Types of Sheet Metal Flanges
Sheet metal is used in many different applications, including installing duct work for HVAC systems. The component or device that connects the sheet metal joints together is called a flange. Flanges can come in different shapes, sizes or types, depending on the sheet metal being connected. The flange can be located on the outside or inside of the sheet metal connection.
Other People Are Reading
-
Lip Flange
-
A lip flange is made out of the sheet metal being installed. Fold the ends of the sheet metal, either to the outside or inside, on the ends of the sheet metal, making an "L" shape. You must use the same bend on the connecting sheet metal, so the two pieces match up. Drill a hole through the two lip flanges and connect with bolts, nuts and washers. You can also use self-tapping sheet metal screws to connect the two flanges together. A lip flange does not make a seal between the sheet metal connection points. You have to use a sealant or caulk to waterproof the connection.
Slip-on Flanges
-
Slip-on flanges come in many shapes and sizes. The flange slips onto the outside of the sheet metal, so two pieces of sheet metal can be connected. The slip-on flange aligns with the opposite flange located on the adjoining sheet metal. You can use sheet metal screws or bolts to fasten the two pieces of sheet metal together. You need to seal the gaps between the flanges and sheet metal with a caulk or sealant, to prevent leaks.
-
Reducing Flanges
-
A reducing flange is a type of flange used to move from one size sheet metal to another size. Commonly used to attach sheet metal HVAC ducts together, the flange slides onto the outside of the larger duct and has a reduction flange, or smaller flange, so it can connect to a smaller ducting or ventilation system. Sometimes the reducing flange is shaped differently. Some HVAC systems have a main ventilation system that is rectangular in shape, but connects to a circular ventilation duct that runs to a room. One end of the reduction flange attaches to the main rectangular duct, and the other end is circular so it can connect to the round duct. The joints must be sealed with a joint or seal compound or duct tape, to prevent air loss.
Connector Types
-
Connector type flanges come in many different shapes. The purpose of the connector flange is to snap onto the ends of the shaped sheet metal. The sheet metal end is bent into a particular position during manufacturing. The position matches the type of connector clip or flange clip you need to use to join the sheet metal together. The drive slip connector flange looks like an "C" shape and clips onto the lips of the sheet metal. A hemmed "S" and standing "S" connects two flat pieces of sheet metal. Other types of connector types can be used, depending on the end designs of the sheet metal.
TDF Connector
-
Some rectangular sheet metal, such as HVAC duct work, use a traverse duct flange. The flange is a separate piece of material that attaches to the sheet metal by screws or bolts. Sometimes the TDF connector is attached by welding the flange into place during manufacturing. A separate TDF connector allows you to cut the sheet metal to size, then add the TDF to both ends of the sheet metal. You can get the TDF connector that fits onto the corners of the rectangular shaped sheet metal or runs completely across the width and height of the rectangular sheet metal. The TDF connector must be sealed with duct tape, joint compound or sealant, unless the connector was welded into place.
-
References
- Photo Credit Jupiterimages/Photos.com/Getty Images
