Gas control valves and gas pressure regulators calculator is now available at:
http://www.pipeflowcalculations.com/gascontrolvalve/
With gas control valve and gas pressure regulator sizing calculator you can calculate flow coefficient Cg and Kg and choose correct valve from manufacturer's flow table. Also, for known flow coefficient Cg or Kg you can calculate the maximum capacity of control valve or pressure regulator for given upstream and downstream pressure.
Gas control valves and pressure regulators new calculator
Gas control valves and pressure regulators new calculator
Pipe flow calculations - since 2000