Frequently Asked Questions

Frequently asked questions and terms about ISO tanks!


The most effective way to carry liquids, gases, and hazardous chemicals is in a tank container. By reading on, discover all there is to know about ISO tank container sizes, types, and applications.


0-9 | A | B | C | D | E | F | G | H | I | J  | K | L | M  N | O | P | Q | R | S | T | U | V | W | X | Y |  Z
Term Definition
0 or Ph Phase. Applied to the electrical power supply
AAR American Association of Railroads
Approval Agency/Inspection Authority The organization is approved by a competent authority to inspect and certify equipment.
ASME American Society of Mechanical Engineers. Publisher of internationally recognized codes for pressure vessels.
ATP Agreement on the International Carriage of Perishable Foodstuffs and the special equipment for such carriage.
Ball Valve A valve is closed by rotating a ball with a central hole through 90 degrees.
BAM Bundesanstatl Fur Materialforschung und Prufung.
Bar Unit of pressure. (International Bar = 100 Kilopascal = 14.5 psi)
BS British Standards. UK standards organization
BS Table D Specification for bolted flanges for pressure applications.
BSP British Standards Pipe Thread. A thread form is shared on pipe fittings.
BSW British Standard Whitworth. A screw thread is commonly used on clamp bolts. Sometimes interchangeable with ISO metric coarse threads.
Bursting Disc A pressure-relief device that breaks at a pre-determined pressure. Used for emergency relief or as an airtight seal for relief valves to prevent the release of toxic or especially hazardous vapours.
Butterfly Valve A valve containing a circular plate rotates 90 degrees to close the opening. Easy to clean but restricts the fluid flow slightly.
Camlock A quick-release type coupling is sometimes used on bottom-outlet systems.
CCC Customs Convention on Containers. Allows temporary admission of tanks into member countries.
CFM Cubic Feet per Minute. Imperial measurement of rate flow. They were usually applied to airflow.
CFR Code of Federal Regulations
Closed Cup (CC) Describes a method used to ascertain the flash point of a liquid.
Competent authority Regulating authority for a national government.
CSC International Convention for Safe Containers
Design pressure The pressure is calculated to calculate the thickness of the tank's shell. Depending on the applicable regulation, design codes require the design pressure to equal or exceed the maximum allowable working pressure or equal or exceed the test pressure.
Dipstick (dip rod) Calibrated stainless steel bar situated in the manhole at the volumetric center to measure the level to which the tank has been filled.
DNV Det Norske Veritas (a Norwegian approval society)
DOT US Department of Transport. The competent authority for the United States of America.
EIR/RE Equipment Interchange Report/Repair Estimate
Filling ratio  Maximum permissible mass of cargo as a percentage of the capacity.
Flame Trap A metal gauze that permits gases to pass through but does not permit flame to pass (flashback)
Foot valve Internal bottom-outlet valve situated in the knuckle of the dished end. Also known as an emergency valve and is specified for hazardous products.
GRP (FRP) Glass-reinforced plastic (fiber-reinforced polyester) resin sheet with glass fiber is used to encase insulation.
IMO International Maritime Organization
In Hg Inches of Mercury. Unit of measurement for low pressures (usually vacuum).
ISO International Standards Organization. The organization aims to achieve a standard approach to cargo container design and handling, an advisory body whose recommendations have been accepted and incorporated into the official technical standards of many countries in transportable containers.
ISO 9002 An internationally recognized quality system intended to satisfy a user's needs or requirements.
Kg/cm2 Kilograms per square centimeter. (Unit of pressure)
K Pa (KN/M2) Kilopascal (Unit of pressure)
MARPOL  International Convention for the prevention of pollution from ships.
MAWP Maximum allowable working pressure
MGW Maximum Gross Weight = TARE + MAXIMUM PAYLOAD
MSDS Material Safety Data Sheet. This identifies the physical properties and hazards of a product.
NPT  National Pipe Thread. The thread form for pipe fittings used in the USA
Passivation A process that encourages the corrosion resistance of stainless steel by forming a chrome oxide layer on the steel surface.
Payload Mass of cargo that can be carried
PCD Pitch Circle Diameter. Diameter of the circle upon which bolt holes are positioned.
Pickling A chemical or electrochemical method removes mill scale, rust, metal oxides, and similar coatings from steel.
Plate valve A valve consists of a plug moved in and out of its seating by an operated mechanism. Most foot valves and some top-outlet valves are plate valves.
PSI (Ib/in2) Pound per square inch (unit of pressure)
PTFE Polytetrafluorethylene. It has a wide temperature tolerance and is resistant to most chemicals.
P/V Valve Combined pressure and vacuum-relief valve to protect the tank against excessive overpressure and vacuum.  
PR Valve A pressure relief valve protects the tank against accidental overpressure, like the P/V valve (above) but without the vacuum relief facility.
Reference Temperature A temperature is allocated to particular zones throughout the world.  
SNCF Societe Nationale de Chmin de Fer Francais.  French Railways competent authority.
Steam trap Valve, which permits only water to pass
SWG Standard Wire Gauge. Standards for metal sheet and wire thickness.
Syphon tube (dip tube) A tube from the top outlet to the bottom of the tank allows liquid to be discharged or loaded through the top outlet/inlet using pressure (or suction)
Tare Mass of an empty tank in operational condition
Thermostat  A temperature sensor operates an electrical switch. It is used to maintain a temperature within set limits.
TIR The international agreement to standardize the Customs sealing of road vehicles crossing international boundaries. This agreement does not apply to containers that must be approved under the Customs Convention on Containers. The term TIR, however, is still commonly used to denote the approved sealing of a container. (See International Transport of Goods Under Customs Seal. Conditions of Approval Publication VE 505 Published by DOT UK)
Total containment pressure The sum of the internal pressures to which a tank container is subjected in standard service. This total pressure must not exceed the maximum allowable working pressure of the tank.
UIC Union International des Chemin de Fer. Publisher of regulations for tank container marking and registration for international rail transport.
Ullage (Outage) Free space within the vessel after loading.
UN Number A numbering system was recommended by the United Nations Committee of Experts on the Transport of Dangerous Goods with the aim of worldwide harmonization in this field.
Vapor pressure The developed pressure within a closed vessel contains a liquid. Each liquid has its vapor pressure, which varies with temperature.
Viton A Synthetic rubber is used for seals. It has good sealing properties and is tolerant of many chemicals.