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Teflon hose: some myths dispelled

01 November 2011

Hoses made with a core of Teflon (PTFE) have a richly deserved reputation for outstanding performance under severe application conditions. But along with that reputation come a number of customer reservations based on myths that this article will attempt to dispel

While it is true that the Teflon PTFE paste used to make high grade hose is a premium material, the hose itself is often a more economical choice than traditional products when total lifecycle-cost is considered. There are a number of factors to consider when comparing hose acquisition cost and performance.

Cost  -  In almost all cases a hose made with Teflon will outlast an ordinary rubber or thermoplastic hose under virtually any operating condition. But whether this factor alone is enough to justify the higher initial acquisition cost of a hose made with Teflon will vary from application to application; in most cases the answer will be “no”. However, that begins to change when costs other than the initial purchase price are considered – particularly costs related to downtime, contamination and effusion. A Teflon fluoropolymer hose core will inhibit the accumulation of contaminants, the loosening of which may cause damage to downstream equipment, for example.

There are also intangible benefits. Hoses made with Teflon generally have exposed stainless steel braids which lend a look of quality to the equipment to which they are attached. However, all hoses with stainless steel braid are not necessarily made of Teflon. Braided stainless steel hoses are commonly used in cryogenic applications, which have a corrugated steel core. A quick and easy way to tell which is which is by looking for welded-on fittings, which are never used on hoses made with Teflon.

Kinking and crushing  -  The truth is that all hoses tend to kink and crush easily, especially when they are not properly installed. Hoses made with Teflon are no better or worse than other materials when recommended bend radii and loading are adhered to.

In applications where kinking or crushing is a possibility, it is a simple matter to add internal or external spring guards to reinforce the hose at critical points. Selecting a hose with thicker walls or a convoluted bore will also minimise kinking and resist crushing.

It is worthwhile to note that a hose made with Teflon having a convoluted bore has a recommended bend radius that is three to four times tighter than a PTFE hose of the same size with a smooth bore. Convoluted bores also provide greater crush resistance in vacuum applications.

All hoses made with Teflon are the same  -  Teflon is the DuPont trademark for its family of fluoropolymer- materials, not all of which have the same properties. Two different Teflon fluoropolymers are typically used in the hose industry, a melt-extrudable form (such as PFA, FEP, or ETFE) and a paste-extrudable form (PTFE). Melt-extrudable materials necessarily have a lower melting point than paste-extrudable materials. They also have lower flex fatigue resistance.

The premier PTFE resin used in hose construction is a grade of Teflon called T62. Because Teflon T62 is not a thermoplastic, it cannot be continuously extruded, which has traditionally limited the length of hose that can be produced. This problem is now largely overcome by the latest generation of paste extrusion equipment, which has the capacity to produce much longer continuous lengths of PTFE hose – up to four times longer than that produced using traditional equipment.

Hoses made with Teflon are not the answer for every application, but they can deliver lower lifecycle costs than rubber or thermoplastic hoses in a much broader range of applications than the relatively restricted range for which they are commonly considered. If you have not considered using hoses made with Teflon, it may be time to take a second look.

Teflon T62 is standard in Eaton’s PTFE hoses. The company can produce long lengths of PTFE hose – around 120m continuous length for a hose with an internal diameter of 25mm, for example. That means fewer joints and less waste for end users.
 


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