WARNING : As of 2024, the Custom Valves Concept company ceased all operations worldwide. We don't know of any replacement solution on the market.

Custom Valve Concepts (former Kates cy) has been manufacturing flow rate controllers for every type of application.
Successful in a variety of liquid and gas applications, the Kates FC Valve combines an adjustable orifice with an internal regulating valve, maintaining a constant pressure drop across the metering orifice.
  From air to zinc hydrosulfate, Kates Controllers provide a simple alternative for numerous complex flow applications.