Processing Magazine

When Are Fused Glass/Metal Sight Glasses Appropriate in Biopharm Applications?

September 27, 2006

Metaglas windows are widely used in sanitary service. Here one is shown configured to accept a sanitary-service clamp.

Myth: Fused glass/metal sight glasses using ordinary soda-lime glass are appropriate for most low-pressure applications.

Fact: For a good reason, MetaClamp® fused glass/metal sight glasses are made of borosilicate glass to DIN 7080 as standard. That''s because, in addition to having less strength than borosilicate glass, soda lime is also more susceptible to corrosion, thermal shock, and high temperatures.

Myth: Fused glass/metal sight glasses have small bubbles and crevices along the glass/metal seam that create bacteria traps.

Fact: It is possible that tiny bubbles will develop at the transition from glass to metal in the manufacturing process when using either soda-lime glass or, to a lesser extent, borosilicate glass. But, in a MetaClamp sight glass such bubbles are inconsequential since they are quite small and few in number, and they will not be found at or near the surface. Also, these sight glasses comply with DIN 7079 which dictates the allowable number and size of bubbles resulting from the manufacturing process.

Myth: MetaClamp fused glass/metal sight windows are limited in that they cannot be electropolished.

Fact:All MetaClamp sight glasses can be electropolished to any desired finish.

The versatile MetaClamp window meets many needs. Here one is shown installed as an observation port illuminated by a fiberoptic light source.

Myth: Traceability can be a problem with fused glass/metal sight glasses.

Fact: This may be true of some sight glasses but not MetaClamp sight glasses. They are permanently marked with Heat Number, Material, Size, and Manufacture. Other markings are available upon request.

Myth: Compliance with USP Class VI is vital in many biopharm applications.

Fact: That''s not a myth, it''s true! And MetaClamp sight glasses are fully compliant with USP Class VI, tested to confirm biocompatibility