Designing a new bulk handling machine around the work it must do

Establish the design basis and working cycle

For a new machine designed to AS 4324.1:2025, a technical specification is required. Clause 1.8 and normative Appendix B identify the information to be established. Define the operating duty, design life, site conditions, relevant configurations and assessment methods. Identify which inputs remain provisional, who will confirm them and what evidence is needed before the affected decisions proceed. Missing specification information does not remove the designer’s responsibility to obtain an adequate understanding of the intended use. [8, cl. 1.8, p. 10; Appendix B, pp. 99 to 108]

A nominal throughput does not describe the complete duty. Define the bulk material characteristics, stockpile or vessel geometry, operating positions, movement speeds, starts and stops, and time in each mode. Bucketwheel reclaimer output varies through the cut, including partial bucket filling, digging air and interruptions between benches. [6, PDF pp. 1231 to 1232] Convert this working cycle into the load ranges and lifetime cycle counts required for fatigue assessment. Geometry changes during slewing, luffing or travelling can change component loads even when the carried mass stays constant. [8, cls. 3.6.1 to 3.6.2, pp. 39 to 40]

Separate normal encrustation, abnormal accumulation associated with special events, blocked chutes and excess conveyor material. Their locations and combinations affect strength and stability. [2, PDF pp. 2 to 3] Clause 3.3.3 specifies encrustation allowances and addresses local accumulation and material within chutes; blocked chutes and excess conveyor material are addressed separately in Clauses 3.5.5 and 3.5.6. [8, pp. 16 to 17, 32 to 33] Regular removal of spillage and heavy deposits remains an operating responsibility. [1, PDF p. 28]

First examine how the layout can reduce spillage, build up and material traps. This follows the preference for design measures ahead of administrative controls. [9, PDF p. 8] Define the residual allowance and a practicable cleaning arrangement. A cleaning instruction alone does not establish that a design load can be reduced. Any specified omission or reduction under AS 4324.1:2025 requires the documented risk assessment and technical justification prescribed by Clauses 1.2 and 3.1.1, including the effectiveness of controls and the consequences of the event. [8, pp. 1, 15]

Coordinate protection and wind conditions

Stopping movement, holding position and recovering from a fault are different functions. [3, PDF p. 230] Define the required safe condition and the loads developed while reaching it. Where structural loading relies on a protective device or function, Clause 3.1.2 requires its use to be defined in the technical specification, with the protection and setting recorded in the structural calculations and operating and maintenance manual. [8, p. 15] Carry relevant stopping times, distances and decelerations through the structural, drive, hydraulic and control assessments, and define how the response will be verified.

Resolve wind conditions as part of the same design process. Distinguish operation, relocation, stopping and stationary restraint. Clause 3.4.2 recommends assessing a machine stranded outside its storm tie down system and requires the technical specification to define whether that case is included. Identify the configuration and restraints used for each assessed condition. Overturning stability and resistance to drifting require separate checks; an adequate parked tie down arrangement does not establish that the machine can reach it or stop safely on the way. [8, cls. 3.4.2, 3.5.10 and 4.1 to 4.2, pp. 22 to 23, 36 to 37, 49 to 50]

Let the existing site inform the new arrangement

Establish the condition and assessed capacity of retained rails, foundations or wharves before fixing the new machine arrangement. Define the permissible actions, support movements and restrictions on wheel positions. Section 6 requires the technical specification to define how the machine load cases apply to supporting structures, rails, tie downs and major maintenance works. Agree those interfaces, including their configurations and supporting equipment. [8, cls. 6.2 to 6.4, p. 63; Table B.1, p. 108]

Total machine mass alone cannot establish compatibility. Wheel spacing changes how loads act on a rail girder; the position of wheel groups affects the reactions reaching columns or piles. A different bogie arrangement may reduce one governing effect while increasing another. Adding wheels does not guarantee equal sharing or reduce every infrastructure demand.

Exchange concurrent actions and their machine configurations with the infrastructure designer, then assess the corresponding support movements in the machine model. Record the agreed interface loads, movements and limits. A three point machine support can have four corner wheel assemblies, so counting corners does not establish its load sharing behaviour. [1, PDF p. 21] Confirm that the intended equalisation is achievable within the joints’ movement limits.

Develop the layout and load paths together

Consider a hypothetical drive support moved sideways to clear a chute. The equipment now fits, but its load may enter the side of a member rather than align with the principal frame. The resulting torsion and local plate bending can require a different connection or support arrangement. Checking that the larger member has acceptable stress does not, by itself, establish adequate equipment alignment.

Trace gravity, operating and restraint actions from significant equipment through its mountings and connections to the main structure. The supports need a clear force path and must control deformation that could damage bearings or mechanical components. [3, PDF p. 255] Compare calculated movements with the selected equipment supplier’s requirements while alternative positions remain available.

