Guidance for material selection – and for determining which information is important for a specific application
When selecting a seal, the material and design must be suitable for the operating conditions. In addition to the medium, temperature, and pressure, factors such as movement, the installation space, and the condition of the sealing surfaces also play a role.
PTFE, elastomer, or metal?
PTFE offers advantages in many applications, for instance due to its chemical resistance and low friction. Depending on the requirements, pure PTFE, modified PTFE, or PTFE compounds may be suitable. These variants differ, among other things, in their behavior under pressure and their wear characteristics.
Elastomers, often colloquially referred to as rubber, can undergo elastic deformation and conform to sealing surfaces. They are available in various material types; the appropriate choice depends on factors such as the medium and the temperature.
Metallic seals can be a suitable solution for certain operating conditions – for instance, when the design requires withstanding high loads. However, they must be precisely matched to the specific application and the sealing surfaces.
No single material is the best solution for every application. The decisive factor is the set of properties the seal must exhibit during operation.
What to consider regarding PTFE seals
Pure PTFE can deform under sustained load. This behavior is known as cold flow. Modified PTFE or PTFE compounds reduce this tendency. The appropriate version to use depends on the specific operating conditions.
For an informed material selection, the following information, among other things, is helpful:
- Which medium comes into contact with the seal?
- What temperatures and what pressure occur?
- Does the seal move during use?
- What is the condition of the sealing surfaces?
- What are the characteristics of the mating surfaces?
- What are the requirements regarding service life and maintenance?
The more precise this information is, the more accurately the materials can be selected.
PTFE Nünchritz manufactures custom-designed seals and structural components made from PTFE, modified PTFE, and PTFE compounds. These include, for example, seals for valves and ball valves, as well as bellows for pumps and valves—or for use as expansion joints and stem covers.
Are you looking for a seal for a specific application? Talk to us about your requirements. Together, we will determine which material and design are suitable.
