On the job testing

28 July 2011

Ansys, a firm in South Africa, is developing a Continuous Rope Monitoring System (CRMS) to increase the rope life on mining hoists by halting them before failures occur.

Ten CRMS systems are currently being prototype tested on long mining ropes in deep South African gold mines. The company has eight rope monitoring systems installed at mines in Moab Khotsong, and two at a mine in Mponeng, all of which belong to the AngloGold Ashanti group.

While the CRMS system is now geared for monitoring mining ropes delivering payloads of ore, it may eventually be used for monitoring ropes used for lifting loads on cranes. Johan Kotze, marketing executive at Ansys, says, “We are seriously looking at it for cranes and also for anchoring prototypes for underwater testing.”

The principle behind rope testing units and the CRMS is the same, with sensors feeding data to online monitoring stations, but the CRMS is using much stronger magnets and more sensitive sensors. The CRMS is installed next to the crown wheel on a mining hoist.

The stronger magnets of the CRMS make testing rates much faster. A ‘bolt in test’ produces data every time the rope stands still compared to rope testing units, which test every 6 months. The CRMS monitors the full length of rope every time the rope moves through the head. When the rope is standing still, the test itself is accomplished more quickly, at 16-35m per second rather than at 2m per second. This rate makes it possible to conduct a real-time analysis of how usage is affecting rope wear.

“We measure all the same parameters as mobile units but we also correlate it with time,” Kotze says. “By doing that, you open a new dimension of the rope. If there is any change in the rope, you can pick it up immediately and monitor the progress of the deterioration with time,”

Ansys can integrate an alarm system to halt drums each time damage is registered. In the event of a malfunction of the system such as wire breakages, or slackness/tightness, the danger can be registered and processes can be automatically halted for immediate repairs. Rope life is lengthened by the possibility of fixing early.

Continuous monitoring of rope health can reduce the costs in several ways. It can indicate which configurations effect rope wear, in other words, how your system might be inadvertently fatiguing your rope, to increase rope life. And the system is designed to compare new and old data. Koatze says, “We have staff that monitors the rope.” The staff can notify maintenance crews to indicate any changes in rope health, and can provide engineering recommendations. They may also be able to monitor the amount of product that is moved in a period by looking at the wear, but this feature is in the development stage.

An added advantage for mining applications is the possibility of increasing loads without fear of a failure. “You can increase productivity by as much as 43%, Kotze says.