This valve is intended to be used in power
steering systems. Its purpose is to retain
all of the hydraulic fluid in the steering
system itself when the power-driven
hydraulic pumps are not operational, so as
to allow the use of the helm pump without
loss of hydraulic fluid.
All hydraulic valves, because of their
mechanical fit tolerances, lose fluid in
various amounts at some seals and joints.
Consequently this would cause the
hydraulic fluid to drain from the highest
level to the lowest level. In most cases,
the helm pump is located in the
wheelhouse which is well above the main
hydraulic tank. The oil will eventually drain
back to the main tank thus leaving the
manual steering system run dry.
The 7243 valve, however, will retain all of
the fluid in the system and will allow the
helm pump to be used almost indefinitely in
an emergency condition.
If this unit is used with a 7147 or 7148
Kobelt Power Assist Unit, it is important to
have a buffer system in order to get these
units to shift to manual mode.
If the 7243 is installed on the servo
steering system, all helm pumps must have
a non-vented plug. The header tank must
also be sealed (non-vented). The return
line from the header tank must go directly
to the main tank. The flow controls
supplying oil to the header tank must be
opened far enough to allow all the pressure
from the hydraulic system to vent via the
header tank back to the main tank.
However, if the flow control is too widely
opened the header tank will be pressurized
and could cause possible damage to the
sight glass or cause leakage between the
tank and the cover. A minimum amount of
oil should pass through the flow controls,
yet has to be sufficient enough to allow the
pressure to drop off in the system.
