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Handling Crusher Liners, Mill Liners, and Heavy Wear Parts

Crusher mantles and concaves, bowl liners, arm-guard liners, and grinding-mill shell liners are made to wear out, so every crushing and grinding plant lifts, blocks, and replaces heavy parts inside its own machines on a recurring schedule. UTEC Industrial designs, engineers, machines, fabricates, and installs custom material handling systems for aerospace and heavy industry from its Spokane Valley, WA facility, integrating Allen-Bradley PLC and motion control with in-house CNC machining, heat treating, and stress relief. This article works from the mine operator's side: what the maintenance-fatality record shows about wear-part work, what two recent MSHA fatality investigations found during crusher liner and guard changes, which Title 30 rules govern the lift, and what a purpose-built liner handler needs in its structure, sensing, and controls. A liner handler is designed and built along one chain, design → engineering → parts machining → fabrication → assembly → weld fatigue → stress relief → drives → controls → tuning → monitoring, and a lifting point or interlock left out at the design link ends up improvised in the field.

Why is a crusher or mill liner change a heavy-handling problem?​

A liner change is maintenance performed inside a machine that was built to break rock, not to be worked in. The wear parts are heavy, irregular, and often seated in tight clearances, and the crew works around them from temporary platforms. MSHA's investigation of a 2023 gyratory crusher fatality gives a sense of the geometry:

  • What the parts protect. Arm guard liners protect the crusher's two support arms and its pinion shaft arm from rock abrasion and wear during crushing.
  • Part weight. The narrow arm guard liner being lifted weighed approximately 320 lb.
  • Clearance. The clearance between the edge of the work platform, set on top of the eccentric bushing, and the concave wear plates lining the chamber above the arm guard was 14.5 in. Because of that clearance, the crew chose to lift the arm guards and clean under them rather than remove them completely.

The same pattern shows up across the industry. An analysis of U.S. mining fatalities from 2002 to 2011 found 172 that occurred during maintenance and repair work, and the largest single task category, at 79 deaths or 45.9%, was equipment maintenance and repair, defined as repairing or replacing a part on equipment or troubleshooting an equipment problem. Replacing a worn liner is exactly that task, so the handling method for each wear part deserves the same engineering attention as the crusher or mill it goes into (MSHA, July 17, 2023 Fatality -- Final Report; Reardon et al. 2014, IIE Transactions on Occupational Ergonomics and Human Factors vol. 2 no. 1, pp. 27-38, Table 2).

What do mining maintenance fatalities show about wear-part work?​

Reardon, Heberger, and Dempsey reviewed all 575 U.S. mining fatalities from 2002 to 2011 and classified the 172 that involved maintenance and repair (47 in coal, 125 in metal and nonmetal mining) by energy source, task, and contributing factor. Several results bear directly on liner and wear-part handling:

  • Gravity dominates. Potential energy, meaning gravity causing an object to contact the victim or the victim to fall, accounted for 80 deaths (46.5%) overall and 52.8% of metal and nonmetal maintenance deaths, against 29.8% in coal.
  • Props fail. An object falling from a prop onto the victim, where the prop is whatever supports the object from above or below, caused 33 deaths (19.1%). Falls from height caused another 23 (13.3%).
  • Contributing factors. The most frequent were failure to de-energize or lock out and tag out equipment (44 deaths, 25.6%), work procedures not followed or not provided (36, 20.9%), safety equipment missing, inoperative, or improperly used (35, 20.3%), and blocking (34, 19.8%).
  • Blocking versus suspended load. The authors define blocking as failure to support a raised object properly from beneath, such as missing or misused jack stands or blocks, and suspended load as failure to support it properly from above, such as a missing or misused hoist or a person under or close to the load. Suspended load contributed to 8 deaths (4.7%).

The authors describe the typical blocking failures: not blocking equipment in all directions, so the equipment shifts and falls off its blocks; using a jack alone to support an object; and removing bolts that support part of the equipment without putting blocks in place. Each has a direct equivalent in a liner change, where a mantle, bowl, or head is raised on jacks and liner bolts are removed one by one (Reardon et al. 2014, IIE Transactions on Occupational Ergonomics and Human Factors vol. 2 no. 1, pp. 27-38, Tables 1, 3 and 4).

