INSTALLATION AND OPERATING INSTRUCTIONS FOR
KELCO D40 DISPLACEMENT LEVEL SWITCH
The D40 top entry level switch operates by Archimedes
principle. When an object is immersed in a liquid its weight
is reduced by an amount equal to the weight of the liquid it
displaces. In the D40 level switch a magnetically actuated
switch detects the weight reduction that occurs when liquid
submerges a solid Polypropylene displacer suspended from
a cord below the switch. Since it is the change of weight
sensed by the displacer as it is submerged that actuates the
switch, the specifi c gravity of the liquid will directly effect the
operation of the switch. The D40 level switch will only
operate in liquids that have a specifi c gravity that is 0.95 or
greater (water). They will not operate if used in liquids with
an S.G. of less than 0.95.
The D40 level switch is an extremely versatile device. It can
be used to detect a liquid level in wells, tanks, pits, sumps,
bores and bund areas. The inert materials of construction
mean the switch can be used in water, sea water, mild acids
and in many common chemical solutions. The D40 is highly
tolerant of liquids containing solids, slurries or pulp. It will
also work reliably in froth or foam and in applications where
there is fl oating scum or debris of various kinds.
The electrical enclosure on the D40 level switch is sealed
and separated from the switch’s actuating arm by a solid
metal wall. The switch is actuated magnetically through the
solid wall. This means the electrical housing is totally sealed
and weatherproof provided the lid is fully tightened and the
cable gland is properly utilised. The Polypropylene
suspension cord and the displacer are the only components
in contact with the process liquid. Polypropylene is a very
inert material and is well known for its resistance to many
commonly encountered chemicals.
The D40 is ideal for warm liquid applications provided the
electrical head is mounted well above the liquid and is
protected from hot vapour. The wetted components, the
cord and displacer are highly tolerant of liquids at elevated
temperatures.
INTRODUCTION
INSTALLATION
OPERATING ENVIRONMENT
The D40 level switch is supplied with a fl at mounting plate
for installing the switch against the walls of pits or tanks. In
addition to the fl at plate, an angle bracket is also supplied.
The angle bracket can be used to mount the switch on any
fl at horizontal surface such as tank lids or horizontal bracing.
M5 threaded mounting holes are provided in the sides of the
switch body so the switch can be oriented with its cable entry
pointing to the right or left.
Whichever mounting bracket is used, ensure that once
installed, the top face of the D40’s lid is perfectly horizontal.
This ensures the cord and displacer hang vertically beneath
the switch and apply force to the switch arm directly
downwards.
Thread the supplied cord through the hole at the end of the
switch actuating arm and tie a double knot in it so the cord
can’t pull back through the hole. Thread the free end of the
cord through the hole in the top of the displacer and tie it off
securely. D40 level switch is supplied with 3 metres of cord.
Cords up to 20 metres in length can be used with the D40
switch and are available from Kelco or your supplier if
required.
TYPICAL INSTALLATIONS
Fixed switching differential 40mm +/- 5mm
Maximum distance
between D40 & displacer.
20 metres (3m of cord is
supplied with the switch)
Minimum distance from
displacer to the fl oor of a
tank or sump.
20mm
Minimum inside diameter
of pipe housing or shroud.
70mm
Maximum liquid
temperature.
90°C
Specifi c gravity of process
liquid.
0.95 or greater
LIMITATIONS
20m
long
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