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End Seals

End Seals

Cement Provides protection against some thicker liquids and dust, however it is not waterproof. It is also somewhat brittle and subject to cracking in high impact or high vibration applications. Up to 2600°F. 
Ceramic A steatite endpiece provides excellent strength and temperature resistance.  However it offers little protection against moisture or other contaminats.
Lava Seal A swaged in lava plug protects the internal cartridge from contamination. Up to 1500°F. 
Teflon® Seal
  • Teflon Seals are a mechanical seal constructed by compressing a solid piece of Teflon in the end of the heater creating a seal between the Teflon piece and sheath, and a seal between the Teflon piece and the lead wire.
  • Teflon lead wire is used in conjunction with the Teflon end seal. While Teflon seal has a temperature rating of 350°F, it softens slightly above 300°F and can relax and compromise the seal.
  • An unheated section of 1” at the end of the heater is generally required to avoid overheating the seal.
Epoxy Potting Provides a very good seal with excellent mechanical strength. However, it's adherence to Teflon or silicone rubber lead wire is only fair. It is rated up to 265°F and bonds well to Duraflex lead wire.
Epoxylite Potting Provides similar mechanical properties as epoxy potting. Up to 600°F. 
RTV
  • RTV Potting, when used in combination with silicone rubber insulated lead wire, provides the best seal of all options.
  • The down side to silicone is that it is limited to 500ºF and while extremely flexible, it is not as strong mechanically as other options.
  • Although the RTV is rated for 500ºF, silicone rubber leads are only rated to 392ºF. An option is to use Duraflex lead wire instead. Duraflex is rated to 1000ºF and has a heavy silicone coating.
  • While Duraflex is not sold as a waterproof wire, it performs very well in wet environments.
  • Another option is to use crimped on leads, then the power pins are sealed where they enter the heater and the type of lead wire does not matter.

Chart

  End Seal Type Max Temp Moisture Protection Contamination Mechanical Strength Vibration Resistance Moisture Applications Vibration or Flexing
Cement Potting 2600°F Poor Fair Good Poor Poor Poor
Ceramic End Piece 2500°F Poor Poor Excellent Excellent Poor Good
Mica Seal 2500°F Poor Good Average Average Poor Fair
Lava Seal 1500°F Poor Good Fair Poor Poor Poor
Epoxylite Potting 600°F Good Very Good  Very Good Excellent Good Excellent
Cartridge Heater with RTV Potting RTV w/ Silicone Rubber Leads 392°F Excellent Excellent Fair Good Excellent Average
Teflon® Seal 350°F Good Excellent Very Good Excellent Good Excellent
Epoxy Potting 265°F Good Good Excellent Excellent Good Good
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