Marine Hydraulics Service Highlights
Denis Korablev
  • 03.11.2021
  • 2,156

Marine Hydraulics Service Highlights

The hydraulic system of a sailing vessel is compared to a workhorse, as it does so much useful things on board and does not require much attention. The hydraulic winch paired with the hydraulic thruster operates from dusk to dawn and does not overheat. With good pitching, hydraulic stabilizers come to the rescue. As the specialists 2yachts note, nothing can work forever, but with timely maintenance, the life of ship hydraulics will increase significantly.

From history ...

As early as the sixth millennium BC, devices were used that were filled with liquid under pressure. The beginning was laid by water mills, in which the wheels were provided with the help of water under the influence of gravity. Many useful devices have emerged from this engineering idea, which has been augmented with belts and pipes over time.

By the mid-19th century in England, William Armstrong realized that hydraulics could be used in cranes to lift loads by pressurizing the system with water from a nearby water tower. This invention was used quite effectively in the port of Newcastle upon Tyne.

Later, he invented a hydroaccumulator, consisting of a water tank with a plunger (rather heavy) on top, whose principle of operation resembled the action of a medical syringe. Lowering, the plunger, with its weight, provided the required pressure in the pipeline.

How does the hydraulic system work?

Today, on yachts, pressure is provided with the help of pumps, high-precision equipment is made of modern material, but the fundamental principle remains the same. The system (hydraulic) transfers fluid to the hydraulic motor through pipes, which, using the received energy, makes the mechanism work. In such systems, oil is often used as a working fluid.

Marine hydraulics is a closed system consisting of an oil tank, pistons, thrust, pipelines, etc. With the help of a pump, pressure is built up from one end, distributing it throughout the system (and its dimensions do not matter). At the opposite end of the pipeline, mechanisms are connected, actively responding to changes in pressure indicators, and due to this, performing a certain job. For example, consider the action of the hydraulic cylinder of the steering device: the pressure has changed - the hydraulic cylinder is forced to move and turn the rudder.

Hydraulic power is used most widely on large vessels, and on small boats it is used in the operation of the steering gear and transom plates.

What is timely service?

Some yachts have an integrated system in which only one hydraulic pump is installed in the engine room, feeding ladders, stabilizers, davits, thrusters. Such systems are much easier to maintain, they are made by special order; main advantage - the electric drive does not depend on the main engine, but works autonomously.

It happens more often that a separate mechanism has its own pump, and also when one pump feeds adjacent mechanisms, occasionally working together (for example, windlass and thruster).

Rule # 1: Check the oil level.

You can observe the change in the oil level through the sight glass; very convenient, you do not need to unwind or measure anything with a ruler. If the system is installed correctly, then oil leaks are extremely rare. If the level drops, add oil, immediately find out and eliminate the problem. It is necessary to add oil through a clean funnel, it is good to pass it through a paper filter.

Rule # 2: Take samples and send to the laboratory.

Pay attention to the purity of the oil, conditions of its keeping should be practically sterile, i.e. open the equipment only if necessary.

Once a year, and with intensive work, once every six months, samples should be taken from the systems and sent for laboratory analysis. The color of the oil should not change during the entire period of operation, if only it darkens a little. Thick, dark oil indicates overheating, for example, when the boat is moving, the stabilizers are constantly working, and sometimes even during anchorage.

If impurities get into the oil, it becomes black, for example, if metal dust has entered (with significant wear of the pumps). If water or dirt is noticed in the sample, then there is a problem somewhere. Details will be indicated in the report from the laboratory.

Rule number 3: change filters and oil after consultation with the masters.

An oil change should be in accordance with the manufacturer's recommendations, most often every three years, and for stabilizers after 4,000 operating hours. The shaft seals on the pumps are also changed every 3 years. Whether it is necessary to change the filters is determined by the readings of the operating pressures.

Rule # 4: Don't forget your cooling system.

Sometimes the hydraulic mechanisms work almost non-stop and the oil gets pretty hot. It is required to reduce the heating temperature, which means to drive it through the cooling system. If the overheated oil burns the paint in the oil tank, this is a 100% symptom that there is a problem with the cooling system. To prevent such a situation when the stabilizers are operating, it is recommended to regularly monitor the oil temperature.

To ensure the smooth operation of marine hydraulics, do not forget that the outboard cooling system also requires maintenance. According to the schedule, replace the impellers in the circulation pumps, check monthly how the heat exchanger and the anode protection are "feeling", monitor the Kingston grilles for clogging.

What if there is only a hydraulic steering gear on board?

Rejoice, as it rarely causes problems, if you do not drop anything heavy on the hydraulic cylinder. Yachtsmen most often do not look into the tiller compartment, only occasionally, if suddenly a tight steering wheel turns or some other nuisance. This is usually due to either a low level of working fluid, or the ingress of air into the system; adding oil can eliminate this problem.

The main advantage of such a steering gear is high efficiency and the ability to obtain high torques, besides, it is durable and allows you to change the yacht's speed quietly and quickly.

Typically, two-line systems are used (the handwheel is connected to the pump) and three-line, pressurized; both are reliable and easy to maintain. The type of system influences the filling method: if the pump is connected directly, then the liquid should be filled at the highest point of the system, and if under pressure, then you can simply add it to the supply tank.

Features of the two-line system

When the steering wheel is turned clockwise, fluid is directed from the steering unit to the hydraulic where it pushes the piston attached to the outer rod. As the piston moves, the rod retracts or stretches and the yacht turns.

In the system, the movement of oil occurs under the influence of gravitational forces. Thanks to the bypass between the 2 handwheels, fluid flows downward and air rises and exits through the air valve at the top of the system. It is often enough to remove the plug and add oil, which you need a little.

If a significant amount of air enters the system, as well as a sharp decrease in the level of the working fluid, it will be necessary to refill the system. One person turns the steering wheel at maximum speed in one direction, expelling the oil through the drain, while the other picks up whatever spills. Then repeat the procedure, but in the opposite direction. Actually, the manual should have detailed instructions for the steering gear.

Features of the three-line system

Used on large boats, they have a special pressure reservoir and a safety valve. From a technical point of view, the system is more intricate, but it is quite simple to test it. If it is necessary to increase the level, then it is required to just add oil to the reservoir, having released the pressure in advance; then pump the expansion joint with a simple air pump.

After filling the system, it is required to repeatedly turn the steering wheel in opposite directions to get rid of the air. In order to find leaks, you need to create pressure by resting the steering wheel at the end of the rudder blade movement. At the same time, another person should wipe all mechanisms and connections with paper to ensure they are sealed. Move the steering wheel and repeat the same actions.

If a connection with a broken tightness is found, but it cannot be tightened, then the entire section will have to be changed. On the yacht itself, it is possible to fix only minor problems of the hydraulic system: assemble or disassemble individual connections, replace oil seals or seals (if spare parts are available). It is much worse if the seal of the hydraulic cylinder has leaked; its replacement is carried out only in a clean workshop with dismantling.

If you are going to update the hydraulic system, you first need to carry out proof tests in order to accurately identify malfunctions. Experts recommend repairing the entire hydraulic system at once, and not in parts. Some owners send scattered hydraulic mechanisms for restoration, not paying attention to fittings, as well as pipelines, which is not very correct, especially if it is charter yacht where everything should work flawlessly. In fact, the source of contamination of the hydraulic fluid can be working hydraulic mechanisms, and not those that are out of order. If you do not go through all the elements of the hydraulic system and do not flush it, it is unlikely that it will work for a long time after assembling the repaired mechanisms.