A pipeline construction crew in Kazakhstan was laying 48-inch diameter gas pipe through clay-heavy soil in autumn conditions. The CAT PL87 pipelayer’s sideboom was carrying a 7-metre pipe section (weight: approximately 9 tonnes) when the operator noticed the boom drifting slightly to the load side under a static hold. Investigation found that the counterweight mounting rubber on the load side had partially failed — the counterweight, which provides the structural counterbalance to the boom load, was no longer in its correct position. The drift was minor (less than 50 mm) but on a lift of this mass, even small changes in counterbalance geometry affect stability margins. The boom was lowered immediately and the machine taken out of service. Counterweight rubber replacement cost: $220. The alternative — a counterbalance failure during a loaded lift — doesn’t bear calculation.
Pipelayers are specialized tracked machines derived from the bulldozer platform, fitted with a cantilevered side boom crane and a counterweight system to carry and lower large-diameter pipe sections into trenches. The rubber components in pipelayers serve both the standard bulldozer mechanical functions and the specialized lifting safety systems that make pipelayers unique.
This guide covers the rubber parts for the two dominant pipelayer platforms: Caterpillar (PL61, PL72, PL87) and Komatsu (D355C-3), plus the older D8/D9-derived Komatsu D355 series.
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Sideboom and Counterweight System Rubber
The pipelayer’s defining feature — the side boom and counterweight system — requires rubber components in positions that don’t exist on any other machine.
Counterweight Mounting Rubber
The counterweight (typically 8-20 tonnes) is mounted to the opposite side of the boom to balance pipe loads during lifting and lowering operations. The counterweight attaches to a sliding or pivoting frame through rubber isolation cushions that:
- Absorb shock loads when the counterweight shifts position during machine travel (many pipelayer designs allow the counterweight to be pulled inward for transport)
- Prevent metal-on-metal impact when the counterweight reaches the end of its travel
- Distribute the counterweight’s load across the mounting contact points
The Kazakhstan case above illustrates the safety consequence of counterweight mounting rubber failure. These rubber elements are load-bearing components in a lifting safety system — their specification and maintenance criticality is equivalent to load-bearing hardware, not a standard vibration isolation component.
Counterweight mount specifications:
– Shore A: 60-70 (firm enough to maintain counterweight position accurately; compliant enough to absorb travel impacts)
– Compound: NR or NR/SBR with heat resistance for operation in Central Asian and Middle Eastern climates
– Fatigue life: Specified for 100,000+ counterweight movement cycles
Boom Heel Rubber Cushions
The sideboom attaches to the machine frame at its heel (inner end) through a pivot point with rubber cushion elements. These cushions:
- Allow the boom to pivot slightly under varying load conditions
- Absorb shock loads when the boom encounters off-center loading (pipe sections being lowered onto uneven pipe saddles)
- Prevent boom heel contact stress from concentrating at hard contact points
Boom heel rubber replacement requires removal of the boom and its load-handling hardware — a full maintenance task typically done at major overhaul intervals (5,000-8,000 hours).
Hook and Sheave Block Rubber
The pipelayer hook block uses rubber isolation mounts in the swivel bearing to:
– Allow the pipe sling to rotate freely during positioning without transmitting swivel binding to the boom
– Seal the swivel bearing against contamination from the construction environment
Undercarriage: Derived from Bulldozer Platform
Pipelayers use the same tracked undercarriage as equivalent bulldozers — the CAT PL87 is based on the CAT D8 platform, the PL61 on the D6 platform. The rubber undercarriage components are therefore identical to their bulldozer equivalents.
Final Drive and Track System Rubber
For detailed specifications on bulldozer-derived undercarriage rubber — including Duo-Cone O-rings, track pad rubber, and equalizer bar bushings — see our comprehensive bulldozer rubber parts guide for CAT and Komatsu.
The key pipelayer-specific undercarriage consideration: pipelayers often work in wet, clay-heavy trench environments that are more contaminating to final drive seals than typical dozer work. Inspect Duo-Cone seals on pipelayers at 2,500 hours (versus 4,000 hours on a dry-work dozer) when working in water-saturated soil conditions.
Track Rubber Pads
Pipelayers, like bulldozers, can be fitted with rubber track pads for work on paved surfaces or near finished pipe welds that must be protected from steel track damage. Track pad rubber specifications are identical to bulldozer equivalents for each platform.
Engine and Powertrain Rubber
Engine Mounting System
The CAT PL87 uses the Cat C18 engine (397 kW). Engine mount specifications are identical to the CAT D8T bulldozer on which the PL87 is based. For detailed CAT D8 engine mount specifications including compound requirements and part references, see our bulldozer rubber parts guide.
Pipelayer-specific engine mount consideration: pipelayers often work with the machine in a tilted attitude (following the slope of the trench bottom to position the boom optimally). Engine mounts see asymmetric loads under this tilted condition — the load distribution shifts from nominal as the machine tilts. This creates one mount working at higher-than-nominal load, which shortens the life of that specific mount. Rotating inspection can catch asymmetric wear early.
