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Encyclopedia of Marine Technology


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Back haul

The return movement of a means of transport providing a transport service in one direction.


The removal of weld metal and base metal from the weld root side of a welded joint to facilitate complete fusion and complete joint penetration upon subsequent welding from that side.


A material or device placed against the backside of the joint, or at both sides of a weld in electroslag and electrogas welding, to support and retain molten weld metal.

Backing pass, backing weld

A weld pass made for a backing weld

Backing ring

Backing in the form of a ring, generally used in the welding pipe.


The pressure existing on the exhaust side of a system, e.g. the pressure opposing the motion of an engine piston during its exhaust stroke.

Back-up navigator

Any individual, generally an officer, who has been designated by the vessel master to be on call if assistance is needed on the bridge.

Baffle plate

A plate used to direct fluid flow, e.g. the hot gases in a boiler furnace or the oil in a sump tank.

Bagged cargo

Various kinds of commodities usually packed in sacks or in bags, such as sugar, cement, milk powder, onion, grain, flour, etc.

Balance ratio

The ratio, of the blade area situated forward of the rudderstock to the total rudder blade area.

Bale capacity, bale cubic

The cubic capacity of a cargo hold measured to the inside of the frames or cargo battens.


Any solid or liquid weight placed in a ship to increase the draught, to change the trim, or to regulate the stability. Ballast water is allocated during the voyage to accommodate changes in the distribution of cargo and consumables...

Ballast movement

A voyage or voyage leg made without any paying cargo in a vessel tanks. To maintain proper stability, trim, or draught, seawater is usually carried during such movements.

Ballast pumps

Electric-driven pumps, usually vertically mounted and fitted with separate motor-driven priming systems. Close-coupled designs have the pump rotor mounted on an extended motor shaft.

Ballast system

Piping and pumping system arranged so that water can be drawn from any ballast tank or the sea and discharged to any other ballast tank or the sea.

Ballast tank

Watertight compartment for holding water ballast.

Ballast Water Discharge Requirements

1. Ballast Water Convention, 2004 -The International Convention for the Control and Management of Ships’ Ballast Water and Sediments, 2004.

Ballast water exchange at sea

The practical method to minimize the introduction of unwanted organisms from the discharge of ballast water. The exchange procedure shall be carried out in an “open ocean condition” at least 200 nautical miles...

Ballast water exchange standard D1

Ships performing ballast water exchange shall do so with an efficiency of 95% of ballast water. For ships exchanging ballast water by the flow-through method...

Ballast water management

Various measures to prevent, minimize and ultimately eliminate the risk of introduction of harmful marine organisms within ballast water. Ballast water management includes theballast water exchange...

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