Safety valve calibration bench operating procedures

by:Lianke Valve     2022-09-17
Safety valve calibration bench operating procedures 1. Preparations before calibration 1.1 Before using the calibration bench for each shift, a sealing test should be carried out, and the calibration bench should be sealed with a blind plate or a special valve. According to the indicated value of the pressure gauge, judge whether there is leakage in the air source valve, each control valve, pipeline, pressure gauge and the working seat of the calibration table, and maintain the pressure for 2 minutes. 1.2 Before using the calibration table in each shift, check and confirm each pressure gauge, that is, by checking the relative error of each pressure gauge to judge whether each pressure gauge is accurate, otherwise it should be replaced or re-calibrated. 1.3 Before the safety valve verification, the safety valve should be cleaned or cleaned according to the regulations of 'Safety Technology Supervision Regulations for Safety Valves' and 'Inspection and Testing Procedures', and a macro inspector should be carried out, and then the safety valve should be disassembled and inspected for each structure. part. 1.3.1 If the valve disc and valve seat sealing surface, guiding parts, springs, and valve stems are found to be damaged, corroded, or deformed, the safety valve should be repaired or replaced. 1.3.2 The safety valve with cracks in the valve body, sticking of the valve disc and valve seat, serious deformation of the spring, serious damage to the parts and irreparable should be scrapped. 2. Operation of the pneumatic clamping seat 2.1 The calibration table has several working seats, namely large-diameter and medium- and small-diameter pneumatic clamping seats. There is a switching valve under each working seat. When a large-diameter working seat is used, it should be Open the switching valve under the seat, and close the switching valve of the remaining working seats. In short, whichever work seat is used, open the switch valve of this seat, and close the switch valve of other work seats. 2.2 After confirming the working seat and opening the corresponding switching valve, select the center gasket of the corresponding size (note that there are '○'-shaped sealing rings on the upper part), put it on the center top shaft of the existing sealing ring, put it into the safety valve, and then put the three Push the clamps to the center and pull out the corresponding pneumatic switch to clamp. 2.3 When using a large-diameter working seat, first pull out the pneumatic switch to automatically open the three clamping feet, put on the center pad and safety valve, push in the pneumatic switch, and lock the safety valve, then close the release valve on the control cabinet, and When the clamping valve is opened, the safety valve is positioned and clamped to seal. Note: Avoid getting your fingers caught during operation. 2.4 During calibration, first close the pressure relief valve, and slowly open the calibration valve, and the pressure gauge starts to display (at this time, switch the corresponding pressure gauge according to the opening pressure of the safety valve to ensure that the opening pressure is 1/2 of the limit value of the pressure gauge scale or 3/4) until the safety valve opens, remember that the highest value on the pressure gauge is the opening pressure, and repeat this three times. 2.5 If the opening pressure exceeds the check opening value, the screw of the safety valve should be loosened, and vice versa, until the check is completed. Then return the adjustment ring to its original position, screw in the fixing screw, and then tighten the safety valve positioning nut. At this time, it is still necessary to re-check it again. If it is correct, put on the bonnet to complete the entire calibration process. 2.6 After the calibration is completed, the calibration pressure relief valve must be opened first. After the calibration pressure gauge shows the value to zero, then push the pneumatic switch or close the clamping valve, open the release valve, and the safety valve can be removed. 2.7 Points to note in operation: 2.7.1 When checking, there should be no one at the exit of the safety valve; 2.7.2 The three clamps must be pushed in place to be clamped; 2.7.3 The air pressure of the clamping device cannot exceed: ① The large-diameter work seat is clamped Pressure P≤2.5MPa; ②P≤1.0MPa; 2.7.4 The pressure of the pressure reducer should be restored to zero at the end of the calibration work on the day. 3. Check the set pressure (opening pressure) 2.1 Slowly increase the inlet pressure of the safety valve. After the pressure is increased to 90% of the set pressure, the pressure increase speed should not be higher than 0.01MPa/s. 3.2 When it is detected that the valve disc is opened or the continuous discharge of the test medium is seen or heard, the inlet pressure of the safety valve is regarded as the set pressure of the safety valve. 3.3 When the setting pressure is less than or equal to 0.5MPa, the allowable error between the measured setting value and the required setting value is ±0.015MPa; when the setting pressure is greater than 0.5MPa, the allowable error is 3% of the setting pressure. 4. Sealing test 4.1 After the adjustment of the set pressure is qualified, the inlet pressure of the safety valve should be lowered and adjusted to carry out the sealing test. 4.2 When the set pressure is less than or equal to 0.3MPa, the seal test pressure should be 0.3MPa lower than the set pressure; when the set pressure is greater than 0.3MPa, the seal test pressure is 90% of the set pressure. 4.3 When the sealing test pressure is gas as the test medium, for the closed safety valve, the leakage rate shall be expressed by the number of leaking bubbles. GB/T12243 or other safety technical specifications and standards; for non-closed safety valves, the sealing test can be considered qualified if no gas leakage sound is heard within a certain period of time. 4.4 When the sealing test uses water as the medium, the test methods and requirements shall comply with the relevant provisions of GB/T12243. 5. Verification records, seals and reports 5.1 The safety valve verification shall be recorded, sealed and reported according to the following requirements. 5.1.1 During the verification process,The inspectors need to record the relevant data of the inspection in time; 5.1.2 The safety valve that has passed the inspection needs to be re-sealed in time to prevent the adjusted state from changing. One side of the seal is the code of the “XTJ” inspection unit. The other side is the code mark of 'AF' (safety valve); 5.1.3 The lead seal does not have to have a sign, and the sign has the name and code of the inspection agency, calibration number, set pressure, and the date of the current and next school; 5.2 The safety valve that has passed the calibration needs to issue a safety valve calibration report according to the calibration record, and issue it according to the requirements of the quality management system of the calibration organization.
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