Tech Biz Writing

The role of the maintenance engineer has changed dramatically over recent years. With the increased complexity and turnover of hardware devices, it has not been possible to train him sufficiently within the time available as in more expansive days. One of the consequences of this is that the diagnostic/maintenance engineer develops a range of systems skills at the expense of a thoroughgoing knowledge of discrete component technology. He also makes use of a number of modern aids, including specifically designed documentation.

One of the simplest and most cost-effective ways of maintaining a complex system is by the use of an algorithm — usually expressed as a flowchart — or a Functionally Identified Maintenance System (FIMS). An algorithm is a step-by-step procedure, or list of instructions, for a process. A recipe is an algorithm; so is the mathematical base of a computer program.

A flowchart is a diagram representing an algorithm. Certain symbols are taken to depict nodal points in the process. A diamond shape signifies a decision point, the question being formulated within the block, and two of the angles representing yes and no exits. Similarly, a circle is used for a terminal point, either the beginning or end of a process, or as a link to another sheet. Flowcharts are useful, not only in computer programming, but also as a means of simplifying a complicated diagnostic/maintenance procedure. In such a system, the engineer is given a series of specific actions or observations. Questions are posed, to which the answer is either yes or no — proceed or perform some action.

A related method, but of wider scope and applicability, is the Functionally Identified Maintenance system. The FIMS concept is based on functional flow diagrams which depict functional sequences rather than hardware boundaries. The documentation provides the maintainer with a coherent test strategy, logically presented at various levels of complexity. Each level follows on from the preceding one, allowing a structured approach to maintenance not unlike the program steps running a computer.

Fault diagnosis is a logical process beginning with an “overview” and moving down to a lower, or detailed, levels. Certain definite stages may be isolated:

* Collate and analyse symptoms
* Examine equipment.
* Locate fault(s) and cause(s).
* Repair or replace faulty part or unit.
* Test performance.

FIMS documentation reflects this process using a variety of formats at each of three or more levels:

* High or “master” level — general overview showing major functions.
* Intermediate level(s) — functional subsystems within each major function.
* Low level — the most detailed level.

Functional block diagrams depict functional flows in a left to right direction. Hardware configurations are not relevant to the flow of the diagram, but may be indicated in some way within it.
Functional block texts consist of blocks containing textual descriptions of useful testing information.
Maintenance dependency charts show, in graphical form, the functions and the events which define the dependencies between them. It’s a symbolic charting of the functional block diagram.
Symptom analysis charts sometimes replace the maintenance dependency charts at the higher levels.
Test data charts list test points, setting-up procedures, and interpretation of results.
Layout diagrams revert to hardware boundaries enabling the maintainer to locate precise repair points.
Fault-finding and repair are not always carried out by the same technician. Consequently, a division is usually necessary within the documentation to reflect the needs of both diagnosis and maintenance.

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