Vetus EHPA12R2 Instructions D'installation page 10

Hydraulic steering systems
An hydraulic steering system basically consists of one or more
pumps as well as a cylinder.
If the steering system contains only one Electro-Hydraulic
Pump (EHP), then it is not necessary to install a (double) check
valve.
The EHP type 'R2' is already equipped with a built-in check
valve. See diagram '1' *.
In the case of an hydraulic steering system with 2 or 3 pumps,
on the other hand, a (double) check valve definitely needs to
be installed - both to be able to automatically switch over from
one steering pump to the other, and to be able to prevent the
unused steering pump from following. For details please see
diagram no.-'2' and '3'.
Separate check valves
All Vetus EHP's feature a built-in check valve and it is therefore
not necessary to install a separate check valve, see diagrams
'1', '2' and '3'.
There is no need to install separate check valves between the
steering pumps and the cylinder if the (manual) steering pumps
are already equipped with a (built-in) check valve. For details
please see diagram no. '4'.
Relief valve
The EHP already possesses a relief valve to protect the steering
system from damage in the case of a (temporarily) excessive
rudder moment (exceeding the maximum for which the steering
system was originally designed).
By-pass valve
A by-pass valve is necessary if emergency rudder steering is
desired.
When the by-pass valve is open there is no pressure so that
the oil can flow from one side of the piston to the other and
the hydraulic system no longer blocks the emergency (rudder)
steering.
N.B. A by-pass valve can only be used when the cylinders are
balanced.
N.B. The by-pass valve built in the EHP has a very small bore
opening. When this valve is used as by-pass valve for
emergency steering the force required on the rudder is
very high.
Use a 6 mm hexagonal socket wrench to open and close
the by-pass valve.
If emergency steering is desired install a by-pass valve which is
geared to the size of the cylinder; see diagram '5'.
* Individual circuit diagrams are found in the 'Hydraulic dia-
grams' on pages 38-40.
8
020203.06
Assembly
Setup of the electrohydraulic pump
The room in which the EHP is to be set up must be dry and well
ventilated. Make sure that the EHP is positioned as closely as
possible to the cylinder.
In selecting a suitable location, consider the possible noise and
vibration caused by the EHP .
The EHPA R2, EHPB R2 and EHPC R2 models are equipped
with rubber vibration absorbers.
Make sure that the
base of the EHP
rests on a per-
fectly horizontal
surface.
The filler neck
respectively the connection for the compensating line * must
always be located on top; i. e., at the highest point.
* If the installation consists only of a cylinder with an EHP , the
EHP must be equipped with a filler neck and a breather.
If the installation features one or more steering pumps, all oil
reservoirs must be interconnected via a compensating line.
The highest steering pump must be equipped with a filler
neck with a breather. The other pumps must exhibit a filler
neck without an opening.
Assembly of a double check valve
Install a (double) check valve as closely as possible to the
steering cylinder. Make sure that the pipe sections between the
check valve and the cylinder, which are continuously pressu-
rized, are as short as possible.
Install the (double) check valve on an absolutely level surface.
Before installing the steering pump and the cylinder, consult the
instructions for the manual control unit.
Fittings
Never use teflon tape to seal off the screw connections. Liquid
sealants should be applied with great care. Sealants entering
the hydraulic system may cause malfunction.
EHP models with a reversible motor (EHPA R2, EHPB R2,
EHPC R2):
Attach the two connective couplings to the two nylon pipes
which have already been fitted to the EHP .
vetus® Electro-Hydraulic Pumps