LIGO Document M080310-v1

Safety Bulletin: Kovar-Sealed Glass Vacuum Viewports

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M - Management or Policy
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Investigation of the May 2008 vacuum accident at Virgo revealed important information about the safety of certain standard commercial viewports. The viewports in question are those made of Corning 7056 or Kodial glass sealed directly to Kovar alloy, which is in turn welded into a stainless steel vacuum flange (usually a ConFlat type). These may be called “Kovar-sealed”, “zero-length,” “low-profile” or “zero-profile” viewports in catalog descriptions. This document describes how to identify the faulty viewports.
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Notes and Changes:
adding a sketch to help identify the faulty viewports

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