotated to the closed position in sequence, pressure is introduced from the right-angle end, and the other ends are checked simultaneously ； The pressure holding time is 1 to 3 minutes according to the nominal diameter. If there is no leakage or expanding water droplets, it is qualified. ； For gas plug valves, the air tightness test is carried out at 1.25 times the working pressure. 2.6 Diaphragm valve (1) strength test: Introduce the medium at either end, open the valve disc, close the other end, and pressurize to the specified value. If there is no leakage in the valve body and valve cover, it is qualified. ； (2) Sealing test: Reduce the pressure to the sealing test pressure, close the valve disc, and open the other end to check. If there is no leakage at the sealing surface and diaphragm connection, it is qualified. 2.7 Stop valve and throttle valve (1) Strength test: After assembly, the valve is placed on the pressure test stand, the valve disc is opened, and the medium is injected to the specified pressure. Check that the valve body and valve cover are free of sweating and leakage. The pressure can also be tested individually. ； (2) Sealing test: Only the stop valve needs to be done. Keep the valve stem vertical, open the valve disc, and introduce the medium from below the valve disc. After checking that there is no leakage in the packing and gasket, close the valve disc, open the outlet end and check the sealing surface. If there is no leakage, it is qualified. ； When two tests are performed at the same time, the strength test is performed first, and then the pressure is reduced to the sealing test pressure and verified step by step. 2.8 Gate valves (including pneumatic gate valves) (1) Strength test: Consistent with the stop valve strength test method ； (2) Sealing test: Two methods are available. The intermediate pressure test method is not suitable for gate valves below DN32mm. ； (3) Intermediate pressure test method: Open the gate, pressurize it to the specified value, close the gate, check the sealing surfaces on both sides of the gate, or inject the medium through the valve cover plug to check ； (4) Conventional pressure test method: Open the gate to apply pressure, close the gate, open the blind plate at one end to check the sealing surface, and repeat the test in reverse until it passes the test. ； The sealing test of the pneumatic gate valve packing and gasket must be completed before the gate sealing test. Subsequent tests can only be carried out after passing the test. 2.9 Safety valve Safety valve is a safety accessory for special equipment. The test strictly follows GB/T 12242-2021 and special equipment regulations, and simplification of the process is strictly prohibited. (1) Strength test: Water is used as the medium. When testing the lower part of the valve body, the medium is introduced at the inlet end and the sealing surface is closed. ； When testing the upper part of the valve body and valve cover, the medium is introduced at the outlet end and the other ends are closed. ； During the pressure maintenance period, the valve body and valve cover are qualified if there is no leakage or damage. ； (2) Sealing and constant pressure test: The medium is selected according to the working conditions. Steam safety valves use saturated steam, gas safety valves use air, liquid safety valves use water, and important parts use nitrogen. ； The sealing test pressure is the nominal pressure, and the test is no less than 2 times. If there is no leakage within the specified time, it is qualified. ； Leak detection can be done by sealing the outlet flange with tissue paper (no bulging means it is qualified) or by filling with water and bubbling. ； The set pressure and reseating pressure shall be tested no less than 3 times, and the values ​​shall meet the requirements of the instructions and regulations to be qualified.

3. Valve pressure test site management regulations 3.1 On-site visual inspection All valves must be visually inspected after unpacking. Only after passing the test can they enter the pressure test process.: The valve body nameplate is complete and clear, and the product quality certification documents and certificates are complete. ； The valve is in a closed state, and the flange surface has no damage, rust, or dirt. ； The inlet and outlet are equipped with protective covers to prevent debris from entering the valve cavity. 3.2 Personnel and safety requirements Pressure test operators must be proficient in the pressure test bench operating procedures, valve structures and pressure test standards ； Identify potential safety hazards such as high-pressure injection and medium leakage in advance during the pressure test process, equip protective equipment, and formulate emergency preventive measures. ； Illegal pressurization and overpressure tests are strictly prohibited. Warning signs are set up in the test area and irrelevant personnel are prohibited from entering. 3.3 Standard pressure test process (three-step method) (1) Shell strength test: The medium is clean water, the pressure is 1.5 times the nominal pressure of the valve, the pressure is maintained for 5 minutes, and the shell is qualified if there is no leakage or surface moisture. ； (2) Upper seal test: The medium is clean water, the pressure is 1.1 times the nominal pressure, and the pressure holding time is distinguished by DN.: 15s for DN≤50, 60s for 65≤DN≤300, 120s for DN≥350. If there is no leakage at the seal on the valve stem, it is qualified. ； (3)Sealing test: For the low-pressure sealing test, the gate valve uses air medium with a pressure of 0.6MPa. The pressure holding time is 15s for DN≤50, 60s for 65≤DN≤150, and 120s for DN≥200. The leakage amount meets the national standard A-level requirements to be qualified. 3.4 Disposal and ledger management after pressure test (1) After passing the pressure test, immediately use dry compressed air to blow dry the moisture in the valve cavity to prevent corrosion. ； (2) Qualified valve bodies are clearly marked with a "√" mark, and unqualified valves are marked with a "×" mark. Confusion is strictly prohibited. ； (3) After the pressure test, the valves are stacked in sections according to device, model, and specification. Unqualified products are stacked in separate isolation. Eye-catching signs are set up in each section. The valves are restored to protective covers and covered with colored strips of cloth for protection. ； (4) Fill in the "Valve/Pipe Fitting Test Record" in a timely manner, and accurately fill in the valve body purchase contract number in the model column ； For the issuance of qualified valves, fill in the "Valve Issuance Record" and have both parties sign and confirm. ； For unqualified valves, a separate "Unqualified Valve Information Ledger" is established to record defects, disposal methods and whereabouts, and the entire process is traceable.

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