Slew ring bearings are central elements in drive and joint technology. They carry loads, enable rotational and pivoting movements, and protect adjacent components from wear. In the context of concrete demolition, special demolition, rock excavation, and tunnel construction, bearing points are often exposed to alternating impact loads, dust and moisture exposure, as well as vibration. Tools such as concrete pulverizers, hydraulic demolition shears, steel shears, or multi cutters feature highly loaded pivots with pins and bushings; rock and concrete splitters rely on precisely guided hydraulic components. Appropriate bearing selection, assembly, and care are therefore crucial for safe, efficient, and economical operations.
Definition: What is meant by slew ring bearings
A slew ring bearing is understood to be a technical component that guides, supports, and keeps shafts, pins, piston rods, or entire joint connections movable. It reduces friction, limits play, and accommodates radial, axial, or combined loads. Basically, we distinguish between rolling bearings (with rolling elements such as balls or rollers), plain bearings (surface-supported friction pairs, often as a bushing), and spherical plain bearings (spherical bearings for pivoting movements and misalignment). In demolition tools, pivoting bearing points with bushings and hardened pins are common, while precise rolling bearings are frequently used in power units and motor-pump units. The term is occasionally used in everyday site language for parking or storage areas for machines; technically correct, however, it refers to the component for supporting moving parts.
Types and designs of slew ring bearings
The choice of bearing design depends on load case, type of motion, environmental influences, and maintenance strategy. In demolition and cutting applications, robust, dirt-resistant, and easy-to-maintain solutions have proven effective.
Rolling bearings
- Ball bearings: universal, for moderate loads and speeds. More commonly found in electric motors and pumps of power units.
- Roller bearings (cylindrical, tapered, or spherical): high load ratings, suitable for shock loading; common in drives and gearboxes, less so on open pivots of shears.
- Needle bearings: slim design where installation space is limited; sensitive sealing and lubrication management required.
Plain bearings and bushings
- Metal-polymer bushings (e.g., PTFE- or POM-based): low maintenance, good emergency running properties, insensitive to dirt; often used on pin joints of concrete pulverizers and combination shears.
- Sinter bronze/bronze bushings: load-bearing, good heat dissipation, suitable for oscillating movements and slow rotations.
- Steel/steel or hardened bushings: very robust under high surface pressure; require consistent lubrication and effective sealing.
Spherical plain bearings and pivot bearings
- Spherical plain bearings: compensate misalignment, accommodate combined loads; predestined for scissor arms, crusher heads, and cylinder mountings.
- Maintenance-free spherical plain bearings with special sliding layer: suitable where lubrication points are hard to access and in dusty environments.
Axial, radial, and combined bearing arrangements
- Radial bearings: carry forces acting transverse to the axis, e.g., pivots of tool arms.
- Thrust bearings: take up forces along the axis, such as in pressing and clamping mechanisms.
- Combined arrangements: unite both directions, important with obliquely loaded tool heads.
Requirements in concrete demolition, rock excavation, and tunnel construction
Demolition and extraction work generate alternating, impact-type loads, vibrations, and abrasive contamination. Bearings here must:
- Accommodate impact and edge loads, e.g., when concrete pulverizers grip or when steel shears are applied.
- Resist dirt, mud, and drill cuttings; robust sealing and suitable lubricants are essential.
- Minimize corrosion due to moisture, splash water, and potentially chloride-laden environments.
- Consider thermal effects, for example in cutting torch operations on tanks or under intensive continuous load.
- Withstand oscillating movements with small angles without damage (micro-movements promote scoring).
In rock and concrete splitters, precisely guided hydraulic components are used: guide bands, sliding and sealing elements in cylinders ensure exact piston motion and pressure tightness. Bearing points on grippers, wedge, and spreading units are subject to high surface pressures; the material pairing and surface hardness of the pins are critical factors.
Selection criteria for bearings on demolition tools
- Load profile: static, alternating, impact; radial/axial components and peak loads.
- Type of motion: rotation, pivoting, oscillation; pivot angle and frequency.
- Installation space and weight: slim solutions (e.g., needle bearings) vs. massively loadable bushings.
- Lubrication concept: maintenance-free vs. relubricable; access to grease fittings in operation.
- Sealing strategy: sealing against concrete dust, water, and particles.
- Material pairing: hardened pin with coated bushing, metal-polymer, bronze, stainless steel.
- Assembly and service: pressing in and out of bushings, replaceable sleeves, field repair.
- Service life estimation: under real duty cycles, temperature, vibration, and contamination.
Design and assembly: fits, tolerances, preload
Designing appropriately for the bearing significantly increases service life. Interference fits, chamfers, alignment, and surface hardness are as important as a lubrication and sealing concept tailored to the bearing arrangement.
Fit recommendations (general)
- For bushings in housings: usually a light interference fit for secure fixation and heat dissipation.
- For pins in bushings: clearance fit for lubrication-friendly pivoting without edge loading.
