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Control valve performance and standards

by:Sure     2021-08-09
The new national standard pneumatic control valve GB4213-84 'General Technical Requirements for Pneumatic Control Valves' was released on March 21, 1984 and implemented on January 1, 1985. This standard was revised in 1992, and the revised standard code is GB/T4213-92, which was implemented in October 1993. This standard is mainly based on the IEC international standard and is formulated in conjunction with the specific conditions of our country. The original implementation of the new national standard pneumatic control valve GB4213-84 'General Technical Requirements for Pneumatic Control Valves' was released on March 21, 1984 and implemented on January 1, 1985. This standard was revised in 1992, and the revised standard code is GB/T4213-92, which was implemented in October 1993. This standard is mainly based on the IEC international standard and is formulated in conjunction with the specific conditions of our country. The original implementation of the Ministry standard shall be invalidated from the date of implementation of the new national standard. The main differences between the new and old standards are as follows:    (1) The new national standard adds 'life' indicators, a total of 14 performance indicators:    1 basic error; 2 return difference; 3 dead zone; 4 always point deviation; 5 rated stroke deviation; 6 Leakage; 7 sealing performance of stuffing box and other joints: 8 air chamber sealing; 9 compressive strength; 10 rated flow coefficient; 11 inherent flow characteristics; 12 anti-vibration; 13 operating life; 14 appearance. (2) The new national standard divides the basic error, hysteresis, dead zone, point deviation, and rated stroke deviation into 8 levels, A, B, ... H, so as to choose the performance cost ratio according to the requirements of different valves to meet different functions The best index level. The old standard determined a unique corresponding index for each valve, which lacked flexibility.  (3) The new national standard stipulates the leakage amount as A, B...F, these 6 levels, the highest level F is counted by the number of bubbles per minute. The old standard has only one grade, and the high-pressure valve stipulates that the leakage rate is 0 is not in line with reality.   (4) The flow characteristic error inspection method, the new national standard adds a method of inspection according to the slope method.  (5) The new national standard changes the old standard circulation capacity to flow coefficient. The old standard for its values u200bu200bhas been uniformly stipulated, and the new national standard is determined by the manufacturer itself, which is more convenient for the design and finalization of new products.  (6) The test points for basic error and hysteresis are changed from 10 test points to 5 test points from the old standard.  (7) The new national standard requires the air source and ambient temperature of the regulating valve. The air source should be clean, dry air, without obvious corrosive gases, solvents or other liquids. For the regulating valve with positioner, the amount of solid particles in the gas source should be less than 0.1g/m, the particle diameter should be greater than 3μm, and the oil content should be less than 1ppm.  The ambient temperature of the regulating valve is -25~+55℃ or -40~+70℃.   The control valve should meet the above requirements when working. The unclean air source of the positioner is the main reason for the abnormal operation of the positioner, which accounts for more than 2/3 of the failure rate. Special attention should be paid to this point.
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