Gantries remain versatile crane alternative
By Mark Lane07 May 2018
A gantry, telescopic hydraulic gantry or 4-point lift system is a convenient and often cost-effective alternative to a crane. Sometimes these machines are the only solution for a complex movement.
A gantry system consists of independent hydraulic units with telescopic columns of varying capacities, dimensions and operating heights. They can be utilized independently, in pairs or in greater numbers. A benefit of a hydraulic gantry is its versatility to develop a solution given the multiple ways it can be configured and interfaced with other components.
Standard capacities of gantries range from 15 tons up to 325 tons per unit. There are numerous options that can be integrated into a gantry system, such as self-propulsion, stroke monitoring, multiple extension stages, lift links and beam clamps. Self-propulsion can be through powered rollers, integrated with a skid system or another element. The propulsion system can also be utilized to facilitate installation/removal of the hydraulic gantry in to a tight space that would otherwise prevent assembly of the system due to support equipment access. With the links, there are numerous options and features that can be integrated such as self-propulsion by roller or skid to give full directional control of the system and the load being lifted.
For added capacity, multi-unit gantries can be used.
One advantage of a hydraulic gantry over a crane is its relatively small footprint. This advantage is particularly visible in congested brownfield units or inside structures such as nuclear power plants or buildings. The ability of gantries to work inside structures is a key feature of their versatility and functionality when compared to a crane. The assembly of the gantry benefits from its modular components which are relatively easy to handle but minimize integration time once assembled. The overall space requirements relative to lifting capacity are minimal and by design can offer a low hook to piece height requirement. This allows for lifting of large loads in tight spaces keeping required clearances and disruption to surrounding elements to a minimum.
Ground conditions play a vital role in the safety of both cranes and gantries. Both operations rely on the underlying surface to support the load being lifted and the equipment doing the lifting. This support comes not only in overall bearing capacity but also in limiting deflections.
While both a crane and gantry can do the job, the equipment weight for a gantry is significantly less and can accomplish a lift with lower ground bearing pressure (GBP). Furthermore, by having independent support legs, a gantry can work on surfaces that are not all equal. While each support area needs to be level for the gantry to operate, the respective elevations under each leg do not have to be equal thus allowing a gantry to work on different elevations that are not possible for a crane. It is also interesting from a ground preparation perspective that the prepared area for a gantry is often less than for a comparable crane.
A hydraulic gantry is rigged on tower supports.
By keeping the gantry separated into manageable components, it facilitates mobilization to site using a minimal number of trucks. It also minimizes the support equipment needed for loading and assembly ranging from a team of workers to a forklift.
Once on site, the integration of each individual component to form a complete system requires minimal time as the system is typically designed to have minimal interfaces between units to complete a system. This translates into a small amount of hose connections between units and the power pack and integrated attachment points at the top of the units to the gantry beams.
The largest portion of time spent in a hydraulic gantry setup should be on ground preparation and verification of a level surface to prevent side loading the system. Through the utilization of movement in both directions by accessories, a hydraulic gantry system can effectively operate as an overhead crane in certain applications.
In summary, hydraulic gantries are a great tool that can be utilized in a multitude of situations. Given the right job opportunity a hydraulic gantry can offer significant advantages over an all-terrain crane, rough terrain crane or a crawler crane in terms of initial cost, mobilization cost and time and lifting capacity. The gantry option can fill the void left between the two crane options by offering the lifting power of a crawler crane provided access with the speed of assembly offered by a mobile crane. The limits of potential uses for a gantry are seldom limited as it can even be utilized as a replacement for two cranes on a rolling or upending operation. The flexibility of the system when it integrates with other components lends itself well to the heavy lift industry and the custom solutions a project often demands.