Structural Design Review of a Tandem Rotary Tippler

LEC has recently completed an independent third-party structural design review of a new tandem rotary tippler and its associated positioner and wheel grippers. The new tippler was procured in order to increase the annual export throughput of an iron ore port.

Finite element model of the tippler and positioner structures

Typical fatigue stress range calculations

Detailed structural modelling and analysis was carried out independently using advanced Finite Element Analysis (FEA). Due to the cyclical motion of the tippler, design checks were focused on the fatigue service life assessment. Stress fluctuation due to the rotating motion of the tippler was calculated by analysing the tippler in several angular operating positions.

The independent design review was predominantly carried out in parallel with the Original Equipment Manufacturer’s (OEM) design process to meet the stringent project schedule. Design anomalies and structural non-conformance with the relevant design codes were promptly communicated to the OEM, thus allowing any required modification to the design to be implemented early in the design phase. This reduces the risk of potential costly production delays due to design issues and the associated on-site remedial work as well as the potential for commercial and/or legal disputes.

LEC also carried out a design review of the vertical lifting arrangement and transport saddles for land and sea transportation of the tippler cage structure, from the OEM’s fabrication yard to the owner’s site.

Repair & Prevention of Cracking in an Existing Tippler

Photograph of tippler during installation

Cracks in the Cage Structure

A number of cracks were identified in the cage structure of an existing rotary tippler, during routine site inspection, after approximately 10 years in operation. These cracks were immediately addressed using temporary repair procedures by the port operator.

While the temporary repair prevented immediate disruptions to the port operation, a long-term structural solution to the tippler cage structure was required in order to prevent similar cracks from reappearing. A conceptual structural modification was developed with the aid of Finite Element Analysis (FEA). A three-dimensional FEA model of the tippler cage structure was created and analysed to determine the extent of the highly stressed regions. This allowed the structural modification to be designed effectively and efficiently, as well as minimising the tonnage of the structural remediation work.

Comparative analysis with the existing (unmodified) tippler structure was carried out to verify the effectiveness of the structural modification. The final design solution was proposed to the port operator and the Original Equipment Manufacturer (OEM) for their acceptance and approval. The proposed structural modification has since been approved by the OEM and successfully implemented on site.