Tube Extraction Technology

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Heat Exchanger produced by Colmac Coil
Sponsors
Team Name The Extractors
Duration Fall 2015 - Spring 2016
Faculty Advisers Mike Maughan
Mentor
  • Jake Gillis
Students
  • Andy Roybal
  • Alan Edwards
  • Lane Matteson
  • Tony Keys

About Colmac Coil[edit]

Colmac Logo.jpeg

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 Manufacturing Process[edit]

Tube Rupture.jpeg

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[edit]

  • 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[edit]

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

Deliverables[edit]

  • 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:[edit]

  • 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

Tool Prototypes[edit]

Winch Table.jpeg

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.



Initial Concepts[edit]

Expand this section to see the development of the tools and extraction process

Tool Designs:
Image of Tool Description of tool
Using Saw blade to cut pipe
The tool with the saw blade was the easiest to design with only a 1/32" groove cut. Tool was designed to accept a full size 8 inch hacksaw blade and cut beyond the exterior of the pipe-wall. A jam occurred during a full depth pass (0.070"). Afterwards the team trimmed the height of the saw blades to perform a progressive cut discussed in the next section.
Tool using a lathe index-able carbide insert
The lathe tool incorporates a carbide threading insert from a lathe. The first prototype was capable of 0.030" and 0.070" depths, opposed cuts and even an offset cutter with the intention of inducing a spiral which may help extracting the tube later on.
Tool created with a custom made blade to cut pipe
This tool was designed with the intent of using it in smaller applications due to the down-scaling potential. It is composed of a center section with 4 grooves cut at 90 degree angles in which 4 flat bars are mounted. The flat bars contains 4 slip-fit holes for 1/8" round tool-stock that can be ground to any desired shape and depth. This tool is easy to modify its configuration but requires hand-ground custom teeth.
Results from Testing the Tool Designs:
Image of Pipe from Test Description of test
Image of saw blade cut
This shows the pipe after the saw blade had attempted to go through. The tool produced too much drag and stalled the winch attempting to cut the entire wall (0.065") with a single pass. This led to team advancements to pursue progressive depths and increase winch pulls per extraction
Image of the pipe after the lathe blade tool
The lathe blade tool pulled through the tube with the least effort of all three designs. The vertical carbide cutter orientation caused excessive plowing of material and did not penetrate the full wall thickness. The outside of the tube wall showed a bulge proving that the material was being displaced out rather than being cut. This displacement problem occurred with all configurations of cutter depths and positions. The offset cutter was able to provide a consistent spiral if desired.
Lathetubebulge.jpeg
Image of the pipe after the knife blade tool
The round blade scored the pipe but did not cut through it. The tool was tested with only two rows of 3 teeth due to concern of excessive pulling force. The 3 teeth cut at progressive depths of 0.020", 0.050" and 0.070". Material built up on the cutter face forcing the tube wall to displace outward similar to the lathe tool.

Secondary Concepts[edit]

Tool Designs:
Image of Tool Description of tool
Using Saw blade to cut pipe
Tests were performed with lubricant and progressive cuts which were achieved by trimming the bottom of the blades. The blades were swapped out between each pass to progress cuts from 0.040" to 0.070" to 0.090" then to a final cut of 0.120". The final cut did damage the coil fins.
Tool using a carbide lathe insert
The second lathe tool adjusted the cutting angle from perpendicular to 15 degrees with chip relief area to prevent material buildup in front of the cutter. Cutter depth is adjustable by grinding the carbide insert on a basic pedestal grinder.
Tool for removing cut strips of pipe
This tool was to be used after two parallel cuts are made of equal width. It is to be used only if the walls have been fully cut . The strips are fed into the ring at the rear of the tool and the tool's forward motion is intended to pull the strips away from the wall and leave the strips loose inside the tube.
Results from Testing the Tool Designs:
Image of Pipe from Test Description of test
Image of saw blade cut
Progressive cuts worked very well with this tool, the pulling force was reduced enough for the winch to operate correctly. The tool was able to separate the pipe into 2 separate pieces with 8 total passes on a 4 foot coil. Testing on the 12 foot coil revealed that the tool cut in a slight spiral which prevents successful strip extraction discussed later on. It was believed that the initial cutting blade was not fully engaged with the wall (only the last few inches of teeth were cutting) causing a lack of straight cuts.
Revised lathe blade tool with chip spirals
This lathe blade tool showed promising chip removal during the first few inches then the aluminum started galling on the tooth preventing a clean cut. This may be due to a lack of steady lubrication. This tool only needed 2 cutter depths: 0.035" and 0.070" for the winch to pull. This tool did not cut straight which was a primary concern for the strip extractor.
Image of the strip extractor within pipe
The strip extractor was able to separate the walls of the pipe and remove the cut strips but with a failure of intended method. Afterwards the remaining pipe walls were able to be removed with some damage to the coil fins. The wall sections being removed stuck on the edge of the extractor, formed a loop that pushed into the fins and then peeled the rest out. The failure of this tool lead to the design of the strip peeler.
Pipeafterectraction.jpeg

First Successful Extraction Method[edit]

