As designed – as built – as maintained

WHAT IS IT?

The parts list is typically a hierarchy of components, sub-assembles and modules that together make up a complex product. The hierarchy and content of the parts list are not set in stone, but vary according to the perspective of the user, the process to which the parts list belongs, as well as the particular way in which a company is organised.

For example, someone working on the design of an internal combustion engine will organise their hierarchy by function and physical sub-assembly, for instance, crankshaft, valve train, cylinder head, the cooling system, etc. In Aftersales, on the other hand, the emphasis will be on packages of similar parts, such as a set of engine gaskets containing all the gaskets used in the cylinder head, the cooling system, etc.

WHAT DOES IT DO?

Parts lists are therefore normally divided into three categories:

• as designed: the status as defined by the designers.
• as assembled/as built: the status of the machine after is has been built.
• as maintained: the status brought about by maintenance activities.

During their service life, parts are often replaced by ones that are similar or improved, so the as-maintained parts list is modified and customised each time maintenance is carried out.

WHAT ARE ITS BENEFITS?

As the parts list forms the basis of all processes, it must – as far as digitised processes are concerned – be totally accurate in terms of serial numbers and be always kept up to date. In many sectors, like automotive, the parts list is the most important specification in design, assembly and service. IoT processes, predictive maintenance or digital spare parts catalogues are only really useful if an up to date and consistent parts list exists.