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46-624 Series 3 Liquid Level Switches ASME B31.1 Construction
4.3.1 Check Switch Mechanism
1. Pull switch or otherwise disconnect power to the control.
2. Remove switch housing cover.
3. Disconnect power wiring from switch assembly.
4. Swing magnet assembly in and out by hand to check care-
fully for any sign of binding. Assembly should require
minimal force to move it through its full swing.
5. If binding exists, magnet may be rubbing enclosing tube.
If magnet is rubbing, loosen magnet clamp screw and shift
magnet position. Retighten magnet clamp screw.
6. If switch magnet assembly swings freely and mechanism
still fails to actuate, check installation of control to be
certain it is within the specified 3° of vertical.
7. Check continuity of switch with ohmmeter.
8. If switch mechanism is operating satisfactorily, proceed to
check sensing unit.
NOTE: Spare switches should be kept on hand at all times.
4.3.2 Check Sensing Unit
1. Reconnect power supply and carefully, manually actuate
switch mechanism (use a non-conductive tool on electrical
switch mechanisms) to determine whether controlled
equipment will operate.
Caution:
With electrical power on, care should be taken to avoid
contact with switch leads and connections at terminal
block.
2. If controlled equipment responds to manual switch actua-
tion test, trouble may be located in the level sensing portion
of the control, float(s), stem(s), and magnetic attraction
sleeve(s).
3. Check to be certain liquid is entering float chamber. A
valve may be closed or piping plugged.
Caution:
Be certain to pull disconnect switch or otherwise ensure
that electrical circuit(s) through control is deactivated.
Close operating medium supply valve on controls
equipped with pneumatic switch mechanisms.
4. Disconnect wiring from supply side of switch
mechanism(s) and remove electrical conduit or operating
medium line connections to switch housing.
5. Perform system shutdown to relieve pressure from float
chamber of control and allow unit to cool.
6. Close shutoff valves (if equipped) to isolate control from
vessel. Drain off liquid in chamber if necessary.
Optional blow-down
or drain valve
Shutoff valve
(if used)
Conduit
outlet
Switch
actuating
level reference
mark
Optional liquid leg
connection to vessel
Shutoff valve
(if used)
Figure 21
