Starting at $282.00
  • Usually ships in 2-3 weeks



  • Unique Cam Design Assures Low Pressure Drop and Does not Require Bellows, Seals, or Mechanical Linkages
  • Minimum In-Line Restriction
  • Pipe Line Size: 1 1/4" and up
  • Primary Construction Material: Stainless Steel or Brass
  • Maximum Operating Pressure: 2000 PSIG
  • Pressure Drop: 3 PSIG Maximum
  • Operating Temperature: -30 to 300°F
  • Set Point Accuracy: ± 25%
  • Switch: SPDT, 20 VA
  • Repeatability: ± 5%


The Gems FS-550 series are high pressure, metal paddle flow switches that sense liquid flow in either direction to monitor flow/no-flow conditions. Featuring rugged brass or stainless steel bodies, the FS-550 utilizes a simple and reliable design suitable for operating temperatures from -30 to 300°F and line pressures up to 2000 psig. The FS-550 is available with a standard SPDT switch or an optional 3-pin J-box electrical connection.

The FS-550 series is for use in pipes from 1-1/4 to 4". The unit has two paddle lengths dependent upon pipe size. The short paddle, for 1/1/4" pipes has actuation (or de-actuation) rates from 5 to 29 gpm. The long paddle, for pipes from 1-1/2 to 4" has actuation (or de-actuation) rates from 15 to 52 gpm. Paddles are 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.

Applications for the Gems FS-550 Series flow switch:

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


This product can be used in the following applications: