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Bigge’s Lift Tower System meets challenge of congested refinery upgrade
October 2008: With escalating fuel prices shining a spotlight on energy issues in this election year, it may surprise some to read that not a single new grass roots refinery has been constructed in the U.S. for 30 years. Instead, the desperately needed added capacity is being created by erecting new refining units within existing facilities. This simplifies the often contentious permitting process, but brings with it technical challenges in shoe-horning new units into an already congested footprint.
Building within an operating refinery means limited access for the delivery of large and heavy refinery vessels and modules, and limited areas for the operation of cranes and other construction equipment. Safety of plant and personnel is always the top priority. Naturally, the next priority is project cost and schedule savings.
Lifting frames have long been recognised as a good alternative to large cranes for lifting very heavy loads on sites where space is restricted. Large cranes need a lot of space to set up and also for tail swing. However, as sites become ever more congested, the design of these lifting frames is being refined to increase their versatility and further minimise their land-take requirement.
Bigge Crane & Rigging of San Leandro, California has developed what it believes to be the most versatile lifting frame yet developed – and proven its benefits on a refinery project in California.
Bigge’s new Lift Tower System (LTS) pushes the envelope with a design that combines four lattice framework towers that can each be constructed using either three or four legs, with variable leg spacing (or gauge) depending on the space available. The modular design uses 38ft tower sections, allowing height to be adjustable. It can be used either with or without guys, as required.
With every component able to be stowed into a standard 40ft container, the system can easily be transported to job sites not just all over the country, but all over the world.
The system has proved itself at an ongoing Hydrocracker Expansion Project (HEP) near San Francisco, California. The HEP is designed to boost diesel fuel production with no increase in crude deliveries through the further refining of bunker grade products.
Faced with the task of lifting three hydrocracker reactor vessels into place, the heaviest weighing 615 tons and standing approximately 100ft high, Bigge’s Lift Tower System was custom-configured to be able to carry out all three HEP hydrocracker lifts from a single location, saving set-up time. The conventional two-tower approach would have required the whole structure to be stripped down after each lift and re-assembled over the location of the next vessel. Bigge’s four-tower approach saved as much as six weeks of strip down/re-build time.
The four lattice framed towers, standing 105ft high, were topped with two pairs of box girders across the top. The main girders in the X axis were 86ft long and 8ft deep, and the transverse girders in the Y axis were 60ft long and 8ft deep. By mounting strand jacks on a hydraulically powered trolley, coupled with a girder hydraulic skid system, Bigge was able to place loads with precision anywhere within the envelope between the towers.
All three hydrocracker lifts were completed within a little over two weeks once the Lift Tower System was constructed. The Lift Tower System took three weeks to put up and a week to demobilise.
A further constraint was that the contract proposal indicated that a new HEP pipe bridge and furnace would be installed by the time the lifting operation would begin, reducing the available space to set up a lifting frame. Thanks to the versatility of its modular design, Bigge’s LTS could be erected with two three-legged towers (each with a triangular footprint) and two four-legged towers (with a square footprint).
For added versatility, the legs can be constructed with a gauge of either 14ft or 12ft. At the Rodeo refinery the four-leg towers were set at a 12ft gauge due to space constraints, while the three-leg towers were set at a 14ft gauge to maximize their lateral load resistance while still fitting within a tight space.
While a four-leg design has effectively twice the capacity of a three-leg design, calculations by Bigge engineers showed that there was plenty of scope for the space-saving three-leg solution at the rear side of the Lift Tower System, since most of the weight was to be taken by the front side of the structure.
Hydrocracker lifts were conducted by a pair of computer controlled Hydrospex HSSL 580 strand jacks each with a rated lift capacity of 580 tons. Jacks were configured with 48 strands of 15.2 mm diameter ASTM A416A strand. With a jack stroke of 18 inches, the rate of lift was 30ft per hour. Operational safety was guaranteed during upending and traversing by the jacks’ positive locking during lifting, lock-out if power is lost to the jacks, and computerized balancing of the load between jacks.
The three hydrocracker vessels, fabricated in Italy and delivered to California by a Jumbo heavy lift ship, had earlier been received by Bigge onto a 317 foot barge and then conveyed 15 miles to the refinery’s staging area where they were brought ashore over Bigge’s 120ft long, 1,000 ton capacity bridge using a self-propelled Goldhofer hydraulic platform trailer.
For setting operations, the Goldhofer trailer conveyed the hydrocrackers over two miles of county highway, and through the refinery, to the LTS. With the nose of the hydrocracker connected with links to the powered swivel of the LTS, the lifts were conducted with the platform trailer hydraulically re-configured for tailing the vessel. Upending was accomplished in less than four hours, with longitudinal and transverse positioning of the hydrocracker to the anchor bolts requiring a further three to four hours.
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