Preserve removal routes, adjustment space, inspection access and maintenance lifting provisions. [6, PDF p. 1247] A support that works with the equipment installed may obstruct its replacement. Show how the component will be disconnected, supported and removed. A small layout change can avoid reinforcement and a complicated shutdown method later.

Control mass and its location as the design develops

Keep an assembly based mass schedule with centres of gravity and a distinction between estimates, supplier information and verified values. The schedule needs to include installed equipment, liners, platforms and services as well as structural steel. Rasper’s breakdown illustrates these separate contributions. [4, PDF p. 234, Table 32] Under Clause 3.3.2, dead load covers the completed machine ready for service, including ballast, liquid fillings, coatings and permanently installed auxiliary or spare components. Track handled material and encrustation separately. [8, p. 16]

Mass location changes the demands. Moving equipment towards the boom tip increases its gravity moment about the boom pivot. Moving mass away from the slew axis increases its rotational inertia and the torque associated with a specified angular acceleration. [3, PDF p. 226] Use the actual assembly locations when assessing changes.

Develop counterweight selection with the arrangement. Matching a luff cylinder force at one position is only one part of the assessment; the added ballast still increases the weight carried by the supporting structure. Check the effects on the luffing mechanism, bearings, travel system and stability across the relevant configurations. Changes to masses on either boom require corresponding balance checks and records. [3, PDF p. 266]

Plan mass and centre of gravity verification during design, including access and load paths for jacks and measurement equipment. [3, PDF p. 266] Clause 5.9 requires accurate determination of the as built mass and centre of gravity. Weighing the whole machine, or at least its superstructure, is the preferred method; the weighing equipment and technique must achieve ±1% accuracy. The technical specification must define the method and extent of verification. [8, cl. 5.9, pp. 61 to 62]

Compare the completed machine with the dead load mass used in the design calculations. An increase of more than 5% requires the design actions and stresses to be rechecked. If the technical specification applies this comparison to the superstructure, the recheck includes its effects on the substructure. Stability and balance must be rechecked using measured masses regardless of the percentage difference. The 5% trigger is therefore not a general acceptance tolerance. [8, cl. 5.9, pp. 61 to 62]

Where stability requirements are not met, Clause 5.9 requires re ballasting. If the as built balance differs from design parameters such as luff cylinder forces or slew bearing moments, it must be corrected by re ballasting or shown acceptable by recalculation. Assess the consequences of those changes for the rest of the machine. The clause’s note also recommends rechecking an underweight machine below 95% of the design mass, depending on its mass distribution. [8, cl. 5.9 and its note, p. 62]

Design fatigue behaviour into the details

Strength, fatigue and stiffness answer different questions. A member can resist a peak action while a connection remains sensitive to repeated local bending. Clause 5.2 requires fatigue life to cover the specified design life of normal operation, subject to a minimum of 100,000 operating hours. Additional and special load cases also need consideration where their frequency and stress ranges significantly affect fatigue life. [8, cl. 5.2, p. 51]

Define the relevant cycles, potential crack locations and joint details. Clause 5.5 requires conformity with AS 4100 fatigue requirements and permits more rigorous assessment using established methods such as IIW, EN 1993 1 9 and BS 7608, with the standard and parameters identified in the technical specification. [8, cls. 5.5.1 to 5.5.2, p. 57] Match the model, stress extraction and resistance data to the selected method; nominal, structural and local weld notch stresses are not interchangeable. [7, PDF pp. 1 to 2]

Examine where forces enter members, how stiffness changes through joints and where reinforcement terminates. Where relative stiffness governs load sharing, a thicker plate may reduce stress locally while attracting additional load or moving deformation into an adjacent connection. Assess that redistribution before accepting the extra mass. The finite element idealisation needs to represent the relevant stiffness, including weld stiffness where it affects thin walled behaviour. [7, PDF pp. 1 to 2]

Fabrication misalignment can introduce secondary bending. [7, PDF p. 3] For a fatigue sensitive detail, connect the assessment to the drawing: specify the weld geometry, relevant tolerances and examination requirements, with access to execute and inspect the work. Inspection cannot compensate for an unsuitable detail or an incorrect duty spectrum. Avoid arrangements that trap material or water around these connections.

Do not dismiss fatigue because the calculated stresses remain compressive. Clause 5.5.3 requires apparent fully compressive stress ranges to be treated as equally damaging as tensile or fully reversed ranges, recognising residual tensile stresses around welds. [8, p. 57]

Use damage on older machines to identify questions for the new design. Before adopting a repair detail, establish whether its loading, restraint and damage mechanism are comparable. Carry forward the understood lesson and assess the detail for the new machine.

Give equipment the support it actually requires

Clause 5.4.4 requires serviceability assessment, including deflection, dynamic behaviour, connection serviceability and corrosion or erosion protection. [8, p. 57] Conveyor supports need to maintain the alignment of idlers, pulleys and drives. [5, PDF pp. 39, 51] Define the permitted movements and other relevant criteria at each mechanical interface, then compare the connected structure’s response with those limits. Acceptable structural stress alone does not establish acceptable equipment support.

