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All hydraulic valves, because of their mechanical fit, lose fluid in various
amounts and this would consequently 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 above the main hydraulic tank, the oil will eventually drain back to the main
tank and leave the system dry. The 7143 valve, however, will retain all of the fluid in
the system and will therefore, in an emergency condition, allow the helm pump to be used
almost indefinitely. If this unit is used on 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 7143 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 be opened far enough to allow all the pressure from the hydraulic
system to vent via the header tank back to the main tank. If flow control is too widely
open the header tank will be pressurized and could cause possible damage to side glass
and cause leakage between the tank and the cover. A minimum of oil should pass through
the flow controls, but sufficient enough to allow the pressure to drop off in the system.
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