Bluefield was investigating premature failures on D11 dozer track master links for a client. This investigation highlighted the following learning.
On inspection of the failures it was noted that the failures were on the new style single tooth master link configuration. The new style Master Link has one tooth interlock versus 5 tooth interlock for the older design.
Investigation of the failure mode identified the following:
- The new style master link bolts had been over tensioned by rotating a further 180° as required by the 5 tooth design.
- The 5 tooth master link bolt tension differs from the single tooth master link bolt tension. The thread pitch also differs from imperial to metric, see below.
- The second grouser plate was also fouling on the master links, see photo below.
The Recommended Tasks to Prevent the same failures:
- Remove the root cause - To ensure proper master link life and bolted joint integrity, the specified torque plus turn procedure must be followed.
- Identify where this could occur in other machines and eliminate the defect - Inspect other tracks for fouling of the grouser plate on the master link, which was evident in the over tensioned master links and correct as required.
- Improve the system so that similar incidents can not occur - Implement the change management procedure for changes such as these, where a work procedure change is required, with the introduction of a newly designed (changed) component.