Magnetic Level Indicators and Controls for Industrial Process Applications

Fluid process control operations frequently involve the storage of liquids in a vessel or tank. The continuous and accurate indication of the liquid level within the tank is an important data point for process control decision making and safety. Several tank level measurement methods and instrument types are available, each with its own set of characteristics that may be advantageous for a specific installation. 

A tank liquid level indicator's selection criteria often include: 

• Does the process require direct or indirect measurement of level?
• What level measurement accuracy and reliability is needed?
• What is the tank shape, regular or irregular?
• Are there concerns with media compatibility with measurement device materials of construction?
• How often will maintenance or calibration be needed?
• Is the instrument capable of operating at the process temperature and pressure for the application?
• Does the application require local display and visibility or remote?
• Are control signals from the level indication required? What type and transmission protocol?
• What kind of redundancy and safety devices, such as additional switches, are needed?

Magnetically coupled liquid level indicators, or MLIs, are widely used in the process industry. They are accurate, consistent, and reliably indicate liquid level. These units are completely sealed and do not require any maintenance. MLIs also eliminate the vapor or liquid emission issues that plague sight and gauge glasses. 

Most Compelling Reasons for Using MLI's:

• Level measurement is continuous. 
• Operable without the use of electricity. 
• Regardless of tank shape or profile, they provide a direct visual tank fluid level indication. 
• They are available in wide operating temperature and pressure ranges. 
• MLI construction is resistant to breakage.
• A variety of materials are available to accommodate corrosive media. 
• Externally mounted measuring indicators, switches, and transmitters do not come into contact with the process media. 
• MLI's provide a continual operation that requires little maintenance. 
• The level indication is viewable from a greater distance than glass sight gauges. 
• With a single instrument, it is possible to measure large fluid level ranges.

Magnetic level indicators have a strong presence in tank liquid level measurement and should be considered a candidate for meeting those application requirements. There are numerous options for customizing the level indicator for each application.  Work with your local Sales Engineer,  a specialist in level measurement, about your application challenges and positive outcomes. 

For more information, contact your local Miller Energy, Inc. regional office:

South Plainfield, NJ Office
Serving Northern NJ, New York, and Fairfield County Connecticut
South Clinton Ave.
South Plainfield, NJ 07080
Phone: 908-755-6700
Toll Free: 800-631-5454
Fax: 908-755-0312

Exton, PA Office
Serving Southern NJ, Eastern PA, Delaware and Central and Eastern Maryland
505 Gordon Drive
Exton, PA 19341
Phone: 610-363-6200
Toll Free: 888-631-5454
Fax: 610-524-7254

Cleveland, OH Office
Serving Ohio
555 Golden Oak Parkway
Cleveland, OH 44146
Phone: 440-735-0100
Fax: 440-735-0123

White Paper: Improving Health and Safety with Magnetic Level Indicators in Ammonia Refrigeration Applications

Anhydrous ammonia is a versatile commodity in many manufacturing applications, including cold storage and food processing facilities. In comparison, anhydrous ammonia raises a range of safety and environmental issues to be addressed when determining some form of process instrumentation. Traditionally, visual level indication of anhydrous ammonia was obtained using sight glasses. This white paper discusses key areas in the ammonia refrigeration process where magnetic level indicators (MLIs) can provide a safer , more reliable method of level measurement over conventional technologies.

The goal of this document is to highlight the benefits of MLIs that will lead to improved personnel safety , reduced risk of fugitive emissions, reduced environmental impact, and reduced maintenance costs in large commercial and industrial ammonia refrigeration systems.

DOWNLOAD THE WHITE PAPER FROM THIS MILLER ENERGY WEB PAGE

Contact Miller Energy for any industrial level control application. Call  800-631-5454, or visit their website at https://millerenergy.com.

How Do Magnetic Level Indicators Work?

Magnetic Level Indicators also known as MLIs, have revolutionized the global visual indication market by offering a safer, reliable, and high-visibility alternative to common gauge glass assemblies.  They provide high-visibility representation of the liquid level in a vessel. MLIs can be mounted to tanks in a number of different ways. The most popular configuration, however, is called a side-mount.

The Magnetic Level Indicator (MLI) working principle is widely used in many industrial level applications. The operating principle behind a magnetic level indicator is that the MLI shares the same process fluid as the vessel, and therefore shares the same level.

The three primary components to a Magnetic Level Indicator are:

• The float
• The chamber
• The visual indicator

The float (contained within the chamber) interacts with the externally mounted visual indicator. As liquid rises and falls in the vessel and MLI chamber, the float follows. The magnets in the float interact with magnets inside each indicator flag. As the float rises and falls in the chamber, the magnets slowly turn each flag 180 degrees. This allows the visible flag color to change to a high-contrasting, highly-visible representation of liquid level.







Utilizing a combination of proven buoyancy principles along with the benefits magnetism, MLIs can be customized to fit virtually any process connection arrangement on the vessel.

The chamber and magnetic float is available in a variety of materials and pressure ratings to accommodate the wide variety of complex process applications present in the world’s major industrial facilities.

Areas Where Magnetic Level Indicator Are Applied:

• Feed water heaters and boilers
• Refinery and chemical industries
• Energy and power plant technology
• Pulp and paper applications
• Oil and gas industries
• Gas plants
• Pipeline compressor applications
• Pharmaceutical applications
• Food and beverage applications

For more information about Magnetic Level Indicators (MLI's), contact Miller Energy by calling 800-631-5454 or visit their web site at https://millerenergy.com.

Selecting the Right Magnetic Level Indicator

Companies in the process industry need the ability to visually monitor liquid levels in vessels (boilers, storage tanks, separators, etc.). Traditionally, armored glass sight gauges have been used. However, many companies want an alternative to sight gauges to avoid problems such as breakage, leaks, or bursting at high pressures and temperatures. In addition, the visibility of the sight glass can be poor and often affected by moisture, corrosion, or oxidation.

Many companies are increasing the use of automation and desire a 4–20 mA, HART®, FOUNDATION® fieldbus, or other output for level—which is difficult to do with a sight glass. Magnetic level indicators (MLIs) do not have the shortcomings of glass sight gauges and are suitable for a wide variety of applications.

Orion Instruments, a Magnetrol company, has authored an excellent Magnetic Level Indicator selection guide.

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You can download the selection guide from this Miller Energy, Inc. web page.

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Miller Energy, Inc.
https://millerenergy.com
In NY/NJ 800-631-5454
In Eastern PA 888-631-5454

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.

Eliminate Glass Tube Level Gauge Maintenance Costs

Magnetic Level Indicators
Courtesy Orion Instruments

Industrial process control often requires the accurate measurement of liquid level within a tank or other vessel. There are numerous device technologies and vendors from which to choose. A recent post on this blog detailed one of the available methodologies, the magnetic level indicator. I urge you to review that short post to familiarize yourself with the operating principles and advantages of applying a magnetic level indicator, not only on future projects, but as a possible replacement of some of your existing level indication instruments.

Orion Instruments, a Magnetrol company, has authored a case study showing how the replacement of glass tube level gauges with magnetic level indicators can reap substantial cost savings over the product lifetime. The case study, included below, takes but one minute of your time to read, and delivers a compelling incentive to consider magnetic level indicators (MLI) for your new projects, even as cost saving replacements for existing glass tube level gauges.

Read the case study. Contact a product specialist to discuss your application for new or replacement level indicators.

Orion instruments magnetic level indicators case study from Miller Energy, Inc.