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764 / 766 / 768 (W)

Welded Chamber Mount Level Switch

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764 / 766 / 768 (W)

For refinery and chemical plant engineers, terminal operations teams, maintenance supervisors, and EPC designers who need two independent mechanical level trips in demanding, pressurized applications, the Omnitrol 764W / 766W / 768W provides dual-actuator displacer switching inside a welded bypass chamber.

Unlike flanged solutions that introduce additional gasketed joints and potential leak paths, the welded W-Series offers:

  • Two switching points in a single chamber
  • Extended welded body for predictable switching differential
  • Factory-set specific gravity calibration
  • Hydrostatic proof testing at 1.5× design pressure
  • Service capability up to 1000 psig at 500 °F
  • UL and CSA hazardous-location approvals

This design is ideal for pump start and stop control, high-high or low-low protection, and critical shutdown applications where mechanical certainty, safety, and long-term reliability are essential.

764 / 766 / 768 (W)
764 / 766 / 768 (W)
764 / 766 / 768 (W)

Features

Dual Actuator Configuration

Two independent setpoints in one welded chamber enable pump start/stop control or high-high/low-low alarms without adding second instrument, reducing vessel penetrations and installation complexity.

Welded Long-Body Construction

Eliminates gasketed flange joints present in removable designs, reducing potential leak paths and fugitive emissions while supporting special body lengths and custom displacer materials.

Factory SG Calibration

Each unit calibrated to specified liquid specific gravity up to 1.4 maximum before shipment, ensuring predictable switching differential and eliminating field trial-and-error during commissioning.

High Pressure Temperature Rating

Standard ratings from 150 to 1000 psig at 500°F cover most refinery, chemical, and industrial water services where electronic instruments struggle with extreme conditions.

Adjustable Switching Gap

Distance between lower switching points adjustable from 2 to 4 inches at standard specific gravity, allowing differential tuning to prevent pump short-cycling in surge conditions.

Hydrostatic Proof Testing

Every chamber pressure-tested to 1.5 times maximum design pressure before shipment, providing documented mechanical integrity and verifiable compliance for audits and safety reviews.

Applications

  • Overflow Protection Systems: Two independent trips in single welded chamber provide high and high-high alarms, reducing vessel penetrations and lowering installation costs while minimizing potential leak paths.
  • Pump Start/Stop Control: Upper actuator stops pump while lower actuator starts pump with 2-4 inch adjustable differential, reducing short-cycling and stabilizing sump or tank levels.
  • High-Pressure Hot Services: Mechanical switching rated to 1000 psig and 500°F provides dependable control where electronic transmitters struggle, ideal for refinery and chemical plant extreme conditions.
  • Space-Constrained Retrofit Installations: Long welded chamber with enclosed displacer mounts externally to vessel side, providing compact solution without internal stilling wells or extensive vessel modifications.
  • Fugitive Emission Reduction: Welded construction minimizes gasketed joints compared to flanged designs, lowering leak paths and reducing potential fugitive emissions for environmental compliance in regulated facilities.
  • Variable Density Process Control: Factory SG calibration with clear guidance on differential changes accommodates blend variations and temperature drift, maintaining accurate switching despite density fluctuations.
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Specifications

Models

764W (4″ body), 766W (6″), 768W (8″) dual-actuator welded chamber.

Pressure/Temperature

150–1000 psig at 500 °F (standard).

Materials

Chamber in Carbon Steel, 304SS, 316SS; graphite displacer (316SS optional).

Process connections

1″ NPT standard; other sizes/configurations available.

Switching Gap (Lower Switch Points)

2–4″ adjustable, 4″ default.

Max specific gravity

1.4 (760 series).

Approvals

UL & CSA.

Testing

Hydrostatically tested to 1.5× max design pressure.

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Why choose the welded W-Series instead of a flanged chamber?

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  • Use the W-series when you want fewer gasket joints, a simplified welded body, and the ability to specify special lengths.
  • Choose the F-series when removable, flanged isolation is required. The main advantage is long-term integrity and reduced fugitive emissions. The welded body eliminates the gasketed joints required by flanged designs, which are potential points of failure and leakage.
  • The “W” chamber is also often selected when special non-standard body lengths are needed.

Do these devices require field calibration?

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No — they ship factory-set to your specific gravity.

Why is the actuator spacing adjustable?

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The actuator spacing defines the switching differential (the distance between the START and STOP points for a pump). Adjusting this spacing allows engineers to tailor the control logic to the vessel’s dynamics, preventing the pump from running on and off too quickly (short-cycling) and extending pump life.

How many vessel nozzles are required for installation?

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One instrument — one chamber — two independent setpoints. No additional vessel penetration required.

What environments are these switches best suited for?

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High-pressure, hot, corrosive, and hazardous service including refineries, chemical plants, terminal operations, and utilities.

⁠Can this switch be used for pump control?

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Yes — this is a primary use case, with adjustable differential to prevent pump short-cycling.

Summary

The  Omnitrol  764/766/768(W) delivers two dependable, mechanical level trips in a welded, long-body external chamber, ideal when integrity, simplicity, and minimal leak paths matter. With factory SG calibration, UL/CSA approvals, hydrostatic proof testing, and service to 1000 psig/500 °F,  it’s a robust choice for pump control and alarm duties across refining, chemical, and water markets. If you need removable flanged construction, the dual-actuator (F) variant or other models from the chamber-mount family may be a better fit; otherwise, the (W) gives you the cleanest, most compact dual-point package.

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