Ullage

Ullage

Ullage refers to the unfilled space in a container of liquid.

Etymology

The word comes ultimately from the Latin oculus, “eye”, which was used in a figurative sense by the Romans for the bung hole of a barrel. This was taken into French in the medieval period as "oeil", from which a verb "ouiller" was created, to fill a barrel up to the bung hole. In turn, a noun "ouillage" was created, which was the immediate source of our word, first recorded in Norman English about 1300, at first in the sense of the amount of liquid needed to fill a barrel up to the bung hole.

Wine and spirits

By an obvious extension, "ullage" came to refer to any amount by which a barrel is unfilled, perhaps because some of the contents have been used. And it is also applied to the unfilled air space at the top of a bottle of wine, which in this case is essential to allow for expansion of the contents as the temperature changes.

Rocketry

In liquid rockets, ullage is the space within a fuel tank above the liquid propellant. This term derives from the term 'ullage' in winemaking, where it refers to the space above the liquid in a container such as a barrel or wine bottle.

Liquid, cryogenic rockets keep their propellant in tanks. These tanks are never completely filled in order to allow for the expansion of the cold liquid propellant. On the ground, the space between the top of the propellant load and the top of the tank is known as "ullage space".

In zero-gravity conditions the gas may float around and threaten to be sucked into the engines, which is typically very undesirable. Small rocket engines are sometimes used to settle the propellant prior to the main engine ignition. These are called ullage motors.

Industrial use

"Ullage" is also widely used in industrial or marine settings to describe the empty space in large tanks used for fuel or chemicals. In accordance with IMO regulations, the Code of Federal Regulations, and the ABS Rules for Steel Vessels, certain pressurized tanks on steel ships may not be filled greater than 98% full( Although there are exceptions). This is so that the pressure relief valve is always in contact with a gas or vapor. Certain pressure relief valves for chemical use are not designed to relieve the pressure when in contact with liquids.

ources

ABS Rules for Steel Vessels 2007, Part 5C

External links

* [http://www.spaceline.org/rocketsum/saturn-V-apollo.html Description of Saturn V engines]


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Look at other dictionaries:

  • ullage — UK US /ˈʌlɪdʒ/ noun [C or U] PRODUCTION, MEASURES ► the space in a closed container of liquid that is not filled by the liquid: »Most wines are bottled for immediate consumption, and the ullage should be small. »The requirement to determine… …   Financial and business terms

  • Ullage — Ul lage (?; 48), n. [OF. eullage, ovillage, the filling up of a cask, fr. ouillier, oillier, euillier, to fill a wine cask; properly, to add oil to prevent evaporation, as to a flask that is nearly full, fr. OF. oile oil. See {Oil}.] (Com.) The… …   The Collaborative International Dictionary of English

  • ullage — index deficiency Burton s Legal Thesaurus. William C. Burton. 2006 …   Law dictionary

  • ullage — (n.) amount by which a cask or bottle falls short of being full, late 15c., from Anglo Fr. ulliage (early 14c.), Anglo L. oliagium (late 13c.), O.Fr. ouillage, from ouiller to fill up (a barrel) to the bung, lit. to fill to the eye, from ueil eye …   Etymology dictionary

  • ullage — ► NOUN 1) the amount by which a container falls short of being full. 2) loss of liquid by evaporation or leakage. ORIGIN from Old French euillier fill up , from Latin oculus eye (with reference to a container s bunghole) …   English terms dictionary

  • ullage — [ul′ij] n. [ME ulage < Anglo Fr ulliage < OFr ouillage, a filling up to the brim or the bunghole < ouiller, to fill (a cask) to the bunghole < ueil, an eye, fig. bunghole < L oculus, an EYE] the amount by which a container, esp. of …   English World dictionary

  • Ullage — Unter Ullage (englisch u. a. für Freiraum , Füllstand bis Tankdecke ) versteht man in der Seeschifffahrt den freien Raum zwischen der Oberfläche einer Flüssigkeit in einem Tank und dem oberen Abschluss des Tanks. Analog bezeichnet Ullage auch den …   Deutsch Wikipedia

  • ullage — [15] Ullage denotes the amount of unfilled space in a wine bottle or barrel. It goes back ultimately to Latin oculus ‘eye’ (a distant relative of English eye), in the metaphorical sense ‘bung hole of a barrel’. As the word passed into Old French… …   The Hutchinson dictionary of word origins

  • ullage — /ˈʌlɪdʒ/ (say ulij) noun 1. the amount by which the contents of a container, tank, ship, etc., fall short of filling it. 2. the loss of wine or the like from its container by reason of leakage or evaporation. 3. Aeronautics the volume of a full… …  

  • ullage — [15] Ullage denotes the amount of unfilled space in a wine bottle or barrel. It goes back ultimately to Latin oculus ‘eye’ (a distant relative of English eye), in the metaphorical sense ‘bung hole of a barrel’. As the word passed into Old French… …   Word origins

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