What failure mode does the gyratory crusher arm-guard fatality document?​

On July 17, 2023, a miner at a Massachusetts traprock quarry was killed while helping replace an arm guard on the plant's primary gyratory crusher. The investigation found a chain of improvised handling decisions:

  • An improvised lifting point. A foreman welded a 4 × 4 × ½ in steel lifting lug onto each arm guard so it could be lifted by crane, and an irregular hole of about 1.75 in diameter was burned through each lug for the rigging. The weld was a single pass on each side and across the front of the lug; the back edge was not welded because the concave lining plates made it inaccessible.
  • A load that was strong enough, until it snagged. MSHA calculated the weld strength at between 26,000 lb and 59,700 lb, depending on the angle between the sling and the weld, which is far more than the 320 lb guard. The sling and the 8.5-ton shackle were also found adequate.
  • The hang-up. The guard, suspended and unrestrained while a foreman cleaned beneath it with a compressed-air wand and pry bar, became caught on the underside of the concave lining plates or wedged against the crusher. The crane's boom or load-line controls were engaged, and the load rose rapidly beyond the strength of the weld.
  • The release. When the weld broke, the lug, shackle, and sling traveled at least 16 ft upward. In the sling manufacturer's simulation tests, 12,480 lb of force was needed to throw the rigging the full 12 ft height of the test apparatus.

MSHA's root cause was that the operator did not ensure the miner was clear of the suspended load, and it cited 30 CFR 56.16009, which requires persons to stay clear of suspended loads. The engineering lesson is that a snagged part turns a hoist into a puller: the crane had a load moment indicator that displayed load magnitude, but nothing stopped the load from climbing past the weld's calculated minimum strength, more than 80 times the part's own weight (MSHA, July 17, 2023 Fatality -- Final Report; MSHA 30 CFR Part 56-2026, §56.16009).

What does the cone crusher liner-change fatality teach about hydraulic pressure and hot work?​

On December 22, 2025, a contract field-service technician died at a Virginia limestone quarry while disassembling a roller cone crusher to change its liner. The manufacturer's procedure used a pump connected to the crusher's hydraulic system to power jacks that raise the upper assembly, so the shims on the bottom portion of the adjusting bolts could be removed by hand. The system was then depressurized, the adjusting nuts loosened if necessary, and the top shims removed by hand, without a torch.

The investigation found that the procedure was not followed:

  • The technician pressurized the hydraulic system, loosened all but one adjusting nut, and removed the shims from all but one adjusting bolt.
  • Unable to loosen the last nut, the technician used an oxygen and acetylene torch to cut a top shim. A hydraulic line ran directly behind it.
  • Heat from the cut ruptured the line, and the torch ignited the escaping hydraulic fluid. The fire stopped only when a mechanic de-energized the generator powering the pump, which depressurized the system.

MSHA cited both the contractor and the mine operator under 30 CFR 56.4604, which requires pipelines or containers that have held flammable or combustible liquids to be drained, ventilated, and thoroughly cleaned of residue, vented to prevent pressure build-up, and either filled with inert gas or water where compatible or checked with a flammable-gas detector before and during heating. It cited the contractor under 56.15007, which requires protective clothing and face shields or goggles when welding or cutting. The corrective actions required all associated hydraulic systems to be fully depressurized and, where practical, vented to atmosphere before cutting, welding, or other hot work close to any hydraulic component, and a heat shield placed to protect the hydraulic system. The failure mode is trapped hydraulic pressure next to a heat source, created by working the procedure out of order (MSHA, December 22, 2025 Fatality -- Final Report; MSHA 30 CFR Part 56-2026, §56.4604 and §56.15007).

Which MSHA rules govern lifting, blocking, and hose connections during a liner change?​

The Part 56 rules for surface metal and nonmetal mines that apply to a liner change are short, and each one maps to a handling-equipment requirement:

