The present invention relates to a hydraulic system for a unit, such as a ship.
In many ships a number of important regular functions are performed by means of a hydraulic system for which oil has been used as the drive medium. In those known ships a separate installation has been used for fighting fire.
US-A-4786239 discloses a pumping system for shipboard use comprising a submersible centrifugal pump driven by a high pressure hydraulic motor mounted directly on the submersible pump. The hydraulic motor is connected by a hose to a hydraulic pump which is located on deck and driven by a standby fire pump.
The aim of the present invention is to provide a hydraulic system in a unit which can also be used for fighting fire.
Accordingly, the present invention provides a hydraulic system according to claim 1.
It will of course be understood that the water employed in the system of the present invention can include certain additives, for example anti-corrosion additives. The power source of the hydraulic system is preferably a hydraulic pump having a high operating pressure and a high volume capacity. The pump is usually driven by a main power source, such as an electric generator.
In a preferred embodiment at least some of the sprinklers or spray heads are connected to a pressure line of the hydraulic system.
Some of the sprinklers or spray heads can be connected to a return line of the hydraulic system, the return line being arranged to be closed downstream of the last sprinkler or spray head when the hydraulic system is activated.
Use of the present invention means that double pipe systems and double power sources are not necessary since the same system can be utilized for fire fighting as well as for performing the regular hydraulic functions. In addition to considerable savings in installation hardware and installation work, a significant reduction in weight is also achieved; this being of particular advantage in high-speed ships.
In some cases it may be of advantage to connect at least some of the sprinklers or spray heads to the power source through at least one further line separate from the at least one line of the hydraulic system.
In such an embodiment the subsidiary lines can be utilized for performing certain additional functions essential when a fire has broken out, such as closing fire doors, driving elevators, etc.. If the regular main power source, usually an electric generator, fails in a fire, an emergency generator, often having less power than the regular generator, can be capable of providing sufficient power for fighting the fire and for performing at least a limited number of additional important functions. The main lines can then if necessary be disconnected.
The inventive concept can generally be considered to be that the same system is utilized for fire fighting in addition to other regular hydraulic functions.
Hydraulic systems in ships and the like generally have a high operating pressure, for example 100 bar or more. The use of sprinklers or spray heads disclosed in International patent application nos. PCT/FI92/00060 and PCT/FI92/00155 (publication nos. WO92/15370 and WO92/20453) is recommended. Those sprinklers and spray heads capable of operating at a high pressure provide effective fire extinguishing with small amounts of water and can be made to produce concentrated fog-like sprays having a good penetration power.
The installation of such sprinklers or spray heads in a hydraulic system is considered to fall within the normal skill of a person skilled in the art and is therefore not described in detail in the present patent application.
In an oil tanker the hydraulic system of the present invention can be utilized for spraying a fog of water droplets, having a typical diameter size of from 30 to 150 microns, into the oil tanks for fire extinguishing and cooling, respectively.
Although the invention is principally intended to be used in ships and other comparable units, the invention can also be employed in other units of which steel plants and mines are examples.