Magnetic Level Indicators

Configurations of magnetic level gauges
Image courtesy Orion/Magnetrol

Fluid process control operations often involve vessel or tank storage of liquids. Continuous and accurate indication of the liquid level within the tank is an essential data point for process control decision making and safety. Several methods and instrument types are available for tank level measurement, each with its own set of attributes that may be advantageous for a particular installation. Selection criteria for a tank liquid level indicator may include:

• Direct or indirect measurement of level
• Level measurement accuracy and reliability
• Tank shape, regular or irregular
• Media compatibility with measurement device
• Requirements for maintenance or calibration
• Compatibility with process temperature and pressure range
• Local display and visibility
• Level indication signal type and transmission
• Level alarm switches or other indicators

The selection of a magnetic level indicator, also referred to as a magnetic level gauge, for the project will likely be based upon at least one of the instrument's strengths. Magnetic level gauges have a host of potentially positive features for level indication.

• Continuous level measurement
• Operable without electric power
• Direct visual tank fluid level indication, regardless of tank shape or profile.
• Wide range of operating temperature and pressure
• Breakage resistant construction
• Range of construction materials available to accommodate corrosive media
• Measuring indicators, switches, and transmitters mounted externally, without contacting the medium being measured.
• Low maintenance operation.
• Readable level indication from greater distance than glass sight gauges.
• Applicable to large fluid level ranges with a single instrument.

Magnetic level indicators have a strong position in the tank liquid level measurement field and should be considered as a candidate for fulfilling those application requirements. There are many options available to customize the level indicator for each specific application. I have included a technical data sheet from Orion Instruments, a manufacturer of level instrumentation, for more detail. Share your application challenges with a sales engineer that specializes in level measurement. Combining your process knowledge with their product application expertise will yield positive solutions.

Magnetrol Orion Magnetic Liquid Level Indicators from Miller Energy, Inc.

Magnetic Liquid Level Gauges

Magnetic level indicator with supplemental
guided wave radar instrument
Gemini Model - Magnetrol

Magnetic liquid level gauges are an excellent alternative to sight glass level gauges for many process measurement applications. Their reliable performance and adaptability has made them the primary choice in a wide variety of industrial settings.

Essentially, a magnetic level gauge or magnetic level indicator, is a sight glass with enhancements that provide better readability and a form factor that enables the inclusion of additional level monitoring functions on the same device. Where a sight glass requires operator proximity to read liquid level, the magnetic level gauge's indicating scale, or flags, can be clearly viewed from a considerable distance. A sight glass gauge can also be hindered by difficulties in visually determining liquid level because of deterioration of the glass surface or properties of the liquid. Magnetic level gauges remove the need to observe the liquid directly by incorporating a float device within a tube connected to the liquid containing vessel. As the float moves in response to liquid level changes, its magnet causes the indicator flags on the scale to rotate and display either a black face to indicate no liquid present, or a colored face.

Magnetic level indicators are available with numerous options, including armored casings to protect the tube and float arrangement and limit switches to signal the attainment of specific level conditions. Combining a MLI with another level measurement technology, such as guided wave radar or magnetostrictive, can provide an analog process signal representing liquid level and serve as a redundant measuring device for critical applications.

The document included below provides illustrated detail about the devices and their proper application. Share your process measurement requirements and challenges with instrumentation experts. The combination of your process knowledge and their product application expertise will produce effective solutions.

Magnetrol Orion Magnetic Liquid Level Indicators from Miller Energy, Inc.