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Pneumatic actuator inspection standards and methods
With the widespread use of pneumatic valves, pneumatic actuator technology is getting better and better, the domestic pneumatic actuators and imported pneumatic actuator gap is getting smaller and smaller, more and more types, and now pneumatic actuator inspection Method to do the following description: A) calibration preparation and visual inspection 1 All test instruments must be pre-heated 30 minutes before the power supply; 2 test gas pressure to meet 0.6 ± 0.1Mpa; 3 actuator appearance no obvious damage, gas guide copper The tube has no obvious scars and the assembly is firm. The length of the connecting screw of the 4-position transmitter must meet the technical requirements of the type of the executing agency to be inspected. The plane formed by the connecting rod and the connecting screw fastened on the axis of the transmitter should be perpendicular to the horizontal plane ; 2) Test standards and methods 1 Pneumatic actuators are fixed to the calibration platform, respectively, access to gas source, control of air supply and displacement detection link; calibration of the calibration instrument on the stage accuracy; 2 mechanical zero calibration: input 4mA current signal (0%), the control gas signal should be 0.02Mpa, the cylinder piston stroke should be zero; if not zero, by adjusting the zero screw (Zero high tighten the nut); zero and span need to be adjusted repeatedly; zero error to ≤ 1%; 3 mechanical full-scale calibration: input 20mA current signal (100%), the control gas signal should be 0.10 Mpa, then the cylinder piston stroke should be the upper limit; if not for the upper limit, can be adjusted by adjusting the tension of the tension spring to adjust the range (small range of loose spring, pull the spring range); zero and range Need to repeatedly adjust; full-scale error to ≤ 1%; 4 mechanical range of mid-point positioning: Zero and span alignment, input 12mA current signal (50%, 0.06Mpa), adjust the position of the transmitter connecting rod position At this point, it should be kept perpendicular to the horizontal plane. 5) Calibration of Full Travel Deviation: Enter the control gas signal 0.02Mpa (0%), and then gradually increase the input signal of 0.036Mpa (20%), 0.052Mpa ), 0.084 Mpa (80%), 0.1 Mpa (100%), the cylinder piston to go the full stroke, the deviation of each point should be less than 1.5%; 6. Nonlinear deviation test: input control gas signal 0.02Mpa Then gradually increase the input signal To 0.10Mpa (100%), and then the signal down to 0.02Mpa (0%), so that the implementing agencies take full travel, and record the increase / decrease of 0.008Mpa signal pressure corresponding to the trip value, the actual pressure-stroke relationship and Nonlinear deviation between the theoretical values ​​of ≤ 1%; ※ 7 positive and negative stroke variation test: the same with the non-linear deviation test method, the actual positive and negative pressure-stroke relationship, the same pressure value of the cylinder piston forward and reverse stroke value Of the maximum difference to ≤ 1%; 8 Sensitivity test: Increase and decrease the pressure at the signal pressure 0.03,0.06,0.09 Mpa stroke, test the signal pressure changes required when the cylinder piston rod begins to move 0.1mm, The maximum change of ≤ 0.2%; 9, the piston cylinder sealing test: the pressure of 0.5 Mpa access to any one of the cylinder chamber, and then cut off the gas source, in 10 minutes, the cylinder pressure drop should not Over 0.01 Mpa; ※ 10 position transmitter electrical zero point detection: Open the transmitter cover position, connect the wire; input 12mA current signal (0.06 Mpa), then adjust the transmitter circular eccentric, so that Of the black line and white line above the board alignment; then enter the 4mA current (0.02 Mpa), then adjust the transmitter zero potentiometer so that the output current is 4mA; electrical zero error should be ≤ 1%; 11 position Transmitter full-scale electrical test: input 20mA current signal (0.1 Mpa), then adjust the transmitter potentiometer to adjust the output range so that the output current of 20mA; full-scale electrical error should be ≤ 1%; 12-position feedback current full stroke Deviation Calibration: Input a 4mA current (0%), and then gradually increase the input signal by 8mA (25%), 12mA (50%), 16mA (75%), 20mA (100% 0%, 50%, 100% point feedback current error should be ≤ 1%, 25%, 75% point feedback current error should be ≤ 2%; 13 Position feedback current positive and negative stroke variation test: the same Cylinder positive piston anti-stroke variation test method is the same, the actual positive and negative position feedback current-stroke relationship, the same feedback current value of the cylinder piston forward and reverse stroke value of the maximum difference ≤ 1%; 14 to make calibration records, Press on the calibration record form The contents of one by one carefully fill in, the inspector must sign; 15 After the above tests are qualified, the transmitter should be plugged in the location of the transmitter, tighten the back cover, and then the valve positioner gas inlet plug with plastic plug Good; ※ This item can be decided according to the actual situation