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Encyclopedia of Marine Technology


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ULEPSI tank support system

Manufactured by Beele Engineering of the Netherlands, the support system suitable for tanks with cargo temperatures up to 250°C.


The distance from the top of the hatch, or from the top of the inspection cover in the hatch, down to the surface of oil in the cargo tanks of oil tankers.

Ultra large crude carrier HELLESPONT ALHAMBRA

During the golden boom years on the tanker market, from 1967 until the oil crisis of 1973, orders for about 80 VLCCs (200,000-320,000 dwt) and 40 ULCCs (over 320,000 dwt) were placed.

Ultra long stroke engine

A slow-speed, two-stroke engine which uses a large stroke to bore ratio to utilize the improved thermodynamic efficiency resulting from the uniflow scavenging.

Ultra low sulphur diesel

Diesel fuel having sulfur content of 0.0015 percent (15 ppm) of sulfur or less, (EPA).

Ultrasonic testing

The use of high frequency sound waves to test a material. They are reflected from the far side and can be displayed on a cathode ray oscilloscope.


The connecting hose to a tethered submersible unit and from this unit to the divers. It may contain life support, surveillance, communication, remote control and power supply cables, (ABS).


A groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld metal.

Underwater complex

A complex comprising of any combination of habitats with transfer chambers, and may include a tethered or untethered submersible unit and its launch and recovery system, (ABS).

Underwater container

A permanently unmanned submersible vessel containing equipment that is to be protected from water. It may be anchored to the ocean floor, (ABS).

Underwater system

A system comprising of one or more units with all their support components necessary to conduct a specified manned underwater operation such as a diving system and an underwater complex, (ABS).

Underwater vehicles

Self-propelled crafts intended for underwater operations that may or may not be independent of surface support, (ABS).


A person participating in an underwriting syndicate or group that provides insurance cover for a vessel.


The manner in which ships and other vehicles of transport are insured.

UNIC davit

A new space-saving lifeboat davit system for cruise vessels, developed by Schat-Harding.

UNIC engine automation system

Modular, embedded control system for control and monitoring of diesel and gas engines developed by Wärtsilä.


The MacGregor universal twistlock that can be used as a semi-automatic twistlock, an automatic fixing cone or bottom automatic fixing cone.

Unsymmetrical flooding

The entry of water into a compartment on one side of the ship which will cause heeling, in addition to the effects of flooding.

Upper flammable limit (UFL), upper explosive limit

The concentration of a hydrocarbon gas in air above which there is insufficient amount of oxygen to support and propagate combustion.


A metal casing or large-bore piping which carries exhaust gases up through the funnel to the atmosphere.

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