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Arithmetic Average Roughness Height
Method of determining surface roughness.
Further Reading
Flange Surface Finish Toolbox Page

Absolute Pressure

The measurement of pressure relative to the pressure in a vacuum.
It is equal to the sum of the pressure shown on a pressure gauge and atmospheric pressure.
Further Reading



The closeness of the agreement between the result of the measurement and the conventional true value of the quantity.

Further Reading


AF - Across the Flats

Measurement between 2 parallel faces on a nut. Indicates the size of spanner or socket required to tighten or loosen the nut.

Further Reading


AGA - American Gas Association

Promoters of gas use in the US and publishers of widely used calculations for gas density (AGA 8) and gas flow (AGA 3).

Further Reading



As Low As Reasonably Achievable.
Most often used in reference to chemical or radiation exposure levels.
Further Reading



As Low As Reasonably Practicable.
Applied to the reduction of risk by taking measures to reduce risk until the cost of further measures is grossly disproportionate to the benefits they would deliver.
Further Reading


Alliance Contract

A contract that generally relates to a specific and discrete set of services such as design or maintenance.
Not as extensive as an Integrated Service Contract.
Further Reading



The process of using heating and slow cooling to toughen steel (or glass) by reducing its brittleness and internal stresses.

Further Reading



A device that uses Pitot tubes to measure the gas flow rate within a pipeline.

Further Reading


ANSI - American National Standards Institute

A private non-profit organization that administers and coordinates the U.S. voluntary standardisation and conformity assessment system.

Further Reading



Active Pharmaceutical Ingredient

Further Reading


API - American Petroleum Institute

A trade association founded in 1919 sponsored by the oil and gas industry to develop Recommended Practices for the industry.

Further Reading



American Standard Code for Information Interchange established to achieve compatibility between various types of data processing equipment.

Further Reading
ASCII Code Toolbox Page


American Society of Mechanical Engineers.
Professional organisation focused on technical; educational and research issues of the engineering and technology community.
Further Reading



American Society for Testing and Materials.

Further Reading



EU Directive 94/9/EC covering equipment and protective systems for use in potentially explosive atmospheres.

Further Reading
Hazardous Area Toolbox Page

AWG - American Wire Gauge

A standarised method for specifying the properties - including diameter - of electrical and electronic wire.

Further Reading
Electrical and Electronic Wire

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