Flanges are commonly used to connect valves into pipework making it easier for removal and maintenance. There are many common flange standards and flanges within the same standard can etiher be flat or raised face. Here is a reference table for critical flange dimensions to help identify what standard you have.
Flow Rates for Butterfly Valves - CV Value
Even though we work on a metric system, measures of flow are commonly given as a CV value which is an; Imperial measure flow in US gallons per minute of water at 60° fahrenheit with pressure drop of 1 psi across the valve. Here is the link for the table of the flow rates for Butterfly Valves at different opening stages between zero degrees (fully closed) and ninety degrees (fully open). Please note that a CV value is not a linear progression so it cannot be extrapolated out just by looking at the values, it is really just meant to give you a comparison flow rate.
Steam Chart pressure versus Temperature. Here is the link for the table of steam pressure at different temperatures.