I need a spectacle blind flange rating chart is there one?

A few months ago, I was asking the same question. I did a search online to see if I could find a pressure rating chart and came across the Sweco Fab website. The fact of the matter is that the charts on the Sweco Fab are a little confusing and do not provide accurate information. I tried to contact Sweco Fab to get more information and asked if they could send me a pressure rating chart. They never responded to my request.

There are a lot of variables that go into determining the pressure rating of a spectacle blind. Size of pipe, flange size, type of material, corrosion resistance, thickness of blind, etc. Your best bet is to manually calculate the pressure rating by using equation (15) in section 304.5.3 found in the ASME B31.3-2002 specification. If you are using a standard thickness you can solve for pressure. I would recommend using the standard thicknesses that can be found in ASME B16.48-2005 (Line Blinds) specifications.

If you don't have the time, ability, or resources to figure out the pressure ratings yourself, you can also contact manufacturers of spectacle blinds and request the information. I didn't have any luck with Sweco Fab, Inc. but I'm sure there are manufactures out there that are willing to help.