• Used in 1/2" Lines and Larger
  • Explosion Proof and Nema 4X Locations
  • 316L Stainless Steel Sensor, Exotic Alloys Available
  • Temperatures to 900F
  • Pressures to 10,000 PSIG
  • Extremely Low Flow Rate Detection
  • Explosion Proof Enclosures
  • Exotic Alloys for Corrosion Resistance
  • Relay Energization is Field Programmable
  • No Moving Parts
  • 12VDC, 24VDC/VAC, 120VAC, or 200-240VAC Power Input

The FX series flow switch is the most reliable flow switch available. The thermal dispersion principle of operation features no moving parts and provides an extremely reliable and repeatable switch for the most demanding industrial applications. The sensor head employs two temperature sensors with a constant very low power heating source physically attached to one of the temperature sensors. The second temperature sensor is isolated from the heating source and provides compensation for changing process temperatures. As flow changes so does the temperature differential.


This allows the device to be used as a flow/no flow sensor, or to switch at any velocity shown in the flow switch range chart. Our dual switch-point option allows two separately adjustable switch points to be set using the same instrument.


Extremely low flow rates can be detected with rangeability up to 300:1. These devices are ideal for use in virtually all liquids, gases, and slurries. With no moving parts exposed to the process end users are provided an extremely reliable and repeatable instrument even in viscous or corrosive applications. This line of thermal dispersion flow switches can withstand temperatures to 900F and pressures to 10,000 PSIG. Type 316L stainless steel sensors are standard with options for exotic alloys for corrosion resistance. Many different process connections are available, including threaded, flanged, and retractable probes. Typically this series is used in 1/2” and larger line sizes with our IX Series used in smaller lines.

The electronics are available with single or dual switch points. Relay outputs are standard and are offered with several different configurations and contact ratings. Temperature monitoring is also available with either a switch output or a linear 4-20 mA output. Remote mounting of the electronics is available and recommended for high temperature applications or hard to access installations.

For more information please download a brochure, call us at 1-800-910-6689, or use our part number configurator to Request a Quotation.

  • Pump Protection: The FX series flow switch can reliably shut down pumps on low or no flow
  • Bearing Lubrication: Detects loss of lubricant flow
  • Seal Leakage: Switch verifies positive seal flow or detects excessive leakage indicating maintenance requirement
  • Chemical Feed and Metering Pumps: Indicates low or no flow of chemical additives to process fluids down to .02 feet/sec
  • Safety Shower and Eye Wash Station: The FX series switch detects high flows from a safety shower and the low flows of an eye wash station. It can be wired to sound an alarm, turn on an emergency light, and/or send a signal to the control room for emergency help.
  • Analyzer/ Gas Chromatographs: Confirms continuous sample flow to instruments
  • Control Rooms: A flow switch can be used for monitoring of plant equipment such as pumps, valves, and fans, providing a contact closure when the process condition changes.
  • Purge Air: Detects or verifies flow to meet plant safety requirements
  • Spray Nozzles: A flow switch can reliably detect nozzle blockage in coating applications
  • Relief Valve/Rupture Disks: The FX switch can provide automated detection of flow or leakage of safety relief valves or rupture disks
  • Chiller Lines: Automatic shut down of chillers on low or no flow
  • Heater Burnout Prevention: The FX series flow switch can initiate heater shutdown on loss of flow to prevent overheating of elements
  • Tank Car Loading: The FX senses dry line or phase change from liquid to nitrogen gas flow
  • Drain Line Sensor: Capable of detecting low flow in partially filled lines
  • Agitation Monitor: Provides positive indication of agitation in tanks, vessels, or ponds
  • Flare Stack Monitor: The FX series no moving parts thermal dispersion flow switch is ideal for monitoring dirty gases in flare stack applications