External Liquid Level Switch
Model CB

The Model CB is an external service, side mounted liquid level switch. Models are available for service to 800 PSIG; operating temperature to 1000°F with cooling fins; and specific gravity as low as 0.375. The many optional and special constructional features make the CB practical for a wide range of applications.


Float Chamber: The chamber is available in carbon steel, 304 SS, or 316 SS. The float chamber has a flange removable head. See the Type S if all-welded construction is required (for operating pressures above 800 psig).
Chamber Gasket: A spiral wound with a graphite filler is standard.
Float: Float material is standard in 300 series stainless steel.
Trim: The trim, which includes the float rod with its related hardware, is standard in 300 series Stainless Steel. The enclosing tube assembly is standard in 316 Stainless Steel.
Process Connections and Mounting: The standard connections are 1" located on the side and bottom having an 11-1/2" centerline dimension. Male connections usually ease field installation by eliminating the need for an extra union. Other connections are available as follows: female, socket weld, or flange. Specify in the RFQ with your required centerline dimension.
Differential: With a single switch, the standard differential is approximately 5/8". Wide differential options are available. Field adjustment of the actuating points can be made by raising or lowering the switch on the enclosing tube.
Switch Housing: A water-tight/dust-tight or hazardous rated housing is available. Hazardous housing is rated to:

  • Class I, Groups B,C,D
  • Class II, Groups E,F,G
  • Class III
  • Class I, Zone 1, AEx d IIC
  • Ex d IIC
  • Type 4X
  • IP 66
  • 4X, 7BCD, 9EFG

and listed as:

  • FM Standard 3615
  • UL Standard 1203
  • CSA Standard C22.2 No. 30
  • NEMA Compliance
  • UL 60079-0/UL 60079-1
  • CSA 60079-0/CSA 60079-1
  • ATEX Directive 94/9/EC
  • UL 50
  • IEC 60529

Conduit Connection: 3/4" NPT is standard, 1/2" NPT or M20 are available.
Switches: See Model OF or Z.

Optional Features:

Cooling Fins: For application with a process temperature above 400°F, cooling fins are used to dissipate as much as 200°F which would otherwise be transmitted to the switches.
Wide Differential: For applications with a differential greater than provided by the standard model, the following options are available:

  1. Two Switch: With two switches up to 4 1/2" of differential can be obtained.
  2. Sliding Piston: With this design, the piston travels along the rod, making contact with high and low-level stops. The magnet is strong enough to hold the piston in place while the liquid level raises and lowers the rod. The maximum differential with this design is three inches.
  3. Sliding Float: With this design, the float travels along the rod, making contact with high and low-level stops. This design is used for differentials larger than 4".

Higher Pressures: For float-type control applications with operating pressures of 1000 PSIG to 3000 PSIG and self-purging floats not being suitable, see the Model S.
Note: Model CB level controls manufactured before March 1, 2000 might not match the current specifications. However, replacement controls can be built to retro-fit the existing, as long as a complete description is provided. The serial number and other nameplate data will aid in specifying replacement units.

Interface: The controls are available for interface service. The difference in specific gravities between the two liquids must be 0.20 or more. The float for interface service is weighted in order to sink in the lighter liquid, but float in the heavier liquid. If the difference is between 0.12 and 0.19, a custom design is available.


Starting in the unactuated position, a rising liquid level will lift the float and rod, raising the actuating piston towards the magnetic operating zone of the switch assembly. A permanent magnet, located within the switch assembly, snaps forward from the magnetic attraction. In doing so, a plunger is depressed, actuating a micro switch. When the level decreases, the float falls away, pulling the actuating piston to its original position, releasing the permanent magnet, re-setting the switch assembly to its unactuated position.