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Functional description
Power end
The Hydro HA4a product range represents motor-driven metering pumps
with hydraulically operated multi-layer diaphragm (6).
The motor moves the hydraulic piston (4) to the front by means of a worm
gear and cam (1). The hydraulic piston is connected positively to the cam
by a bracket (7) so that the discharge stroke as well as the suction stroke
are performed by the force of the motor (so-called "Full Motion Drive"). The
forward motion pushes the hydraulic piston (4) into the hydraulic end and
builds up the pressure in the hydraulic oil in the hydraulic end. The
hydraulic oil then pushes the multi-layer diaphragm (6) into the dosing
head.
The hollow bored hydraulic piston (4) has several spill ports to adjust the
stroke volume. The adjustable control sleeve (3) seals these spill ports at
each discharge stroke. The control sleeve seals the spill ports sooner or
later depending on the position of the control sleeve (3). While the control
spill ports are free, hydraulic oil can escape from the hydraulic end into the
power end housing during a discharge stroke. The multi-layer diaphragm
in the dosing head is then not deflected. If the spill ports are sealed, the
hydraulic piston (4) can then build up pressure in the hydraulic oil in the
hydraulic end. The multi-layer diaphragm (6) is pressed into the dosing
head. However, the multi-layer diaphragm is deflected to a lesser degree
as hydraulic oil can escape from the hydraulic end (into the power end
housing). The suction stroke causes the hydraulic oil to flow from the
power end housing through the spill ports and back into the hydraulic end.
Both power ends work in push-pull mode with pumps with add-on power
end.
The pump has a permanent safety relief valve (5) installed in the hydraulic
part. The safety relief valve provides protection for the pump power end
and the multi-layer diaphragm if the feed pressure becomes too high. If the
pressure side of the liquid end is blocked, the safety relief valve (5) opens
at a pre-set pressure and allows hydraulic oil to flow into the power end
housing.
Fig. 2: Cross-section through the pump
1
Cam
2
Stroke adjustment dial
3
Control sleeve
4
Hydraulic piston
5
Safety relief valve / Automatic vent valve
6
Multi-layer diaphragm
7
Bracket
Functional description
1
7
2 3 4
5
6
P_HY_0082_SW
5
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