Successful blasting innovation
AEL Breaks New Ground with Inverse Drop Raise

AEL Mining Services recently partnered with EBJ Mining Construction to successfully execute mechanised, inverse box hole blasting at Harmony Gold's Elandsrand Mine, which has resulted in increased safety and production.

Inverse box hole blasting has been successfully used in platinum mining. In conventional box hole development in gold mining applications, an incline raise is used to create an ore pass by manually drilling down the host rock to advance to the ore body.

Eugene Fouche, acting mine manager at Elandsrand Mine, comments, "In the past, we used long hole mechanical (raise boring) and short hole conventional development. With the increase in the reef development rate, this method proved to be slow and labour intensive, resulting in a backlog of box holes. We changed to a mechanised method, combining inverse box holes with drop raising.

"This new mechanised method", adds Fouche, “entails drilling the ore pass from the bottom of the rock upwards at an angle using an automatic drilling machine. This minimises the number of people physically involved in the drilling and blasting of the ore passes, resulting in increased safety of personnel.”

Inverse box hole drilling also ensures a more accurate holing point without fracturing the rock, thereby reducing the chances of rock slips and rock-related injuries. “The current advance rate for conventional box holing is on average 1.2 m per day, compared to inverse blasting of 2m per day,” says Fouche.

Elandsrand Mine has converted to the DigiShot range of electronic initiation systems supplied by AEL's sister company, DetNet, which eliminates the need for blast operators, thereby putting more men out of harm's way. Electronic detonators also ensure that the timing and precision of each blast is accurate.

The hole is blasted with a single blast up to 15m from the bottom up. The remainder of the ore pass is blasted from the top of the raise. An homogenous emulsion with glutinous properties is used to charge the hole, and ensure that the explosives do not fall out of the pre-drilled hole when initiating the blast.

Johan Fourie, regional manager at AEL comments on the blasting of the inverse drop raise hole, “With the traditional box hole development method, it would take approximately 12 days to advance 15 metres before loading and blasting the hole. This process could take longer in some of the older gold mines where reef exposure is minimal. With inverse drop raising, we are able to drill the whole length of the tunnel in six days and then blast on the seventh day, reducing the turnaround time from twelve to seven days”.

Staying ahead of our time
AEL's Factory of the Future Embraces Robotics

Since the invention of the first computer, automation has become synonymous with improved production in any manufacturing sphere. AEL's explosives manufacture is no exception in taking mining into the improved technological future, achieving significant strides with its flagship Initiating Systems Automated Plant, or ISAP, as it is known today.

"While the company's first robotic assembly machine has been up and running for quite some time now, the team has been embarking on continuously improving the capability of robotic assembly machines and automation improvements within the explosive environment", says Shane Pheasant automation and robotics manager at AEL.

“We have two robotic assembly machines on commission at the moment, both of which will be addressing high volume product and, while our first robotic assembly machine will continue manufacturing a broad range of products, these two will focus specifically on products that are in high demand by AEL customers.”

All three machines were built using robotics that offer high levels of performance and flexibility in a light package and, as these machines are capable of deciphering faulty products from the right ones and with the added peace of mind offered through its built in vision capabilities, customers can be assured that the final product will be of world class quality.

The machine is light and compact, occupying a tiny footprint of factory floor space and, following on AEL's “Continual Improvement” modus operandi, the two machines that will succeed it are even smaller. These machines can be containerised and shipped to remote sites.

However, all three are armed with built in vision technologies that, with the inclusion of a camera and cable, enable AEL's robotic assembly machines to locate parts, monitor system progress and ensure that manufactured products are error free.

“What these machines enable us to offer our customers is increased efficiency, improved product quality and higher levels of production than we've ever been able to offer,” says Pheasant. “The robotic system is configured to discard faulty components before construction has even begun and the built in cameras perform double checks to ensure that the final product is of a satisfactory quality level.

“We're reporting less waste products on a daily basis and are achieving around 90 plus percent efficiency rates on production", says Pheasant.

"With rapid technological changes and an increasingly competitive global manufacturing market, it's not enough just to innovate to succeed. Automation has become an important consideration to remain competitive in local as well as global markets.” Pheasant adds, "Improving productivity, product quality, reducing waste, reducing downtime, getting products to customer faster – all of these issues are important to manage our business successfully.”

Automation and Robotics involve designing and implementation of intelligent machines which can do work that is dangerous or tedious for humans to perform. "It is a well-known fact that repetitive intricate operations that have to be performed precisely without failure are not ideally suited for man to handle. It is here where a robot comes into its own," says Pheasant.

According to Pheasant, the notion that robotics and automation is not for South Africa should be challenged. "Without this technology we will not be able to compete in world markets", he adds"The Robotic assembly machines are designed and built in South Africa and are custom build to meet customer requirements," he concludes.

In Pursuit of Perfection
AEL Modernises Pyrotechnic and Powder Drying Techniques

AEL has mastered a modern way of manufacturing pyrotechnic and explosives powder called spiral drying.

This approach is not new to the chemicals, pharmaceuticals, confectionary and food industries. Cooling or drying explosives powders on a continuous basis makes spiral drying uniquely beneficial in refining the manufacturing process in comparison to the traditional method of using a batch process involving hot air, steam or vacuum assisted ovens.

The upsides to this approach are numerous. The spraydrying equipment occupies a small footprint and by continuously removing the dry material the building licence is minimised and inventory is kept to a minimum. The old process included the placement of a large quantity of highly energetic material in one or several ovens, an activity which required a substantial explosives building licence and more factory space.

