I have seen the code case but can't seem to find it any longer. It may be expired. It outlines the type of glass that can be used and the allowable design stress as well as any additional requirements for code compliance.
I don't believe you will find glass in the materials of Sec II D. I think that the code is based on materials having a Poisson's ratio of that of steel and glass would be significantly different.
One would handle it as an exception. I certainly may be incorrect, but this is my thought. If you find out differently, please let us know here.
Try the manufacturers of the hardware as well as the glass.
A sight glass would fall outside of the scope of the ASME Code, as the vessel designer could choose to make the extents of the vessel at the sight glass' flanged connection. If I were you I would look at B31.3, and having this scoped as Piping
Here is list of standards from Schott that pertain to sight glasses for use on pressure vessels and boilers. In short of a ASME standard you can cover yourself under the best available practice umbrella. One thing to note is that there are different materials used in manufacture of sight glasses so make sure choice is compatible with your process.
Greetings,
I wrote the sight glass section of our company's mechanical integrity standard and have used sight glasses (including those as the pressure barrier for process cameras) since the 1980's. I would only specify a fused-glass unit and not trust a tempered glass unit in pressure service.
You can install them between standard flanges and treat them similarily to metal spacers. I have also installed dimensionally identical replacements for tempered glass units to increase the level of safety. They are a little more expensive than tempered units, but pay for themselves after one replacement since manufacturer's specify replacement when a tempered unit is removed after initial compression (e.g., cleaning).
You will get different view areas for a given size from different manufacturers depending on the metal used as the outer ring. The two major suppliers I trust are J.M. Canty(Fuseview)and L.J. Star(Metaglas). Contact them and make your decision.
