What is ullage in fuel tanks?

Ullage is the volume which is left empty in a tank so that there is space for the liquid in the tank to expand. The air space between the oil surface and the top of the tank is known as ullage. Keeping the fuel storage tank full at all times keeps the ullage at the top of the tank to a minimum.

What is ullage in aircraft?

Ullage washing is a process that requires displacing the air in the fuel tank empty space, also known as ullage, with nitrogen gas or nitrogen enriched air (NEA). NEA is a term used to describe low purity nitrogen (90-98% pure), generally generated via a gas separation process.

What is fuel inerting system?

An inerting system decreases the probability of combustion of flammable materials stored in a confined space. The most common such system is a fuel tank containing a combustable liquid, such as gasoline, diesel fuel, aviation fuel, jet fuel, or rocket propellant.

What is obiggs?

The OBIGGS is a system composed of well-proven equipment generating directly Nitrogen on board to fully protect the aircraft tanks against explosion.

What does 90% ullage mean?

Ninety percent ullage is the ullage minus 10% of the tank capacity. The 90% ullage volume is the amount of fuel that should fit in the tank without triggering the overfill prevention device. The 90% ullage number can be used to determine the amount of fuel to order.

How do you take ullage out of a tank?

When measuring level by ullage method, the sounding tape is inserted only till the bob/ tape touches some part of the fluid top surface. Instead of measuring the whole depth of the tank, only the free space (from the top of sounding pipe to liquid surface) is measured (Check Figure).

What is the use of ullage?

Ullage is also widely used in industrial or marine settings to describe the empty space in large tanks or holds used to store or carry liquids or bulk solids such as grain.

What does ullage stand for?

British Dictionary definitions for ullage ullage. / (ˈʌlɪdʒ) / noun. the volume by which a liquid container falls short of being full. the quantity of liquid lost from a container due to leakage or evaporation.

What is inerting and purging?

Inerting and purging refer to replacing the atmosphere in a line, vessel or other area with an inert atmosphere, eg the space above liquid fuel in a fuel tank, to reduce the likelihood of combustion. Purging of supply lines, pipelines and tanks is a common step before commencing production or prior to shutdown.

Why is inerting carried out?

Tankers carry flammable cargoes. For this reason, the oxygen level inside the cargo tanks need to be such that even if the source of ignition is accidentally present, the fire triangle would still not complete. The process of reducing the oxygen level in the cargo tank is called inerting.

What is inerting in ship?

The process of reducing the oxygen level in the cargo tank is called inerting. Oxygen content to less than 8% is required to be in the tanks containing flammable cargoes. And to be able to bring the cargo tank to that oxygen level, Inert gas containing less than 5% of oxygen is introduced in the cargo tank.

What is ship ullage?

Webster’s defines ullage as “the amount that a container (as a tank or cask) lacks of being full.” In practical use, it can refer to the amount of empty space in a cargo ship’s hull or in an oil terminal tank; think of the top of a wine bottle.