Heavy Lift Systems

Heavy lift systems are hydraulic lifting and moving systems used for loads that are too heavy, too large or too awkwardly placed for cranes. The main families are strand jacks, which lift or lower loads on bundles of steel strands; hydraulic gantries, which lift loads between telescopic legs; skidding systems, which slide loads horizontally on tracks; and jack-up or climbing systems, which raise loads in steps from below. They are often combined with each other and with self-propelled modular transporters to lift, move and place a single component weighing hundreds or thousands of tonnes.

Unlike cranes, most heavy lift systems are not complete machines that drive to site. They are kits of jacks, power packs, beams, tracks and control systems, assembled around a specific project and often engineered for it. They are used in bridge construction, power generation, oil and gas, shipbuilding, offshore decommissioning and industrial plant construction, and are operated mainly by specialist heavy lift contractors.

Brief History of Heavy Lift Systems

Moving heavy objects with jacks, rollers and skids is an ancient technique, and hydraulic jacks were used for heavy engineering work from the nineteenth century onwards. The modern heavy lift industry grew from the 1960s and 1970s, when larger power stations, refineries and offshore platforms created demand for lifting single pieces far beyond the capacity of the cranes of the time.

Strand jacks were developed from post-tensioning technology for concrete. Their development is generally credited to engineers at VSL in Australia in the late 1960s, who adapted the jacks and strands used to tension concrete structures for lifting. Computer-controlled systems later allowed many jacks to work in synchronisation. Well-known applications include the erection of the London Eye in the late 1990s and the raising of the Russian submarine Kursk from the Barents Sea in 2001, when a large array of strand jacks mounted on a barge lifted the hull. Hydraulic gantries, first used in industrial rigging for machinery installation, grew into much larger systems from the 1980s and 1990s. Skidding systems developed alongside, driven by offshore and plant construction.

How Heavy Lift Systems Work

All heavy lift systems use hydraulic power, but each works in a different way.

Strand jacks. A strand jack is a hollow hydraulic cylinder with a bundle of steel strands passing through it. Clamping wedges at the top and bottom grip and release the strands in turn as the cylinder extends and retracts, pulling the strands and the load up step by step. Reversing the sequence lowers the load. Strand jacks are mounted on a support structure, such as a tower, a gantry or the top of a building, or used horizontally to pull loads.
Hydraulic gantries. A hydraulic gantry has two or four telescopic legs that extend hydraulically and support a header beam. The load hangs from the beam and is raised as the legs extend. Most gantries run on tracks, so the lifted load can be moved horizontally and set down in its final position.
Skidding systems. The load rests on skid shoes that slide along steel tracks, usually on low-friction pads. Hydraulic push-pull cylinders move the shoes along the track in steps. Skidding is used to move heavy structures horizontally over short distances.
Jack-up and climbing systems. Hydraulic jacks lift the load a short distance, and packing or towers are built up beneath it before the next stroke. The load climbs gradually to the required height.
Control systems. Computer control synchronises dozens of jacks or cylinders, monitoring loads, strokes and levels to keep the lift even and within limits.

Types of Heavy Lift Systems

Strand Jack Systems

Used for vertical lifting and lowering, and for horizontal pulling. Individual jacks range from small units to capacities of well over 1,000 tonnes, and systems combine many jacks for very heavy loads.

Hydraulic Gantries

Used for lifting and moving loads in plants, buildings and tight spaces. They range from compact systems for machinery installation to large gantries for transformers, reactors and bridge sections.

Skidding Systems

Used to slide heavy loads along tracks, such as bridge spans, offshore modules, transformers and building sections.

Jack-Up and Climbing Systems

Used to raise loads or structures incrementally, including roofs, tanks and heavy modules. Climbing jacks can also raise heavy loads along a rod or column.

Combined Systems

Many projects combine several systems: strand jacks on towers for lifting, skidding tracks for positioning and self-propelled modular transporters for transport between locations.

Capacity Ranges

System	Typical capacity range	Typical use
Hydraulic gantries	about 50 to 1,000 t and more	Machinery, transformers, plant components
Strand jacks (per jack)	about 15 to over 1,000 t	Vertical lifts, lowering, pulling
Strand jack systems	up to many thousands of tonnes	Bridges, roofs, offshore modules
Skidding systems	from about 100 t to many thousands of tonnes	Horizontal moves of heavy structures

Figures are indicative. System capacity depends on configuration, number of units and support structures.

