INSTALLING 243 wire support feeder mast gantries above an operational rail required some careful consideration of process and logistics. The masts were of two types, 2,000 kg 7.5m tall masts with a 5m arm that overhangs the track and carries the cabling, and a straight mast of either 310 Universal Column (UC) or 250 UC with welded base plate weighing up to 800 kg. The masts were to be placed at 68m intervals along the 10.2 km stretch of line that runs from the north side of Broadmeadows in Melbourne to Craigieburn Station and stabling yard.
As Mick Denic, project organiser from Firstcall Constructions explains, “The weight was never a problem on this job; it was the distance away from the footing that presented challenges”. Firstcall are a Melbourne based company that has experience on a variety of lifting projects including work on the Craigieburn Bypass and more recently, beginning work on the Eastern Link Tollway.
There were also additional issues that complicated the project; these included a very narrow access track, which ran parallel to the outbound track. There were also environmental no go zones and other no go zones that were designed to protect shallow underground services such as water pipes and electrical conduits that ran parallel to the track. Space was also limited in which to assemble the 350 square hollow sections (SHS) that were needed to create the finished masts. Both inbound, and outbound train tracks were in use throughout the assembly and erection process.
Self-releasing sling
Project builders Thiess and Firstcall organised a flexible and adaptable work method and assembly plan whereby tube sections were delivered to a predetermined drop off (sometimes up to 1 km from the installation site), then transported by truck crane and bolted and assembled as close to the installation point as possible. All delivery and assembly was undertaken during weekday working hours. The installation of the masts was done over the weekends and outside of ordinary working hours to minimise disruption to the rail network. Thiess shut down two of the tracks, leaving only the country and freight lines operational during installation and a rail spotter (as opposed to a train spotter) was provided for all works to ensure OH&S compliance.
Without the direct ability get to, or over the tracks, it was not possible to use scissor lifts or boom lifts to gain access to and release the slings once the masts had been lifted into place. Firstcall therefore developed a self releasing sling that could be used. This consisted of a long rope attached to where the slings were choked around the load. After the load was released, the rope could be pulled in the opposite direction to release and pull the slings down. The self-releasing sling greatly increased installation speeds. The majority of the lifting has been carried out by Firstcall’s 20t Kato mobile slewing crane with a crew of three riggers and in this set up, they have been able to install up to 15 masts a day. On occasions, due to time restraints and to keep project costs down, Firstcall brought in their 20t and 30t Tadano mobile cranes and using two rigging crews they were able to double that capacity to 30 masts a day.
The weather was an unwanted complication to the progress of the project. “We were bogged down a few times with our vehicles and the truck crane but luckily not the cranes,” says Denic. “We lost two weekends of installations due to muddy conditions. Thiess helped by having a front loader spreading crushed rock in the worst affected places.”
Without counterweights
The section of rail between Tawonga Street and Barry Road, Dallas presented significant challenges for the team due to a large environmentally sensitive site and an underground service no go zone. To place the masts on the footings on this stretch required Firstcall to lift over the restricted areas. To do this, they hired a Grove 130t mobile slewing crane from Independent Cranes. Used without counterweights, it still had a 45t capacity which was more than adequate. The crane gave the crews the ability to reach the 40m required over the sensitive area to place the masts. The company’s recently acquired LW-160 rough terrain crane also came in handy to reach one particular mast site near the Aitken Creek Bridge. Due to the topography of the site, there was no means of alternative access.
“The LW-160 was used mainly because of its all wheel drive and steering capabilities,” says Denic, “Its high wheel base meant we could drive it up and over the train tracks. It was the perfect crane to use in this particular case.” The LW-160 was driven, straddling the track, from the closest point of access, carrying the required mast for installation. “Overall it was a very challenging project,” says Andrew Scott, managing director of Firstcall. “It also highlighted our team’s professional approach and ability to work with builders as well as our willingness and flexibility to handle any given situation.” The $53 million Craigieburn Rail Project is on target for completion in late 2007.
Source: Construction Contractor