USE  AND CARE
Examine the gage glass regularly for any signs of clouding, scratching,
erosion, or corrosion. In new processes, the glass should be inspected
daily until the need for replacement becomes apparent. This will help
establish the routine inspection and routine replacement cycles.
Keep gage glass clean using non-abrasive commercial glass cleaners. 
Where regular gleaners do not seem to work, use dilute acides shuch as
Hydrochloric (muriatic) acid. Always observe safety rules when handing
handling hazardous cleaning solutions. Never use wire brushes, metal 
scrapers, or harsh abrasives which could scratch the glass.
Scratches, corrosion, chips, surface flaws, or nicks on the surface or
edges weaken the gage glass. To examine for these, shine a very 
bright concentrated light ("Burton Lite" or powerful flashlight) at about
45 degree angle. Anything which glistens and catches the fingernail
or any star-shaped or crescent-shaped mark which glistens, is
cause for replacement. Any gage glass which appears cloudy or
roughened and will not respond to cleaning procedures, should be
Keep gage glasses in original packaging until ready to install.
Avoid bumping, chipping, or scratching gage glass. Any glass-to-glass
contact can cause scratches and must be avoided.
Always follow tubular gage manufacturer's recommended procedures for 
glass replacement.
Before installing a gage glass, remove all deposits from the seal contact
surfaces of the gland nut and the gland (where used). Check sealing
surfaces for cleanliness and smoothness. Once the gage glass has been
removed from its mounting, regardless of the reason for its removal,
discard the glass and replace with a new piece.
Always use new paking, seals, and/or O-rings (if required) when 
replaceing a tubular gage glass. Used packing, seals, and O-rings will
not properly support the gage glass or provide the proper pressure
seal without stressing the glass.
1. Hold fittings rigidly to prevent misalignment, which can cause severe
bending stresses in the glass, when packing nuts are tightened.
2. Provide metal washers so nuts can be tightened without twisting 
packing or tube.
3. Provide positive, but not excessive, clearance between glass, packing
nuts, and bearing washers.
4. Keep glass short enough to allow for expansion.
5. Provide positive clearance between the ends of the gage glass and
the metal fittings. Glass-to -metal contact will keep the gage galss from 
expanding and cause breakage.
6. Tighten packing nuts enough to prevent leakage, but not so much
that you hinder expansion and contraction. Follow gage manufacturer's
7. Generally, you can use cylindrical or conical runner packings for LOW
and MEDIUM pressures. HIGHER pressure and HIGH temperature
may require specialized packings. In all cases you should follow the 
recommendations of the gage manufacturer.
Sources: Corning Incorporated brochure "Tubular Gage Glasses"
Copyright 1991.