FS-550 Series Flow Switch

FS-550 Series Plastic Paddle Type Flow Switch
  • Engineered for Positive Liquid Flow Detection at Pressures to 2000 psig (137.9 bar) 
  • Unique, Patented Cam Design Assures Low Pressure Drop and Does not Require Bellows, Seals, or Mechanical Linkages 
  • Minimum In-Line Restriction; Paddle Pivots to Move Out of Liquid Path with Increasing Flow 
  • Pipe Line Size: 1 1/4" and up 
  • Primary Construction Material: Stainless Steel or Brass 
  • Setting Type: Fixed

Standard FS-550 switches sense liquid flow in either direction to monitor flow/no-flow conditions. They are supplied in two paddle lengths. The paddle is trimmed during installation to permit switch actuation at the desired flow rate. As flow increases in a pipe, the paddle of the switch pivots to move out of the liquid path, producing less than 3 psig (.21 bar) of pressure drop regardless of pipe size.  

Using Gems™ Safe-Pak® Relays and Barriers, these switches provide automatic flow / no flow interlock and are intrinsically-safe without explosion-proof housing and piping. 


  • Compressors 
  • Heat Exchangers 
  • Turbines 
  • Engine 
  • Boilers 
  • Chillers 
  • Valves 
  • Pumps 
  • Regulators