In order to ensure that cryogenic valves can operate safely and reliably at low temperatures, there are some special considerations and requirements in the design and manufacture of cryogenic valves. Similarly, the test of cryogenic valves is different from ordinary valves. The following is a brief introduction to the test methods, test requirements and test equipment of JB / T7749-1995 "Cryogenic Valve Technical Conditions" and British BS6364: R1998 "Cryogenic Valve". 1. Low temperature valve test (JB / T7749-1995) (1) Test conditions The low temperature test of the cryogenic valve is carried out after passing the normal temperature test. Before the test, the moisture and grease of the valve should be eliminated, the bolts should be tightened to a predetermined torque or tension, and the value should be recorded. Connect the valve with a thermocouple that meets the test requirements, and measure the temperature of the valve body and bonnet during the test. The cooling medium for the low temperature test is a mixture of liquid nitrogen and alcohol or liquid nitrogen, and the test medium is helium. (2) Test procedure 1) The low temperature valve test device is shown in Figure 2-46. As shown in the figure, install the valve in the test vessel and connect all the joints to ensure that the valve packing is on the upper part of the vessel and the temperature is maintained above 0 degrees. 2) Under normal temperature and maximum valve test pressure, use nitrogen as initial test to ensure that the valve is tested under appropriate conditions. 3) Immerse the valve in a mixture of liquid nitrogen and alcohol or liquid nitrogen to cool to the valve's low-temperature operating temperature. Its horizontal surface covers the valve body and valve cover. 4) Under low temperature conditions, follow the steps below: ①At low temperature conditions, immerse the valve until the temperature is stable everywhere, use thermocouple measurement to ensure the uniformity of the temperature throughout the valve; ② At the test temperature, repeat the initial detection test of 2.11.1 (2) -2); ③ Under the test temperature and the nominal pressure of the valve, the valve is switched on and off 5 times to perform the low-temperature operation performance test, and the valve equipped with the driving device is subjected to the action test according to the above requirements; ④ Under the maximum valve test pressure, the valve sealing test should be done according to the normal flow direction of the valve. The two-way sealed valve should be tested separately. When measuring the leakage with the flowmeter, the leakage rate should meet the requirements of Table 2-23; ⑤When the valve is in the open position, close the needle valve at the outlet of the valve (see Figure 2-46, and pressurize the valve body to the sealing test pressure for 15 minutes, check the seal at the valve packing, valve body and bonnet connection) Sex; ⑥Check the seal on the valve cover. The valve with the upper seal should be tested for the seal. During the test, the valve is fully opened and the two ends are closed. Inject helium gas into the valve until the seal test pressure is reached. Loosen the packing gland and check Sealing tightness. 5) The test results of low temperature performance should meet the requirements of Table 2-23. 6) Restore the valve to ambient temperature, repeat 2.11.1 (2) -2) helium gas inspection test, measure and record the leakage of the valve, switch the torque and compare the result with the reading obtained in 2.11.1 (2) -2) Compare. 7) After the test, dismantle the valve in a clean and dust-free environment, check the ease of disassembly and check the wear and damage of each part. 8) Valves that pass the temperature test should be cleaned and dried, and the valves are closed. 2. BS6364 "Cryogenic Valve Technical Conditions" standard content about cryogenic valve test The cryogenic valve should not only comply with the provisions of BS6364, but also with the provisions of the corresponding product standards. The scope of application of the BS6364 standard is: ①DN≥15mm, the maximum value of its nominal size is determined by the corresponding product standard; ②The temperature range is -50 degrees to -196 degrees. The test items include: ①shell test; ② shell seal test; ③ valve seat seal test; ④ low temperature test. (1) Shell test The methods and requirements of the body test for cryogenic valves are the same as those for ordinary valves. But pay attention to two points: ①For austenitic stainless steel valves, the chloride content of the water used in the hydraulic test should not exceed 30 × 10-6 (ppm); ② After the hydraulic test, each part of the valve should be washed Clean and remove oil stains. (2) Shell seal test After the water pressure or air pressure shell test, at the connection between the valve body and the bonnet, wipe the valve filler with soap or immerse in water, and use dry oil-free air or nitrogen to conduct the shell seal test. The rest are the same as ordinary valves. (3) Valve seat sealing test Use dry oil-free air or inert gas for the test, the rest is the same as the ordinary valve. (4) Marine valves are to be subjected to low temperature tests. For all other valves, the low temperature test is only carried out when requested by the user. The temperature of the low temperature test is -196 degrees. The test methods, test procedures and test requirements are as follows: 1) Preparation before the test ①Remove oil stains from valve parts, dry them and install the valve in a clean, dust-free and oil-free environment. ② Tighten the bolt to a predetermined torque value or tensile value, and record the value. ③ Connect the valve with a suitable thermocouple, so that the temperature of the valve body and bonnet can be monitored throughout the test. 2) Test ①Figure 2-47 is a low temperature test device. Install the valve in the test vessel and connect it. Make sure that the valve packing is in a position where there is no vaporized gas at the top of the window. ② Perform the initial system verification test with helium gas at the maximum valve seat test pressure at room temperature to ensure that the valve is in a proper state, and then start the test. ③ Immerse the valve in liquid nitrogen for cooling. The liquid level covers at least the connection between the valve body and the valve cover. Helium is supplied to the valve throughout the cooling process. During the cooling process, the temperature of the valve body and bonnet is monitored with thermocouples installed in appropriate locations. ④ When the temperature of the valve body and valve cover reaches -196 degrees, the following procedures a) to e) are carried out: a) The valve is immersed in the test temperature for at least 1h until all temperatures have reached stability. Measure the temperature with a thermocouple to make sure that the valve temperature is uniform. b) Repeat the initial verification test described in ② at the test temperature. c) Open and close the valve 20 times, at least the opening force and closing force of the first and last operation should be measured d) Perform a seat pressure test on the inlet side of the valve. For two-way sealed valves, the two seats are tested separately. Increase the pressure gradually from the increments given in Table 2-24 until it reaches the rated valve seat test pressure. In the case where the rated value of the valve seat has been given by the manufacturer, the value set by the manufacturer is taken as the rated test pressure of the valve seat. Measure and record the leak rate at each pressure level. The leakage rate measured by the flowmeter shall not exceed 200mm3 / s × DN (for check valves) and 100mm3 / s × DN (for all other valves). e) With the valve in the open position, close the needle valve on the outlet side of the valve (see Figure 2-47), and raise the pressure in the valve cavity to the test pressure of the valve seat. Maintain the pressure for 15 minutes and check the valve material and the connection between the valve body and the bonnet for leaks. There should be no visible leaks. ⑤ Return the valve to room temperature, and then perform the following steps a) and b), and compare the result with the result of ④. a) Repeat the helium verification test described in ②. Measure and record the leakage through the valve. b) Measure and record the opening torque and closing torque of the valve. ⑥After the test is completed, the valve is disassembled in a clean, dust-free environment, so as to inspect all parts for wear and damage.
Special Shape Cookware!Stainless Steel Cookware is easy to clean.finest quality stainless steel for body,robust,veratile and durable in use .polished interior and exterior with elegant look.Shape: Belly shape,roll & step edge..Strong handle & knob ensure the safer cooking.impact bonded base for even heat distribution.Suit for Gas,Induction,Glass,Ceramic,Halogen.
Special Shape Cookware Stainless Cookware,Stainless Steel Pot,8 Pcs Economic Stock Pot,Special Shape Cookware JAPOP COMPANY LIMITED , https://www.japopkitchenware.com