Maintenance Practices
Core content
Maintenance practices covers safety, workshop practice, tools, calibration, torque, lockwiring, inspection, non-destructive testing, fault diagnosis and documentation. You must understand how to select and care for tools, why calibration is controlled, and how to apply torque correctly. Inspections may be visual, borescope, dye penetrant, magnetic particle, eddy current, ultrasonic or radiographic. Each method suits different materials and defect types. Fault diagnosis should be systematic: confirm the report, gather information, isolate the fault, test, rectify, and record. Documentation must be accurate, legible, and traceable, and only authorised staff may certify work.
Traps
A frequent error is using a torque wrench as a breaker bar or failing to account for adapters and extensions, which change the applied torque. Another trap is assuming a torque figure applies to lubricated threads when the manual specifies dry threads, or vice versa. In NDT, do not use magnetic particle inspection on non-magnetic materials such as aluminium. In documentation, never sign for work you did not perform or inspect. Calibration out-of-date equipment must be quarantined, not used.
Worked example
A manual gives a torque of 40 Nm, and the conversion is 1 pound-force foot = 1.356 Nm. A setting of 30 pound-force feet is 30 x 1.356 = 40.68 Nm, which is close but slightly high. For critical joints, calculate the exact value and use a calibrated wrench within its range. Rule of thumb: use a torque wrench in the middle of its scale, not at the extremes.
Key points
- Calibration status must be valid before a tool is used.
- Adapters and extensions can alter applied torque.
- Torque values depend on thread condition and lubrication.
- Magnetic particle inspection is for ferromagnetic materials.
- Certify only work you are authorised and qualified to certify.