Navigating Hose Permeation: 5 Factors & Prevention Tips

In some situations, hose is much better than rigid tubing or piping. Generally with hose you'll have fewer connections, aren't limited to straight lines/angles, and don't have to worry about exact lengths. But it's critical to guard against permeation.

“Hose lends itself to convenient bending and routing, and this enables system designers to eliminate many of the connectors required when using rigid materials," says Swagelok in a new video (below), "which can help lower the cost of materials and labour, reduce risk of leakage, minimize pressure drop changes, and more.”

Clearly, gas permeation is a major safety risk if your gas is explosive or toxic. But even if your gas is inert, "an enclosed area could become hazardous as the escaping gas displaces oxygen in the air. [Even] in open areas, permeation can lead to expensive losses in gas."

When using nonmetal hose materials such as PFA and PTFE, it's critical to know about factors that influence permeation rates (or work with fluid systems experts who do).

Let’s look at five factors affecting hose permeation:

1. Materials of construction
2. Fluid being transported
3. Temperature
4. Pressure
5. Hose construction

Different hose materials have varying resistance to permeation. For example, PTFE (Teflon) hoses are generally more resistant to permeation than many rubber hoses. And some chemicals or gasses are more prone to permeate through hose materials than others. Solvents or aggressive chemicals can be more permeative than water, for example.

Hoses without multiple layers, especially barrier layers, are more vulnerable to permeation than hoses with such layers. Higher temperatures usually increase the solubility of media being transported, and that can accelerate permeation. And high pressure can force media through the hose wall at a faster rate, increasing permeation. 

Many of our customers require ultra-pure media, and even minor permeation can introduce contaminants that compromise the quality of the end product. Losing even small amounts of the media being transported can be costly over time. And, as already noted, permeation can also release toxic substances.

"All materials are permeable to a degree," notes Swagelok, "but in industrial hose applications permeation is important to consider when using PFA and PTFE materials."

(PFA stands for Perfluoroalkoxy alkanes. It's a type of fluoropolymer closely related to PTFE, or Polytetrafluoroethylene, commonly known as Teflon.)

We recommend the following to mitigate permeation: 

1. Choose hose materials that are known to be resistant to permeation by the specific media being transported.
2. When appropriate, choose hoses designed with barrier layers that significantly reduce permeation. These barriers can be made of materials like nylon.
3. Regularly inspect hoses for signs of wear, damage, or other issues that might increase permeation. We offer a Hose Advisory service that can help.
4. In cases where permeation is inevitable, venting systems can capture and safely release or contain permeated substances.
5. In critical applications, it can make sense to use hoses that exceed the required specifications. It depends on the risks involved. 

Swagelok Edmonton offers a Hose Advisory Program that puts our highly trained Field Advisors onsite with you. After walking the floor of your facility, learning about your unique situation, and documenting issues, we help you choose the right equipment and implement practices that extend hose life and improve hose performance. 

We also offer customized onsite training. Get in touch about having our Swagelok-certified Trainers familiarize your team with choosing the right hose materials, regularly inspecting hose for signs of permeation, and gauging when to replace worn or damaged hose.

When it comes to Swagelok hose and flexible tubing, you have many options. Stainless steel hose, PTFE-lined smooth bore, and PTFE- lined convoluted-bore hose reinforced by stainless steel or synthetic braid are just a few. Fill out a short form to get our Hose Quicklook PDF showing end connections, quick connects, and a selection guide:

If you need hose selection help, we are here to lend a hand. Please get in touch here →

Also see:

• Routing Hose at Manufacturing & Processing Plants: 4 Rules + Damaged Hose Photos, Video
• Which Hose for the Job? Edmonton Valve Can Help You Decide
• Custom Jobs Are the Norm at Edmonton Valve's Hose Department