Other Flat Glass Gage Accessories

Gage Glass Shields​

Mica Shields
Mica Shields are used with process media that will corrode glass.  The most common is steam above 2069 KPaG (300 PSIG) Working Steam Pressure (WSP).  Transparent glass must be used to provide a flat surface to back the shield.  Mica is a laminate type, naturally occurring material resistant to alkaline and can be used in high temperatures.  As a layer of mica degrades in service, a new layer is exposed.

PCTFE (Formerly Kel-F) Shield

PCTFE shields are a common alternative to mica shields and extremely resistant to chemical corrosion but ineffective in steam service.  These shields are most commonly used in hydrofluoric acid service.  It should be noted that PCTFE is available in varying degrees of optical quality.  While a PCTFE shield is not completely transparent, Jerguson shields are extremely clear and contain a minimal milky-white appearance.  This milky-white appearance is prevalent with third-party product and can make it extremely difficult to read the level in the gage.


Belleville Spring Washers

Jerguson Belleville Spring Washers are recommended for process temperatures over 500°F (260°C) or 600# steam.  Belleville Spring Washers help maintain constant bolt load during thermal expansion and contraction, thereby maintaining both gasket load and an effective seal.


Support Brackets

Jerguson Support Brackets are typically recommended for gages in excess of four or five sections in length.  This length recommendation can vary based on gage type (reflex or transparent) and the amount of piping between the glass level gage and the vessel.

Expansion Loops

Jerguson Expansion Loops relieve piping stresses which can be transmitted to the gage thru thermal expansion and contraction of the vessel.  Expansion loops are typically recommended for steam applications above 750 WSP.


Non-Frost Extensions

Series NF

  • Required for cryogenic installations, should extend 1/2″ (12.7mm) beyond insulation

  • Reflex or Transparent Types

  • Standard or Large Chambers


For low temperature applications where frost has a tendency to build up on the gage, the Jerguson frost preventing unit keeps frost from covering the window and maintains clear visibility at all times.


The Jerguson Non-Frosting Unit consist of a plastic extension which makes direct contact with the gage glass and extends beyond the cover so that the frost build up does not obscure reading of the liquid level.

Mounting of the plastic extension is simple and can be accomplished without dismantling the gage.  The non-frost extension can be installed or removed (for cleaning), either before or after the gage has been put into service.