How to check Level Switch and Limit Switch

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Float or displacer type level switches shall be calibrated in calibration room or site using clean water as the test medium.
Displacement type switches shall be tested in position using water as a test medium. Particular attention shall be paid where the specific gravity of the process medium is different to that of water.
A transparent PVC tube with a scale shall be connected to the bottom of the chamber for level gauge use. Water shall be poured in the chamber for the calibration.
Set the switch to the required value and with a continuity tester, each set of contacts shall be checked for make/break contacts as required.
The high alarm switch values shall be taken at the contact break point when the input value is rising.
The low alarm switch values shall be taken at the contact break point when the input value is falling.
The alarm and differential gap between alarm and reset shall be noted and recorded on approved calibration form.
After testing, all ports and entries shall be sealed to prevent ingress of dirt and moisture.
After the test has been completed, the instrument shall be identified with a color code sticker.

The function of limit switches shall be checked.
Where possible, the function shall be checked manipulating the switch input. The result shall be witnessed and the operation to be recorded.
Triloop/SPA HART position feedback for anti-surge control valve shall be checked.
After the test has been completed, the instrumentation shall be identified with color code sticker.
Results shall be filed and recorded on applicable forms as per approved.

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