AWS A1.1:2016 pdf download.Metric Practice Guide for the Welding Industry
1. Scope
1.1 This metric practice guide is based on the International System of Units (SI) as defined in the U.S. Federal Register notice of July 28, 1998, “Metric System of Measurement: Interpretation of the International System of Units for the United States". (Other source documents and style guides are referenced in Annex D.) This guide contains specifications of the SI base units, derived units, prefixes, and rules for their use in AWS documents and by the welding industry. It also contains factors and rules for converting from U.S. customary units to SI units and recommendations to industry for managing the transition.
1.2.3 Work performed in accordance with this standard may involve the use of materials that have been deemed hazardous, and may involve operations or equipment that may cause injury or death. This standard does not purport to address all safety and health risks that may be encountered. The user of this standard should establish an appropriate safety program to address such risks as well as to meet applicable regulatory requirements. ANSI Z49.1 should be considered when developing the safety program.
2.2 Coherence. Coherence requires that all derived units in the system be obtained from the base units by the rules of multiplication and division with no numerical factor other than the number one (1) ever occurring in the expressions for derived units in terms of the base units. The system of units must also be coherent with its corresponding system of quantities and equations. A system of units is coherent with respect to a system of quantities and equations if the system of units is chosen in such a way that the equations between numerical values have exactly the same form (including numerical factors) as the corresponding equations between quantities.
2.3 Uniqueness. Uniqueness requires that there be one, and only one, unit defined for each quantity. For example, the SI units for force (newton), energy (joule), and power (watt) are the same, respectively, whether the process is mechanical,electrical, or thermal.
2.4 Advantages of the SI. The International System of Units (SI) is the metric system of units in its latest form. SI is the only system of units which fully satisfies all the above three requirements for completeness, coherence, and uniqueness.Within SI, a set of base- ten prefixes is defined to form decimal multiples and submultiples of SI units. SI Units and their base-ten multiples and submultiples are in harmony with our decimal system of arithmetic, facilitating easy numerical calculations. Awkward manipulations of common fractions such as 1/16, 1/32, and 1/64 are completely unnecessary. All industrial nations, including the United States by the Omnibus Trade and Competitiveness Act of 1988 (Public Law 100-418), have chosen the SI as the preferred system of units for all applications in science, engineering, technology,commerce, and trade.AWS A1.1 pdf download.