Check Valves - Raymarine E12139 Installation Manual

Hydraulic fluid
• Before running the pump for the first time, make sure the system contains sufficient
hydraulic fluid. You will damage the pump if you let it run when 'dry'.
• Do NOT use "brake fluid". Use only mineral-based good quality hydraulic fluid com-
patible with nitrile rubber hydraulic seals.
• For suitable hydraulic fluid, refer to the helm pump manufacturer's recommendations
for compatibility. Also refer to the technical data provided in the technical specification
section of this document.

Check valves

For single-steering position boats:
• Consult the steering gear manufacturer to determine whether the helm pump is fitted
with reversing check valves:
• without check valves, the autopilot pump will drive the helm pump (sometimes
referred to as 'motoring the wheel') instead of moving the steering ram
• If the boat has a single helm pump system without check valves, you must incorpo-
rate a double pilot check valve (part number M81166).
• A double pilot check valve may also be necessary on long tubing runs - otherwise tub-
ing expansion may cause poor autopilot performance.
If the boat has two steering positions, it will already have check valves installed so the two
Note:
wheels can operate independently.
Hydraulic steering systems
There are three basic types of hydraulic steering systems:
• two line systems
• two line pressurized systems
• three line systems
On the following pages typical connection points are described for the autopilot pump on
each of these systems. For all of the systems you will need to connect a third hydraulic pipe
(as shown) between the autopilot pump and the helm pump or system reservoir.
Two line systems
Figure 6
shows a typical two line steering system. Hydraulic fluid flows into the ram in either
direction, depending on the direction the helm pump rotates. Connect the autopilot pump to
the steering system as shown in
CAUTION
Figure 6
.
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