Never re-use glass or gaskets.
- Once a conventional sight glass has been removed from its mounting, regardless of the reason for removal, discard the glass and gaskets and substitute new glass and gaskets. Exception: Metaglas® safety windows may be reinstalled, following instructions provided for this procedure.
- Keep glass clean using commercial glass cleaners.
- Never use wire brushes, metal scrapers or harsh abrasives.
- Do not attempt to clean glass while equipment is in operation.
Sight glasses should be regularly inspected for damage.
- To examine for scratches, shine a very bright concentrated light source at an angle of about 45°. Anything that glistens should be inspected closely.
- Scratches that catch the fingernail and any star or crescent-shaped marks that glisten are cause for replacement.
- Sight glasses that appear cloudy or roughened after cleaning should be replaced.
- Also inspect sight glass frames/flanges for corrosion buildup.
Never use damaged glass.
- Never use glass that is scratched, chipped or otherwise damaged.
- Glass seating surfaces must be flat within 0.005˝ with a smooth finish.
- Flanges must be rigid.
- Do not allow the glass to contact metal when assembling.
- Gaskets must be new, clean and smooth.
- Use gaskets of the same diameter and fit them concentrically.
Never tighten bolts on a sight glass while equipment is in operation.
- Follow a regular tightening sequence to ensure even loading of glass.
- Allow a maximum difference of 1.5 ft/lbs between bolts during tightening.
- Tighten only enough to produce a positive seal against the process pressure.
- Bolts may need tightening after initial cycling of vessel.
- Never tighten bolts when the sight glass is hot.