(Was 501BT)

Benefits & Features

  • Glass Fused to Metal Ring per DIN7079
  • Superior clarity with higher pressure and temperature ratings than standard observation plate glass
  • Suitable for sight flow indicators, sight windows, and sanitary indicators
  • Highly resistant to impacts and erosion
  • Resistant to surface damage
  • High tolerance to uneven and or repeated torqueing without damaging the glass
  • Reusable for easy maintenance
  • Bolts to vessel flange without requiring a cover flange
  • Mates to ANSI B16.5 flanges
  • Pressure Ratings: up to 300 PSIG
  • Temperature Ratings: up to 536°F for Duplex 2205 SS and 572°F for Carbon Steel
Standard Specifications*
Wetted MaterialsNon-Wetted Materials
StyleTypeSizesMetal Ring/GlassGasketCover FlangeNon-Steam Pressure Ratings
BTBolt-Through1-1/2” to 8”Duplex 2205 SSFused Borosilicate DIN7080--150 PSIG @ 14 to 450°F
300 PSIG @ 14 to 450°F

*Optional materials are available for ring material, glass and gaskets. See matrix below for standard options or consult factory. Vessel flanges are user supplied. Disc is flat faced and is to be mated with flat face flanges. Also requires full faced gasket (user supplied).

series w14

Fused glass in metal ring disc with bolt-holes. Bolts directly to vessel flange. Gasket and vessel coupling are user supplied. No cover flange required.

BT Dimensions
Size150 PSIG300 PSIG


  • Materials (see matrix for standard options or contact factory)
  • Gasket materials (contact factory)
  • Glass Lens (contact factory)

Application Notes:

  • Saturated Steam Service: Please inquire if needed as Standard units do not conform to requirements for Saturated Steam Service
  • Potable Water: Carbon Steel units are not suitable for potable water, Duplex 2205 SS units are suitable
  • Vacuum Service: Contact Factory
  • Gaseous Service: Not acceptable
  • Compatibility: Before ordering, verify all materials of our sight windows are compatible with the service media(s), intermittently used cleaners, the environment, and cleaning processes in conjunction with the temperatures and pressures of the application(s) and future applications. John C. Ernst Co. does not make chemical compatibility recommendations. Compatibility is the responsibility of the user and/or specifying party.

Warning WARNING: This product can expose you to certain chemicals, which are known to the State of California to cause cancer or birth defects or other reproductive harm. For more information go to:
Replacement Parts


W14 BT Matrix Order