HOISTS AND WINDERS
profiles are bringing a wealth of advantages to the sector . David Waine , Special Profiles ’ Commercial Director , said : “ Our tophats bring valuable benefits in mineshaft construction and use , including speed of installation , fatigue life is improved by up to 70 % and they offer significant operational efficiencies for mine operators . We continue to see a growing trend for larger mineshaft guides and were delighted to have recently supplied our biggest ever tophats to the Canadian Malartic Partnership ’ s Odyssey Mine .”
Measuring in at 175 x 350 mm , these huge mineshaft guides will help Odyssey Mine maximise productivity and service life for its gold mining operations . When up and running , the mine is expected to be one of Canada ’ s largest underground gold mines .
Waine added : “ Our tophats are carefully designed to deliver superior dimensional control and straightness . This means they can operate faster lifts and carry heavier load weights . Their thickness results in stiffer , straighter steel sections , which also allows the conveyances to run faster . And hand-in-hand with this , their inherent stiffness means winding speed can be up to 20 % faster . Their rigidity can reduce the number of buntons needed , so this cuts both cost and installation time .”
Project designers WSP provided detailed engineering services for the Canadian scheme , which included the ore handling infrastructure , such as the headframe , hoist room , hoisting infrastructure and shaft to enable safe and efficient operations . Mickael Hardy , Project Manager at WSP , said : “ The project team evaluated different alternatives for steel guides meeting our requirements for lateral stiffness while reducing space requirement in the shaft and optimising installation sequence . The tophat proved to be best the best product for our application .”
In modern mine hoisting operations , operators are looking for three key attributes : high productivity and minimal downtime ; ease and speed of installation and maintenance ; and durability and long-service life in a potentially highly-corrosive environment
Waine said : “ The two main factors considered in productivity are steelwork stiffness and rebound velocity ratio . In an ideal world , a stiff guide with flexible buntons is considered the optimum for efficient hoisting , while minimising the likelihood of sustained slamming of the conveyance during hoisting is also desirable . Studies show that in the vast majority of cases , the performance of tophat profiles is clearly superior compared to a more traditional square hollow section ( SHS ). Installation is enhanced too . Because the profile shape is open , there is access to both sides during the installation process . This design also lends itself to easier inspections and detection of any defects during the mineshaft ’ s operational life – and because this inspection is easier , more time can be dedicated to high-quality inspection right to the bottom of the shaft .”
It ’ s widely recognised that shaft steelwork deteriorates over time with depth , a consequence of a number of metallurgical reasons . Waine : “ As depth increases , the ambient temperature also increases and there are also larger volumes of oxygenated or acidified water . The thickness of our tophats is 13-20 mm so they offer significantly better corrosion resistance than a comparable 10 mm SHS guide . Although galvanising could be used to increase service life , the thickness of our tophats means this expense can be avoided as their 30-year lifespan matches that of most mines .”
The Malartic mine is not the first time British Steel has worked with WSP . In 2020 , they collaborated on the expansion of Agnico Eagle ’ s gold mine in Finland , once again using tophats as the optimal mineshaft solution . Waine adds : “ As well as being cheaper than the traditional hoisting system for underground mining , our system was easy to install , offering enhanced corrosion resistance , durability and outstanding strength . It was a privilege to work with WSP and Agnico Eagle to provide a solution for the Kittila mine development in Finland . It ’ s very encouraging that after several decades of being the go-to solution in Africa , the product is now so widely deployed to cover the globe , from the Malartic project in Canada through to mining applications in Australia – and new regions are adopting tophats all the time including , for the first time , a project in South America this year .”
WSP weighs up the options
Designing a successful hoist plant takes careful consideration of every element and WSP ’ s Ryan Heppler , a Structural Engineer based in Thunder Bay , Ontario , told IM that it is invaluable to weigh the different options , and understand how each can benefit , or deter your hoist plant operations . “ At the 2023 Hoist and Haul conference , our team is presenting an analysis of two key parts of the design : the headframe and the shaft guides . Each has multiple options that need to be weighed during the design process .”
He adds : “ With almost 40 years passed since the initial development of the paper Headframe Design Selection : Steel vs Concrete Headframe by Butler and Schneyderberg ( published in 1981 ), it is important to re-evaluate the selection principals of the past now that we have seen their performance over a substantial period of time . At the same , it ’ s valuable to introduce new topics that have become important in the design selection process .”
At the event , WSP is presenting a comparison between steel and concrete headframes ,
WSP argues that there are numerous factors involved with determining the right conveyance guide system for any operation
describing the advantages and disadvantages of each , and noting the factors important in the evaluation of the optimum selection . Through this evaluation , WSP concluded that , although many of the fundamentals of headframe type selection are as true today as they have ever been , new considerations have emerged since Butler and Schneyderberg explored the topic in their paper .
“ Factors such as safety , seismic design , modular construction , sustainability , and headframe replacement / rehabilitation have all come to the forefront as important considerations that need to be evaluated . However , even in doing so , both steel and concrete headframes remain a viable option for a mining operation . Both types have their advantages and disadvantages and need to be thoroughly evaluated at the project onset .”
Looking at fixed guides versus roped guides , the conveyance guiding system selection is one of the key influences in shaft layout and hoisting plant design . The two primary guiding system options available are rope guides and fixed guides . “ In comparing the two , we evaluated the factors requiring consideration in choosing the correct solution for the mine ’ s operation . Innovative solutions for both system types were considered , including the fixed guide cantilever bunton system and rope tensioning system for the rope guide system . There are several factors to consider when choosing the optimal conveyance guiding system . The shaft diameter , preferred hoisting speed , the number of conveyances , regulatory requirements , the mine air ventilation velocity , and of course , cost all must be carefully evaluated .”
The research being presented highlights that a ‘ one-size-fits-all ’ solution is not possible , as
30 International Mining | AUGUST 2023