  • Suspended and hoisted loads. Persons must stay clear of suspended loads (56.16009). Taglines must be attached to loads that may need steadying or guidance while suspended, and hitches and slings must be suitable for the material handled (56.16007). Persons must not ride loads moved by cranes or derricks, or ride the hoisting hook, unless that method eliminates a greater hazard (56.16011).
  • Dropping material. Material must not be dropped from an overhead elevation until the drop area is cleared of personnel and then either guarded or a suitable warning given (56.16010), which applies when worn liner pieces or backing material are removed from the top of a crusher.
  • Capacity. Machinery, equipment, and tools must not be used beyond the design capacity intended by the manufacturer where that may create a hazard (56.14205). A crusher's own hydraulic jacks, or a crane rigged to a field-welded lug, are held to that test.
  • Blocking. Repairs and maintenance must be done with the power off and the machinery blocked against hazardous motion (56.14105). For raised components of mobile equipment, 56.14211(d) treats a component as blocked or mechanically secured if it has a functional load-locking device or a device that prevents free and uncontrolled descent, and Part 57 carries the same rule underground in 57.14211.
  • Hydraulic hose connections. Except where automatic shutoff valves are used, safety chains or other suitable locking devices are required at machine connections of high-pressure hose lines of ¾ in inside diameter or larger, and between such lines, where a connection failure would create a hazard (56.13021).

At surface coal operations, Part 77 states the blocking rule directly: no work may be performed under machinery or equipment that has been raised until it has been securely blocked in position (MSHA 30 CFR Part 56-2026, §56.13021, §56.14105, §56.14205, §56.14211, §56.16007, §56.16009, §56.16010 and §56.16011; MSHA 30 CFR Part 57-2026, §57.14211; MSHA 30 CFR Part 77-2026, §77.405).

What should a liner handler or lifting fixture be designed to?​

A purpose-built liner handler, lifting beam, or wear-part fixture that hangs from a crane hook is a below-the-hook lifting device. ASME BTH-1-2023 is the design standard for these devices, and ASME B30.20-2025 is the companion safety standard covering their marking, inspection, testing, and use. Several of their requirements shape a liner-handling device from the first drawing:

  • Design category. BTH-1 assigns each device a Design Category, A or B, and Category B applies where the magnitude and variation of loads are not predictable or where the environment is severe or not accurately defined. Category B carries the higher design factor on static strength, 3.00 against 2.00 for Category A. A crusher interior, with irregular parts and the snag loads described above, is a strong candidate for Category B.
  • Service class. BTH-1 also assigns a Service Class by the number of load cycles over the device's life, beginning with Service Class 0 for up to 20,000 cycles, and the higher classes govern fatigue design of welded details.
  • Marking and proof load. B30.20 requires the rated load to be marked on the device and requires a new, altered, or repaired device to be load tested before first use at not less than 125 percent of its rated load.

The arm-guard investigation shows the gap these rules close. The lug in that case was welded onto the guard by a foreman so it could be lifted by crane, and the investigation report gives it no rated load and describes no design basis or proof test for it as a lifting device; it was strong enough until the load path changed. An engineered fixture puts its lifting points where the part's center of gravity demands them, is proof-loaded before use, and carries its rating where the crew can read it. For welded lifting structures in cyclic service, the weld fatigue and stress relief links of the chain matter as much as static strength, and UTEC Industrial stress-relieves, machines, and NDT-inspects the welded frames of the handling equipment it builds (ASME BTH-1-2023, Chapter 2 and Chapter 3 design factor; ASME B30.20-2025, Chapter 20-1; MSHA, July 17, 2023 Fatality -- Final Report).

How is stored energy isolated before a crew enters a crusher or mill?​

A crusher or mill down for a liner change still holds energy in several forms: electrical energy at the drive, hydraulic pressure in the adjustment and clamping circuits and in any jacks holding an assembly up, and gravitational energy in every raised or partially unbolted part. Title 30 addresses the first directly: electrically powered equipment must be deenergized before mechanical work, and the power switches locked out or other measures taken so the equipment cannot be energized without the knowledge of the people working on it. It addresses the rest through 56.14105, which requires the machinery to be blocked against hazardous motion.

OSHA's general-industry lockout standard does not govern mines, but two of its provisions are useful design tests for a liner-handling system:

  • Stops are not isolation. It defines push buttons, selector switches, and other control-circuit-type devices as not being energy-isolating devices. A PLC stop or an emergency stop on a liner handler removes a command; it does not isolate the hydraulic power unit or the crusher drive.
  • Stored energy must be dealt with after lockout. It requires all potentially hazardous stored or residual energy to be relieved, disconnected, restrained, and otherwise rendered safe after lockout devices are applied. In the cone crusher case, the energy that killed the technician was hydraulic pressure left in the system while hot work was done beside it.

