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020203.06
Electro-Hydraulic Pumps
2
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 stee-
ring pumps and the cylinder if the (manual) steering pumps are al-
ready 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 sys-
tem from damage in the case of a (temporarily) excessive rudder mo-
ment (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 balan-
ced.
N.B. The by-pass valve built in the EHP has a very small bore ope-
ning. 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 gea-
red to the size of the cylinder; see diagram ‘5’.
* Individual circuit diagrams are found in the ‘Hydraulic diagrams’ on
pages
3
Assembly
Setup of the electrohydraulic pump
The room in which the EHP is to be set up must be dry and well ven-
tilated. Make sure that the EHP is positioned as closely as possible to
the cylinder.
In selecting a suitable location, consider the possible noise and vi-
bration caused by the EHP.
The EHPA R2, EHPB R2 and EHPC R2 models are equipped with rub-
ber vibration absorbers.
Make sure that the
base of the EHP
rests on a perfectly
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 pressurized, 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 in-
structions 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 hy-
draulic 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.
