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9321/9321E Pneumatic & Electric Liquid Level Switch

The Wellmark Series 9321 On-Off Pneumatic Liquid Level Switch operates shut-down valves or alarm systems when liquid in a vessel reaches a predetermined level. This switch uses an externally mounted displacer that operates a nozzle-flapper to vent the supply pressure when the switch is activated. The nozzle-flapper has a soft seat for tight shut-off when the switch is in its normal position (flapper against the nozzle).

The Series 9321E is an external cage-mounted electric liquid level switch. Rising liquid exerts a buoyant force on the displacer, producing a torque in the tube. This force will either trip or reset an electrical switch. Falling liquid will trip or reset the same switch if so desired. The WellMark Series 9321E Electric Switch uses the displacer and torque tube movement to trip and reset an electric switch for on-off condition. The displacer can withstand up to 1 1/2 times the maximum working pressure, allowing it to remain in the cage during hydrostatic testing.

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9321/9321E Pneumatic & Electric Liquid Level Switch


  • Pneumatic or Electric
  • Left Hand or Right Hand
  • Hi-Level Alarm or Lo-Level Alarm


  • Output Signal: Pneumatic Output equal to supply pressure when the switch is in the normal position. Output reduced to approximately atmospheric pressure, depending upon size of the bleed orifice and piping configuration, when the switch is activated. Electric output same as supply signal.

Supply signal:

  • Pneumatic: Standard 30 – 60 psi. Optional 60 -100 or 100 -150
  • Electric: 11 AMP, 1 /4 HP @ 125/250 VAC. 5 AMP RES @ 28 VDC. 0.5 AMP RES @ 125 VDC. Leads Factory Sealed
  • Steady-State Air Consumption: Less than 1.0 scfh for all supply pressures when the liquid level is one inch below the normal switch position for high-level switching or one inch above the normal switch position for low-level switching.
  • Maximum Working Pressure: 2500 psi
  • Operating Temperature: -20˚F to 400˚F
  • Displacer Diameter: 4 in.
  • Process Connection Size: 1″ Female NPT

Supply pressure connection size:

  • Pneumatic: 1/4 inch female NPT
  • Electric: 1/2 inch conduit
  • Shipping Weight: Approx. 35 lb.


  • Displacer: Stainless Steel
  • Cage: Cast Steel
  • Torque Tube: Monel®
  • Body: Carbon Steel
  • Nozzle Block: Aluminum
  • Switch Box: Stainless Steel

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