Wrap-On Knurled Footed Fin
This finned tube is basically identical to the Wrap-On fin and produced with a combination of Wrap-On and Imbedded tooling hardware. Production speed is basically the same as with the Wrap-On fin.
Sequence of the fin formation through the preformers is the same as described for the Wrap-On fin. By using the Roller Overarm and adding knurling discs, we are able to knurl the base tube a half-pitch upstream of the pan and spindle roller and ahead of the foot's application to the axial tube surface. As the fin completes the next half revolution the foot of the fin is knurled into the knurled tube surface. |
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Specific to the McElroy system, the toe of the fin points upstream. This makes it possible for the incoming fin, as it enters the nip of the rollers to press and form the toe of the previous fin flat against the tube, providing maximum contact with the tube surface. As the toe of the preceding fin is tucked under the heel of the subsequent fin, there are no gaps on the tube surface and the fin is snug. Fins are stapled at each end of the tube and fin collars may be applied.
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Fin Materials:
Aluminum, Copper |
Maximum Fin Height:
.807" (20.5mm) on 1" Tube (25.4mm) and larger. |
Tube Materials:
Carbon steel, copper alloys, stainless steel, aluminum. RcB hardness of base tube will impact knurling depth. Consult McElroy for specific recommendations. |
Fin Stock Thickness:
Varies based upon tube OD, but typically .016" (.4mm). Copper stock thickness can be reduced by 10%. Maximum aluminum fin stock thickness .030" (.76mm) |
Production Rate:
for Aluminum Fin X 10 FPI on 1" Tube X 40'L: 450-500' per hour (85% efficiency). |
Type of Service:
More severe service than Wrap-On L-Fin. |
Typical Acceptable Tube Wall Operating Temperature:
US 350 degrees F/ 176 degrees C. Europe 260 degrees F/ 500 degrees C. |
Advantages:
Increased contact surface and improved lock of the fin base in the axial surface of the tube. Improved fin bond stability at higher temperatures. More stable during application process than Wrap-On Fin. |
Disadvantages:
Requires more material per foot of tube than the Imbedded or I - Fin (Edgewound).
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Wrap On Kurled Footed Fintube Height Range Chart
(Aluminum 1100-00 or Copper(102 Oxygen Free) |
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Tube Size |
Min. Tube Wall |
Fin Height Range |
FPI Range |
| 9/16 " or 14.29mm |
17 Ga (.058) (1.47mm) |
1/4" (6.35mm)
to 13/32 (10.32mm) |
10 - 12 FPI |
| 5/8" or 15.88mm |
16 Ga (.065) (1.65mm) |
1/4" (6.35mm)
to 9/16" (14.29mm) |
8 - 12 FPI |
| 3/4" or 19.05mm |
15 Ga (.072) (1.83mm) |
1/4" (6.35mm)
to 5/8" (15.88mm) |
7 - 12 FPI |
| 1" or 25.40mm |
14 Ga (.083) (2.11mm) |
1/4" ( 6.35mm)
to 8.07" (20.50mm) |
5 - 12 FPI |
| 1.25" or 31.75mm |
13 Ga (.095) (2.41mm) |
1/4" (6.35mm)
to .807" (20.50mm) |
4 - 12 FPI |
| 1.5" or 38.10mm |
12 Ga (.109) (2.77mm) |
1/4" (6.35mm)
to .807" (20.50mm) |
4 - 12 FPI |
| 2.0" or 50.80mm |
10 Ga (.134) (3.40mm) |
1/4" (6.35mm)
to .807" (20.50mm) |
4 - 12 FPI |
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