- Check alignment and parallelism to avoid uneven load distribution.
Specific fits depend on bearing make, load, and temperature and should be coordinated in the design.
Pins and bushings in crushers and shears
At the pivots of concrete pulverizers, combination shears, multi cutters, and steel shears, hardened pins with wear-resistant bushings are common. A generous lubrication groove geometry and dust sealing reduce scoring and galling. Axial play is limited by shims or shoulders; the axial mounting of cylinder rod ends is often implemented using spherical plain bearings.
Lubrication, sealing, and maintenance
The right lubrication strategy is a primary lever for service life and energy efficiency.
- Lubricants: high-pressure greases (EP additives), NLGI grade suited to ambient temperature; with water exposure, corrosion-protective greases.
- Relubrication intervals: dependent on duty; more frequent under heavy load and dust than in pure rotary motion.
- Seals: lip and labyrinth seals, wipers; keep protective caps on grease fittings clean.
- Cleanliness: clean grease fittings before greasing to keep abrasive particles out.
Maintenance-free bearings are an option at hard-to-reach points. They still require visual inspection, as dirt, moisture, and overload can also cause damage there.
Wear patterns, diagnostics, and repair
Early detection of typical damage patterns prevents consequential damage to tool arms, cylinder eyes, and mounts.
- Scoring and galling: indicate insufficient lubrication or dirt ingress.
- Pitting and spalling: material fatigue, often in rolling bearings under shock loads.
- Brinelling/impressions: due to shock loading at standstill.
- Excessive play: wear on bushings/pins; pivot accuracy decreases.
- Corrosion: moisture influence; promotes fit loosening.
Test methods
- Visual and tactile inspection of bearing points, check seal lips and wipers.
- Measure radial and axial play, document over the service period.
- Observe temperature and noise on rotating units (e.g., power unit).
- Analyze lubricating grease for particles and moisture as an indication of internal wear.
With advanced wear, rebushing (replacing the bushings) and replacing worn pins are common. Rolling bearings in units should be replaced preventively according to manufacturer specifications.
Slew ring bearings in the power unit and in cylinders
Power units contain bearings in motors and pumps. These rolling bearings operate at high speeds and require clean oil, correct alignment, and vibration tolerance. In hydraulic cylinders—as used in rock and concrete splitters as well as concrete pulverizers—guide rings and sliding bearings support the piston rod and piston, limit radial forces, and prevent metal-to-metal contact of moving components. An intact sealing chain with wipers prevents dirt ingress and extends the service life of the bearing arrangement.
Practical examples from the application areas
In concrete demolition and special demolition, the pivot bearings of concrete pulverizers are particularly stressed: short, highly dynamic cycles when gripping and crushing, often in dusty environments. In building gutting and cutting, lateral forces act on combination shears and multi cutters, requiring a combined bearing design. In rock excavation and tunnel construction, finest particles and moisture promote abrasive wear, which is why seal packs and robustly coated sliding surfaces offer advantages. In natural stone extraction, clean lubrication and low-corrosion materials support reliable guidance of splitting cylinders. In special operations—for example underwater or in contaminated areas—the resistance of bearing materials to media and sealing against fine dust or liquids is crucial.
Terminology distinction: bearing as a component vs. bearing as a storage area
In site jargon, “slew ring bearing” can also refer to the parking or logistics area for machines and tools. Technically correct here, the term stands for the component for supporting moving parts. For site organization, however, an orderly, secured storage area is relevant to protect tools such as concrete pulverizers, rock and concrete splitters, cutting torches for tanks, or steel shears from damage and contamination and to ensure accessibility for maintenance (e.g., lubrication points).
Safety, standards, and documentation
Safe operation depends on proper assembly, regular inspection, and documented maintenance intervals. Service-life and load-capacity data from bearing manufacturers are based on test and calculation principles; in real-world use with shock loads, dirt, and vibration, deviations can occur. Test certificates, tightening torques, and assembly records should be maintained carefully. Legal requirements and standard references are context-dependent; safety-relevant decisions must always be aligned with the relevant technical documentation and generally accepted engineering practice.
Sustainability and life extension
With suitable material pairings, coated surfaces, effective seals, and a consistent lubrication strategy, downtime and spare parts demand can be reduced. Replaceable bushings, reusable pins after inspection, and planned maintenance reduce resource usage. Clean bearing points and corrosion protection measures contribute to availability and value retention of tools and units.
Practical checklist
- Analyze load profile and type of motion (pivoting, rotation, oscillation).
- Define bearing design (plain, rolling, or spherical plain) including sealing concept.
- Determine material pairing and surface hardness of pin/bushing.
- Define fits and assembly sequences; plan pressing in and out.
- Set lubricant, intervals, and accessibility of lubrication points.
- Document inspection points and limits for play, temperature, and noise.
- Align spare parts and overhaul strategy with operating conditions.