Barnhart visits Aruba:
Nov 17, 2006
Barnhart visits Aruba:
17 November 2006
US heavy lifting contractor Barnhart was hired to replace the convection section (a 60 x 14 x 14 heat exchanger) in a petroleum refinery in Aruba. The convection section sits 50 above the ground on top of the radiant section of a fractionation unit. The old convention section weighed 250 tons and the new convection section weighed 325 tons. The process would require minimum disruption to plant operation.
When working on a Caribbean island such as Aruba, heavy lift equipment must come from places such as Europe of the US making it quite expensive. When the island refinery needed to quickly replace the convection section of a cracking furnace during an outage, the local rigging contractor Caribbean Heavy Lift and Heavy Transport - Aruba, knew that Barnhart would have an innovative approach. This 300 ton convection section sat about 50' above the radiant section in a very crowded section of the plant. Because the replacement was during an outage, time was critical.
The primary equipment used in the process was Barnhart's Modular Lift Tower (MLT). In constructing the Lift Tower, Barnhart could not lift any pieces over the live unit. This meant that the MLT would have to be built 40-feet away from the lift point and moved into position after the unit was shut down.
Three degrees of movement were required during the lift to miss all the plant interferences that were left in place to minimize the units down time. The MLT was designed to lift and move both laterally and longitudinally. The span of the MLT had to be exceptionally long so that the plant would not have to remove additional equipment. Removing the equipment to allow a shorter span would have increased the outage duration. Barnhart used its 8-foot girders with a new moment connection design to make the required 90 foot span.
The old and new convection sections had eight lugs each that could only be subjected to vertical lifts. This gave the Barnhart team two options. The first option was to use a series of seven spreader bars which would have added 50-feet to the required head room and thus a much taller MLT. The only available crane to lift the girders could not have handled their weight at the higher level. The second option involved Barnhart asking its resident creative rigging genius to develop a lifting arrangement that only used 20 feet of rigging. With the arrangement in hand, Barnhart fabricated eight special swivel links and crossed our spreader bars over one another. They then used snatch blocks to equalize the loads between the lugs. The Barnhart Team also fabricated two new top links for their multi-purpose spreader bars which again allowed us to reduce the required head room for the lift.
Cranes Today ©2006
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