(Was Model 341) (Was Model 320/316) (Was Model 322) (Was Model 722) (Was Model 723)

Benefits & Features

  • Provides direct visual observation of process in vessels or pipe
  • Threads directly into female half coupling
  • Fused Glass units suitable for vacuum service
  • Sizes 1/4” to 3”MNPT
  • Style SF has superior fused glass clarity
Standard Specifications*
Wetted MaterialsNon-Wetted Materials
StyleConnection Size MNPTBodyGasketGlassGlass Retaining RingCushion
LP1/4” to 2”BrassFluorocarbon (FKM)Annealed BorosilicateBrassKlingersil® C-4401
MP3”Carbon SteelFluorocarbon (FKM)Annealed BorosilicateBrassKlingersil® C-4401
1/2” to 3”316SS
MF1/4” to 2”**Zinc Plated Steel-Fused Soda Lime--
HF1/4” to 2”Electroless Nickel Plated Steel-Fused Soda Lime--
SF1/4” to 3”Duplex 2205 SS-Fused Borosilicate--

*Optional materials are available for most sight windows. See matrix or consult factory.
** Style MF 3/8” & 3/4” have MNPTF-Dryseal threads requiring thread sealant

Standard Non-Steam Ratings
1/4”100 PSIG @ 300°F-125 PSIG @ 250°F2000 PSIG @ 69°F1450 PSIG @ 536°F
3/8”100 PSIG @ 300°F-125 PSIG @ 250°F1850 PSIG @ 69°F1450 PSIG @ 536°F
1/2”90 PSIG @ 300°F250 PSIG @ 400°F125 PSIG @ 250°F1750 PSIG @ 69°F1450 PSIG @ 536°F
3/4”80 PSIG @ 300°F250 PSIG @ 400°F125 PSIG @ 250°F1500 PSIG @ 69°F1450 PSIG @ 536°F
1”60 PSIG @ 300°F200 PSIG @ 400°F125 PSIG @ 250°F1250 PSIG @ 69°F1450 PSIG @ 536°F
1-1/4”35 PSIG @ 300°F150 PSIG @ 400°F125 PSIG @ 250°F1000 PSIG @ 69°F1450 PSIG @ 536°F
1-1/2”25PSIG @ 300°F100 PSIG @ 400°F125 PSIG @ 250°F750 PSIG @ 69°F1450 PSIG @ 536°F
2”25 PSIG @ 300°F100 PSIG @ 400°F125 PSIG @ 250°F500 PSIG @ 69°F1450 PSIG @ 536°F
3”-150 PSIG @ 400°F--362 PSIG @ 536°F
Series W16
Visible Diameter

See drawings for more ratings and dimensions.

Application Notes:

  • Saturated Steam Service: Contact factory
  • Potable Water: Carbon Steel units are not suitable for potable water, but Stainless Steel units are suitable
  • Vacuum Service: Style HF and SF only
  • Gaseous Service: Style HF and SF only
  • Compatibility: Before ordering, verify all materials 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: www.P65Warnings.ca.gov
Replacement Parts


Low Pressure – Brass
Matrix Ordering
Medium Pressure – CS & 316SS
Matrix Ordering
Medium to High Pressure – Fused Glass
W16 MF Matrix Ordering
High Pressure – Fused Glass
W16 HF Matrix
Extra High Pressure – Fused Glass
W16 MF Matrix Ordering