Model 621

SKU: 621

Flow Switch, Inline Body

The Delta Controls Model 621 Flow Switch is equipped with inside body dimensions and end connections that conform to the pipeline. The 621 is built to ANSI, ASME, and PED specifications. These switches protect pumps, blowers, heat exchangers, etc. The paddle magnetically connects to the output switch. A heavy-duty solid sealing tube separates the process fluid from the switch mechanism. Failures due to seal, diaphragm, and bellows leaks are eliminated.

Model 621 are factory calibrated to standard or custom setpoints. An internal adjustment allows small switch point changes in the field.

A pivoted paddle extends into the flowing stream creating force as it strikes the paddle. At a predetermined velocity, the force causes the paddle and the attractor to rotate about the pivot point. The magnet reacts to the new attractor position and the output switch operates. As the flow decreases, the paddle and output switch return to the original states.


  • Highly reliable magnetic design
  • Notifies user of flow or lack of flow
  • Multiple process connection sizes available
  • Full bore body
  • Built to ANSI, ASME, and PED specifications


  • Style: Inline
  • Type: Paddle
  • Temperature: -4 °F to +400 °F (-20 °C to +204 °C)
  • Pressure: ≤ +2000 psi (≤ +137.9 bar)
  • Actuation: ≥ 1.6 gpm (6.0 L/min)
  • Deactuation: ≥ 1.3 gpm (4.9 L/min)
  • Accuracy: ≤ 10%
  • Output: SPDT or DPDT, 5 A
  • Wetted Material: 300 Stainless Steel, 400 Stainless Steel, brass, carbon steel (other materials available)
  • Housing: Stainless steel, aluminum
  • Threaded Process Connection: 0.5 in to 4.0 in FPT
  • Flanged Process Connection: 0.5 in to 4.0 in
  • Flange Rating: ≤ 150 lb

Certifications & Approvals

  • Stainless Steel Housing Options Only: Third Party Listed by CSA NRTL/C (USA and Canada)

Required Ordering Information

  • Detailed model number
  • Detailed application number
  • Tag or nameplate detail (if required)
  • Documentation/testing tiers (if required, refer to Additional Resources in the product catalog)

Additional Information


Flow Switch, Inline Body

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