15.5 - Maintenance of Type SD hydraulic diaphragm pump heads
15.5.1 - Operations to be performed on the type SD pump head
Operational principle of the pump head
The SD series type dosing pumps are made of a pump head
that is characterised by the presence of two diaphragms in
PTFE and a stainless steel separator ring interposed to them.
The pump is supplied with the hydraulic part already filled and
ready for use, both with regard to the oil reservoir and the
diaphragm/separator ring unit.
In the top portion of the ring there is a nipple and a uni-
directional valve that, upon customer request, can be connected
to a pressure gauge or a pressure switch that can indicate if one
of the two diaphragms, or both, are broken. This set of elements
constitutes the “BREAKAGE DETECTION KIT” and is
diversified according to the machine type and usage needs.
15.5.2 - Signal and alarm instruments
Pressure switch
Before starting the machine, it is the user’s
responsibility to electrically connect the
pressure switch to the electrical control panel,
to a possible alarm and/or signal system or
any other system compatible with rated
electrical data of the pressure switch suitable
for detecting any anomaly.
The pressure switch can be connected in
Normally open (NO) mode: in case of
intervention, it closes the circuit and sends a
signal; or in Normally closed (NC) mode: in
case of intervention, it opens the circuit.
The choice of the best method is at the user's
discretion.
The typical wiring diagram is represented in
the table. However, depending on the
pressure switch used, the connection diagram
in the terminal board can be shown via the
applied sticker.
Pressure gauge
If the "breakage detection kit" uses a simple
pressure gauge, no intervention is necessary.
In normal use, a vacuum persists between the two diaphragms and performance
is similar to that of a single diaphragm; the pressure gauge indicates a pressure
in the range of 0-1 bar. In case of failure of one of the two diaphragms, there is
no longer a vacuum and the same process pressure is created inside the
separator ring: in this case, the pressure gauge shows the operating pressure.
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