This article will be based on the general principles of fault finding through the application of diagnostic reporting. These principles apply in all disciplines regardless of whether they are civil, electrical, mechanical etc.
Principles of Systematic Fault Diagnosis
Diagnosis of faults requires a logical and disciplined approach. Frequently, past experience or
detailed knowledge will help. Also, an intuitive approach can be used but must be accompanied
by a deductive technique. Faults can be classified as:
• Positive fault − sustained fault
• Intermittent fault − irregular, harder to find
Tools for the Job
Your standard of work is related to the quality and completeness of the tools available to you.
Traditionally this has been:
• Trade skill
• Knowledge of plant
• Problem solving ability
Documentation should be:
• Aimed at the level of the maintenance
• Structured in a standard format
• Logical, precise and factual − no irrelevant material
Facilities for testing equipment are often limited. However, it is desirable that plant users specify (when able to) what is required to make the system maintainable by means of diagnostic methods. Plant manufacturers will often build test points into the system. To do so later becomes very expensive. Built in test facilities are generally for first line maintenance staff, such as lamps, pressure gauges, multi meters etc.
The Logical Diagnostic Process
Experience shows, paradoxically, that the faster a maintainer acts to identify a fault the more likely that he/she;
• fails to find it
• disguises it
• makes it worse
The first golden rule of fault diagnosis therefore is the STOP AND THINK.
Consider the problem then collect and evaluate the facts. The fundamental steps in the logical
diagnostic process for all type of equipment are;
1. Symptom analysis
2. Equipment Inspection
3. Fault stage location
4. Circuit checks
5. Repair or replace (6) Perform test