NPT Sight Glass Windows
Select Stock Configurations Below
  • NPT – ISO standard male tapered threaded sight glass
  • Exhibits no outgassing or contamination of most systems*    
  • Long working life
  • No maintenance required
  • Tested to high safety factor to insure safety & reliability
  • Exceeds all industry and MIL standards
  • Engineered, Manufactured and tested at the Rayotek U.S. facility  
  • Ultra-High Pressure (UHP) tested to 20,000PSI or higher available

NPT Sight Windows, made to ISO 7-1:1994 standards, are a low cost solution for viewing and observation ports for fluid, flame and gas viewing, indicators and sensors. Rayotek NPT Sight Windows utilize glass, sapphire and other transparent materials sealed into a corrosion resistant metal housing to create a hermetically sealed unibody Sight Glass.

Rayotek NPT Sight Windows are exceptionally robust in extreme thermal, chemical, mechanical and pressure environments.  They also perform exceptionally in ultra-high vacuum, high purity, cleanroom rated systems.

Click Configuration for Pricing & Drawings.

Temperature Range
General-purpose indicator & observation, vacuum to ultra high pressure. NACE MR0175/ISO15156 compliant. Zero leak rate. UHP tested to 20,000PSI
0 Kelvin - 400C
Optical quality, extreme scratch and chemical resistance for UV, visible and IR viewing for vacuum and high pressure.
0 Kelvin - 200C
Optical quality for high purity, ultra high vacuum at extreme temperatures
0 Kelvin - 850C
Super high temp for UV, IR & visible inspection, pyrometry & indicators; air, gas and vacuum systems where <10-8 bar-CC/sec leakage is acceptable**
0 Kelvin – 900C


  • High pressure tanks
  • Liquid level view ports
  • Hydraulic level indicators
  • Flame & explosion observation ports for furnace, heater & hazardous systems
  • Supercritical & petroleum research systems
  • All classes of refrigerant systems, including CO2-based R744
  • Sanitary & FDA applications for pharmaceutical & food processing
  • Simple lighting windows for deep sea, ultra high pressure & vacuum systems

Rayotek Sight Windows can reliably meet and exceed the requirements of many applications from industrial to research. The selection of window, housing material and sealing method will help optimize the best sight window configuration for your application.

† Alternative materials are available upon request including, but not limited to:
        Housing: duplex, aluminum, Monel, Inconel, plastics and alumina
        Window: borosilicate (Pyrex®), diamond, Zinc Selenide, fused silica, germanium, MgF2, silicon and YAG

*  For systems where purity & cleanliness are critical, Rayotek recommends testing the Sight Window for specific chemical compatibility.
    Call for information.

** Typical leak rate is 10-8 bar-CC/sec. for air at 22C. Actual leak rate TBD based on window size and maximum operating temperature.
    Call for information.

Contact Us with questions or to discuss your requirements and we'll be happy to help