marine engineering

Home page||Deck machinery||


Hydraulic systems for deck machinery and cargo equipment onboard

Hydraulic systems provide a means of distributing power and of obtaining it from a constant speed and constant direction drive such as an a.c. electric motor. The oil pressure can be used to provide variable speed drives through hydraulic motors and power for actuating devices. Hydraulic power is used extensively for deck machinery and remote control of valves.

Hydraulic systems:

The three essential components for a hydraulic circuit, are the hydraulic fluid held in a reservoir tank, a pump to force the liquid through the system and a motor or cylinder actuator to convert the energy of the moving liquid into a working rotary or linear mechanical force. Valves to control liquid flow and pressure are required by some systems.

Hydraulic fluid:

Water was the original hydraulic fluid and is still used for heavy duty such as operation of lock gates or moving bridges. The disadvantages with water are that it promotes rusting and other forms of corrosion, it is not a good lubricant and it has a limited temperature range.



Hydraulic oils may be straight mineral or special additive oils. Properties of these, enhanced by additives, include oxidation stability, film strength, rust prevention, foam resistance, demulsibility and anti-wear characteristics to enable the fluid to stand up to the higher operating temperatures and pressures of modern systems. Pour point depressants are used to prevent freezing in low temperature conditions. Other fluids used in hydraulic systems may be synthetics or emulsions.

Emulsions have been used in systems such as the telemotor, where force is applied and received by pistons. Oils are preferred for systems using rotating pumps and motors, where good lubrication is essential. In an emergency where short term expediency is the criterion, any thin oil could be used in a system.

Deterioration of hydraulic oils:

Hydraulic fluids which are basically mineral oils, will degenerate very slowly over time due to oxidation. The factors which encourage oxidation are the heating and agitation of the oil in the presence of air and metal, particularly copper.

The process of oxidation is accelerated by overheating and also by contamination with products of corrosion or the presence of metal wear particles. Oxidation products, both soluble and insoluble, increase the oil's viscosity and cause sludge to be deposited. Oxidation tends to encourage the formation of emulsions with any water from leakage or condensation. Acidic products of oxidation will cause corrosion in the system.

Contamination of oils:

Water promotes rusting of steel and must be excluded from hydraulic systems. Rust can be detached and when carried around a circuit can cause the jamming of those valves with fine operating clearance, as well as hastening deterioration of the oil. Sea water can enter through the shaft seals of deck machinery and via system coolers. Condensation on the cold surfaces of reservoir tanks which are open to the atmosphere, is a common source of contamination by water.

Tanks should not be constructed such that cold hull plating forms one wall Metal wear is inevitable and fine filters are installed to remove these and corrosion particles together with any other grit or dirt that finds its way into the system. Care is necessary with hoses, funnels and oil containers used for filling and topping up reservoir tanks, to ensure that they are clean. Fine metal wear particles can act as abrasives causing further wear. All particles could cause blocking of small passages or the jamming of valves.


Summarized below some of the basic operation of deck machinery and maintenance guide :
  1. Powering deck machinery -Systems and components

  2. Pump and motor systems are used for powering deck machinery such as winches and windlasses. Pump and actuating cylinders are normally employed for hatch covers. One or more pumps will be used to supply the volume of fluid at the pressure required to operate one or more motors. ......

  3. Mooring equipment for general cargo vessel

  4. The operation of mooring a vessel has traditionally required the attendance of a large number of deck crew fore and aft. Supervision of the moorings was also necessary to maintain correct tension through changes due to the tides and the loading or unloading of cargo. ......

  5. Hydraulic systems for deck machinery and cargo equipment

  6. The three essential components for a hydraulic circuit, are the hydraulic fluid held in a reservoir tank, a pump to force the liquid through the system and a motor or cylinder actuator to convert the energy of the moving liquid into a working rotary or linear mechanical force. Valves to control liquid flow and pressure are required by some systems. ......

  7. General cargo ship deck machinery electric drives

  8. Electric motors on vulnerable deck areas may be protected against ingress of water by being totally enclosed in a watertight casing. Vents are provided on some winches, which must be opened when the motor is operating in port. ......

  9. Handling deck machinery- Anchor windlasses,Anchor capstan & mooring winches

  10. The windlass cablelifter brakes must be able to control the running anchor and cable when the cablelifter is disconnected from the gearing when letting go'. Average cable speeds vary between 5 and 7 m/s during this operation. ......

  11. General cargo ship deck deck crane

  12. A large number of ships are fitted with deck cranes. These require less time to prepare for working cargo than derricks and have the advantage of being able to accurately place (or spot) cargo in the hold. On container ships using ports without special container handling facilities, cranes with special container handling gear are essential. ......

  13. Mechanically operated steel hatch covers

  14. Hatch cover equipment like the other deck machinery, has to exist in a very hostile environment and the importance of regular maintenance cannot be over-emphasized. Drive boxes and electrical enclosures should be checked regularly for water-tightness. ......

  15. Derricks and cargo winches -Ship cargo handling gears

  16. The duty of a deck winch is to lift and lower a load by means of a fixed rope on a barrel, or by means of whipping the load on the warp ends, to top or luff the derricks, and to warp the ship. ......



Home page||Cooling ||Machinery||Services ||Valves ||Pumps ||Auxiliary Power ||Propeller shaft ||Steering gears ||Ship stabilizers||Refrigeration||Air conditioning ||Deck machinery||Fire protection||Ship design ||Home ||


General Cargo Ship.com provide information on cargo ships various machinery systems -handling procedures, on board safety measures and some basic knowledge of cargo ships that might be useful for people working on board and those who working in the terminal. For any remarks please Contact us


Copyright © 2010-2016 General Cargo Ship.com All rights reserved.
Terms and conditions of use
Read our privacy policy|| Home page||