MSS SP-99 standardizes the face-to-face dimensions to ensure valves from different manufacturers are interchangeable.
The standard does not strictly mandate one material but lists acceptable material standards. mss sp99 pdf
Before this standard, different manufacturers produced instrument valves with varying face-to-face dimensions. This made it difficult for engineers to swap out a valve from one vendor with a valve from another without modifying the piping. MSS SP-99 standardized these dimensions, ensuring that a Class 3000 valve from Manufacturer A fits the same space as one from Manufacturer B. MSS SP-99 standardizes the face-to-face dimensions to ensure
Once you obtain a legitimate copy of the MSS SP-99 PDF, here is what you will find in its typical structure: mss sp99 pdf