4
44-604 Top Mounting Liquid Level Switches
1
Pivot
Return
Spring
Process Liquid
Rising Level
6
5
4
3
2
Figure 1
Process Liquid
Falling Level
Figure 2
1.0
Introduction
T20 and T21 level switches are float operated units
designed for top mounting to a tank or vessel by means of
threaded or flanged pipe connections. T20 standard units
are equipped with a single switch mechanism for high or
low level alarm or control applications. T21 tandem units
are equipped with two switch mechanisms, each operated
by a separate float, for applications requiring widely spaced
separate high and low level switch actuation.
1.1
Principle of Operation
The simple and foolproof operation of the top mounted
float switches is illustrated in figures 1 and 2.
A permanent magnet
➀
is attached to a pivoted switch
actuator and adjustment screw
➁
. As the float
➂
rises
following the liquid level, it raises the attraction sleeve
➃
into the field of the magnet, which then snaps against the
non-magnetic enclosing tube
➄
, actuating the switch
≈
.
The enclosing tube provides a static pressure boundary
between the switch mechanism and the process. On a
falling level, an inconel spring retracts the magnet,
deactivating the switch.
2.0
Installation
This section provides detailed procedures for properly
installing top mounted level switches.
Caution:
If equipment is used in a manner not specified by the
manufacturer, protection provided by the equipment may
be impaired.
2.1
Unpacking
Unpack the instrument carefully. Inspect all units for
damage. Report any concealed damage to carrier within
24 hours. Check the contents of the packing slip against
purchase order. Check and record the model number
against serial number for future reference when ordering
parts.
Model Number
Serial Number
