Liquid Nitrogen Used to Create Frozen Plugs, Avoid Draining Chilled Water System
January 7, 2008
One mechanical contractor needed only 30 hours to re-route an existing 24" dia. chilled-water return line at the Chrysler South Assembly Plant, a Fenton, Mo.-based automobile manufacturing plant.
Mechanical contracting firm Haberberger Inc., St. Louis, took a creative approach to the project, freezing the main chilled water lines in two places to avoid having to drain tens of thousands of gallons of water from the system in order to complete the installation and welding of the line. Haberberger installed rigging as well as new piping and supports before piping services technicians Midwest Pipe Repair, St. Louis, could freeze the line solid with over 3,000 gal of liquid nitrogen. It took another 2,000 gal to maintain the frozen plug of water for the installation period.
Once Haberberger received confirmation that the plug was frozen, a controlled drain of the section between the freeze points was initiated, and the pipe was cut. The old section was taken out, the new section was installed and tacked into place, and four welders completed the four welds needed to finish the project. Upon completion of the welding portion of the project, the freezing shells were removed, and the pipe was allowed to thaw. The new section of the pipe was filled with water to equalize the pressure during the thawing process, and insulation was applied to complete the installation.
St. Louis-based Alberici Constructors served as the general contractor on the project.