L-Foot or Wrap-On Footed Fin
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 The L-foot fin has the advantage of greater contact length to the base tube. The
L-foot anchors the fins in axial position and protects the base tube from corrosion.
The fin is formed through a two-stage preformer section just ahead of the strip guides, primary forming roller and spindle roller. The first stage rolls the fin to a 45 degree foot and the second stage rolls it to a true 90 degree foot. The tooling controls the fin height and therefore each FPI requires a specific strip stock width.
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. 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 also be applied.
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Fin Materials:
Aluminum, Copper |
Maximum Fin Height:
1" (25.4mm) on 1.5" tube (38.1mm) and larger. |
Tube Materials:
No theoretical limits. |
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:
Light to Medium Duty |
Typical Acceptable Tube Wall Operating Temperature:
US 350 degrees F/ 176 degrees C. Europe 195 degrees F/ 90 degrees C. |
Advantages:
Corrosion protection of base tube. |
Disadvantages:
Requires more material per foot of tube than the Imbedded or I - Fin (Edgewound).
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Wrap On Footed and Overlapped Footed Fintube Height Range Chart
(Aluminum 1100-00 or Copper (102 Oxygen Free) |
Tube Size |
Min. Tube Wall |
Fin Height Range |
FPI Range |
| 9/16 " or 14.29mm |
24 Ga (.022) (.558mm) |
1/4" (6.35mm)
to 13/32 (10.32mm) |
10 - 12 FPI |
| 5/8" or 15.88mm |
23 Ga (.025) (.635mm) |
1/4" (6.35mm)
to 9/16" (14.29mm) |
8 - 12 FPI |
| 3/4" or 19.05mm |
22 Ga (.028) (.711mm) |
1/4" (6.35mm)
to 5/8" (15.88mm) |
7 - 12 FPI |
| 1" or 25.40mm |
20 Ga (.035) (.888mm) |
1/4" ( 6.35mm)
to 8.07" (20.50mm) |
5 - 12 FPI |
| 1.25" or 31.75mm |
19 Ga (.042) (1.07mm) |
1/4" (6.35mm)
to .807" (20.50mm) |
4 -12 FPI |
| 1.5" or 38.10mm |
18 Ga (.049) (1.24mm) |
1/4" (6.35mm)
to 1" (25.40mm) |
4 - 12 FPI |
| 2.0" or 50.80mm |
16 Ga (.065) (1.65mm) |
1/4" (6.35mm)
to 1" (25.40mm) |
4 - 12 FPI |
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