Open Cut » Maintenance & Equipment
This report presents the findings of an ACARP research study that continues the investigation, from ACARP project C20026, into the potential of synthetic ropes to provide productivity and safety improvements to mining dragline excavators.
This study focused on testing a scaled synthetic rope to see if it could withstand the load duties and harsh mine environment associated with a dragline application.
High performance synthetic fibre ropes have many properties that could be valuable to the mining industry, including favourable; mass/strength ratio, elasticity, ease of repair, corrosion resistance, increased fatigue life, and the potential for increase bucket payloads. Using scale testing of Dynex synthetic fibre ropes, AMOG has been able to determine the expected life and wear characteristics of synthetic fibre ropes as the drag and hoist rope of a dragline excavator.
The testing was progressed through the design and construction of a testing rig, to conducting quarter scale tests of synthetic fibre rope under conditions and loads representative of the dragline hoist and drag ropes. The final stage of this study looked at options for further synthetic rope developments in addition to gauging interest in the industry for full scale field trials on electric rope shovels.
The key conclusions from this research are listed below:
(i) Current off-the-shelf High Modulus PolyEthylene (HMPE) synthetic ropes without jacketing do not provide sufficient abrasion resistance to be used during the worst case condition that a drag rope is subjected. Contact with abrasion material will dramatically decrease the ropes operational life as compared to a straight bending application.
(ii) The tested synthetic hoist rope surpassed the current average wire hoist rope, achieved 1.3 times
the current hoist steel wire rope life.
(iii) Excessive creep due to overheating of the ropes from sheave contact and high ambient temperatures is a limiting factor in the adoption of synthetic rope in hoist rope mine applications. The severity of the temperature on the rope creep could be combated by using alternate synthetic fibres or hybrid synthetic-steel rope, jacket solutions and/or sheave cooling mechanisms. Further testing would need to be conducted to determine the feasibility of such methods.
(iv) Splices and splice buried tails should be configured to ensure they do not pass onto sheaves as
incorrect groove sizing can cause the rope to overheat and suffer premature failure.
Based on the findings of this research AMOG has identified the following key recommendations for further research and testing:
(i) Conduct workshops to develop a field testing methodology for synthetic ropes on electric rope shovels.
(ii) Develop a specification for using synthetic ropes on an electric rope shovel and include the machinery modifications that would be required to permit the current wire ropes to be replaced with synthetic ropes.
(iii)Conduct further scale testing using the testing rig developed during this research. These tests are recommended to cover a broader range of abrasion conditions with jacketed ropes in addition to investigating solutions to problems uncovered during this research. These scale tests should include:
● Scale steel wire rope tests to provide direct comparison to the synthetic rope test results achieved to date as well as providing for calibration of the test rig.
● Modification of the test rig to incorporate an intermediate sheave(s) to better represent the bend requirements of an electric shovel hoist rope. Electric shovel hoist rope tests should then be conducted on both scale synthetic fibre ropes and equivalent scale wire ropes to provide direct comparison between the two rope materials.
(iv) Investigate viable options to mitigate the rope creep effects due to high temperature. Potential
● Alternate synthetic fibre materials or hybrid synthetic-wire ropes that are more resilient to creep.
● Alternate sheave materials or sheave coatings to reduce the frictional effect.
● Rope jacketing to reduce frictional effects and minimise heat retention.
● Water cooling solution on section of rope passing over the sheaves to keep rope below temperature operating limits.
(v) Develop synthetic rope discard criteria for mining applications. The ability to accurately predict the remaining life and predicted failure location is extremely important for ropes used in mining applications. Through developing a thorough synthetic rope discard criteria, mining inspection and maintenance crew will be able to conduct accurate assessments of rope replacement requirements.
(vi) Conduct field trials on an electric shovel prior to any trials on a dragline. This would minimise any lost production Ume and provide lower risk. The field trials should be preceded by the scale hoist rope tests.