Jerguson external cage float and displacer operated magnetic level switches

External cage switches sit in a chamber piped to the side of the vessel, so the switch can be serviced without entering the vessel. They are used for level alarms, safety shutdowns and pump control on storage tanks, scrubbers, process vessels and high pressure steam generators.

All Jerguson level switches use the Tri-Magnet mechanism. A magnet on the float or displacer rod turns a secondary magnet, which repels a third switch magnet to the other side; the cradle pivots and push rods operate the contacts. The snap action comes from magnetic forces alone, without springs that can fail through heat, vibration or fatigue, and the mechanism was endurance tested to more than 850,000 cycles. The switches are mercury free.

The JX series has a flanged cage that is easy to service, the JB a sealed cage. Float versions take one or more switches; displacer versions suit wide differentials. For pressures and temperatures beyond vertical cages, the JH horizontal cage uses a pivoting, counterbalanced float with a thicker wall.

Selection data we need

Switch function and number of switch points (high, low, pump differential), float or displacer, medium and specific gravity, design pressure and temperature, cage material, process connections and orientation, switch mechanism and contacts, enclosure and area classification.