Roller Expanding Resources

[Snow-Anders]

Any good resources to calculate the required range to roller expand tubes into tubesheets.
Any good resources with images of a good roller expanded tube and quality errors for poorly expanded tube?

Options in Elliott Tool's info online? They provide a good formula and recommended wall reduction, but would like to hear from people out on shop floors.

Thanks!

 

[EdStainless]

Elliot make good equipment, but I am not sure that they are the best at the process issues.
There are two major re-tubers in the US. Re-tubing is more demanding than new construction so they are the real experts. They might sell knowledge and equipment, RETUBECO and Atlantic Group (now part of Day and Zimmer).
Using AWR as a rolling criteria works under some conditions.
1. Strength of tube less than tubesheet
2. Tubes are fairly thick (AWR is very hard when tube walls are less than 0.060")
3. Hole sizes perfect
4. You know the exact tube sizes before (and hole sizes) before and after rolling
In reality the process is controlled by rolling torque. So usually a mock-up is made using various hole sizes and covering a range of AWR. These tubes are then pushed out of the holes and the strength of the roll joint is recorded. It usually rises gently to a plateau before dropping off, you want to be right at the front edge of the plateau.
And QA is critical. Measuring and recording hole and tube sizes on a significant percentage is good, as is 100% go/no-go gaging. This applies both before and after rolling. Checking torque of rolling driver every 50 tubes (or some reasonably small number). You also need frequent checks on the location of the roll to make sure that it is in the correct place. Too near the edge of a tubesheet and you will cause serious issues. Swapping out the rolling quill ever 20 -50 tubes so that they can be inspected for dirt and damage is also critical.
Picking the correct rolling lubricant (compatible with the materials and subsequent processes, such as are you going to seal weld).
Choosing the correct rolling quill and driving gun.
You also need to roll in the correct pattern, or you can distort nearby holes and bow the entire tubesheet.

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P.E. Metallurgy

 

[Snow-Anders]

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