The on-service hydraulic pump is running at all times and is a constant-speed pump. Unless steering is actually taking place, the tilt box of the main hydraulic pump is at zero stroke, and no oil is being moved within the main system. The auxiliary pump provides control oil and super-charge flows for the system. Assume that a steering order signal comes into the differential control box. It may come from either the remote steering system in the ships wheelhouse or the trick wheel. The control box mechanically positions the tilt box of the main hydraulic pump to the required angle and position. Remember that direction of fluid and flow may be in either direction in a hydraulic speed gear. It depends on which way the tilt box is angled. For this reason, a constant speed, unidirectional motor can be used to drive the main hydraulic pump. The pump will still have the capability to drive the ram in either direction.

With the main hydraulic pump now pumping fluid into one of the cylinders, the ram will move, moving the rudders. A rack and pinion gear assembly is attached to the rudder yoke between the rudder links. As the ram and the rudder move, the rack gear moves, driving the follow-up pinion gear. Each pinion drives a follow-up shaft which is mechanically coupled to the differential control box. This feedback (servo) system tells the directional control box when the steering operation has been completed and that the rudder angle is at the position ordered by the helm. As the ordered rudder angle is approached, the differential control box will begin to reduce the angle of the tilt box of the main hydraulic pump. By the time the desired rudder angle is reached, the tilt box should be at zero stroke. When this happens, the ordered signal (from the pilot house or trick wheel) and the actual signal (from the follow-up shafts) are the same. (NOTE: The ram is held in positon between the two cylinders by hydraulic lock due to the incompressible oil, which is prevented by the transfer valve from flowing into or out of the supply and return piping.) If either of these changes, the differential control box will react accordingly to cause the main hydraulic unit to pump oil to one end or the other of the ram. The trick wheels provide local-hydraulic control of the steering system in case of failure of the remote steering system. A hand pump and associated service lines are also provided for local-manual operation of the ram in case of failure of both hydraulic pump units.

Steering Engine Room Watch

As an Engineman, you may be required to stand watch in the steering engine room. The duties of the steering engine room watch include operation and emergency repair of the machinery in your charge. Operating instructions and system diagrams are posted in the steering engine room.

The diagrams describe the various methods of operating the steering gear under normal and emergency conditions and show the relative positions of the valves concerned for each method of operation.

During your watch in the steering engine room, you should take the following actions:

1. Make sure the standby equipment is ready for instant use in an emergency.

2. Inspect the steering gear thoroughly. Check the unit by feeling the various parts. Report any part that feels HOT to the bare hand to the officer of the deck on the bridge and to the engineering officer of the watch (EOOW) in the main engine room.

3. Investigate for binding, overloading, and lack of lubrication.

4. Listen for new or unusual noises, which may indicate loose parts or wear.

5. Bleed all air out of the system.

6. Check for leaks in the line and fittings. Piping leaks usually occur following unusual strain (as from rough seas). Most leaks can be corrected by tightening the flange bolts. Small leaks at ram packing glands are not objectionable since the small flow of hydraulic fluid provides lubrication. Always maintain sufficient liquid level in the storage, operating, and replenishing tanks.

7. Check and ensure all grease fittings and surfaces requiring lubrication are lubricated according to the instructions on the lubrication chart.

8. Observe all applicable safety precautions.

Keep oil off the deck. Exercise extreme caution when working in confined spaces around the ram and actuating gear. All clothing should be free of loose ends that might catch in the machinery.

The Planned Maintenance System (PMS) lists the individual requirements for the equipment. The electricians maintain the electrical portion of the steering system, including the control system.