These fasteners are actually pretty easy to come by... the Xylan line of coatings (fluoropolymer based) are what is typically supplied when people ask for "PTFE coated". In addition to what Duwe6 said regarding galling, the corrosive effects will be severely diminished by the protective coating...
I am going to give you my $.02 as someone who lived day & night in the valve world and shared your frustration... the industry is extremely sloppy, IMO... several different standards are used and many, many factors need to be considered.
Basic flanged valves are built to ANSI classes... 150#...
ASTM is the more common nomenclature used to call out the spec for fasteners... and when you're talking "process" fasteners... i.e. B7, B8, B8M... they're typically dual-rated. The brokers that import the material (which are responsible for most of what is sold in the market) buy dual rated to...
Question 1 is what do you mean by "food grade"... no offense, but it's kind of a nothing term. I used to work with plenty of plans that used standard ANSI class 150# materials for food grade stuff... i.e. flanged ball valves, 304 pipe, Garlock gaskets, etc. etc.
Remember, most "potable" water...
This is a super common question... most fastener houses live in the grade 2/5/8 world and don't know the difference between ASME or ASTM and a flat washer!
Our website has a listing of some common specs for flanges & piping applications. This should help narrow down your choices and then you...
Here's a convenient common one... this is mostly concerning the ASTM/ASME grades that are common in the process piping & heavy industry worlds... not really the grade 5 / grade 8/ SAE type stuff... it has some of the common alloys & a few uncommon ones as well.
www.tech-threads.com
click on...
Duwe6 is right about hardness. Make sure you call out the exact material type of the RTJ gasket, especially in SS or alloys (i.e. 304 and 347 have different hardnesses). The flange can crack the gasket or even vice-versa if the hardnesses are incorrect.
As to the issue of which RTJ type, from...