3.6 VMS – Failure of Structural Support
Field masts, gantries and poles offer the structural support systems for VMS. Failure can cause the VMS to become unstable and vibrate or fall from a height. Prominent causes of structural failure include:
- failure of foundation
- load on structure increased or modifications to the structure (such as additional holes) reducing the structural capacity
- manufacturing defects
- structure commissioned incorrectly
- failure under high winds or extreme weather conditions.
Instability and vibration of the VMS can cause damage to internal components and connectors. VMS falling down can also cause crashes. Structural failure was rated as critical (2 out of 3 levels).
Deterioration of structural components above ground is readily visible and can be easily monitored and rectified as part of the current scheduled inspection tasks. The key issue is foundation failure, which is not easily detectable. Recommended mitigation measures include ensuring that installations are prepared correctly and that random foundation condition assessments are done systematically to identify potential failure trends.
An example RCM process applied to VMS where there has been failure of structural support is presented in Case Study 7.
|Most prominent failure mode|
|Determine criticality||Failure consequence|
|List possible task (if applicable)||On-condition maintenance task|
|Change in commissioning|
|Fault finding (testing)|