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Encyclopedia of Marine Technology


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A device which can lift weights or exert a large thrust in order to move or position some equipment. It is usually hydraulically operated.


1. The passageways which surround the engine cylinders. 2. Steel support framework used to support offshore platform topsides.

Jacket cooling water system

The jacket cooling water system is used for cooling the cylinder liners, cylinder covers and exhaust valves of the main engine.

Jack-up drill rigs, also self-elevating drilling platforms



A shutter or cover with louvers. It provides ventilation while restricting the entry of rain and wind.

Jettison of cargo

Act of throwing cargo or equipment (jetsam) overboard in order to lighten the vessel or improve its stability in case of emergency.

Jetty, pier

A structure that projects into the water to a reasonable depth of water. It enables ships or boats to come alongside to load or discharge cargo or passengers.

Joiner arrangement

There are construction details showing the combination of all structural fire protection materials.

Joule-Thomson effect

When a fluid is allowed to expand without generating external work and no external heat transfer take place, a temperature change results.

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