Because 56.14105 requires the machinery to be blocked against hazardous motion as well as having the power off, a grinding mill's blocking has to reach the shell itself. That is an engineering reading of the rule, not its text: with liners partly removed or the charge unevenly distributed, the shell is out of balance and can turn under gravity after the drive is locked out, so the design needs a mechanical means of holding the shell, not only a locked-out motor. The maintenance-fatality data show why these details matter: failure to de-energize or lock out contributed to 25.6% of maintenance deaths, and an idle machine being activated caused 9 deaths (5.2%) (MSHA 30 CFR Part 56-2026, §56.12016 and §56.14105; OSHA 29 CFR 1910.147-1989; Reardon et al. 2014, IIE Transactions on Occupational Ergonomics and Human Factors vol. 2 no. 1, pp. 27-38, Tables 1 and 3).

What sensing, PLC control, and interlocks does a liner-handling system need?​

A liner handler, whether it is a crane-hung fixture, a floor-mounted manipulator, or a mill relining machine, has to know what it is holding, where it is, and whether the machine it is working in is safe to enter. The two fatality investigations point to the sensing that matters most:

  • Load sensing with a snag trip. In the arm-guard case, the load rose from a 320 lb part to beyond a weld calculated at 26,000 lb or more, and the crane's load moment indicator gave the operator a readout of the load magnitude but did not stop the lift. As a design approach rather than a regulatory requirement, a load cell on the handler or hook with a trip set a modest margin above the expected part weight, plus a rate-of-rise check, stops the hoist the moment a part hangs up instead of pulling harder.
  • Position sensing. Encoders on the handler's slew, reach, tilt, and grip axes report where the part is, so the PLC can limit travel inside a tight crushing chamber; limit switches back them up at the ends of travel.
  • Zone interlocks and permissives. The handler should not move while a person is inside its guarded envelope, and it should not be enabled until the crusher or mill drive reports locked out. Hydraulic pressure transducers on the crusher's adjustment circuit can confirm zero pressure before a hot-work permit is issued, which answers the cone crusher failure mode directly.
  • Drives. A servo drive such as the Allen-Bradley Kinetix 5700 closes position, velocity, and current loops on encoder feedback and has safe torque-off built into the drive, so a guarded-zone entry removes torque without relying on the motion program.
  • PLC and safety logic. Logix 5000 controllers organize code into continuous, periodic, and event tasks, so interlock logic runs at a fixed period. Safety functions run in a separate safety task in a controller such as a GuardLogix 5580, which Rockwell Automation rates for safety applications up to SIL 3 and PL e, Category 4, with a safety partner, and up to SIL 2 and PL d, Category 3, without one.
  • Standards. ISO 12100:2010 covers the risk assessment and risk reduction that identify these hazards, ISO 13849-1:2023 covers the design of the safety-related parts of the control system, and IEC 60204-1:2016 addresses the machine's electrical equipment from the point where the supply connects to it.

UTEC Industrial, a Rockwell Automation Recognized System Integrator, builds UL 508A control panels and integrates Allen-Bradley PLC, servo, and VFD control into the handling equipment it supplies (MSHA, July 17, 2023 Fatality -- Final Report; Rockwell Automation 2198-UM002E-EN-P, Kinetix 5700; Rockwell Automation 1756-RM094N-EN-P-2025; Rockwell Automation 1756-RM012J-EN-P-2025; ISO 12100:2010; ISO 13849-1:2023; IEC 60204-1:2016).

How are liner-handling systems tuned, tested, and monitored in service?​

A liner handler is used a few times a year on a given crusher and then sits, often in a dusty, vibrating plant, until the next change. That duty pattern makes testing before each use and tuning under real load more important than on equipment that runs every shift:

  • Tuning at load. The Kinetix 5700 commissioning procedure includes a tuning step for each axis, and autotuned loop bandwidths depend on the application and can require adjustment once the motor and load are connected. An axis tuned with an empty gripper behaves differently holding a heavy mantle or shell liner, so tuning is checked with representative parts during commissioning.
  • Pre-use checks. Load-cell zero and span, snag-trip function, limit switches, and the lockout permissive can be exercised by a short PLC test sequence before each liner change, with the result logged.
  • Cycle counting. Because the ASME BTH-1-2023 service class is based on load cycles, the control system can count lifts so the device stays within the class it was designed to.
  • Defect handling. A handler that fails its pre-use test is taken out of service, as Part 56 requires of equipment whose defects make continued operation hazardous, rather than used with a bypass.

