Glossary of Useful Terms

Term Explanation

ACC

Acceptable Container Condition

BSP

British Standard Pipe Thread - A pipe thread common on tank container fittings.

Ball Valve

A valve which is closed by rotating a ball with a central hole through 90 degrees. Provides unrestricted flow.

Bar

A metric unit of pressure. 1 Bar equals 14.504 pounds per square inch (psi)

Beam Tank

Tank container design where the barrel is the major load carrying component between the end frames.

Bursting (or Rupture or Frangible) Disc

A pressure relief device which breaks at a pre-set pressure. Used as an emergency relief or used as a hermetic seal for relief valves to prevent the release of toxic or especially hazardous vapors.

Butterfly Valve

A valve containing a circular plate that rotates through 90 degrees to close the opening.

Camlock

A quick-disconnect type coupling sometimes used on bottom outlet valves.

CFM

Cubic Feet per Minute. Imperial measurement usually applied to airflow.

Closed Cup (CC)

Describes a method used to determine the flash point of a liquid.

Design Pressure

The pressure used to calculate the thickness of the barrel (shell) of the tank. Design pressure must be equal to or exceed the maximum allowable working pressure or be equal to or exceed the test pressure, depending on that code which is applicable.

Dipstick or Dip Rod

Calibrated stainless steel bar placed inside the manway to measure cargo fill level.

EIR

Equipment Interchange Report

Filling Ratio

Maximum allowable weight of cargo per unit volume.

Flame Trap

A metal gauze that permits pressure to release but prevents flashback.

Foot Valve

Internal bottom outlet valve also known as emergency valve.

Frame Tank

Tank container design where a structural frame with continuous side rails is the major load support of the barrel.

Fusible Link

A heat-sensitive pressure relief device designed to relieve pressure when a specific temperature is reached, such as during a fire.

GRP

Glass reinforced plastic resin used to encase insulation on a tank container.

ISO

International Standards Organization - A specialized agency of the United Nations promoting the safe maritime transport of dangerous goods.

Material Safety Data Sheet (MSDS)

The product manufacturer's data sheet containing precise chemical name, composition, hazard information, transport and regulatory information and other pertinent data.

MAWP

Maximum Allowable Working Pressure.

MGW

Maximum Gross Weight: Tare + Maximum Payload

NPT

National Pipe Thread. The threading form for pipe fittings used in the USA.

Payload

Amount of cargo that can be transported.

Periodic Testing

Tank containers must undergo periodic inspections to uphold the validity of approvals.
5 Year Test - Includes a hydrostatic pressure test, a visual inspection (internal and external), a leakage test and a test of the satisfactory operation of all service equipment (including all valves and fittings).
2.5 Year Test - Includes a visual inspection (external and internal), a leakage test and a test of the satisfactory operation of all service equipment (including all valves and fittings).

PSI

Pounds per square inch - unit of pressure (1 psi = 0.069 bar)

PTFE

Polytetrafluorethylene - A plastic used for seals and gaskets that has a wide temperature tolerance and resistant to most chemicals.

Safety Relief Valve (SRV) or PV Valve

(pressure, vacuum or combination relief valve) Designed to protect the tank against excessive overpressure or vacuum. As pressure relief, the valve is activated by inlet pressure and characterized by rapid opening or pop action. As vacuum relief, the valve is activated by inlet vacuum. The device is designed to re-close and prevent the further flow of fluid after excess pressure or vacuum has been relieved.

Specific Gravity (SG)

Ratio of density of substance to water. (Weight of water = 8.345 lbs/gal or 1 kg/litre.)

Steam Trap

Valve that only permits water to pass thereby trapping the steam until it condenses.

Syphon (or Dip) Tube

A tube inserted from the top outlet to the bottom of tank that allows liquid to be discharged through the top outlet by the use of pressure or suction.

Tare

Weight of container or vehicle without contents.

TIR

A term commonly used to denote the approved Customs sealing on a container.

Ullage (or Outage)

That portion of the total capacity of a tank container not occupied by its liquid cargo expressed as a percentage of that capacity. The fill ranges between a minimum of 80% and a maximum of 97% for hazardous commodities.

UN Number

Refers to the United Nations (UN) four-digit identification number assigned to a hazardous material that is recognized for use in international and domestic commerce and transportation.

Vapor Pressure

The pressure that develops within a closed tank containing a liquid. Each liquid has its own vapor pressure that varies with temperature.

Vessel

As in "pressure vessel" - the liquid-carrying portion or tank portion of an intermodal tank container.