Previous oven temperatures had to be set at conservative levels to avoid potential ignition or degradation of the materials, which largely extended drying times. Loading of the ovens was manually achieved and led to non-uniform powder depths, resulting in uneven drying. In the spraydrying process the vibratory action of the conveyor ensures that the powders are constantly fluid and therefore more evenly dried and the process lends itself to drying on customer demand.The maintenance of these ovens is costly and time consuming whereas the spraydrying equipment is extremely easy to clean and maintain.

AEL's new approuch

The new approach uses a stainless steel spiral that can be set to vibrate at a frequency that conveys powders upwards through a spiral trough. The flights of the spiral are individually connected to a separate pressurised heating unit that allows water to pass through the spiral jacket. Hot water, or possibly oil, if higher temperatures are required, heats the spiral flights and this heat then transfers directly to the material being dried.

This process has been evaluated for PETN drying on a pilot plant unit installed at the R&D department at AEL and trials indicate that the required moisture content for further processing of PETN can easily be achieved using the spiral dryer. AEL's ultimate aim is achieved – production of a better fluidity in explosives powders under the best factory conditions.

Hybrid assembly for hybrid quality
Automation Machines get the thumbs up

AEL's new Products to Markets division serves to meet two constant mandates:

To ensure that AEL brings new products to market responsibly and to certify that, as part of AEL's drive to expand into international markets, all export orders meet AEL's stringent internal specifications. This is achieved through the application of rigorous product qualification, for all new products, and process certification of all new and existing plants.

Derek Anthony, AEL's Product Development Manager who manages the certification of export orders, as well as product qualification of Initiating Systems and related processes, reports that the company is fast achieving its core initiatives surrounding the Automated Assembly machines currently being certified at its Modderfontein factory.

“Our objective, amongst others, is to deliver to the production environment a certified plant which is capable of producing a high volume output of robust, reproducible, quality products, that meets both internal quality requirements, safety legislation and economic targets as set by AEL customers,” he says.

“A User Requirement Specification was raised prior to the start of the project and this was used as the basis for the product qualification which was performed on the automated Uni-Delay (Reefmaster) Assemblies produced on these automated machines.”

“The initial hybrid assembly has completed all levels of the product qualification process namely, critical parameter testing, range trials and field trials. In excess of 400 000 units have been deployed to date with very positive results from the trial venues,” says Anthony.

“The next stage will be to certify the last of the equipment planned for AEL's automation factory, ISAP, which will lead to the final stages of the project being implemented, including online statistical process controls (SPCs).

AEL's Products to Markets team is an integral part of the process that ensures that the automated assembly machines have the capability of producing a robust product which meets the desired customer demands around quality, functionality and reliability.

“The SPC system provides statistics around stipulated product characteristics, identified as critical process and product parameters, which will notify the operator if a product component is faulty.

It also identifies when maintenance or repair is required on the machine itself (process drift) which negates the possibilities of faulty products being manufactured and distributed to customers.

The automation process is also supported by strategic product testing to verify compliance to standards on the most critical product parameters.”

World class Explosives Research and the people behind it
AEL Spearheads Research at Cape Town University

The Research and Development (R&D) division at AEL Mining Services has awarded researchers at the Cape Town University of Technology (CPUT) R1-million to further their efforts in a research project that will focus on emulsion technology and the development of a safer, more accurate blasting practice for the South African mining industry.

Over the past nine years, the Material Science and Technology group, which is based at the Cape Town campus, has been conducting research in collaboration with AEL; an exercise that has proved so beneficial to AEL and its customers that the company has committed to funding the project for a further three years.

“Led by Professor Irina Masalova, the team at CPUT has enabled AEL in the development of an eco-friendly version of its repump, doped and blend emulsion bulk explosives,” says Larry Wilson, group technical manager: Explosives at AEL.

“They have accomplished this by innovating the use of waste fuel oil initially generated by mining machinery in the manufacture of these products. Waste oil levels between 15 and 60 percent have been tested and are used at these ratios depending on the requirements of the various manufacturing sites.”

Masalova says the team has managed to successfully apply rheology, which is the study of the flow of complex and multi-phase liquids, as a tool to assist in predicting the stability and pumpability of AEL's bulk emulsion explosives.

The team at CPUT has also developed a theoretical model for the vertical transfer of underground emulsion explosives to the underground workings. This model serves an excellent platform for minimising the risk during the design of such systems.

“Methods for investigating surfactant characteristics have been developed as well, which will allow AEL to perform quick optimisation of the quality and quantity of the right surfactants in order to make the cost effective manufacture of emulsions with optimal levels of stability a reality,” she says.

The scope of the evaluation work has been extended further with the aim of developing new surfactants. Various PIBSA-based head groups are currently being evaluated and the intellectual property gained by this research will go a long way to ensure that AEL remains at the forefront of cutting edge technology.

The funding provided by AEL, in conjunction with the NRF's Technology and Human Resources for Industry Programme (THRIP), amounting to around R8.5 million thus far has helped CPUT establish a world class rheology laboratory, the only of its kind in South Africa.

The provision of funds has aided AEL in meeting its objectives in supplying quality innovation to South African mining operations as well as those of THRIP, which are to improve the competitiveness of South African industry through supporting research and technology development activities while growing the number of skilled individuals in the country.