Beyond the walk-around: Building a rotary drum inspection protocol that prevents downtime 

From agglomerating ore for heap leaching pads to drying concentrates for shipment, rotary drums are accomplishing a variety of beneficiation and processing objectives throughout the mining industry. Miners producing copper, nickel, potash, gold and rare earth elements across the Canadian Shield, Alberta oil sands and northern Saskatchewan’s uranium district rely on rotary drums for reliable, high-capacity scrubbing, drying, cooling and calcining.   

The critical role this equipment plays throughout the transition from ore to metal — and the high costs associated with its downtime — makes preventive maintenance a top priority for mine sites alike. And one of the easiest, most cost-effective ways to prevent downtime is to implement a comprehensive inspection program to catch problems before they have a chance to cause an issue.  

The cost of a run-to-failure approach 

Mines are often working with high tonnages, relentless production schedules and valuable materials, the combination of which makes any amount of downtime incredibly costly.  

While mining-specific cost studies are scarce in the public domain, a clear theme emerges across heavy industry. The U.S. National Institute of Standards and Technology (NIST) found that reactive maintenance increases downtime by a factor of 3.3. While this does not translate directly to mining industry costs, authors found that for the year studied (2016), the manufacturing industry suffered preventable losses amounting to $119.1 billion. 

Industry experts recognize regular monitoring as the most effective approach to preventing larger issues. Factory Mutual Insurance Company’s Property Loss Prevention Data Sheet 6-17: Rotary Kilns and Dryers (2025 revision) notes that documented dryer and kiln losses almost always originated from a minor issue that was either ignored or remained unidentified.  

The data is clear: early identification and intervention, of which a solid inspection program is the foundation, prevents small issues from becoming major problems.  

Building a strong foundation: Prerequisites 

While site managers can implement inspection protocols at any time, laying the proper foundation ensures that inspections are as safe and effective as possible. The following elements are the basis for a successful inspection program: 

1. Data collection 

The first step in any inspection program is to gather baseline data. OEM documentation, work reports and changes to the production line provide a valuable starting point against which to compare new data.  

2. Safety  

While safety is a top priority in any type of facility, the unique hazards found in the mining industry make safety precautions even more critical. All operators and maintenance personnel interacting with the equipment must be properly trained in relevant safety practices, and equipment and infrastructure should be kept in safe working order.  

3. Personnel training 

In addition to reducing potential safety hazards, proper training also helps personnel to expedite troubleshooting and issue resolution when problems arise. Operators should be trained to distinguish normal operating sounds from early warning signs, such as the chatter of a misaligned gear or the high-pitched squeal of a bearing losing lubrication. Maintenance technicians should be capable of using dial indicators and UT thickness gauges for shell and refractory assessment.  

4. Tools and infrastructure 

Successful inspections are backed by the right tools and infrastructure. Calibrated instruments (dial indicators, feeler gauges, etc.), standardized checklists with numerical ratings (not just a pass/fail indicator), safe access in the form of platforms and catwalks and permanent measurement marks ensure inspections are carried out and documented safely and consistently.  

Inspection types and frequencies 

Inspection needs vary widely across operating conditions and rotary drum type. These diverse conditions emphasize the importance of an inspection program designed around the site’s unique equipment and operating environment. Typical inspection programs may include the following:  

1. Daily walkthroughs 

• Each drum should receive a daily or shift-change walkthrough, with personnel following an itemized checklist of visual and auditory observations while the drum remains in operation. The objective of a daily walkthrough is to identify the start of subtle changes and maintain familiarity with the drum’s “normal” operating condition. A daily walkthrough confirms the following:The drum is smoothly rotating without vibration. 

• Trunnion pits are free from fugitive material and debris. 

• Drum float (positioning between thrust rollers) is adequate. 

• All safety guards, labels, signs and precautions are in place. 

Tire (riding ring) and trunnion faces are free from wear or damage and achieving proper contact.Operators should record even seemingly minor observations, as these often reveal trends or the onset of an issue when monitored over time.  

2. Weekly and/or monthly inspections 

• Depending on operating conditions, inspections may be required on a weekly, monthly or combined basis. These inspections should center around observing the drum in operation, while also gathering the following quantitative measurements indicative of the mechanical health of drum components: Tire creep. 

• Bearing temperatures. 

• Vibration amplitude. 

• Pinion-gear contact (gear and pinion drive assemblies only — should be even and engaged). 

• Chain tension and lubrication (chain-driven drums only). 

• Graphite block condition (must be sufficient for maintaining lubrication). 

The following components should be monitored to confirm proper operation and satisfactory condition: V-belt. 

• Coupling alignment. 

• Reducer. 

• Trunnion wheel and pinion drive bearings. 

• Thrust roller assembly. 

• Thrust roller contact. 

• Drum shell temperature (hot drums only). 

The drum shell should also be regularly examined to check for signs of wear or damage. Internals such as spray systems, flights, liners and refractory should also be inspected monthly, or as production schedules allow.  

3. Quarterly or semi-annual (may require a shutdown) 

The following components typically experience minimal wear, requiring only quarterly or semi-annual review, though this may differ depending on the site’s specific operating conditions:   

• Seals. 

