Avoid inferior metal duct that requires you to cut it to length and snap it together. This type of duct is time consuming to install because it requires you to seal all the seams with silicone and screw the components on the ends with sheet metal screws. Another disadvantage is the rough internal seams and crimped ends that unavoid- ably increase static pressure.
Flexible Duct
Flexible hose is generally used for short runs, small shops and at rigid duct-to-tool connections. There are many dif- ferent types of flex hose on the market today. These are manufactured from materials such as polyethylene, PVC, cloth hose dipped in rubber and even metal, including steel and aluminum.
The superior choice here is metal flex hose that is designed to be flexible, yet be as smooth as possible to reduce static pressure loss.
There are also many kinds of pure plastic flexible hose, such as non-perforated drainage type hose and dryer vent hose. Drainage type hose, while being economical, does not quite have the flexibility required for dust collection. The inside of the duct is also deeply corrugated and can increase the static pressure loss by as much as 50% over smooth wall duct. Dryer vent hose, while being complete- ly flexible, is non-resistant to abrasion and has a tendency to collapse in a negative pressure system. We DO NOT recommend using dryer drainage-type vent hose in your dust collection system.
If using flex-hose, you should choose one of the many types that are designed specifically for the movement of solid particles, i.e. dust, grains and plastics. However, the cost of specifically designed flexible duct can vary greatly. For example, polyethylene hose is well suited for the removal of particulate matter, especially sawdust, since it is durable and completely flexible. Also, it is very eco- nomical and available in a wide variety of diameters and lengths for most applications.
Plastic Duct
The popularity of plastic duct (Figure 42) is due to the fact that it is an economical and readily available prod- uct. It is also simple to assemble and easily sealed against air loss. The primary disadvantage of plastic duct for dust collection is the inherent danger of static electrical build- up.