A common failure mode is the handler whose snag trip or load cell has drifted between uses; a logged pre-use test catches it before the part is on the hook (Rockwell Automation 2198-UM002E-EN-P, Kinetix 5700; MSHA 30 CFR Part 56-2026, §56.14100; ASME BTH-1-2023, Chapter 2).

What should a mine operator define before requesting liner-handling equipment?​

A request that names only a crane capacity leaves out most of what drives a wear-part handling design. A complete specification from the operator defines:

  • The parts. Every wear part the device must handle, with weight, center of gravity, lifting or gripping surfaces, and how the part is seated and fastened, since 56.14205 limits the device to its design capacity.
  • The space. Chamber and platform clearances, crane hook coverage, and access routes, measured on the installed crusher or mill. The 14.5 in clearance in the arm-guard case shows how tight that space can be.
  • The rule set. Part 56, Part 57, or Part 77, which sets the blocking, lifting, and lockout rules the procedure has to satisfy.
  • The lifting-device basis. The ASME BTH-1-2023 design category and service class, the rated load, and the ASME B30.20-2025 proof test and marking.
  • The energy sources. Every hydraulic circuit, accumulator, and raised assembly on the host machine, and where each is isolated and verified at zero before work or hot work begins.
  • The controls. Load sensing and snag trip, position sensing, permissives to the host machine's lockout, the PLC and safety controller platform, and data logging.
  • Acceptance. Factory and site tests, including the proof load and a functional test of every interlock with representative parts.

UTEC Industrial performs factory acceptance testing and on-site commissioning, so these criteria can be written into the purchase order and demonstrated before the handler goes into a crusher (MSHA 30 CFR Part 56-2026, §56.14205; MSHA 30 CFR Part 57-2026, §57.1; MSHA 30 CFR Part 77-2026, §77.1; ASME BTH-1-2023; ASME B30.20-2025).

Related Articles

References​

  • MSHA 30 CFR Part 56-2026: Safety and Health Standards—Surface Metal and Nonmetal Mines. U.S. Department of Labor, 2026.
  • MSHA 30 CFR Part 57-2026: Safety and Health Standards—Underground Metal and Nonmetal Mines. U.S. Department of Labor, 2026.
  • MSHA 30 CFR Part 77-2026: Mandatory Safety Standards, Surface Coal Mines and Surface Work Areas of Underground Coal Mines. U.S. Department of Labor, 2026.
  • MSHA. July 17, 2023 Fatality -- Final Report (Gyratory Crusher Arm Guard Replacement, Suspended-Load Fatality). Mine Safety and Health Administration, 2026 (undated web documentation, accessed September 2026).
  • MSHA. December 22, 2025 Fatality -- Final Report (Cone Crusher Liner Disassembly, Rockydale-Flatrock Quarry). Mine Safety and Health Administration, 2026 (undated web documentation, accessed September 2026).
  • Reardon LM, Heberger JR, Dempsey PG (2014). "Analysis of Fatalities During Maintenance and Repair Operations in the U.S. Mining Sector." IIE Transactions on Occupational Ergonomics and Human Factors, 2(1), 27-38. DOI 10.1080/21577323.2014.911222
  • ASME BTH-1-2023: Design of Below-the-Hook Lifting Devices. ASME, 2023.
  • ASME B30.20-2025: Below-the-Hook Lifting Devices. ASME, 2025.
  • OSHA 29 CFR 1910.147-1989: The Control of Hazardous Energy (Lockout/Tagout). Occupational Safety and Health Administration, 1989.
  • IEC 60204-1:2016 (Ed. 6.0): Safety of Machinery -- Electrical Equipment of Machines -- Part 1: General Requirements. International Electrotechnical Commission, 2016.
  • ISO 12100:2010: Safety of machinery — General principles for design — Risk assessment and risk reduction. ISO, 2010.
  • ISO 13849-1:2023: Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design. International Organization for Standardization, 2023.
  • Rockwell Automation 1756-RM012J-EN-P-2025: GuardLogix 5580 and Compact GuardLogix 5380 Controllers Safety Reference Manual. Rockwell Automation, 2025.
  • Rockwell Automation 1756-RM094N-EN-P-2025: Logix 5000 Controllers Design Considerations. Rockwell Automation, 2025.
  • Rockwell Automation 2198-UM002E-EN-P (2018): Kinetix 5700 Servo Drives User Manual. Rockwell Automation, 2018.

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