8-Ton Telescopic Cantilever Assembly Rig for Vessel Fabrication | Hai Phong, Vietnam

Resolving the cantilever deflection of dynamic extension decks while holding an 8-ton working payload required a rigid mechanical synchronization backbone and heavy telescopic framing. Engineering this vertical assembly lift platform around a four-screw mechanical transmission, motorized ball-screw cantilever decks, and multi-tier interlocked access pathways eliminated elevation racking and platform drift. The mechanical drive margins, deck leveling tolerances, and cantilever structural deflections met verified acceptance criteria under a 22,000 lbs (10,000 kg) factory proof-load test prior to shipment.

• 4-Column Synchronized Screw Drive & Heavy Mechanical Shaft Coupling: Platform elevation is driven by four heavy-duty precision lifting screws (Ø90 mm shaft diameter, self-locking low-pitch trapezoidal threads) housed inside 250 × 250 × 10 mm corner structural steel box columns. The four column drives connect through heavy-wall cross-connecting torque tubes and spiral bevel gearboxes powered by top-mounted electric gearmotors with integrated electromagnetic disc brakes. Shop laser tracker verification under a full 125% proof load capacity (10,000 kg / 22,000 lbs proof weight blocks) demonstrated that diagonal elevation deviation across the 6500 mm stroke remained below 0.8 mm under the rated 8000 kg dynamic assembly payload, eliminating nut racking and thread galling.

• Motorized Telescopic Extension Deck on Heavy Linear Profile Rails: Horizontal cantilever reach relies on an onboard motorized telescopic extension deck powered by heavy-duty linear electric ball-screw actuators. The 1000 mm cantilever extension modules traverse induction-hardened profile linear guide rails recessed into the platform floor framework. Under full tool and personnel loading on the cantilever lip, dial indicator measurements recorded maximum edge deflection at 2.2 mm. The rigid dual-web beam geometry eliminates slide pinching, permitting motorized extension and retraction under full load.

• Multi-Tier Interlocked Access Stairs with Intermediate Rest Landings: Safe technician transit between floor grade and 6500 mm elevations without ladder climbs relies on an integrated multi-tier access staircase equipped with intermediate rest platforms, ensuring no single stair flight exceeds the 3000 mm vertical rise limit mandated by ISO 14122-3:2016. Fabricated from precision-machined stringers and slip-resistant grating, the staircase provides an ergonomic 45-degree incline. Digital inclinometers confirmed that each tread maintained horizontal level within $\pm$0.5°, while full-height wire mesh enclosures isolate climbing personnel from vertical drive components.

• Zero-Drift Mechanical Screw Holding for Optical Alignment: Eliminating vertical platform drift during prolonged bolting and laser metrology sequences was achieved through direct-drive mechanical screw gearing. Unlike hydraulic cylinders vulnerable to valve bleed and thermal fluid contraction, the positive screw-thread geometry provides zero-drift mechanical screw holding. Dial indicators measured 0.0 mm of elevation creep across continuous 8-hour static hold tests under full 8000 kg payload, locking in a steady multi-tier ergonomic positioning height for precision optical boresight instruments.

• Expanding Telescopic Guardrails & Continuous Fall-Arrest Cable: Fall prevention incorporates a tubular sleeve-in-sleeve telescoping handrail design along moving deck sections. As the cantilever decks stroke outward, perimeter handrails expand to maintain an unbroken perimeter barrier without opening fall gaps per ISO 14122-2:2016. Spanning the entire platform, an overhead rigid rail with a sliding trolley allows fitters to tether five-point harness lanyards without unhooking, ensuring 100% tie-off compliance across both fixed and extended sections.