The product
External cage switches – Technology
A permanent magnet is attached to a pivoted switch actuator. As the float/displacer rises following the liquid level, it raises the attraction sleeve into the field of the magnet, which then snaps against the non-magnetic enclosing tube, actuating the switch. The enclosing tube provides a static pressure boundary between the switch mechanism and the process. On a falling level, the float/displacer deactivates the switch.
Features
- Temperatures from -50 to +100 °F (-45 to +40 °C)
- Maximum working pressure to 400 psig (28 bar)
- Housing is completely sealed against entrance of moisture
- Conduit seal with 24 in. (610 mm) lead wires
- Welded float chamber assembly
Options
- ¾” NPT or ¾” socket weld connections
- Housing choices of NEMA 4X steel, NEMA 4X/7/9 explosion proof, and NEMA 4 transparent Lexan®
- Optional cryogenic insulation available, see bulletin 41-106.
Operating principle
The buoyancy force of a process liquid on the float causes the float to ride on the liquid surface. The movement of the float with the liquid level moves an attraction sleeve into the field of the switch magnet, pulling the magnet toward the sleeve and actuating the switch.
Approvals
| CSA | XP |
| FM | XP |
| EAC (GOST) | Ex ia |
| SIL | SIL 2 (1oo1) |
Other approvals are available. Consult factory for more details.
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