Entry & progression
Passerelles, cranes, tenders, stabilisers, hatches, anchor winches. High-pressure hydraulics, operated by deck crew, over people's heads, alongside a quay full of the public. Treat it accordingly.
The circuit, in the order faults occur
- Reservoir — level, temperature, water content, cleanliness. Most hydraulic failures start here.
- Pump — fixed or variable displacement. Noise and heat are the first symptoms of wear.
- Relief and pressure control — the system's protection. Never wound up to make a sticking machine move.
- Directional and proportional valves — where contamination lodges and spools stick.
- Actuators — rams and motors. Seal failure, scored rods, drift under load.
- Filtration and cooling — the two things that determine how long everything else lasts.
WARNING — Contamination is the failure mode. Everything else is a symptom. The overwhelming majority of hydraulic faults are dirt and water. Dirt scores the pump, sticks the spools and jams the proportional valves. Water destroys the additives, corrodes the internals and makes the oil milky. Filter to specification, check differential pressure, cap every open port instantly, and take an oil sample. Topping up with a dirty funnel undoes an entire filtration system.
Passerelles and cranes — machinery over people
A passerelle deploys over water and over the quay. A tender crane lifts several tonnes over a swim platform where crew are standing. These are lifting operations, and they carry the hazards of lifting operations.
- Know the SWL — and know it for the boom angle and radius actually in use. Capacity falls with radius.
- Inspect wires, slings, shackles and the hook before every lift, not annually.
- Nobody under the load. Nobody. This is not negotiable and it is the second engineer's job to enforce it when the deck department is in a hurry.
- Check for drift. A ram that creeps down under load has a failing seal or a leaking check valve, and the load will land.
- Test the emergency stop and the manual lowering before you need them.
Stabilisers
Fins and their hydraulics are what the owner will actually notice. Zero-speed stabiliser systems run hard at anchor — high duty cycle, high oil temperature, big cycling loads on seals — which is precisely when the boat is full of guests. Watch reservoir temperature, watch for drift in the fin position, and keep the cooling clean.
TIP — Accumulators store energy after you shut everything down A hydraulic accumulator holds pressure long after the pump is stopped and the power is off. It will move a ram, close a hatch or drop a passerelle with the whole system apparently dead. Discharge accumulators and prove zero pressure at a gauge before you break any joint. Then check for stored mechanical energy — a raised tender, an unsupported boom — before you go near it.
Steering gear
The most important hydraulic system aboard, and the one people think about least. Know how to change over steering pumps, how to operate the emergency steering, and how long it takes to get someone into the steering flat and steering by hand. Test it. On a schedule. Before you need it, in a channel, in traffic, at night.