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Blow-down should be conducted on a routine basis, or as necessary based on water quality.
Conducting blow-down more often than required to keep glass clean can lead to premature
mica and glass wear, and eventually leakage or glass failure.
Maintenance
Inspecting Glass: Inspect the glass regularly for any signs of clouding or scratching. In
new processes, the gage glass should be inspected routinely until the need for
replacement becomes apparent. To examine the glass for scratches, shine a very
bright, concentrated light at about a 45° angle. Anything that glistens brightly should
be looked at closely. Any scratch that glistens and catches a fingernail and/or any star-
shaped or crescent-shaped mark that glistens is reason for replacement. An inner
(chemical) glass surface that appears cloudy or roughened and can’t be cleaned has
likely been chemically attacked and should be replaced.
Cleaning Glass: Glass gages may be taken out of service and the glass cleaned
through a top-mounted offset pattern valve. Keep glasses clean using commercial
glass cleaners (Windex, Glass Wax, Bon Ami, Lava Soap, Super Soilax, household
detergents, etc.). Where regular cleaners do not work, use dilute acids such as
hydrochloric (muriatic) acid. Carefully observe safety rules when handling these
chemicals. Cleaning should be done without removing the glass. This may require
circulating the cleaner if the process side of the glass is not accessible. Never use
harsh abrasives, wire brushes, metal scrapers, etc. that could scratch the glass. DO
NOT attempt to clean any glass while the gage is in service.
Receiving / Storing Glass: Upon receiving replacement glass, inspect the container and
glass for shipping damage. When inspecting glass, unwrap and rewrap carefully.
Avoid contact of the polished faces with any object (including table tops). Keep the
glass in its original box until ready to use. Take care not to bend mica when handling,
and avoid touching the face of the mica shield. Store it with the glass in the original box
to protect against accidental breakage.
Disassembly: Prior to disassembly, be sure the gage is depressurized and at ambient
temperature. Failure to do so may result in a sudden release of pressure and/or glass
breakage. Loosen the end nuts/bolts first, working from opposite ends toward the
center.
Reassembly: The cutaways below show the construction of Reflex and Transparent
glass gages.
