Ullage
Encyclopedia
Ullage or Headspace refers to the unfilled space in a container
, particularly with a liquid.
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.
In liquid rocket
s, 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 micro-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 motor
s.
s used to store or carry liquids or bulk solids such as grain
. 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.
In some cases the ullage in a ship's hold can be relevant to stability
; dry bulk cargo
in a part-filled hold can shift asymmetrically towards one side as the ship heels to one side and the other, reducing the margin of stability when compared with a full hold.
Container
Container may refer to:* Items used to contain, store, and transport products, such as:** Carton** Bottle** Can , several meanings* Shipping containers include** Crate** Wooden box...
, particularly with a liquid.
Etymology
The word comes ultimately from the LatinLatin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
oculus, “eye”, which was used in a figurative sense by the Romans for the bung hole of a barrel. This was taken into French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
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
Normans
The Normans were the people who gave their name to Normandy, a region in northern France. They were descended from Norse Viking conquerors of the territory and the native population of Frankish and Gallo-Roman stock...
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
Liquid rocket
A liquid-propellant rocket or a liquid rocket is a rocket engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be relatively low, and it is possible to use lightweight pumps to pump the propellant from...
s, 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 micro-gravity
Weightlessness
Weightlessness is the condition that exists for an object or person when they experience little or no acceleration except the acceleration that defines their inertial trajectory, or the trajectory of pure free-fall...
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 motor
Ullage motor
Ullage motors are relatively small, independently-fueled rocket engines that may be fired to accelerate the rocket prior to main engine ignition, when the vehicle is in a zero-g situation....
s.
Industrial use
Ullage is also widely used in industrial or marine settings to describe the empty space in large tanks or holdHold (ship)
thumb|right|120px|View of the hold of a container shipA ship's hold is a space for carrying cargo. Cargo in holds may be either packaged in crates, bales, etc., or unpackaged . Access to holds is by a large hatch at the top...
s used to store or carry liquids or bulk solids such as grain
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
. In accordance with IMO
IMO
The three-letter acronym IMO may refer to:* International Mathematical Olympiad* International Maritime Organization** IMO ship identification number, unique identity numbers issued to seacraft * International Meteorological Organization...
regulations, the Code of Federal Regulations
Code of Federal Regulations
The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...
, 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
Relief valve
The relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire....
is always in contact with a gas or vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....
. Certain pressure relief valves
Relief valve
The relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire....
for chemical use are not designed to relieve the pressure when in contact with liquids.
In some cases the ullage in a ship's hold can be relevant to stability
Ship stability
Ship stability is an area of naval architecture and ship design that deals with how a ship behaves at sea, both in still water and in waves. Stability calculations focus on the center of gravity and center of buoyancy of vessels and on how these interact....
; dry bulk cargo
Bulk cargo
Bulk cargo is commodity cargo that is transported unpackaged in large quantities. This cargo is usually dropped or poured, with a spout or shovel bucket, as a liquid or as a mass of relatively small solids , into a bulk carrier ship's hold, railroad car, or tanker truck/trailer/semi-trailer body...
in a part-filled hold can shift asymmetrically towards one side as the ship heels to one side and the other, reducing the margin of stability when compared with a full hold.