Section 11 Hydraulic power actuating systems

11.1.1 The requirements of this Section are additional to those contained in Vol 2, Pt 7, Ch 5, 2 Construction and installation of this Chapter. The requirements do not apply to steering systems that are covered in Vol 2, Pt 6, Ch 1 Steering Gear.

11.1.2 The arrangements for storage, distribution and utilisation of hydraulic and flammable oils employed under pressure in power transmission systems, control and actuating systems, heating systems and hydraulic media in systems which are part of Mobility systems or Ship Type systems, are to comply with the requirements of this Section.

11.1.3 Hydraulic power actuating systems are to deliver hydraulic fluid under pressure for actuation of hydraulically driven machinery and for operation of remote controlled equipment.

11.1.4 Hydraulic fluids are to be suitable for the intended purpose under all operating service conditions and conform to the Owner's safety policy where applicable.

11.1.5 Materials used for all parts of hydraulic seals are to be compatible with working fluid at the appropriate working temperature and pressure.

11.1.6 Hydraulic power actuating systems for hydraulically driven machinery and for the operation of remotely controlled equipment are to be independent of each other.

11.2.1 Tanks and reservoirs for service and the storage of hydraulic fluids are to be made of steel and suitable for the maximum head of fluid to which the tanks may be subjected. In general, tanks are to have a minimum plate thickness of 5 mm, but in the case of very small tanks, the minimum thickness may be 3 mm.

11.2.2 The storage capacity for hydraulic fluid(s) is to be sufficient to recharge the largest system on board plus normal usage during a typical mission. Storage capacity is to be sufficient for each type of hydraulic fluid used on the ship. Storage capability sufficient to handle the full capacity of the largest hydraulic system on board is also to be provided for dirty hydraulic fluids.

11.2.3 Tanks and reservoirs are to be provided with two connections at diagonally opposite corners, one top and one bottom to permit the contents to be circulated through portable flushing equipment.

11.2.4 The capacity of hydraulic fluid reservoirs at normal working level is to ensure a residence time for the fluid of not less than three minutes.

11.2.5 A vertical baffle plate is to be fitted dividing each reservoir into two compartments interconnected at the top of the baffle. Return fluid, drains, etc. are to be made to one side of the baffle whilst pump suctions are to be taken from the other side.

11.2.6 All tanks and reservoirs are to be provided with approved means of hydraulic fluid level indication.

11.2.7 All tanks and reservoirs are to be provided with approved means of sampling the contents and a means of access for cleaning.

11.3.1 Two or more hydraulic pumps are to be provided for each power actuating system. The pumps are to be of sufficient capacity to supply the system under defined operational requirements stated in the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2 with any one pump out of action.

11.3.2 All hydraulic pumps are to be provided with relief valves. Each relief valve is to be in close circuit, i.e. arranged to discharge back to the suction side of the pump and effectively to limit the pump discharge pressure to the design pressure of the system.

11.3.3 The power supply to all independently driven pumps used for pumping flammable fluids is to be capable of being stopped from a position outside the space. It shall be possible to activate the stop from this position in the event of a fire occurring in the space containing the pumps, in addition to any stop facilities provided in the space.

11.3.4 Where pump units are provided with accumulators, a shut-off valve is to be provided between the pressure line and the accumulator with a bleed valve fitted between the shut-off valve and the accumulator.

11.3.5 Where accumulators are provided with gas pressurisation, isolating valves are to be fitted in the gas lines at each accumulator. A relief valve is to be fitted in the gas supply line to limit prevent the accumulator being pressurised above its maximum working pressure.

11.4.1 Supply systems to hydraulic power actuating systems are to be as short as practicable.

11.4.2 Where hydraulic pipes penetrate watertight or fire zone bulkheads, isolating valves are to be provided.

11.4.3 The use of flexible hoses is to be restricted to positions where it is necessary to accommodate relative movement between items of equipment and fixed pipe-work.

11.4.4 Where emergency fire valves are hydraulically operated, accumulators are to be provided in the common supply lines to facilitate rapid operation of the valve actuators in the event of fire.

11.4.5 Provision is to be made for emergency hand pump or hand wheel operation of hydraulic systems.

11.4.6 Where a hydraulic securing is applied, the system is to be capable of being mechanically locked in the closed position so that, in the event of hydraulic system failure, the securing arrangements will remain locked.

11.4.7 Where pilot operated non-return valves are fitted to hydraulic cylinders for locking purposes, the valves are to be connected directly to the actuating cylinder(s) without intermediate pipes or hoses.

11.4.8 Hydraulic circuits for securing and locking of bow, inner, stern or shell doors are to be arranged such that they are physically unable to be affected by operation of other hydraulic circuits when securing and locking devices are in the closed position. For requirements relating to hydraulic steering gear arrangements, see Vol 2, Pt 6, Ch 1, 5.3 Components.

11.4.9 Suitable oil collecting arrangements for leaks shall be fitted below hydraulic valves and cylinders.

11.5.1 Cooling arrangements for hydraulic fluids are to be provided where the operating temperature of the fluid may exceed the maximum design temperature limitations of the fluid or equipment in the system as defined in the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2.

11.5.2 Where the provision of cooling arrangements is necessary to maintain hydraulic fluid temperatures, not less than two means of cooling are to be provided and configured such as to provide cooling with one means out of action.

11.6.1 All pumps which are capable of developing a pressure exceeding the design pressure of the system are to be provided with relief valves. Each relief valve is to be in closed circuit, i.e. arranged to discharge back to the suction side of the pump and effectively to limit the pump discharge pressure to the design pressure of the system.

11.7.1 The locations of pipe joints, valves, and other potential leak paths in piping systems for flammable hydraulic fluids are to be arranged so that, in the event of a leak, fluid will not come into contact with hot surfaces, machinery air intakes, electrical equipment or other sources of ignition.

11.7.2 Pipes conveying hydraulic oil under pressure are to be of seamless steel or other approved material, and are to be placed in sight above the platform in well lit and readily accessible parts of the machinery spaces.

11.7.3 For requirements relating to flexible hoses, see Vol 2, Pt 7, Ch 1, 13 Flexible hoses.

11.8.1 Filling stations are to be isolated from other spaces and are to be efficiently drained and ventilated.

11.9.1 On completion, the tanks are to be tested by a head of water equal to the maximum to which the tanks may be subjected.

11.10.1 Hydraulic oil tanks and filters are not to be situated immediately above boilers or other highly heated surfaces.

11.10.2 Hydraulic oil pipes are not to be installed above or near high-temperature equipment. Hydraulic oil pipes should also be installed and screened, or otherwise suitably protected, to avoid oil spray or oil leakages onto hot surfaces, into machinery air intakes, or other sources of ignition such as electrical equipment. Pipe joints are to be kept to a minimum and where provided are to be of a type acceptable to LR. Pipes are to be led in well lit and readily visible positions.

11.10.3 Pumps, filters and heaters are to be located to avoid hydraulic oil spray or leakage onto hot surfaces or other sources of ignition or onto rotating machinery parts. Where necessary, shielding is to be provided and the arrangements are to allow easy access for routine maintenance. The design of filter and strainer arrangements is to be such as to avoid the possibility of them being opened inadvertently when under pressure. This may be achieved either by mechanically preventing the pressurised filter from being opened or by providing pressure gauges which clearly indicate which filter is under pressure. In either case, suitable means for pressure release are to be provided, with drain pipes led to a safe location.