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Friday, July 31, 2009

Historic Repair of 88-Inch Cyclotron’s Suspended Two-Ton Cover Plate

By Jim Morel

riggers Lab riggers move the Dee truck into the vault

The 88-Inch Cyclotron has just completed a complex vacuum repair on the cover plate of its accelerating Dee structure. This was a historic event since the last time this structure was removed was over 30 years ago. The 2,400 lbs massive copper structure is suspended 14 feet into the Cyclotron’s main tank and moving it safely is an engineering challenge.

The removal of the Dee did require the re-fabrication of a counterweight truck that provides support for the Dee structure when it is removed from the Cyclotron. Tim Loew, the mechanical engineer coordinating the Dee pull, had the Dee counterweight truck built from archived drawings. In a team effort, Tim Loew and Bob Shannon (Engineering), and Jim Morel (Nuclear Sciences), developed a plan that enabled this repair without moving the permanent shielding blocks of the cyclotron vault, which made the repair faster, safer and more efficient.

dee cartDee truck installed in Vault

In preparation for the Dee pull, the 88 technical staff removed the interfering infrastructure to allow the Dee truck to be moved into position and installed. The Lab’s riggers moved the 750-pound Dee truck into the Cyclotron Vault and placed it in position. The Dee truck was then loaded so it would support of the 14-foot cantilevered Dee and Dee stem structures. This repair was an important step towards developing plans in case other repairs to the Dee structure become necessary.

It took just one week to roll back the Dee, remove the old O-Ring, clean the sealing surfaces, install the new O-Ring and reinsert the Dee back into the Cyclotron. The 88’s mechanical crew completed the repair work on time with no air leaks detected during the Cyclotron pump down. In this time of increased safety awareness, the use of regular work planning sessions each day allowed for effective utilization of ISM core functions. The integration of feedback each day regarding the previous day’s work and problems proved to be an asset for keeping the project moving forward.

The Dee pull crew included (l-r) Bob Shannon, Tim Doolin, Reba Siero, Brian Reynolds, Jeff Trigg, and Tom Perry

The O-Ring replacement project was a team effort by the technical staff at the 88, including the mechanical group (Shannon, Tim Doolin, Jeff Trigg, Tom Perry, John Garcia and Brian Reynolds), with support from the electrical group and the operations group. Environment, Health and Safety support was provided by Building 88 RCT Jeff Bramble. The project execution plans were developed by Morel, with the help from Loew.

The Cyclotron is on schedule for beam delivery in the beginning of August.

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