• Hammers, where applicable. 

• Trunnion bearing oil.  

• Backlash and root gap (gear and pinion drive assemblies only). 

• Tire/wheel surface (should be smooth, with proper contact). 

4. Annual inspections 

The aforementioned inspections can be carried out by on-site personnel and should be part of internal maintenance practices. Annual inspections, however, require the OEM or a qualified service provider equipped with specialized tools and expertise.  

Annual inspections should be scheduled to coincide with a planned outage to give the inspector lockout/tagout (LOTO) access to the drum. During an annual inspection, the provider will thoroughly evaluate the condition of all mechanical components both internally and externally, both while in operation and while shut down.  

During this time, the technician will take the following measurements (note that this may vary by provider):  

• Tire and trunnion hardness. 

• Tire and trunnion diameters. 

• Cold gap/creep (floating tires only). 

• Trunnion alignment. 

• Shell thickness. 

• Backlash (gear and pinion drive assemblies only). 

• Shell run-out. 

• Refractory thickness and condition, where applicable. 

• Girth gear radial and axial run-out. 

Known maintenance issues can also be addressed during the shutdown. In settings where operating conditions are especially harsh, this type of analysis may be necessary on a semi-annual basis.  

Beyond the inspection: Using your data 

While inspections are arguably the most effective approach to catching potential issues before they have a chance to escalate, they can also be a gateway to elevate maintenance planning procedures, but only if used strategically.  

By keeping thorough and accurate inspection documentation (standardized measurements, observations and even photos), reliability engineers and maintenance teams can use the data to analyze trends that inform parts management, maintenance planning and changes to inspection protocols.  

Linking inspection findings to a computerized maintenance management system (CMMS) can enable automated work-order generation when data exceeds predefined thresholds. Use of a CMMS can also house valuable equipment history for reference and maintenance planning.  

Personnel should also track rate-of-change data for all measurements as well. The rate of change can reveal the need for further investigation that simply reviewing absolute values might miss. A bearing temperature that slowly creeps from 55°C to 65°C over six months, for example, could indicate a potential underlying issue, despite the absolute reading still falling within the “normal” operating range.  

Common pitfalls 

A comprehensive inspection program can offer gains in production, lower maintenance costs, reduced downtime and a longer equipment service life. The following common mistakes, however,  

can put those gains at risk, negating the program’s value:  

1. Treating symptoms without identifying the cause 

Whether knowingly or unknowingly, continuously treating the symptoms of an issue without addressing the root cause quickly leads to inefficiencies in resource utilization, accelerated component wear and escalating maintenance costs.  

This is frequently seen with repeated tire and trunnion grinding when misalignment is the underlying cause. Instead of having the drum realigned, the site manager repeatedly hires a grinder to resurface tires and trunnions, after which wear immediately resumes. This not only neglects the alignment issue, which puts additional strain on mechanical components, but also leads to a shorter service life for tires and trunnions, as each grind reduces diameter. This underscores the importance of working with a provider that can evaluate and address the root cause of an issue.  

2. Ignoring housekeeping 

The importance of adequate housekeeping is frequently overlooked, both as a maintenance practice and as a safety precaution.  

Poor housekeeping may seem like a non-issue compared to maintaining equipment and meeting production timelines, but has the potential to degrade equipment over time, particularly at mine sites, where the material is often corrosive, abrasive or both.  

Allowing fugitive dust to collect around trunnion pits, for example, can lead to material migrating to the pinch point between tire and trunnion, promoting aggressive abrasion. Similarly, fugitive dust building up in and around motors degrades mechanical components, reducing their lifespan.  

Insufficient housekeeping also creates the potential for slips, trips and malfunctions that put personnel at risk despite being easily preventable.  

3. Poor parts inventory management 

The lack of a strategic and ongoing approach to spare parts inventory management can also jeopardize even the best maintenance programs. Site managers should work with their OEM to maintain an inventory of wear-critical parts and wear items to prevent the lack of a part from holding up production when an issue occurs.  

4. Lack of standardized data 

While any amount of data is better than none, standardized data is significantly more usable and scalable. Consistent documentation, fixed measurement points and calibrated instruments ensure data is collected as thoroughly and accurately as possible, allowing it to be translated into trends and reports.  

5. Overlooking internal inspections 

External mechanical components tend to receive the bulk of attention when it comes to inspection, simply because they are more accessible. Internal components, while less accessible, are often more vulnerable to issues owing to regular contact with the material and the addition of heat in hot drums. Internals should be inspected at every available opportunity.  

Concluding remarks 

Rotary drums reliably carry out the fundamental tasks of mineral beneficiation, from calcination to agglomeration, but only when they are properly maintained. A strategic inspection program is the most cost-effective way to catch and curtail more serious issues at their onset.  

The most effective inspection program is the one that is consistently executed, thoroughly documented and continuously improved. By establishing the right prerequisites, implementing an inspection cadence based on site-specific conditions, working with a qualified partner and avoiding common pitfalls, mining operations can transition from the problematic run-to-failure approach to one that prioritizes catching issues early, minimizing unnecessary downtime and maintenance costs. 

Craig Peppin is customer service manager at FEECO International. 

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