020203.06
9
Electro-Hydraulic Pumps
ENGLISH
1
Introduction
The installation of an electrohydraulic pump (EHP), integrated into
an hydraulic steering system, makes it possible to steer a boat via
automatic steering gear (autopilot) or selector switch (gear lever ‘joy
stick’ or a manual remote control unit) options.
The capacity of a suitable EHP should match the stroke volume of the
respective cylinder (displaced oil volume for board-to-board rudder
deflection) and the required board-to-board steering time.
Calculation of an EHP
Determine the volume of a cylinder that has been or is to be instal-
led. For details please see the technical specifications published by
the supplier of the control unit.
Divide the cylinder capacity by the required board-to-board time to
determine the capacity of the suitable EHP.
Example:
The board-to-board time of a given boat is 15 seconds.
The selected cylinder is a VETUS MTC72 model. This cylinder has a
volume of 146 cm3.
Capacity calculation:
Cylinder volume in cm
3
x 60
in cm
3
/min
Board-to-board time in seconds
146 cm
3
x 60 = 584 cm
3
/min (35.6 cu.inch/min)
15
Thus, the required EHP must exhibit a capacity of approximately 584
cm
3
/min (35.6 cu.inch/min).
A suitable EHP type for this purpose is the VETUS EHP type ‘EHPB
R2’ with a capacity of 700 cm
3
/min (42.7 cu.inch/min). The board-to-
board time is 12.5 seconds.
General
There are two types of cylinders; i. e., ‘balanced’ or ‘symmetrical’ cylin-
ders (with a continuous piston rod) and ‘unbalanced’ cylinders (with
a non-continuous piston rod ).
The VETUS EHPs may be connected to balanced as well as unbalan-
ced cylinders, due to the fact that the EHPs possess a bypass. Thus,
the oil volume which enters the oil pump from one side of the cylin-
der does
not
need to equal the volume which leaves the oil pump in
the other direction.
Besides, the VETUS EHPs also lend themselves to use with a cylinder
set
(2 cylinders with a
non
-continuous piston rod, a double rudder,
or two single rudders).
The following recommendations should be observed to prolong
the lifetime and improve the performance of your electrohy-
draulic pump (EHP).
- Only use hydraulic oil in accordance with the technical spe-
cifications
- Make sure the battery voltage is correct
- Limit the voltage loss over the battery cables by using cables
with an adequate diameter
- Ensure regular maintenance
Operation EHP with a reversible motor (EHPA R2, EHPB R2,
EHPC R2)
The EHP consists of an oil pump (driven by a
reversible
electromo-
tor), relief valves, suction valves, a check valve, a by-pass valve and
a tank.
Depending on the rotation direction of the electromotor, the oil is
pumped from one side of the piston to the other side of the piston
- and vice versa.
