ASME Standards for Typical Valve Requirements
ASME - American Society of Mechanical Engineers. Founded in 1880 this organization works to ensure standards are met/improved to ensure safety and efficiency in engineering practices. www.asme.org
ANSI - American National Standards Institute www.ansi.org
ASME/ANSI B16.34 is the American Society of Mechanical Engineers standard for which valve pressure/temperature ratings are derived. This spec. indicates at what temperature/pressure rating a valve must adhere to to meet certain standards. The specification is for "steel valves- flanged & buttweld ends".
ASME/ANSI B16.10 lists all the face to face dimensions for flanged/buttweld end valves. Valves designed to this spec must meet standard face to face dimensions depending on size/pressure class. It should be noted that threaded and socket-weld valves are not designed to this spec.
Copies of these specs can be purchased directly from the American Society of Mechanical Engineers at http://www.asme.org/kb/standards#des=B16
Contact - The Valve Pipeline
In really low pressure applications sometimes a trunnion ball is better than a floater given that the spring will help seal the flow instead of the weak flow in the line.