With no hesitation

Equipment allows more accurate and controlled operation, ensuring no variation of drilling quality during the process

Used always in severe works, drilling jumbos are high-tech machines which allow accurate precision, carrying out an important role in tunnel excavation and in construction and mining drilling of most types of soil.

When selecting these machines, the priority is to consider the necessity of high drilling performance, reducing work deadlines and increasing the quality of the works which are being carried out. “Depending on the section to be excavated, a jumbo with just three workers may develop the same job that would need tenths of workers with manual drill rigs”, says Paulo Ribeiro, business manager from Atlas Copco.

Thus, the first criterion to be considered when selecting the solution is the status of the rock to be drilled. “Sometimes the use of drilling and blasting is not feasible due to the condition of the rock”, says him, pointing that—since the use of jumbo is defined—some criteria have to be observed. “This includes the selection of equipment based on the dimensions of the tunnel (width and height) which define, for example, machine size and number of arms.”

In fact, the number of arms of the machine (which may vary from one to four) depends on the area to be excavated, as explained by the manager of Sandvik Mining and Rock Technology, Armando Bernardes. “In the case of a large area, it is recommended to use more arms to reduce drilling time”, explains Bernardes. “For medium-size areas it is possible to use jumbos with two arms, to make maneuvering easier, reduce equipment weight and improve operating flexibility. In low-size sections, the best is to use a one-arm jumbo, usually available in low-size mining works.”

Still in terms of technologic criteria, Ribeiro, from Atlas Copco, points out the type of rig to be used, which will depend mainly from the required productivity, the availability of electric power and other factors. Another point to be considered is related to attachments and optional features, based on the application, rock condition, stability of the drilling front, etc. “Many times the equipment is used for auxiliary drilling to install tethers, in addition to the drilling for rock breaking. This demands specific configurations such as the use of basket and telescopic feeding”, remembers the manager from Atlas Copco.

In fact, the heavier jumbos with two or three arms may be equipped with one or eventually two optional baskets. “Basically, this item is used in maintenance, support to tether installation or drilling for reinforcement systems”, says Bernardes from Sandvik.

LEVELS

On-board technologies are highlighted in jumbos—especially in rock drilling operations—since they effectively contribute to remove one of the main problems of excavation: the lack of consistency in the drilling quality. They ensure there will be no variation along the process. “This way, the team of explosive loading will be sure that the drilling which is being carried out is very close to the ideal situation. This allows a more accurate calculation of the load and the correct use of delay devices”, says Bernardes. “This will increase significantly the blasting efficiency, reducing vibrations and explosive consumption and giving a perfect control of overbreaking and underbreaking.”

According to Ribeiro, machines that may carry out drilling in fully automatic mode—where the operator is merely an operation supervisor—are available in the market. “In addition, specific softwares which ensure a total management of the drilling plan and its results, and even having features of equipment telemetry are also available”, says him.

In this line, Sandvik, for example, has two different levels of on-board technology in its drilling jumbos. One of them is the TCad+ system, a feature that allows effective control on the placing, orientation and slope of each hole, although this action continues to be carried out by the operator. But the iData system allows independent operation of the equipment, in a way to remove any interference of manual operation. “The operator assumes the operation only in case of any operating or maintenance abnormality”, says Bernardes.

But the executive emphasizes that—specifically for the Brazilian market—the first set of technology ensures better return on investment. “The TCad+ increases operating flexibility and does not impose that the system would be operative to allow the use of the jumbo because it is embedded into the operating system, compelling it to constant utilization”, says him. In addition, it does not prevent failures, even having a computer just for failure diagnosis during the operation. “It just reports the failures before they cause the equipment stop”, points Bernardes. “The system informs immediately the potential failure to the operator, who calls the maintenance crew to carry out the repairs.”