Tube Extraction Technology

About Colmac Coil
Colmac Coil is a third generation, family-owned company founded in 1971 that has grown to be one of the world’s leading manufacturers in new and replacement refrigeration coil markets. They specialize in custom fin and tube heat exchangers with the majority of business focused on industrial refrigeration. Colmac Coil is based out of Colville, Washington with an additional manufacturing facility in Paxton, Illinois and a South American sales office in Guadalajara, Mexico. Their mission is to provide heat transfer and refrigeration markets worldwide with products that are innovative, built to customer specifications, and shipped on-time, with fast friendly service for the mutual benefit of customers, employees and shareholders.

Description of Process
Colmac Coil produces fin and tube heat exchangers with a hydraulic expansion process. The tubes are fed through the stamped coil sheets to form a loose assembly. Then a plug larger than the diameter of the tube is inserted and hydraulic pressure forces the plug along the tube. This expands the tubes within the stamped coil sheets forming a mechanical bond for structural support and heat conduction. The expansion process is not foolproof however, the tubes can rupture and require replacement. The partially expanded tube must be extracted with minimal damage to the coil pack or else the entire assembly will have to be scrapped. The Extractors have been tasked with designing a tool-set and process to quickly and effectively remove the ruptured tubes.

Problem Details

 * Colmac Coil will fully expand the ruptured tube from the other end to eliminate the diameter change midway
 * A winch used for later operations can be used to drag a tool down the tube
 * Tube material is 3003 Aluminum seamless and between 0.060" and .080" wall thickness
 * Tubes will be 5/8", 7/8", and 1" inner diameter and up to 30 feet in length
 * The device and process must be successful on every attempt to prevent scrap
 * Process must take less than 1 business day to complete tube removal
 * Tool must not drag or severely damage heat exchanger fins
 * Safety is of utmost concern and extraction process should not endanger workers

Team Goals

 * Target removal time of less than 2 hours
 * Separate tools for each tube size
 * A safe and reliable tube removal process

Deliverables

 * Prototype removal tools for each tube size
 * Demonstration of tool on Colmac test coils
 * Detailed report discussing reason for choosing final design tool, tool usage and maintenance instructions, and a self-evaluation of this product

Tool Specifications:

 * Tool set must cost less than $6,000
 * Replacement parts must be commercially available
 * Must be able to cut a wall thickness of .060" to .080"
 * Low maintenance
 * Tool must be able to attach to existing winch cable

First Test of Designs
All of these tools use the winch supplied by Colmac Coil to operate. The supplied winch is capable of a 2,000 pound pull force, less than the winches in use at Colmac Coil. The winch is attached to a platform to secure assorted sizes of heat exchangers. The team focused on developing tools for only the 7/8" tubes until a satisfactory result was achieved before attempting 5/8" and 1" extractions. All tools are machined from 1018 round stock steel. The diameter of each tool is 0.765" which allows 0.020" diametrical clearance between the tool and the sample coil tube walls.