CALIBRATION OF VALVES WITH ACTUATOR AND ACCESSORIES
Note:Valve calibration will be carried out at warehouse up to 2” (inch) without transportation and the 3” (inch) above are carried Site calibration.
· TSO Valves shall be calibrated after the seat leakage test. Hand wheel test as the part of calibration, manual operation of the hand wheel shall override the automatic operation.
Self-Actuating Valves (i.e., pressure regulator)
Visual checking shall be carried out to ensure that there is no damage on the body.
Tag no., range, & type shall conform to the data sheet.
If required, detailed calibration procedure for self-actuating valves shall adhere to manufacturer’s manual and shall be confirmed.
Final set point adjustment is required during start-up operation in order to make it suitable with process variables.
Note: No such confirmation (final set point) is required for pressure regulator with internal relief feature (i.e., air filter regulator for CV, I/P, etc.).
Diaphragm Actuator, Spring Adjustment (Bench Set)
The following items shall be checked:
· Size and type
· Stroke range
· Spring range
Hook up testing equipment as illustrated below:
Procedure for Valve calibration With Pneumatic Calibrator:
1. Adjust pneumatic signal so that the valve closes slowly, and stop when the valve fully closed.
2. Dynamic error band, which is the difference between upscale and downscale plots at any given input signal, shall be less than 3.0% which valve travel. If the desired value cannot be obtained with spring
adjustment, change stem length by adjusting connector assembly.
3. Adjust pneumatic signal so that the valve opens slowly, and stop when the valve fully opened.
4. Read the pneumatic signal value and compare it with the actuator’s range. If the difference is greater than 3.0%, change spring and recheck closing and opening.
5. Adjust position indicator scale so that the indication works correctly.
6. Inject pneumatic signal 0%, 25%, 50%, 75% and 100% of its range and read valve position with signal rising and falling.
7. Check air failure action by disconnecting air supply.
8. Check power failure action by disconnecting power supply.
9. Speed of stroking time from full open to full close shall be checked, if required. Note down in form and compare with datasheet.
Other Type Actuator
The actuators other than diaphragm type shall be checked for the following items before the stroke check
Piston Type Actuator
· Size and type
· Stoke range
· Electrical insulation of motor and other electrical parts
· Limit switches and/or torque switches
· Positioner assembly
· Power requirement
· Local open/close/stop switch
· Hand wheel operation
Positioner (Stroke check) Procedure Calibration:
II. Determine signal range and characteristics curve through full stroke of valve. Before calibration curve shall be provided.Select proper travel character cam if provided.
III. Connect Power Supply and and/or air supply to the positioner and actuator.
IV. Connect proper input signal source (4-20mA) to the positioner.
V. Adjust input signal so that the valve closes slowly, and stop when the valve is fully closed.
VI. Read the input signal and adjust zero adjustment when error is found. Repeat steps until the valve corresponds with closing signal within error limit.
VII. Adjust input signal so that the valve opens slowly, and stop when the valve fully opened.
VIII. Read the input signal and adjust zero adjustment when error found. Repeat step until the valve corresponds with closing and opening signal within error limit.
IX. Inject signal 0%, 25%, 50%, 75%, and 100% of its range and read valve position with signal rising and falling. Action of the positioner shall be checked (direct or reverse).
X. Analyse the stroke characteristic curve and figure out the reproducibility which includes dead band and hysteresis.
XI. If the character or the reproducibility is not acceptable, check feedback cam style and/or mechanical condition of all moving parts and correct existing deficiencies.
XII. Mechanical stops shall be checked as per data sheet.
Calibration of On-Off Valves
Visualcheck for the valve and accessories mounted shall be carried out to ensure size, rating, tag no. and model no. with respective data sheet and to ensure that there is no damage on the bodies.
Note: The following calibration shall undergo during the pre -commissioning stage, which is after installation of the on-off valves.
A. Connect air/hydraulic supply to the valve and electric power to solenoid valve.
B. Check valve stroke by applying on and off signals to solenoid valve.
C. Valve stroke shall be checked if the stem travel is from fully close to fully open as indicated on travel indicator and also if valve operates freely through its full stroke length. Failure action also shall be confirmed by disconnecting supply air.
D. If limit switch is assembled within the valve,valve open and/or close signal shall be checked by using circuit tester.
Note: Seat leakage test for on-off valves shall be done by others.
E. Volume tank accumulation test can be done in pre-commissioning stage after installation.
F. Verify the maximum air pressure of volume tank as per data sheet.
G. Apply medium or plant air if available at on site.
H. Bubble test/ leak test by snoopy soap.
I. Required time lapsed for leak testing/ percentage.
J. Record in data sheet for result.
Calibration of Solenoid Valves
a) Connect an appropriate power supply via switch.
b) Connect an air supply to the appropriate port(s).
c) Check the operation of the valve by operating the switch and observing correct change over action.
d) Correct the tightness of shut-off by connecting a flexible tube to the outlet port(s) and immersing the free end in water to ensure that the valve closure is bubble-tight at the stated design pressure.
e) Check where applicable, electrical and manual reset, override and time delay features as called for on the valve specification.
f) Check that the coil resistance is correct to specification.
g) After the test has been completed, the instrument shall be identified with a color code sticker.
Calibration and Stroke Check of Motor Operated Valves
i. Ensure that the valve is correct according to instrument specification.
ii. Ensure that the valve is upright and supported prior to carrying out test.
iii. Ensure that no sand or foreign material is in the body of the valve.
iv. Using the hand wheel, fully close and open the valve.
Check all switches when valve stem is in the open and close position.
i. Disconnect all wiring and replace cover tightly.
ii. After the test has been completed, the instrument shall be identified with a color code sticker.
iii. Results shall be filed and recorded on applicable forms.
iv. All MOV valves will be checked at site during loop check.
Checking of Limit Switches (Inside Valves)
1. The function of limit switches shall be checked.
2. Where possible, the function shall be checked manipulating the switch input. The result shall be witnessed and the operation to be recorded.
3. Tri-loop/ SPA HART position feedback for anti-surge control valve shall be checked.
4. After the test has been completed, the
instrumentation shall be identified with color code sticker.
5. Results shall be filed and recorded on applicable forms.