TROUBLE SHOOTING

We can usually have a presence on site within 2-3 days if necessary for an initial assessment of the the problem.  This usually indicates the way forward.  We then offer a structured program of work tailored to meet the precise needs of the client. Typically this type of problem solving may involve:

1. Investigation of the problem (discussion with client, review of existing technical data, review of any previous attempts at solving the problem)

2. Data acquisition (Visual inspection, vibration monitoring, temperature measurement, ultrasonic inspection)

3. Analysis of the system to understand the cause of the problem (FEA or classical theoretical analysis)

4. System redesign or modification to rectify the problem

5. Generation of production drawings and documentation

6. Manufacture of replacement components

7. Installation and testing

8. Monitoring the performance of the new system (improve if necessary)

TRAILER DESIGN

Trailers featuring a swivel table made under sub-contract were being used by a major motor manufacturer to transport components around the factory.  The trailers had suffered a number of failures, ranging in severity from loosening bolts, leading to wheels becoming detached through to the failure of the swivel ring attachment and dropping a pallet. A combination of a visit to the factory, a general inspection of some of the trailers, a detailed inspection of the drawings and stress analysis of one of the most highly loaded components established the conclusion that the trailers were poorly designed with little thought having been given to dynamic loading, poorly fabricated and poorly inspected before release. Despite these serious deficiencies, the trailers could be refurbished to produce a very rugged and reliable design if the recommendations by DCW&P were implemented.

The design requirement was for a loading of 1500 kg uniformly distributed over the full surface of the table.  In fact the pallets could only apply their loading along two sides at their skids.  To check the effects of this loading a finite element model was prepared to look at the two forms of loading.  The adjacent model represents a quarter of the table, using symmetry boundary conditions to represent the other sections. Contours of imposed stress are shown with a peak of 259 N/m², 60% higher than the upper allowable figure.  This stress occurs in the edge strips which span between the skids.  If the dynamic effect is included, the peak stress is of the order of 2.25 times the yield of the material, clearly unacceptable.

Barry Redford, Managing Director, Welconstruct Customer Solutions, 16 June 2004