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Answer Posted / gireesh gokuldas
1)Obtain Permit to work. Confirm proper isolation of process.
2)Depressurize the system by draining or venting.
3)Disconnect the process tubing and replace with correct fittings for calibration with pressure source.
4)Wear goggles to avoid splashing of liquid into eyes when depressurizing.
5)Use a Digital Multimeter (DMM) set to the continuity range to check and verify that the switch contacts are as indicated: NO (Normally open) and NC (Normally close).
6)Connect the DMM between the normally open contacts (NO) and the common terminal (C) of the switch. The meter should read "open circuit"
7)Adjust the hand pressure regulator to increase the pressure to the set point of the pressure switch until the contacts change over.
8)The meter should now read "short circuit". Note the pressure reading and write it down. This pressure is the switch set point for a "rising" pressure.
9)Increase the pressure to the switch to its maximum rating.
10)Slowly reduce the pressure to the switch until the switch changes over from closed to normally open again.
11)Note and write down this pressure reading. This pressure is the switch setting for a "falling" pressure.
12)From the readings you have taken work out the pressure difference between the rising and falling pressure settings. This is called the "dead-band" of the switch.
13)The dead-band calculated should be equal to or less than the manufacturers’ dead-band
14)Disconnect the calibrator and restore the process tubing and put the switch in service.
15)Complete the calibration form and apply the appropriate calibration label.
16)Clean the area and clear Permit to work.
| Is This Answer Correct ? | 16 Yes | 3 No |
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