The Company, upon evaluation of the problem, requested from the Contractor, a procedure for the safe removal of the Mud Drum as well as well as how to complete the project in a timely manner and not negatively effect the sites need for steam and operation.
The Contractor immediately developed a written procedure that included a rigging plan that involved building a structural cart and trolley system to not only safely remove the old drum but allow for transport to the shop and subsequently to safely reinstall the new drum.
Upon the approval of the Company, the Contractor constructed the cart and trolley and planned for the removal of the old drum. Simultaneous to the removal of the old drum, the Contractors shop operations immediately began procuring ASME code com-pliant materials for the new drum and developed tooling that would be needed to facilitate the drilling of the 562 holes in the new drum.
Upon completion of the rigging plan and construction of the trolley, the contractor effected the safe removal of the existing Mud Drum. With the exception of ten tubes on the east and west end of the Mud Drum, all of the existing tubes were removed carefully and intact and transported back to the bending shop. As was previously part of the original project, all of the new tubes had to be bent to match an existing and corresponding bent assembly upon re-installation. After the trolley was rolled into place under the existing Mud Drum and secured, the remaining tubes were safely cut away from the Mud Drum and freed it to be rolled out of the boiler and building and to an awaiting truck to be shipped back to the fabrication shop.
Upon the safe delivery of the old Mud Drum to the fabrication shop, the Contractor immediately began the task of fabricating the new Mud Drum. To facilitate the drilling of the 562 holes, the 18 in. pipe for the new piece was placed onto a pipe pantograph which allowed the piece to circumferentially rotate. Then using carbon steel structural shapes and plate, the shop then built a drill press platform that would remain secure while drilling the laid out holes with a “Mag Drill”. The platform could then be moved along the total length of the new drum, and the piece easily rotated by the pantograph machine.
While the shop continued to drill the new holes and complete the fabrication of the new Mud Drum, the Contractor’s bending shop began the forming operation of the new boiler tubes. The Contractor uses special hydraulic pipe and tube benders outfitted with tooling and boosters that minimize the amount of wall thinning and out-of-round.
While the shop continued to make the new Mud Drum and bend the new boiler tubes, the Contractor’s field crew kept going with the other required maintenance and preparations for the new pieces. When the new Drum was ready it was placed onto the trolley and returned to the jobsite. The new Mud Drum was safely re-install and the trolley used to support the drum until enough new tubes had been installed to support the drum. By this time all of the new boiler tubes had been bent and the task of the re-installing the 562 tubes began.
In the course of installing the new tubes, replacement of the boiler refractory and insulating firebrick was also performed.