The Shark Link gantry system overcomes space and time constraints

The Shark Link heavy lift gantry extension system was born out of a need to overcome space and time constraints on a major energy project in the USA. Steve Sparrow, co-designer of the system, explained it to Alex Dahm.

In October 2009 Bay Crane Service was awarded a contract to install a steam generator and turbine system at the US$1.3 billion Astoria Energy II project in New York, USA. The 575 MW gas‐fired power generation project started commercial operation on 1 July.

Expectation during the bidding process was that Bay would use a traditional hydraulic telescopic gantry and strand jack setup to install the components on the 40 foot (12 metre) high foundation. After the job was awarded, however, Bay was informed that the HP turbine would need to pass over the 3 foot 6 inch (1,067 mm) IP turbine lower shell, and under the turbine building's overhead crane rail that was scheduled to be installed weeks before the steam generator and turbine components.

This left an "opening" of only 25 feet (7,620 mm) to pass through. Using strand jacks, the minimum height would need to be 35 feet (10.67 m) or more. Staging the turbine and reconfiguring to a gantry-only configuration to reduce headroom would have added at least a month to the schedule. This was unacceptable to the client.

To help engineer a cost-effective solution Kenneth Bernardo, Bay Crane Service president, discussed alternatives with Texas-based heavy lift and transport planning specialist, HLI Consulting. John Derrick, Shark Link design engineer and partner at HLI, says, "We understood the main goals were to utilise as much of Bay's existing equipment as possible, while finding a low-headroom alternative to strand jacks."

After several days of "napkin sketching", the basic outline of a system of removable lift links was developed. With Bay Crane's approval, HLI moved forward with the design and began preparing support calculations and fabrication drawings.

As part of the design process, HLI prepared a three-dimensional computer animated simulation of the system. This ensured the interaction of the components and that the structures did not interfere with each other. It was also useful in communicating to the end client how the system would work.

Fabrication began in January 2010 and continued until the complete system was assembled for function testing in early March.

Erection at site began on 2 April and the first lift of the 180,000 pound (82 tonne) LP Turbine lower shell was completed two weeks later using just two legs of the gantry system. "The system operated flawlessly and, as the crew of five became more familiar with it, cycle times dropped from 10 minutes to three," explains Steve Sparrow, director at HLI and Shark Link co-designer. Total time from trailer to rough set was 2 hours 50 minutes.

For the HP turbine and steam generator the two additional gantry legs were incorporated, giving a capacity of 500 tonnes. The 372,500 pound (168,963 kg) HP turbine was raised, and cleared the overhead obstruction by 9 inches (229 mm). The 682,800 pound (309,713 kg) steam generator was the final lift, and was completed in less than two hours.

Despite being designed to overcome a specific site limitation, Sparrow says the Shark Link system demonstrated several benefits over a traditional strand jack system:

Simplicity. The system can be assembled and operated by any crew with hydraulic gantry experience. No specialized knowledge is needed.

Reliability. The system requires no electronics or complex components to operate.

Durability. The system is unaffected by harsh operating conditions (dust or rough handling) both in operation and storage. The system is available containerised for easy shipping.

Cost. The entire system costs less than an equivalent strand jack setup, and has no consumable or operating costs.

Safety. Unlike strand jacks, the system is fail-safe. It is positively engaged at all times, and issues such as strand release through insufficient load are eliminated.

"Since the system was so well received during its first project, we knew we had to offer it as either a complete system or as an accessory for those already owning a hydraulic gantry system," Sparrow says. The Shark Link system will work with any hydraulic boom gantry and different capacity versions are available, Sparrow says.

"We entered into a manufacturing and marketing agreement with J&R Engineering to produce the Shark-Link Heavy Lift System worldwide, and are now offering 250, 500 and 800 tonne capacity models. The response from US rigging companies has been overwhelmingly positive and, due to its simplicity and ruggedness, we expect a similar response from Middle-Eastern and Asian clients," Sparrow continues.