LL-Foot Fin Tube– Overlapped L type fin tube is commonly known as double L or overlapped L fin, are used in applications where temperatures do not exceed about 350 degrees Fahrenheit The fins are manufactured from strip in similar to the L type except that the foot is preformed into an accurately controlled stepped double L shape, rolled into a taper which causes it to curl. LL-Foot Fin – Overlapped L is then continuously helically wound under tension onto a tube. The fin hugs the tube with one fin overlapping the foot of the next fin with complete coverage of the base tube. This gives good corrosion protection to the tube. This type of tube is often used as an alternative to the more expensive extruded type fin in corrosive environments. The fins are secured at each end in a similar way as L fin.
Fin foot is pre-formed into an LL shape (overlapped LL) and applied to base tube under tension. However, foot is pre-shaped to give overlap of one foot onto another, thereby improving base tube protection and thermal contact area Fin materials: Aluminum Base tube materials: Any metallic material. The smooth flat fins perpendicular to the tube surface give rise to very low resistance to air /gas flow and ensure that fouling is kept to a minimum. The foot of the fin is in contact with base tube and provides a complete sheathing over the finned length.
The Overlapped "L" fin design has interlocking fins that are wound together to prevent movement and separation. The fin protects the entire tubes, so the designation works well for the applications where corrosion is a factor.
This type of finned tube is often used as an alternative to the more expensive extruded type fin in corrosive environments.
Common Applications: Steam Coils, Air Pre-heaters.
Max. Working Temperature: 180 °C
Atmospheric Corrosion Resistance: OK
Mechanical Resistance: Poor
Fin Material: Copper, Aluminum
Base Tube materials: Any material available, such as Carbon steel Tube, A179, A192, A210, stainless tube A269/A213 T5 T11 T22 304 316