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April 2, 2019

Insulator Seal Inc. (ISI™), a division of MDC Vacuum Products, LLC, manufactures electrical & optical ceramic-to-metal sealed components for harsh environments. ISI has been the innovation leader in the industry for over 30 years. Evolving from being a high vacuum solutions provider only, ISI now delivers world-class components for harsh environmental connector applications around the globe. They recently had the opportunity to work with the aerospace industry on junction boxes for jet engines.

Type K Junction Box - Insulator Seal ISI

Type K Junction Box


These are stud connection plates for Junction Boxes used on jet aircraft engines. These Junction Boxes and Terminal Blocks are part of the temperature sensor circuit that monitors intake and exhaust of the engine in operation.

boeing 747 jet engine

A jet engine seen on a Boeing 747



A jet engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. This broad definition includes air-breathing jet engines (turbojets, turbofans, ramjets, and pulse jets). In general, jet engines are combustion engines.


Jet Gas Turbine Engine

Exposed Gas Turbine Jet Engine



Jet engines date back to the invention of the aeolipile before the first century AD. This device directed steam power through two nozzles to cause a sphere to spin rapidly on its axis. It was seen as a curiosity.

Aeolipile Illustration - Jet Engine

Hero’s Aeolipile




  • Operating Temperature: -65ºF to +800ºF
  • Overall Height: .900”
  • Width:1.340” (Square)
  • Leak Rate: 1 X 10-8 STD AT. cc/sec Helium
  • Voltage Rating of 1000V AC at 50-60 Hz.
  • Max Leakage Current: 1 mA
  • Torque: ¼-28 Studs: 70 in-lbs.; 10-32 Studs: 27 in-lbs.


junction box example and junction box with gauge

Example of a jet engine junction box




  • Ceramic: 94% Alumina
  • Studs: Gold-Plated Type K (+ and -)
  • Housing: 321 Stainless Steel
  • Flange: Silfon (42% NiFe)




Jet Engine Plane Diagram


Jet Engine Test Example

A jet engine being tested



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