Critical Standards for Specifying Sight Glasses

Sight glasses are highly engineered products. Although brands look alike, differences in their specs have tremendous importance for worker safety, sanitary processes, and maintenance costs. Here are the critical specs and standards for sight glass selection:

DIN 7079 Standard for Fused-Glass
Sight Glasses in Metal Frames


The DIN 7079 standard for fused-glass sight glasses sets standards for fusion, thermal properties, strength, and chemical resistance. This is a stringent standard, and not all sight glasses can meet its specifications.

DIN 7080 Standard for

Borosilicate Glass Quality


The DIN 7080 standard means the glass has passed tests for material strength, shock endurance, chemical resistance and compression. There is no reason not to insist on this high quality glass.

Factory Mutual (FM)


Factory Mutual has defined standards that sight glasses should meet in order to provide safe operation. Use of FM approved products may in some cases reduce plant insurance costs.

ASME-BPE


The ASME BPE (Bio-Processing Equipment) Standard standardizes specifications for the design, manufacture and acceptance of vessels, piping and related accessories for use in equipment used in the biopharmaceutical industry. Sanitary sight glasses should meet ASME-BPE standards at a minimum.

UP Glass Standards for Pharmaceutical Use

The USP (United States Pharmacopoeia) provides standards that govern the classification of glass into types suitable for specific pharmaceutical uses.


USP Type I (Borosilicate Glass)

USP Type I borosilicate glass is the least reactive glass available. It can be used for all applications and is most commonly used to package water for injection, un-buffered products, chemicals, sensitive lab samples, and samples requiring sterilization. All lab glass apparatus is generally Type I borosilicate glass. To meet this standard, a sight glass must pass test procedures defined by USP29-661. USP standards require the use of Type I glass for many applications. Many sight glasses on the market fail to meet this important standard, and some sight glasses are not even Type II or Type III; rather they are non-parenteral, which means they should not be used in applications where chemical durability and heat shock are factors.

USP Type II (De-Alkalized Soda-Lime Glass)

USP Type II de-alkalized soda-lime glass has higher levels of sodium hydroxide and calcium oxide. It is less resistant to leaching than Type I but more resistant than Type III. It can be used for products that remain below pH7 for their shelf lives.

USP Type III (Soda-Lime Glass)

Factory Mutual has defined standards that sight glasses should meet in order to provide safe operation. Use of FM approved products may in some cases reduce plant insurance costs.

USP Type NP (Non-Parenteral)

USP Type NP soda-lime glass is a general purpose glass and is used for non-parenteral applications (non-injectable drugs) where chemical durability and heat shock are not factors. These containers are frequently used for capsules, tablets and topical products.

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