Page 29 - Coulson Richardson's Chemical Engineering Vol.6 Chemical Engineering Design 4th Edition

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CHEMICAL ENGINEERING
1.6. CODES AND STANDARDS
The need for standardisation arose early in the evolution of the modern engineering
industry; Whitworth introduced the first standard screw thread to give a measure of
interchangeability between different manufacturers in 1841. Modern engineering standards
cover a much wider function than the interchange of parts. In engineering practice
they cover:
1. Materials, properties and compositions.
2. Testing procedures for performance, compositions, quality.
3. Preferred sizes; for example, tubes, plates, sections.
4. Design methods, inspection, fabrication.
5. Codes of practice, for plant operation and safety.
The terms STANDARD and CODE are used interchangeably, though CODE should
really be reserved for a code of practice covering say, a recommended design or operating
procedure; and STANDARD for preferred sizes, compositions, etc.
All of the developed countries, and many of the developing countries, have national
standards organisations, responsible for the issue and maintenance of standards for the
manufacturing industries, and for the protection of consumers. In the United Kingdom
preparation and promulgation of national standards are the responsibility of the British
Standards Institution (BSI). The Institution has a secretariat and a number of technical
personnel, but the preparation of the standards is largely the responsibility of committees
of persons from the appropriate industry, the professional engineering institutions and
other interested organisations.
In the United States the government organisation responsible for coordinating infor-
mation on standards is the National Bureau of Standards; standards are issued by Federal,
State and various commercial organisations. The principal ones of interest to chemical
engineers are those issued by the American National Standards Institute (ANSI), the
American Petroleum Institute (API), the American Society for Testing Materials (ASTM),
and the American Society of Mechanical Engineers (ASME) (pressure vessels). Burklin
(1979) gives a comprehensive list of the American codes and standards.
The International Organization for Standardization (ISO) coordinates the publication of
international standards.
All the published British standards are listed, and their scope and application described,
in the British Standards Institute Catalogue; which the designer should consult. The
catalogue is available online, go to the BSI group home page, www.bsi-global.com.
As well as the various national standards and codes, the larger design organisations
will have their own (in-house) standards. Much of the detail in engineering design work
is routine and repetitious, and it saves time and money, and ensures a conformity between
projects, if standard designs are used whenever practicable.
Equipment manufacturers also work to standards to produce standardised designs and
size ranges for commonly used items; such as electric motors, pumps, pipes and pipe
fittings. They will conform to national standards, where they exist, or to those issued by
trade associations. It is clearly more economic to produce a limited range of standard
sizes than to have to treat each order as a special job.