Ancillary Equipment

A heavy lift system is more than its jacks. Hydraulic power packs supply oil to the cylinders, while strand recoilers or guides manage the strands above the jacks. Lifting lugs, trunnions and spreader frames transfer loads into the structure. Load cells and pressure sensors measure the load at each point, and laser or inclinometer systems track levels and alignment. Tracks, packing and cribbing distribute loads into the ground or structure, and temporary towers or beams provide the support points needed to jack or lift from.

Main Manufacturers and Contractors

Enerpac, with strand jacks, hydraulic gantries, skidding and jack-up systems.
Dorman Long Technology, a specialist in strand jacks and heavy lifting systems.
VSL, one of the pioneers of strand jack technology.
J&R Engineering, an American manufacturer of hydraulic gantries.
Hydra-Slide, a specialist in skidding systems.
Mammoet, Sarens and Fagioli, heavy lift contractors that design and operate such systems.

Main Uses of Heavy Lift Systems

Bridge construction, including lifting and sliding spans into position.
Installation of transformers, generators, reactors and turbines.
Lifting roofs and large structures in buildings and stadiums.
Offshore module load-out, installation and decommissioning.
Shipbuilding and ship salvage.
Relocation of historic and industrial buildings.

Planning a Heavy Lift

Engineering first. Heavy lifts are engineered operations. Loads, centres of gravity, support structures and ground conditions must be calculated and checked.
Choose the right method. Where a crane cannot reach, cannot be assembled or would be oversized, a jacking, gantry or skidding solution can be simpler and more precise.
Support structures. Towers, beams, foundations and the structure being lifted must carry the concentrated loads from jacks and gantries.
Synchronisation and monitoring. Computer control and load monitoring keep loads balanced. Manual systems are limited to simpler lifts.
Time and weather. Strand jack lifts can be slow, but they are less sensitive to wind than crane lifts. Offshore and outdoor lifts still need weather windows.
Specialist contractors. Complex heavy lifts are usually carried out by experienced contractors with in-house engineering.

Safety

Heavy lift operations involve extreme loads, so safety depends on engineering, planning and discipline. Main hazards include structural failure of supports, uncontrolled load movement, hydraulic failures, uneven loading and people entering exclusion zones. Lift plans and method statements define every step, and loads must be monitored throughout. Strand jacks have mechanical clamping systems that hold the load if hydraulic pressure is lost, while gantries and jack-up systems use locking and packing to keep the load secure. Only trained crews should operate the systems, and clear communication between the lift supervisor, the operators and the client is essential.

Trends and Technology

Heavy lift systems are becoming more capable and more automated. Wireless controls, real-time monitoring and digital lift planning allow very large arrays of jacks and cylinders to be controlled from a single station. Modular systems that can be reused in different configurations reduce costs. The growth of offshore wind, modular construction and large infrastructure has increased demand for heavy lifting and skidding. Contractors are also combining heavy lift systems with self-propelled modular transporters and ring cranes in integrated solutions for moving entire structures.

Key Terms

Strand jack: a hollow hydraulic jack that lifts or lowers a load by gripping steel strands.
Hydraulic gantry: a lifting system with telescopic legs supporting a header beam.
Skidding: moving a load horizontally on tracks using hydraulic push-pull cylinders.
Jack-up: lifting a load in steps with jacks and packing.
Synchronous lifting: computer-controlled operation of many jacks to keep a load level.
Load-out: moving a heavy structure from shore onto a vessel or barge.

Frequently Asked Questions

When is a strand jack used instead of a crane? When the load is extremely heavy, when a crane cannot fit or reach, or when a very slow and precise lift is needed, such as for bridge spans or large roofs.

How much can a strand jack lift? Individual jacks range from about 15 tonnes to over 1,000 tonnes, and many jacks can work together to lift loads of thousands of tonnes.

What is a hydraulic gantry used for? It lifts and moves heavy loads in confined spaces, such as installing transformers, presses and machinery inside buildings.

Can heavy lift systems move entire buildings? Yes. Skidding, jacking and transporter systems have been used to move bridges, industrial structures and historic buildings.