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FAQ page
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Q: What can cause a viewport to crack?
A: There are two main sources for viewport failure: thermal stress and mechanical stress. Thermal stress means the viewport is not heated evenly or the thermal gradient is too high. Mechanical stress is usually caused during flange installation and the bolts are not tightened evenly in small increments.
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Q: What does "nonmagnetic glass" mean?
A: The term "nonmagnetic" refers to the sleeve material used to make the viewport rather than the viewport material itself. A nonmagnetic sleeve is made of stainless steel, and because of the difference in thermal expansion between stainless steel and glass, the sleeve must be constructed with an extended length to allow for that expansion difference.
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Q: What does "zero profile" mean?
A: The total overall thickness is either equal to or very close to the thickness of the flange itself. Sometimes referred to as "zero-length". For viewports, it means the thickness of the entire unit is nominally the same at the thickness of the flange.
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Q: Can a viewport be repaired?
A: Yes. However, it may frequently be more cost effective to go with a totally new viewport. The main expense in a viewport is the viewport itself and making the seal between the sleeve and other materials. There is more work involved in cleaning out a damaged viewport and prepping the flange for a new sleeve than starting from a new flange.
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Q: Why does a shutter angle depend on the mounting of the shutter?
A: As a shutter opens, the unhinged end is the first part of the shutter to hit a port tube. As a port tube is shortened, the interference with the shutter is reduced. The least interference would occur with a flush mount or zero length port.
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Q: Can a double-ended glass adapter be used as an electrical break?
A: Yes. However, the electrical properties are severely limited when compared with ceramic breaks. MDC ceramic-to-metal adapters are recommended for high and ultrahigh vacuum system applications requiring high-voltage insulation.
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