FW Murphy MLS Series, Инструкция по установке и эксплуатации

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Section 15 00-02-0730
2019-01-15 - 7 -
Testing MLS Switch Manually
– MLS Models
We suggest using the FW Murphy magnetized screwdriver approach to test the micro-reed
switch and float position.
CAUTION: Be sure to follow hazardous area electrical procedures.
The Principle of Test Method
The reed switch in the MLS is operated by an applied magnetic field. The magnetic field is
designed so that the switch will be actuated at a location further from the terminal under
normal working conditions. When the float is missing, the counter balance will drop, raising the
end where the float should be because of the weight of the counter balance. The movement of
the counter balance will bring the magnetic field to a lower position through the mechanism.
Using this approach can easily test the float status and operation of the switch.
Considerations

Be careful not to damage or short wires connected to the MLS either at the switch or the
annunciator or controller connection point (control panel).

Check terminal connections and wiring before replacing the cover of the MLS for proper
operation.
Test Preparation
1. Check the sight glass to make sure any liquid level is below the MLS. (If the float is
already raised by liquid, the test procedure may suggest the float is missing and that the
counter balance has forced the assembly into the high liquid level state.)
2. Make sure the area is non-hazardous, getting a hot work permit, for instance. This only
needs to be done if the circuit connected to the MLS is not intrinsically safe or non-
incendive.
3. Disconnect the wiring once it is de-energized to use a meter to perform the test, or use
the test function of the annunciator or controller to verify switch operation.
NOTE: Manual testing is always used with the standard FW Murphy MLS
Series Liquid Level Switches and can be used on any MLS model.
MLS Model (standard) MLS TF Model (Optional)