Control Valve Calibration

August 24, 2017 | Author: Bruno Megam K | Category: Calibration, Valve, Electrical Engineering, Electronics, Technology
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calibration of control valves in industry...


Required Material: 1) Data sheet 2) Hart Communicator Step wise Procedure: *Ask panel man to put the controller in manual mode for control loop *Isolate the Control valve from the process. WARNING The Isolation of control valve from the process shall be done by field o perator. Careful step shall be done to ensure no upset to the operation. *Hook up HART Communicator and verify some parameters by refer to data sheet suc h as Tag Number, OP and etc. *Change from normal mode to setup mode *Select auto find stop (wait some minute) *If full open is more than 100% select open adjustment and put new number as per calculation *Make an auto calibration ( wait some minute) *Verify the linearity by increasing and decreasing the travel (0%,25%,50%,75%,10 0%,75%,50%,25% and 0%of range) *After completion of the job ask panel operator to put loops back in normal mode *Fill the calibration form and file it for future reference. Example calculation A: Max travel from stem 70mm B: Scale plate 50mm New open adjustment should be (50/70) X 100 = 71.48%

How to Calibrate Control Valve? Which Instrument is Used? For the calibration of a control valve a loop calibrator or a pressure calibrato r can be used between 3-15psi.Check the valve position for 3psi which is to be 0 for a NC type valves.In such manner check the valve position for various ranges (6psi,9psi,12psi & 15psi).the valve position should be 0 for 3psi and 50% for 9 psi and completely opened for15psi. The same procedure is applicable for NO type valves.The valve is open for 3 psi and completely closed for 15psi.Any errors occurred may be rectified by Zero spa n adjustment. In the case of HART , you can use a HART communicator ( Emersson 375 ,475..etc ) for calibrating a valve , apply 4 mA for 0% , 20 mA for 100% ,

alibration instrument required. 1.portable pneumatic calibrator INPUT signal OUTPUT Generate 0.2 kg/cm 0% of v/v travel 0.4 25% 0.6 50% 0.8 75% 1.0 100% If you observe any deviation adjust accordingly. BY using DRUG calibrater we can easily calibrate just we

need a air line having pressure of 6kg as input of CV. by giving 4-20mA signal through DRUG. for example 4mA CV in close position 8mA 25% 12mA 50% 16mA 75% 20mA 100% To calibrate a valve first check the input signal range if it is 0.2 to 1.0 Kg/cm2 or different. Calculate the span ( Difference between higher limit to lower limit=1.0-0.2=.8 ) Now divide it in four equal parts that is 0.2 Kg/cm2 this is 25% of the span. Now check the valve travel like 2 inches, 3 inches or any other value Divide it in four equal parts 25% of the travel. Apply 25% of the span value+ 0.2= 0.4 Kg/cm2 it is 25% of travel and apply full span value and see you get the complete travel if you find difference adjust the spring accordingly. before do the stroke checking we have make sure the bench calibration after that we should check 0-100% stroke irst you have to now your limits if its pneumatic work from 20 to 100kpa if current i 4 to 20ma supply pressure, 1.bench set 2.beam alignments 3.calibration

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