Flanges with flats in their bolt circles

[whotmewory_again]

Can anyone tell me what the name is for pipe flanges that have flats machined into them? I am trying to source replacements for OLMSTED FL-series flanges with flats in them, but I don't know what this style of flange is named.

Thanks, from Chris in South Florida.

 

[XL83NL]

What is an OLMSTED FL-series flange?

 

[LittleInch]

A drawing or picture would help as well as size, pressure rating, design code, etc

Flats where?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Rputvin]

Is it possible you're talking about a raised-face (RF) flange?