Mechanical buoyancy type liquid level switches were one of the first technologies used to measure fluid levels in process industries, and the devices remain a workhorse for reliable level detection in a wide range of applications, including those in the most challenging or hazardous environments.
When considering the specification of mechanical buoyancy level control instrumentation, it’s important to recognize that the design and construction of the magnetic switch mechanism – the driving component within mechanical buoyancy liquid level switches – has significant bearing on the performance characteristics of the unit.
Magnetrol®, the manufacturer of the first magnetic switch designed for liquid level detection, has spent more than 80 years perfecting mechanical buoyancy switches. The following MAGNETROL switch design features demonstrate how intelligent design impacts the quality and reliability of mechanical buoyancy liquid level control solutions:
- Completely isolated from the process environment to prevent magnetic interference and protect integrity of switch activation.
- Magnet placed on non-wetted side of pressure boundary to prevent magnetic particles from adhering to magnet and affecting switch action.
- Alnico magnet material ensures stability.
- All magnets are stable to over +1000°F (+540°C).
- Magnets “saturated” and “knocked-down” to ensure stable charge over the lifetime of the switch.
Return Spring Design
- Return springs heat-treated to ensure consistent properties and performance over a vast temperature range.
- All return springs used only within their elastic range to prevent damage and distortion.
- Each return spring designed for required reset force of micro switch.
- Pivot pins machined for precision fit and smooth rotation.
- Designed with “play” at pivots and magnet to prevent binding.
- Adjusting screw factory-set for optimal micro switch actuation point and over-travel on both pull-in and fall-out, to ensure reliability over changing conditions.
- Mercury-free, high-temperature switches for process temperatures greater than +1000°F (+540°C).
- Silver or gold contacts that work for standard or low current applications.
- Standard or hermetically sealed micro switches.
- Ceramic terminal blocks provided on highest temperature applications.
- Lead wire insulation for all application temperatures
The design integrity of MAGNETROL switch mechanisms has allowed our level controls to provide years of safe, accurate, reliable level control – with many clocking in more than a half-century of trouble-free service. For more information about MAGNETROL liquid level switch solutions, download the Mechanical Buoyancy Switch Mechanism Design Guide.