Balance Machine Slew Bearing Failure

Boltstress Ultrasonics worked with a large mining company situated in Port Hedland, in Western Australia to ensure the integrity of machines used in heavy-duty tasks. This includes a highly-automated, out-loading circuit, responsible for processing iron ores that are ready for transportation.

The machine involves a bucket wheel reclaimer, and this reclaims bulk ore coming from stockpiles, which are ready for conveying to the Lump. The bucket reclaimer typically obtains a flow rate of around 14,000 tons per hour. Hence, it is very critical to maintain this piece of equipment to its operational level with regular servicing.

In addition to the bucket wheel reclaimer, there are stackers and ship loaders that transport massive tonnage of iron ore for export all over the world. These are highly critical items.

Following some premature bearing and drive rack failures, Boltstress Ultrasonics was called in to investigate the condition of the critical fasteners that secure these in position.


The bucket reclaimer rotates on a vertical axis during its operation. Thus, it allows a horizontal boom that allows it to move in any position to reach the ore. The slewing ring is responsible for lateral movement. It also accommodates the loads that act in any direction.

The bearings are assembled in an annular arrangement of bolts. Hence, accurate tensioning is required to ensure their optimal performance.

Problem Identified

Initially, two personnel serviced these slew ring bearings prior to the Boltstress Ultrasonics' involvement. A standard torque wrench or a hydraulic bolt tensioner was used. And while these were effective for tightening the bolts, there was a limitation in measuring the bolt tension.

Our findings showed that most bolts had low residual tension, some were completely loose.

Risks Involved:

Moreover, the method was laborious, time-intensive, and inaccurate at the same time. Only 10 percent of the bolts were thoroughly checked. As a result, the bearings undergo premature wear rates. Eventually, they undergo premature wear and tear requiring untimely replacement costs and expensive production losses.

Our Recommended Solution:

To re-tighten the loose bolts and prevent catastrophic problems should these critical fasteners remain unsecured in position. Trained engineers and supervisors will carry out the necessary techniques with the use of essential tools to complete the task at hand.


Using our "designed to fit" hydraulic bolt tensioner we re-tightened them and adjusted these to within the correct tolerances using our Boltstress G6.

Tools Required

Among the tools utilized by the Boltstress Ultrasonics team are the following:

  • Specialist ultrasonic bolt measurement instruments (Boltstress G6)

  • Bespoke engineered hydraulic bolt tensioners

  • 1500 Bar Hydraulic Tensioner Pumps

  • Die Nuts

  • Access equipment

Post-Work Analysis: The Outcome

After carrying out a more accurate and highly efficient technique in re-tightening, adjusting, and servicing the slew bearings, we have observed the following outcomes:

  1. Increased Accuracy

    The ultrasonic bolt stress monitoring was highly accurate at 2 percent. Thus, this extended the statutory replacement by nearly double.

  2. Fast and Efficient

    The Boltstress Ultrasonics team improved the speed and servicing to 15 seconds per bolt. Additionally, the experience and expertise of the technicians sped up the job while achieving their goals for the task. This makes it a more cost-effective technique overall.

  3. Safe and Ergonomic

    And lastly, ultrasonic bolt stress monitoring eliminated pinch points and the laborious lifting in tight spaces. Hence, the Boltstress Ultrasonics team was able to carry out the task with greater safety and preventing discomfort or physical strain.

Bottom Line

Ultrasonic measurement is without a doubt the most efficient, time-saving, and highly effective technique in identifying and addressing problematic bolts in the industry. With the application of the smartest tools and state of the art techniques, safety hazards and unplanned downtimes can be prevented in the workplace, which leads to better productivity and increase in your bottom line.

To learn more about how we at Boltstress Ultrasonics can help you out, please contact us via email or phone.

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