External Cage Level Switches

Features

• → Tri-Magnet Switching
• → Vibration Resistant
• → Weatherproof
• → Flameproof
• → Sealed (standard) or Flanged Cage Body
• → 316 SS Trim
• → ASME B31.1/B31.3 Design

Operation

The float drives a stainless steel sheathed permanent magnet attached to the float rod in the glandless pressure tube. As the float rises and falls with changing liquid level, the float assembly moves upward inside the pressure tube. A switch mechanism mounted inside the enclosure adjacent to the pressure tube is activated by the rising or falling magnet. The vertical movement of the float magnet simultaneously actuates the secondary and switch magnets within the switch mechanism to operate the contacts. This "three-magnet" system enables the float magnet to pass the switch and actuate switch mechanisms at other levels. Switch mechanisms which are actuated will not reset until the float magnet actuates the switch mechanism on a falling level. Switching is achieved with the unique tri-magnet snap-action switch system.

Features

• → Tri-Magnet Switching
• → Vibration Resistant
• → Weatherproof
• → Flameproof
• → Sealed (standard) or Flanged Cage Body
• → 316 SS Trim
• → ASME B31.1/B31.3 Design

Operation

The displacer element — made of either 316 Stainless Steel or Ceramic — is suspended on a Stainless Steel Rod from a spring. The displacer element is always heavier than its equivalent volume of the liquid in which it operates, so it will extend the tension spring at all times. In free air, the spring extends to a known length, controlled by a mechanical stop to prevent overstressing. Attached to the spring is a rod and magnet assembly, free to move up and down as the spring extends or contracts within the pressure tube. As liquid rises to cover the displacer element, a buoyancy force is created equal to the weight of the liquid displaced. This force reduces the effective weight seen by the spring, causing the spring to contract and moving the magnet upward inside the pressure tube to actuate the switch mechanism. On a falling liquid level, the displacer element is uncovered and the spring sees an increasing effective weight, causing the spring to extend and move the magnet to re-set the switch mechanism. Switching is achieved with the unique "tri-magnet" system, giving snap-action "latch-on" switching.

Features

• → Tri-Magnet Switching
• → Vibration Resistant
• → Sealed Cage
• → ANSI B31.1 Design
• → ANSI B31.3 Design

Operation

A unique counter-balance design allows for a much heavier float than those used in a traditional external caged level switch, enabling it to withstand extreme pressure and temperature. As the float rises and falls with liquid level, it moves a pivot arm attached to the end of the float rod. On the end of the float rod is a sheathed permanent magnet. A switch mechanism mounted inside the enclosure adjacent to the pressure tube is activated by the rising or falling magnet. The vertical movement of the float magnet simultaneously actuates the secondary and switch magnets within the switch mechanism to operate the contacts. Switching is achieved with the unique tri-magnet system providing positive snap-action anti-vibration switching.