CODES AND STANDARDS

CLASS OF WORK
There are many types of work which require engineering materials to be joined by welding, for example:

Pressure vessels
Bridges
Oil rigs
Earth moving equipment
Aero-engines
Ventilation systems
Storage tanks
Heavy vehicle chassis
Car bodies
Food processing plant

The quality requirements of the joints in these fabrications depend on their fitness-for-purpose and differ significantly from one application to the next. Pressure vessels require welds, which can withstand the stresses and high temperatures experienced in operation. Oilrigs are designed to withstand the effect of wave formation and wind loads. Earth moving equipment has to accommodate differences in terrain and earth conditions and is subject to fatigue loading. Welds in food processing plants must withstand corrosion by hot acidic liquors.
Below are listed some typical codes of practice and standards which cover various types of constructions fabricated by welding.

Code----------- Class of Work
BS 5500-------- Unfired fusion welded pressure vessels
ASME VIII------ American boiler and pressure vessel code
BS 2633-------- Class 1 arc welding of ferritic steel pipe work for carrying fluids
BS 4515-------- Process of welding steel pipelines on land and offshore
BS 5950-------- Structural use of steelwork in building
AWS D1.1------- Structural welding code (American)
BS 5400-------- Steel, concrete and composite bridges
BS 6235-------- Code of practice for fixed offshore structure
API 1104------- Standard for welding pipelines and related structures

These documents can also provide a useful source of data for applications where codes do not exist. It should be remembered, however, that the principal criterion in the codes listed is the quality of the joint in relation to the service conditions. There are other applications where success is judged by different criteria, such as dimensional accuracy.
Another important consideration is controlling the cost of welding. Variations in weld times and quantities of consumables can readily result if the method of making a weld is left to the welder to decide.
The continuous and satisfactory performance of weldments made to various codes requires that specific guidelines are laid down to cover all variables. These guidelines are usually grouped under the general heading of a Weld Procedure.

CODE OF PRACTICE

A code of practice is a set of rules for manufacturing a specific product. It should contain:
Design Requirements (e.g. fit-up, preparation and type of joints)
Material (e.g. types, thickness ranges)

Manufacturer’s Working Practice
Inspection Criteria (e.g. 100% visual, percentage other NDT)
Acceptance Criteria (e.g. defect size, limits, etc.)
Welding Process (e.g. type, consumables)
Types Of Tooling (e.g. use of strongbacks)

Contractual Information
The difference between a code and a standard is that a code states how to do a specific job and does not contain all relevant information, but refers to other standards for details.
A code or standard generally mentions three parties - the customer or client, the manufacturer or producer and the inspection authority. In a code the term ‘shall’ means mandatory - must be done, and the term ‘should’ means recommended - not compulsory.
A concession is an agreement between the contracting parties to deviate from the original code requirements. (BS 5135)