Step of Process:
Image of Tool Being used Description of
Step 1: Using Saw blade to cut pipe
The hacksaw tool and method of use has been slightly modified to engage more teeth for a straighter cut. This was achieved by reducing the angle the blade meets with the wall; the front teeth were raised and the rear teeth stayed at the same height. With 2 sets of 4 progressive passes spaced 0.3" apart the stripper tool discussed below was able to successfully remove the cut section.
Step 2: Using the Stripper tool to remove 0.3" strip
The failure of the strip extractor provided insight to this design. The stripper tool acts as a hook to pull the cut strip back onto itself and out the other end of the tube. Pliers must be used to fold the strip into the loop to set up the tool. This step requires that the strip is a constant width down the length and the tube wall is mostly cut through. If the strip gets too wide the strip is too difficult to pull, too narrow and the strip breaks midway.
Step 3: Using the Plug to remove remaining section of tube
This tool pulls the tube out of the coil after a small strip has been removed. The tube can be pulled out in 2 pieces: the strip and the remaining section. The tool has successfully pulled out several 4' and one 12' tube.

Final Tool Designs[edit]

Tool Designs:
Image of Tool Description of tool
Final design of saw tool
The original saw holder was modified to streamline the tool use and increase effectiveness. A 1/8" hole was drilled at the rear of the tool to insert a scoring tooth ground from a piece of drill rod; this tooth scores the wall of the tube for the next cut to follow at the correct width. An access hole was drilled to easily remove the blade with pliers. The final cutting tools will be in a set of 4 to avoid trimming hacksaw blades by increasing the depth of cuts with different tools. The final design uses a 10 inch saw blade opposed to the original 8 inch. The blade is angled shallower with the front teeth penetrating deeper than the original. These adaptations ensure a straight cut every time. A diagram of the tool is below.
Saw diagram.png
Strip Peeler
This tool was designed based on the failure of the strip extractor. The tool is inserted into the tube, then the strip is folded and clamped. Forward motion of the tool peels the strip out of the tube; the entire strip bends 180 degrees as shown in the diagram below.
Strip Remover Diagram.png
Plug Tool for Extracting Tube
This tool was to be used after The strip peeler has been successfully run. The pressure on the tube-wall needs to be relieved by extracting the strip. The Plug Tool slides into the end of the tube with a shoulder that presses against the walls. Forward motion of the winch removes the tube from the coil with very little damage. A diagram of the tool is below.
Plug diagram.png
Results from Testing the final Tool Designs:
Image of Pipe from Test Description of test
Image of saw blade cut
The final revision of the saw tool was not built but each concept put into the final design was tested with modifications to the original saw tool. The tool performed very well when tested on a 12' coil; the tool did not spin and the cuts were even width down the entire length. The final design scaled up and down to work within a 1" and 5/8" tube very well.
Image of the strip peeler within pipe
The strip peeler is the key part in the entire extraction operation. This tool needs the strip to be approximately .30" in width the entire length of the tube. If the cuts converge, the strip breaks at the site of convergence. If the cuts diverge, the strip becomes too difficult to pull and the strip will break at the clamp. Either failure is very difficult to fix adding to the importance of straight and consistent cuts.
Image of the plug set up and ready to extract the tube
The Plug is a very simple tool and performs reliably. It scaled up and down to work within a 1" and 5/8" tube very well.

Team Information[edit]

Extractor Group Photo.jpeg
Andy Photo.jpeg
Andy Roybal Biography:
  • Andrew is a senior studying mechanical engineering at the University of Idaho. His favorite courses have involved computer aided design software. He loves the outdoors and especially fishing and snowboarding. He is graduating May 2016.
Mechanical Engineering Undergraduate
Hometown: Idaho Falls, Idaho
Email: royb9754@vandals.uidaho.edu
Alan Photo.jpeg
Alan Edwards Biography:
  • I am a senior in Mechanical Engineering. I was in the construction industry for 12 years before coming back to school to get a degree in Mechanical Engineering. I enjoy hiking, fishing, and being outdoors while spending time with my family.
Mechanical Engineering Undergraduate
Hometown: Idaho Falls, Idaho
Email: edwa7949@vandals.uidaho.edu
Lane Photo.jpeg
Lane Matteson Biography:
  • Hi, my name is Lane Matteson and I am a senior studying mechanical engineering. My favorite classes have been fluids and thermodynamics. I have worked in the food processing industry and studied abroad in San Sebastian, Spain this past summer. In my spare time I enjoy hunting, fishing, and other outdoor pursuits. Unfortunately I had to take the Spring semester off and withdraw from the project.
Mechanical Engineering Undergraduate
Hometown: Homedale, Idaho
Email: matt8513@vandals.uidaho.edu
Tony Photo.jpeg
Tony Keys Biography:
  • Tony Keys is also a senior undergraduate in mechanical engineering. His work experience includes a summer internship at the Exotic Metals Forming Company and he has been an electrical apprentice for his father’s company in Nampa, Idaho. Tony is passionate about snowmobiling, enjoys the outdoors as well as any hands-on experience.
Mechanical Engineering Undergraduate
Hometown: Boise, Idaho
Email: keys5218@vandals.uidaho.edu

Document Archive[edit]

Meeting Minutes[edit]

Schedule[edit]

Project Schedule Fall Project Schedule Spring

Presentations/Reports[edit]

Expo Poster

Expo presentation Power Point

Detailed Design Review Power Point

Saw DFMEA (Design Failure Mode and Effect Analysis)

Strip Peeler DFMEA (Design Failure Mode and Effect Analysis)

Project Learning Key Points