SAILTEC's Kobelt Hydraulische Steuerung Katalog - page 63

h y d r a u l i c s t e e r i n g a n d a c c e s s o r i e s
61
• On a power hydraulic system we recommend using an
I.S.O. #32
hydraulic oil. This oil has excellent lubricating qualities for power
driven hydraulic pumps. It is important that these are well lubricated.
It is recommended to use the electrical solenoid valve via the Jog
Lever or Full Power Follow-up Lever, to bleed the main cylinder. The
main cylinders can therefore be bled and filled with hydraulic fluid
without use of the manual helm pumps. If the main cylinder and the
power part of the system is full with oil, the same procedure should
then be followed as when filling the manual system.
Expansion Tank for Power System
• On a power operated system (engine or motor-driven pump), the
Expansion Tank level can be maintained off the main pressure
line, with a small manually operated needle valve. However, only
a small volume should be supplied into this tank from the main
source of supply. The return line from the header tank to the main
oil tank should be no less than 1/2" in diameter and if an auto fill
system is used, the header tank should not be vented. The main
tank should be vented and the return line from the header tank to
the main tank should terminate on the cover plate and not go to
the bottom of the main tank.
Power Driven Hydraulic Pump, Tanks and Basic Accessories
• It is highly recommended to have two sources of hydraulic pressure
for a steering system. The hydraulic pumps must also be selected
to provide enough hydraulic fluid to turn the rudder from hardover
to hardover as requested by the customer. In our cylinder tables, the
volume of the cylinders are specified. This is quite readily converted
into gallons per minute. Use the following equation;
VOLUME
(cubic
inch) times
0.26
divided by
SECONDS
(desired hard-over speed) =
Gallons per Minute, e.g. 440 x 0.26 / 14 = 8.2 Gpm.
• Kobelt recommends using pressure-compensated pumps for two
basic reasons. The pressure-compensated pump only produces
volume as required by the hydraulic steering system. If no
volume is required, the pump will destroke itself to a minimum
volume, requiring very little energy and since very little energy is
consumed, very little heat is created in the oil. A hot oil system is
not desirable.
• We also recommend that the pumps are gravity fed from the
tank. This prevents the pump running dry and causing enormous
damage during the start-up period. The oil storage tank should
be a minimum of five times the volume of the maximum pump
output. It is recommended that the tanks are equipped with a
sight glass, vented filler, suction strainer, high pressure and
return line filter, low pressure alarm and oil level alarm. If two
units are connected, a one-way check valve must also be installed
in each pumping output line.
Caution: Oil temperatures must not exceed 120°F (55°C).
Temperatures above this will damage the seals.
• When the pump units are shipped, they are usually shipped without
any oil (dry). Before starting the motor, it is important to fill the tank to
near top level with light hydraulic oil (i.e. Shell Tellus 32 or equal).
• The pump is normally marked with an arrow for direction of
rotation. It is very critical that the rotation of the motor is checked
to ensure the pump is turning in the right direction. As mentioned
earlier, it is of extreme importance that the pipes and fittings are
kept immaculately clean on the inside during installation.
• We recommend that the pump system, after start-up, should be
run for no more than an hour and all filter elements should then be
changed.
• If any impurities are found in the oil, it may also be necessary to
change the oil itself. One other important factor is that if there is
dirt in the hydraulic system, it will eventually lodge itself between
two moving components and score items to the point where they
can no longer be successfully used in the system and must be
replaced. Dirt can also cause items to physically seize in their
respective housings.
• Once the system is up and running, the oil storage tank must be
topped and maintained at its appropriate level.
Teflon tape should not be used on pipe fittings. A liquid pipe sealant
applied at the end of the fitting is preferable. Pipe fittings should
not be over-torqued since the tapered thread can cause splitting of
the control components. The table below indicates torque required
for tapered pipe fittings.
1/8" N.P.T.
10 ft. lbs.
1/4" N.P.T.
20 ft. lbs.
3/8" N.P.T.
30 ft. lbs.
1/2" N.P.T.
40 ft. lbs.
F i l l i ng and Bleed i ng a Power Hydraul i c System
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