A jack-up barge is designed for the support of cranes, excavators and other equipment for nearshore construction, drilling and maintenance works in port and harbours.
The current ABH fleet size comprises eight jack-up barges with deck capacities ranging from 10t to 250t. All of ABH’s jack-up barges are of modular design for flexible and efficient solutions; the modular jack-up barges can be containerised and are easily mobilised anywhere in Oceania.
Due to the modular design, the jack-up barge comprises multiple standardised floating pontoons that are coupled together through a pin/connector system. Modules are sized to allow them to be transportable by road or containerised for sea (or road) transport into 20′ or 40′ ISO containers.
The jacking system is installed on each corner of the barge and uses an onboard hydraulic power pack to raise and lower the legs. Apart from operating the jacking system, the power pack services the hydraulic deck crane and there are spare hydraulic connectors to operate other deck equipment.
The jack-up barges do not have their own propulsion and require towing using a utility/ towage vessel.
The operation of a jack-up barge is different to the dumb or flat top barge in that the dynamics change once the barge deck is elevated above the water. The barge deck becomes isolated from the effects of wave, swell, tide and current; therefore providing a stable and level platform for crane operations to continue in conditions above those which may limit a floating barge solution.
The jack-up barges are fitted with spud legs that range from 12m to 36m in length, depending on which jack-up barge is used and in which configuration. A jack-up barge fitted with 36m spud legs can safely operate in the nearshore environment in water depths of up to 27m.
Spud legs are sectional and designed for ease of transport by land or sea. Typically, a 36m spud leg would comprise three sections of 12m. The longest spud leg element is 18m.
Parameters that require consideration when selecting a jack-up barge are:
- A desktop site assessment to review the key physical characteristics of the site such as water depth, currents, tidal range and maximum waves (environmental, meteorological, water depth, and wave height conditions).
- A loading assessment to produce the various load cases to reflect all of the scenarios when the jack-up barge is conducting its lifting duties.
- An estimation of the penetration of the spud legs into the seabed (sand = hard/ mud = soft).
- The operational air gap for the wave crests to safely pass beneath the hull of the elevated barge (with a margin of safety).
- The towing parameters of the jack-up barge when it has to be jacked down to relocate.
The calculation of the safe operational air gap is based on existing metocean data for the area and typical wave heights. Where wave heights can potentially exceed the safe working air gap (e.g. in the event of a cyclone), the project will adopt the “risk managed” approach and move the jackup barge to a sheltered location where a forecast could see safe operating limits exceeded.
When jacked down or in the floating condition, the towing conditions for jack-up barges can be reduced compared to normal dumb barges due to their shallow draft and higher centre of gravity (due to the weight of the spud legs above deck). Maximum parameters for a modular jack-up barge with the spud legs installed is a 1.5m wave height and maximum towing speed of three knots.
For longer open sea tows, a modular jack-up barge can be relocated onto a larger transport (dumb) barge for a dry tow or disassembled into its modules for transportation by road or barge.
Common applications for jack-up barges include (but are not limited to) crane and lifting duties, jetty maintenance, port construction, marine drilling and piling, vessel maintenance, bridge access and maintenance work in the oil and gas, civil, mining, and renewable energy industries.
The ABH jack-up barges have played an integral part in some of the major marine construction projects over the past few years such as:
- Lucinda Wharf repairs following Cyclone Yasi: Sea Lift 4 with a 150t crawler crane onboard assisted with the lifting of concrete panels, piles and equipment to enable repairs to the 5km long jetty structure.
- Hay Point Coal Terminal Third Expansion Project (HPX3): The Sea Lift 4 jack-up barge worked alongside GeoSea and the Walz Group as a support platform for the construction phase for the coal loading terminal.
- QCLNG Project (Curtis Island): John Holland used the Sea Lift 4 jack-up barge as a heavy crane platform to support the piling works for the new Module Offloading Facility (MOF) Wharf Construction project.
- Cape Lambert: Monadelphous recently chartered the Sea Lift 5 jack-up barge to assist with dolphin repairs at Cape Lambert. The 36m spud legs allow the barge deck to be elevated to the level of the dolphin so that workers can readily move between the dolphin and barge.
- Yamba Outfall Construction Project: Working with principal contractor Ledonne Constructions and HDD contractor Pipeline Drillers in 2016, the Sea Lift 6 jack-up barge assisted with the submarine section of the 1.65km Yamba outfall construction project.
Planning to use a barge
A lead-in period of a month is usually sufficient for ABH to conduct the initial desktop site assessment and the planning and execution of mobilisation. Barges are currently located in WA, NSW and Queensland but can be relocated depending on demand.
ABH can provide the complete marine package of personnel transfers and towage services if required, or have the client provide those services if that is more efficient.
The jack-up barge is supplied fully assembled at the client’s point of mobilisation, with ABH organising all trucking and cranes required for its assembly.
The size of the ABH fleet means that it can supply multiple jack-up barges if required to reduce program time (e.g. a shutdown) or reduce project overheads. Some projects have required three barges.
This article was originally published in the July/August issue of Cranes and Lifting.