Torque Converter and Transmission Mounts
The power-shift transmission and torque converter in the PL87/PL61 are mounted using the same rubber arrangements as the equivalent bulldozer models. The Komatsu D355C uses a similar power-shift arrangement with NR compound transmission mounts.
Cab Isolation: Pipelayer-Specific Challenges
Pipelayer cab isolation faces a unique requirement not present in regular bulldozers: the operator must have clear visibility of the pipe being lowered while remaining in a comfortable, vibration-attenuated cab. Some pipelayer cabs are laterally offset or use additional windows/cameras to provide boom visibility — these configurations can affect cab center of gravity and therefore cab mount loading distribution.
Cab Mount System for CAT PL-Series
The CAT PL87 cab uses the same ROPS cab mounting system as the CAT D8T, with four-point isolation. However, the cab viewing additions (boom visibility camera mounts, additional displays) add weight that can alter the front/rear load distribution on the cab mounts.
When adding operator assist technology (camera systems, boom load monitoring displays) to older pipelayers, verify that the new equipment weight doesn’t push the front cab mounts above their rated load. If it does, the front mounts require replacement with higher-rated equivalents.
Komatsu D355C Cab Design
The Komatsu D355C uses a modified cab compared to its D355A bulldozer ancestor — the cab is designed with visibility to the boom side as a priority. Komatsu’s D355C cab mounts are softer than D355A equivalents because the lighter cab structure (more glass area, less structural steel) requires softer mounts to achieve the same natural frequency isolation target.
Hydraulic System Rubber for the Lift System
The pipelayer boom and hook are hydraulically controlled. The hydraulic system rubber components include:
Winch Motor and Gear Seals
The pipelayer winch motor drives the boom hook cable. The motor seals must handle:
– Hydraulic pressure during load lowering (typically 160-210 bar)
– Holding load pressure when the hook is stationary under load (sustained static seal loading)
– Cyclic pressure during lift/lower operations
The sustained static seal loading during the pipe hold phase (which can last many minutes while welds are inspected or pipe is positioned) is more demanding on seal elastomers than cyclic loading — compression set resistance is the critical compound property.
For detailed guidance on anti-vibration mount selection including principles applicable to pipelayer lift system isolation, see our mining equipment vibration isolation guide.
Safety Considerations for Rubber Component Maintenance
Pipelayers are lifting machines. Several rubber components are integral to the safety of lifting operations:
- Counterweight mounting rubber: Failure can compromise boom counterbalance geometry
- Hook block swivel seals: Failure creates binding that can create unexpected side load on the lift line
- Boom heel cushions: Failure can allow boom deflection outside design parameters
For these safety-critical components, the standard should be:
– Shore A hardness testing at each annual service
– Visual inspection before every operational period
– Zero tolerance for visible rubber-to-metal bond separation
Non-critical rubber components (engine mounts, track pads, cab mounts) follow standard condition-based maintenance.
Babacan Group manufactures pipelayer rubber components under ISO 9001:2015 quality management with full traceability documentation suitable for lifting equipment service records. Our range covers CAT PL61, PL72, PL87; Komatsu D355C; Liebherr RL-T series pipelayers. Browse our rubber parts catalog or request a technical quote.
Replacement Intervals
| Component | Criticality | Interval |
|---|---|---|
| Counterweight mounting rubber | Safety-critical | Annual inspection + 3,000 hrs or on condition |
| Boom heel cushions | Safety-critical | Annual inspection + 5,000 hrs |
| Final drive Duo-Cone O-rings | High | 2,500 hrs (wet soil) / 4,000 hrs (dry) |
| Engine mounts | Standard | 4,000-6,000 hrs |
| Cab isolation mounts | Standard | 3,000-5,000 hrs |
| Track pads (road work) | Wear item | Condition-based |
| Winch motor seals | Standard | 4,000 hrs or annual |
Conclusion
Pipelayers share their mechanical foundations with bulldozers but add safety-critical rubber components in the boom and counterweight system that have no equivalent in other equipment. Managing these components requires the same rigor applied to lifting gear — documented inspection records, Shore A hardness testing, and zero tolerance for visible degradation in load-path rubber elements.
Key takeaways:
– Counterweight mounting rubber is a safety-critical lifting component — treat it accordingly
– Undercarriage rubber follows bulldozer specifications; consult the bulldozer parts guide for details
– Wet trench environments require shorter final drive seal inspection intervals than dry-work equivalents
– Tilted machine operation (following trench grade) creates asymmetric engine mount loading — inspect for uneven wear
Babacan Group ships pipelayer rubber parts to pipeline construction contractors and equipment dealers in 84+ countries. Request a quote for your CAT or Komatsu pipelayer model.