Valve Sizing Technical Bul let in

Valve size often is described by the nominal size of the end
connections, but a more important measure is the low that
the valve can provide. And determining low through a valve
can be simple.
This technical bulletin shows how low can be estimated
well enough to select a valve size—easily, and without
complicated calculations. Included are the principles of low
calculations, some basic formulas, and the effects of speciic
gravity and temperature. Also given are six simple graphs for
estimating the low of water or air through valves and other
components and examples of how to use them.

Sizing Valves
The graphs cover most ordinary industrial applications—from
the smallest metering valves to large ball valves, at system
pressures up to 10 000 psig and 1000 bar.
The water formulas and graphs apply to ordinary liquids—and
not to liquids that are boiling or lashing into vapors, to slurries
(mixtures of solids and liquids), or to very viscous liquids.
The air formulas and graphs apply to gases that closely
follow the ideal gas laws, in which pressure, temperature,
and volume are proportional. They do not apply to gases or
vapors that are near the pressure and temperature at which
they liquefy, such as a cryogenic nitrogen or oxygen.
For convenience, the air low graphs show gauge pressures,
whereas the formulas use absolute pressure (gauge pressure
plus one atmosphere). All the graphs are based on formulas
adapted from ISA S75.01, Flow Equations for Sizing Control