MAURI Foods: Wheat Grain Silos

MAURI has a history stretching back nearly 150 years and has been supplying baking products for Australians since 1870. A division of George Weston Foods (GWF), MAURI produces everything from bakers’ flour and bread mixes to gluten-free ingredients and leavening agents. 

Among its numerous facilities, MAURI operates 22 wheat grain silos at their Enfield Grain Mill in New South Wales. These are large storage units: twenty of these silos have a capacity of 250 tonnes each, while the other two can store 125 tonnes of grain per silo. 

Following the occurrence of a structural event at the Enfield facility, a Soto team provided a rapid response that included an immediate site visit. Soto conducted a structural engineering assessment of the silos’ design, root cause event analysis, and a suitability for future use study. This initial work demonstrated the Soto team’s advanced skills in complex Finite Element Analysis (FEA), in addition to their overall meticulous engineering proficiency, as well as their facility for quickly building relationships and collaboration – talents that are deeply rooted in Soto culture.  

All initial analyses were delivered to MAURI in a preliminary assessment report. The promptness and thoroughness of the report gave MAURI sufficient confidence to retain Soto for subsequent phases of the assessment project. For these phases, Soto adopted a rigorous methodology (see box) in order to test the suitability of the original silo designs and the structures’ safety for ongoing use. The entire exercise started with a complete understanding of MAURI’s requirements and involved continual and open communication and collaboration with the MAURI team, progress reporting on all deliverables, and timely hitting of milestones. The Soto FEA experts prepared 3D models of the steel silo structure using state-of-the-art software. Complex modelling analysed the silos against the most demanding scenarios, in accordance with relevant Australian standards.  

Soto used this detailed and robust structural analysis approach as it can identify whether silo design complies with the current Australian Standards for structural and mechanical design and, if present, the cause of structural failure. For example, the strength and stability criteria that may have been used as the basis for older designs may not allow for the margin of safety afforded by factored load combination cases required by current standards. A report utilising the above methodology was delivered to MAURI, providing a logical and factual basis for recommendations on the cause of structural failure and future safe operations. This is critical information upon which business leaders at MAURI can make informed decisions.   

A job well done is the best reward of all, as it was again for the Soto team involved in the MAURI silos assessment project. At the conclusion, the team allowed themselves a quiet moment of pride at another win notched up for the venerable Soto motto: Everything Engineered. 

The Silos

Number: 22 silos

Dimensions & Capacity:

• Twenty of the silos are 3.8m x 3.15m x 29.5m high with a capacity of 250 tonnes each
• Two silos are 3.8m x 1.575m x 29.5m high of 125 tonnes capacity per silo.

Location: MAURI ANZ grain mill operation, Enfield, NSW

The methodology adopted by Soto

• Conducted a desktop review of reference documentation including silo drawings, previous investigation reports, inspection reports, and repair works. 
• Prepared a 3D model (for Finite Element Analysis) of the steel silo structure using SpaceClaim software and analysed with ANSYS Workbench. The model consisted of four silo segments and allowed for the analyses of the silos in the most onerous fill scenarios and load combination cases, and included concentric bulk solid discharge flow actions.  Normal and shear pressure distributions were considered acting on the inner faces of the silo, and wall pressures were determined using the silo geometry and bulk solid parameters. Wind actions were determined in accordance with AS 1170.2.
• The maximum calculated wind pressures were considered in the orthogonal (perpendicular) X and Y directions to represent the most onerous loading state.
• Soto selected specific silos for analysis that were representative of the structural and mechanical behaviours for all silos. This minimised the extent of analysis necessary to achieve the project objectives. 
• Derived the grain material initial fill and discharge loads to Australian Standard AS 3774. 4. 
• FEA analyses, review of results, and silo design assessment to AS 4100.  
• Prepared a structural assessment report including recommendations and options.