Standards, Standardization, Standardizing Organizations

Traceability is the property of a measurement result by which it can be related to national or international standards through an unbroken chain of comparisons, each with a stated uncertainty. It assures that a reading taken in a workshop agrees with readings taken elsewhere.

Classification of standards

Standards may also be classified as line standards (length between two lines, such as the old metre bar), end standards (distance between two flat faces, such as slip gauges) and wavelength standards (based on the wavelength of light).

Hierarchy

 International standard (BIPM)
            |
 National standard (national lab)
            |
 Accredited calibration laboratory
   (secondary / reference standard)
            |
 Company reference standard
   (master slip gauge set)
            |
 Working standards (workshop gauges)
            |
 Inspection of the product

Accuracy decreases by a factor of about 3 to 10 at each step, and each step is documented by a calibration certificate. For length, the unit is now defined by the speed of light: the metre is the distance travelled by light in vacuum in $1/299\,792\,458$ s.

Importance

Traceability ensures interchangeability of parts made in different places, gives confidence to customers, and is required by quality systems such as ISO 9001 and ISO/IEC 17025.

Standardization is the process of establishing and applying agreed rules, dimensions and procedures for a product, process or service so that they can be used widely and repeatedly with the least variety.

Levels

• Company standardization: set inside one firm for its own products, materials, tools and methods (for example preferred sizes of its fasteners).
• National standardization: set by a national body for the whole country, such as Nepal Bureau of Standards and Metrology (NBSM), BIS in India, BSI in the UK, ANSI in the USA, DIN in Germany.
• Regional and international standardization: by bodies such as ISO (International Organization for Standardization), IEC (electrotechnical) and ITU (telecom); ISO standards (for example ISO 286 for limits and fits) allow international trade.

Formulation and implementation

1. A need is identified by industry, consumers or government.
2. A technical committee of experts prepares a first draft.
3. The draft is circulated to manufacturers, users and the public for comments.
4. Comments are reviewed and the draft is revised.
5. The final standard is approved and published.
6. It is implemented through training, quality control and certification marks, with inspection by the body.
7. It is reviewed periodically (usually every 5 years) and revised or withdrawn.

Advantages

Interchangeability and reduced variety, lower cost through mass production, better quality and safety, simpler design and purchasing, easy maintenance and spare parts, and smoother national and international trade.