Minimize Shovel Boom Jack Harm With Training and Technology

For those unfamiliar with the term, boom jacking might sound like the latest TikTok craze or a type of industrial theft. For owners, maintainers and operators of high-payload electric rope shovels, however, boom jacking indicates a detrimental operator error that, at the least, can degrade loading cycle timing and in the worst case, result in critical equipment failure.

Boom jacking occurs when the cables supporting the shovel’s boom go slack after the boom is pushed upward by the dipper handle as a result of improper operator digging technique. When the jacking action ends, the boom can drop abruptly – violently snapping cables back into tension and stressing the whole boom suspension system.

Modern shovels have dig optimization systems and design features that can protect against this, but an operator who consistently triggers boom jacking alerts isn’t helping the mine’s productivity. For example, Komatsu has for years offered Smart Crowd on its P&H mining shovels – a feature designed to optimize the crowd motion for improved bank penetration in hard toe. An Opti Toe control function improves cutting force and encourages the operator to
“dig close” to help increase productivity. Shovel design includes an integral fleeting sheave that is intended to keep hoist cables taut to reduce maintenance and help eliminate boom jack events.

Caterpillar also offers protective features on its large rope shovels, as well as after-sale support, aimed at minimizing or eliminating the problem. As the company points out in a recent case history article, boom jack incidents can often be a headache at new operations with inexperienced operators, and Cat was able to help Anglo American dramatically reduce this problem on three Cat 7495 electric rope shovels at the global mining company’s new Quellaveco copper operation in Peru.

When those shovels began experiencing a series of boom jack events, a team from Caterpillar and its local dealer was able to provide a solution that combined a feature called Operator Assist – Enhanced Motion Control (EMC) with training and skills development for the greenfield site’s rope shovel operators, many of whom are inexperienced. The solution, according to Caterpillar, not only reduced boom jack events but also delivered gains in productivity and machine availability.

A boom jack occurs when machines crowd against the bank floor and lift the boom with the dipper handle. There a couple of ways an operator can cause a boom jack:

• By running the crowd out at full speed without tension on the hoist ropes.

• By applying full crowd while the hoist is just starting through the bank, which can rock back the boom.

These mistakes trigger faults that adversely affect cycle times, explained Caterpillar Site Performance Manager Paolo Tapia in the case history narrative. “The software on the rope shovel allows extension on the crowd system until it sees resistance,” he pointed out. “It will stop the crowd force if there is no tension in the hoist ropes, so once the operator applies tension to the hoist ropes, this will allow the crowd to continue to apply force.”

While downtime is an obvious outcome from a boom jack event, the long-term impact on the shovel can be catastrophic. “Conditions that trigger boom jack events can lead to failure of the suspension ropes and of the frame — and both are going to cost the site a significant amount in terms of both lost production and repair costs,” said Tapia.

Data from Quellaveco showed that one of the site’s 7495s experienced a significant number of boom jack events in a single month. A month later, a different shovel registered a similar amount. These numbers, according to Cat, would have been even higher if the shovels were not equipped with EMD, which can reduce boom jacks by up to 50%.

“The system was able to prevent half of all the boom jacks — and protect the machine — as it is designed to do,” said Tapia. “So even though the technology was making a positive impact, the cause of the boom jacks still remained.”

Caterpillar then proposed a Continuous Improvement (CI) project that would identify the causes and find a solution, based on a business case that outlined the impact if the problem wasn’t addressed. Using calculations on the price of copper, plant capacity and other known parameters, the proposal estimated production losses of $8 million per shovel over 5 years due to the downtime associated with the boom jack events. In the event of a catastrophic failure of suspension ropes and A Frame, the site could expect an additional potential loss of $25 million.

“Considering the number of boom jack events per month, we estimated suspension ropes would fail at 10,000 hours, with 60 hours needed to repair,” Tapia said. “The worst-case scenario combines those previous losses while adding a frame failure that would stop the machine for up to eight weeks.”

After Quellaveco agreed to the CI project, the team gathered feedback from Cat electric rope shovel product engineers, engaged with the Quellaveco maintenance and operations management teams, and ensured the boom jack sensors were mechanically regulated to spec.

However, the primary focus of the CI initiative was the rope shovel operators.

“Making sure that the operators have the correct training and develop good skills to prevent boom jacks is the most important thing we can do to correct this problem,” said Tapia. “And while ECM is an important technology tool on its own, it delivers the greatest value when operators are properly trained and understand it.”

The training included assessment of individual skills, classroom and one-on-one training, feedback on performance and regular follow-ups. A Caterpillar rope shovel instructor spent several weeks on site to provide specific training on boom jack events. In addition, the training went beyond boom jack events to improve the overall skills of each individual, recognizing that each operator has different levels of expertise. Each operator received about 3 days of focused training.

According to Caterpillar, the number of boom jack events at Quellaveco has dropped by more than 80% per month, allowing the mine to avoid downtime related to those events. Some of the additional benefits provided by implementation of EMC at Quellaveco include:

• 7% decrease in crowd overspeeds.

• 7% increase in production rate (dollars per ton/hour).

• 5% increase in shovel fill factor.

• 36% decrease in shovel loading cycle time.

• 15% decrease in truck idle time around the shovel.

There are also other alternatives available to mine operators intent upon solving or minimizing the damage resulting from boom jack problems. Operator training and evaluation can be crucial and simulation training offers a relatively risk-free training approach with a variety of shovel simulator packages available from various vendors. These can range from complete simulator kits such as those offered by ThoroughTec – which recently announced renewal of its global cooperation agreement with Cat, continuing the manufacturer’s recommendation of ThoroughTec as an approved simulator supplier – or from Immersive Technologies, for example, down to basic simulation hardware and software packages that require minimal space and setup.

For instance, Montreal-based Simlog’s PC-based electric rope shovel personal simulator enables customers to either use their own PC or choose a PC bundle with Simlog software already installed, licensed, and immediately usable in a variety of language formats.

Another option can be to replace steel-rope support cables with synthetic fiber cables – a move that fiber cable suppliers claim can reduce unwanted shock loads incurred from boom jacking by up to 50%, while providing improved damping properties that curtail excessive vibration effects often encountered with heavier steel rope rigging.