For a slew bearing, agree the interface requirements with the supplier while the support arrangement can still change. Provide the concurrent actions and operating duty, and establish how support flexibility affects the bearing assessment. Support flatness and variations in stiffness can change rolling element load distribution. [3, PDF pp. 216 to 217; 1, PDF pp. 37 to 38] The review needs to cover the bearing, mounting flanges, fastening arrangement and supporting structure.

Distinguish mounting surface flatness from deformation under load. A survey checks the fabricated surface in the stated measurement condition; structural analysis assesses how that surface deforms under the relevant loads. Manufacturer guidance addresses both companion structure rigidity and measurement before installation. [10] Agree criteria for each check with the selected supplier and retain the survey and analysis results. A satisfactory flatness survey alone does not establish acceptable support behaviour in service.

Assess dynamic response where operating excitation, starts, stops or control actions could govern. Changes in mass and stiffness can alter natural frequencies and mode shapes; the significance depends on the arrangement. Relate the analysis to the relevant operating conditions and use it to select commissioning measurements and acceptance criteria. [2, PDF pp. 3 to 4, 5 to 6]

Design smaller steelwork and maintenance configurations

An access platform may also be where personnel handle a removed component. A chute support may carry retained material and repeated vibration. A small bracket can restrain a nearby plate and change its local loading. Temporary welded attachments, including lifting lugs, can also affect fatigue in the permanent structure. [7, PDF p. 3]

Define these functions before sizing the steelwork. Clause 3.4.9 requires access structures to be designed for additional temporary loads where these exceed the prescribed access loads. [8, p. 29] Show where removed components will be placed and provide designated handling points and supports. Lifting beams and lugs require visible working load limit or maximum rated capacity labels under Clause 5.10. [8, p. 62]

Assess component removal, jacking and temporary restraint as distinct configurations. Removing a bucketwheel drive can change balance, while bearing or bogie replacement introduces separate support load paths. [1, PDF pp. 30 to 31, 40 to 41] Clauses 3.4.10 and 3.4.11 require erection, dismantling, weighing and special maintenance loads to be included. Define the sequence, wind restraint and stability basis, and the specified allowances for as built balance in jacking design. [8, p. 29; Table B.1, p. 103] Include transport loads where they differ from operation. [7, PDF pp. 2 to 3]

Design reuse needs the same scrutiny. WA Mines Safety Bulletin 103 records yielding at reclaimer jacking points after a changed service position left stiffeners and webs in unsuitable locations. [11] When a previous design is reused, identify changes to the maintenance geometry and verify the resulting load paths.

Use independent review while decisions can still change

Agree the review scope and information requirements while significant choices can still change. Informative Appendix K recommends review before contract placement and progressively during design, with satisfactory review of selected parts before manufacture. Establish the project’s audit obligations and release conditions in the contract and specification; Appendix K itself is guidance. [8, Appendix K, pp. 142 to 144] The following examples connect decisions with the evidence needed.

Keep design, checking and approval responsibilities clear. Review can challenge assumptions without taking over the designer’s accountability. Record which conclusions are supported, which remain conditional, who will resolve each condition and what evidence is required.

Where supplier data are incomplete, use documented assumptions and sensitivity checks to establish a defensible design envelope. Preliminary component masses can increase as the design develops. [3, PDF p. 255] A mass increase at the boom tip may have different consequences from the same increase near the slew centre. Reassess affected decisions when confirmed data fall outside the accepted envelope.

Hand over the reasons as well as the drawings

Preserve the basis for details whose purpose may not be obvious: a plate governed by jacking, a support positioned for equipment removal, or a stiffness requirement needed for alignment. Record the relevant configuration, load case and verification evidence. Capture commissioning changes in the final drawings; otherwise later repairs may reproduce an arrangement that was superseded during testing. [1, PDF p. 35]

Define commissioning requirements in the technical specification, as required by Clause 1.11.3, and establish acceptance criteria before testing. [8, p. 11] Relevant checks may include mass and balance, alignment, movement, vibration and protection response. Staged conveyor checks and slew bearing measurements under known conditions provide practical verification and a baseline for later inspection. [5, PDF p. 52; 1, PDF pp. 33, 39] Record the test configuration and compare results with the design assumptions. Untested extreme and fault conditions still require their own assessment.

Give the owner a usable design baseline: the final configuration, applicable limits, maintenance arrangements, residual risks and supporting calculation or test records. Safe Work Australia’s guidance identifies intended purpose, assessment results and conditions for safe use as information to pass through the plant supply chain. [12] For each unresolved condition, state the affected activity, any restriction, the responsible party and the evidence needed for closure. Unverified conditions that affect safe operation or maintenance need a defined restriction until resolved.

ACE supports OEMs and owners with structural and mechanical design development and independent review, connecting the machine arrangement with its duty, equipment interfaces and supporting infrastructure.