Flexible Duct – Important Considerations

Which material to choose for your application?
The material composition of a flexible duct is one of the most important factors to consider for your intended application. A flex duct’s material can determine the difference between the success of your application or its failure. Certain materials are better suited for specific applications compared to others. For example, if you have a high temperature application involving temperatures beyond 400° F, it is best to use a flex duct made of silicone or stainless steel or silicone because those materials can survive contact with extreme temperatures much better than PVC or a neoprene-coated fabric.

What should I consider for Air Movement applications?
To put it simply, an air movement application is any application that involves the transfer of air. This typically involves the transfer of cold or hot air for HVAC (heating, ventilation, and air conditioning) purposes, but it also applies to other gases such as smoke and light fumes. When looking for a flexible duct for your air movement applications, you want to consider what specific type of air being transferred. It is best to know the temperature and whether the situation calls for positive pressure (blowing) or negative pressure (suction). Temperature ranges in HVAC applications typically do not go beyond 180° F, so a flex duct made with PVC is a good option to consider.

What should I consider for Light Dust applications?
Flex ducts are regularly used to transfer light dust particulate away from a specific area. This is often done for safety reasons in many occupational fields because dust can be harmful to health. The type of dust involved in these applications can vary from very fine wood dust to fertilizer particulate. You want a hose with a firm but flexible body. The right mix of durability and flexibility makes PVC great materials for a flexible duct. For the more heavy duty dust applications, such as in debris-related dust collection, flex ducts made of neoprene coated fabrics, thermoplastics, and urethane in that order come highly recommend in the industry.

What should I consider for Materials applications?
Material handling applications generally consist of moving physical debris that is more than just dust. This involves the transfer of dirt, pollen, animal dander, and even liquid materials. Hoses that have thicker walls are highly suitable for transferring these materials. It is also a good idea to consider whether a flexible duct will have a smooth interior in order to prevent this material build up in the flex duct. We highly suggest Urethane hoses for any material movement due to their durability and flexibility.

What should I consider for Industrial Exhaust applications?
Industrial exhaust involves the transfer of highly caustic materials. This involves everything from harmful toxins to industrial-grade hot air. In most industrial exhaust applications, more premium grade materials such as silicone and stainless steel are recommended. Silicone flex ducts are ideal for most high temperature industrial exhaust. They exhibit a light to moderate level of flexibility, but flexible hoses in this class are needed to have a level of physical sturdiness. They typically perform towards over 500 degrees.

What should I consider for Abrasives applications?
Abrasives transfer applications are physically demanding on hoses because of the thick and damaging materials involved. Gravel, dirt, loose leaves on the lawn, these are all everyday materials that need to be suctioned away from residential and workplace areas. Physical durability is preferred over flexibility in abrasives transfer. Thermoplastic and urethane hoses are among the most sought after flexible duct materials due to their durability in these applications.

What is flex fatigue?
Flex fatigue is a flex duct’s ability to withstand repeated flexing before failing or breaking. Hoses that have smaller ID sizes and exhibit a good degree of compressibility tend to have a higher flex fatigue compared to those of larger ID sizes and solid non-compressible bodies. For example, a 4-inch ID flexible duct made from PVC and PU hoses will have a better flex fatigue compared to a stainless steel or even thermoplastic ducts at 8-inch ID. Be aware that some hoses are designed to be firm and non-flexible, meaning that they do not have flex fatigue.