Most of the draglines currently operating in Australia were supplied with OEM designed access systems (walkways, platforms, stairs etc) that do not comply with Australian design codes. Safety reviews combined with high maintenance costs, due to fatigue cracking, have lead to mining companies seeking design solutions that are AS 1657 compliant. CMP Engineers has designed access systems (walkways, platforms, stairs etc) for BE 1370W and Marion 8050 draglines which incorporate a number of innovative features.
Tri-axial accelerometers have been used to measure the loading on the supports connecting the access systems to the dragline structures (boom, mast etc) and an equivalent fatigue load calculated. Using these loads the supports and access system has been designed for a 25 year life, using finite element analysis to calculate the stresses.
Dispensation has been received from Australian Standards to depart from some of the requirements of the standard where this can be justified on the basis of a risk analysis. In some cases the length of a set of stairs has been increased to 25 steps between full change of direction platforms.
A specially rolled channel section has been designed for the stair stringers to minimise the weight. Hand rails are fabricated from pipe rather than using proprietary products, to minimise the weight.
Hand rail stanchions are welded at the base and have a Stauff clamp bolted to the kick plate to mitigate against fatigue of the welds. The stair treads are Webforge treads with nosing instead of bent expanded floor mesh. All step treads are attached to the stringers using Huck Fasteners to eliminate fatigue cracking initiating at weld details. Stairs are mounted to the platforms using a sliding connection to reduce the loads induced onto the stair structure caused by boom flexing under load.
Download specifications in PDF format