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PTFE is a very popular choice in applications such as seals, bearings … and bellows.  

In this blog post, we are going to review four fast facts about PTFE bellows, including their applications, the benefits they provide, their manufacture, and what the key design choices are for them.

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Fact 1: Applications of PTFE Bellows

There are many applications for PTFE bellows.  They are commonly used to ….

  • Protect delicate processing equipment made of materials such as graphite, glass lined steel, etc.
  • Absorb dimensional changes (axial, lateral, angular, torsional offset), including thermal deformation
  • Isolate vibration hazards
  • Provide pulse dampening
  • Absorb shock loadings
  • Act as protective covers for reciprocating equipment

A wide variety of industries make use of PTFE bellows, including industrial machinery, pollution control, medical equipment, piping systems, wastewater treatment plants, paper and pulp processing, semiconductors, pharmaceutical processing, food and dairy processing, and chemical equipment. PTFE bellows are a common component in lined pipes, sampling valves, stem valves, and solenoid valves as well as metering equipment.

Fact 2: Benefits of PTFE Bellows

PTFE is an ideal choice for bellows for several reasons, beginning with its chemical compatibility. Because of PTFE’s resistance to corrosion, outstanding thermal properties, its hydrophobic nature, it is ideal for applications that involve corrosive media, intense cleaning, purity, and hot applications.  It is commonly used with high concentrations of acids, strong oxidizing and reducing agents, and chemically active organic compounds.  PTFE’s resistance to heat (including steam) and chemicals also makes it incredibly easy to clean and sanitize compared to similar polymers.  PTFE is also available in FDA approved grades, making it well adapted for applications in food and drug processing.  

In addition, PTFE has a long flex life and very low spring rate – key characteristics for bellows and expansion joints.  The low spring rate of PTFE makes it a perfect choice for protecting fragile or brittle equipment.  In addition, it is available in static-dissipating grades that make it valuable in the semiconductor industry.

Fact 3: Key Design Criteria for PTFE Bellows

The major design criteria for bellows are the geometry, number of convolutions, and wall thickness. For example, the thinner the walls the more flexibility, but thin walls also severely limit the operating pressure of the bellows.  Convolutions provide the structural integrity needed to contain the pressure (including vacuum pressures).  In general, fewer convolutions make it possible to achieve higher temperature and pressure ratings.  There is a cost, however, for having fewer convolutions:  the fewer the convolutions, the more limited the flexibility.

Fact 4: Manufacturing of Polymer Bellows

Most polymer bellows (including PTFE) are manufactured through a precision machining process beginning with a solid polymer blank.  The blank was usually produced through extrusion or compression molding.  Note that sometimes bellows are blow molded.  

Don’t Forget the PTFE Bellows

If you find yourself preparing the specifications for bellows or expansion joints, take a few minutes to review the benefits and applications of PTFE bellows to see if they may be right for your project.  They are a trusted component in many different industries and find various applications from wastewater treatment to semiconductors.  PTFE works with a wide variety of chemicals, cleaning agents, and sanitizing processes while providing a long flex life coupled with a low flex rate.

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