Pyrex, Borofloat and Vycor sight glasses provide outstanding chemical services, however certain corrosives may reduce the useful life of the sight glass by chemical action. Protection against the effects of most corrosives can be provided by mica, plastic film, or thin cover glass. Tempered glass should not be used if subject to corrosive attack. Annealed ware is a much better choice for these applications

Sudden temperature changes may be harmful. Assume a temperature difference limit of 200° F for fluid to ambient temperature. When glasses are used above 300° F use a vented shield or deflector to provide protection against chilling by blasts of air or water.

DESIGN RECOMMENDATIONS

Mounting rings must have smooth, clean gasket seats, flat to within .005" T.I.R. which dish no more than 1/2° regardless of the load imposed. Rings should be counter bored, accepting gaskets and glass to a depth of 3/16", holding minimum thickness indicated in tables.

The ASME Unfired Pressure Vessel Code treats the general subject of gaskets thoroughly. Use only gaskets that are approved by the maintenance supervisor or engineer. The gasket material depends on the fluid in the vessel, however in all cases gaskets should be smooth, without hard spots or wire inserts.

Use more bolts of smaller diameter than ASA flange standards to provide uniform loading. Check bolts and nuts for burrs. Lubricate them thoroughly with graphite grease. Use a torque wrench to tighten to values shown in the table. Follow a regular tightening pattern to avoid uneven loads on the glass. Conical spring washers will keep the joints tight during temperature cycling.

GOOD MAINTENANCE PAYS DIVIDENDS IN SAFETY

Inspect and replace glasses on a regular schedule depending on the type of service. Keep glasses clean using commercial glass cleaners, do not use wire brushes, scrappers or harsh abrasives. Use a very bright light to inspect for glistening marks in or on the glass, and for cloudy or roughened surfaces on the vessel side. Also feel for any rough scratches which catch your fingernail. If you find any of these signs, replace the glass regardless of the maintenance schedule.

INSTALLATION & GASKET VIEWS / MOUNTING BOLT DATA