MARATHON HEATER - OEM Heating Elements Manufacturer

End Seals

Comparison Chart

 

End Seals and Lead Wires

Type

Temperature

Moisture Applications

Vibration or Flexing

Cement

2000 °F

Poor

Poor

Epoxylite

600 °F

Good

Excellent

Teflon Seal

450 °F

Excellent

Excellent

Teflon Leads

450 °F

Excellent

Excellent

RTV

400 °F

Excellent

Average

Silicone Rubber Leads

350 °F

Excellent

Excellent

SJO Cord

250 °F

Excellent

Excellent

Epoxy

200 °F

Good

Good

 

Descriptions

Lava Seal

 A swaged in lava plug protects the internal cartridge from outer contamination.

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.
Rated to 2200º F.

Epoxylite Potting

 Provides similar mechanical properties as epoxy potting, however it is rated to 650º F.

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.
Rated to 400º F. and bonds well to Duraflex lead wire.

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 has a temperature rating of 400º F., it softens slightly above 300º 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.

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 500º F. and while extremely flexible, it is not as strong mechanically as other options.
  • Although the RTV is rated for 500º F., silicone rubber lead wire is only rated to 400º F. An option is to use Duraflex lead wire instead. Duraflex is rated to 1000º F... 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.

 

Images / Chart

 

End Seal Type Max Temp Moisture Protection Contamination Mechanical Strength Vibration Resistance
Ceramic End Piece for Cartridge Heater Ceramic End Piece 2500 F Poor Poor Excellent Excellent
Teflon end piece for cartridge heater Teflon End Piece 300 F Excellent Excellent Very Good Excellent
Mica seal for cartridge heater Mica Seal 2500 F Poor Good Average Average
Cement potting for cartridge heater Cement Potting 1800 F Poor Fair Good Poor
Epoxy potting for cartridge heater Epoxy Potting 265 F Good Good Excellent Excellent
Epoxylite potting for cartridge heater Epoxylite Potting 650 Fair Very Good Very Good Excellent
Silicone rubber potting for cartridge heater Silicone Rubber 500 F Excellent Excellent Fair Excellent