Level Measurement Using Isolating Air Flow

Bubbler method of liquid level
measurement is simple and reliable
Courtesy Yokogawa

Remotely utilized measurements of tank liquid level are common throughout the fluid processing industries. Various means of inferential or direct measurement are available, each with its own set of performance, maintenance, and cost attributes that may make it the preferred choice for a particular application.

Inferring liquid level using a hydrostatic pressure measurement is a simple, easy to implement strategy for delivering a continuous level signal to the process operating and control system. There can be situations where mounting the measuring gear near the bottom of a tank or other vessel may be impractical or undesirable. A pressure transmitter mounted low on a tank may expose it to damage from plant traffic or other physical hazards. It is also possible that the tank may not have a suitable fitting located low enough to provide the needed measuring range. Having a potential leakage point at a fitting low on the tank may also be undesirable. Another, and certainly not final, scenario would be an application involving a corrosive liquid which must not come in contact with the pressure sensor.

The bubbler method of liquid level measurement employs an arrangement that overcomes all of the previously mentioned impediments. It can utilize connections at the top of the tank, above the liquid level. The way in which the method works will keep the pressure sensor out of contact with the process liquid, providing isolation from potential corrosive effects.

The apparatus for level measurement using the bubbler method employs a simple dip tube that extends from the pressure sensor or transmitter to nearly the bottom of the tank or vessel. A small amount of purge air or gas continually flows through the dip tube and will bubble out the bottom of the tube. This dip tube arrangement essentially transfers the hydrostatic pressure at the bottom opening of the tube to the pressure transmitter, while the purge gas keeps the liquid from advancing up into the pipe. The bubbler can be used on atmospheric or pressurized tanks with a properly configured pressure or differential pressure transmitter.

Probably the most significant application point of the bubbler method that will distinguish its use from many other level measurement methods is the importance of maintaining air or gas flow in the dip tube. The flow provides isolation of the sensor, but the flow must also be set to a level that will not impact the pressure measurement in the tube itself. If the flow is excessive, backpressure in the tube can be offset from the level imparted by the tank contents, with the result being an incorrect measurement.

Below is an application note from Yokogawa, showing how their pressure transmitters and rotameters can be used to create the setup. Share your process measurement challenges and requirements with instrumentation experts, combining your own process knowledge with their product application expertise to produce effective solutions.

Liquid Level Measurement Using the Bubbler Method from Miller Energy, Inc.

Yokogawa Differential Pressure Transmitter from Miller Energy, Inc.

Yokogawa Rotameter Flowmeters for Industrial Applications 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.

Ultrasonic Contact Level Switches Provide Reliable Overfill Protection

Echotel® Ultrasonic Level Switches

Magnetrol

Requirements for safety regulation compliance continue to grow. Business operators want increased levels of risk aversion and contingency management. In industrial settings where fluids are processed or stored, meeting these goals calls for new layers of protection and redundancy for existing layers.

Tank overfill is a serious concern of any fluid processor. Providing multiple methods of measuring tank or vessel fluid level provides substantially greater assurance against overfill. One scheme involves using a continuous level measurement instrument, such as guided wave radar, to provide the real time tank level signal and an ultrasonic level switch as a tank overfill indicator.

The operating principal of an ultrasonic level switch is quite simple. A transducer sends an ultrasonic pulse across a gap. When liquid media is present in the gap, the sound wave is transmitted with little attenuation across the gap and detected. When liquid media does not fill the gap, the sound wave is strongly attenuated and fails to transmit across the gap.

Tuning fork level switches are commonly applied as the overfill detection device, but Magnetrol, a recognized global innovator in level measurement, feels they have a better solution with their Echotel® ultrasonic level switches. The video below provides an illustration of how the ultrasonic level switches can be applied, as well as a comparison between ultrasonic and tuning fork methods.

Share your level measurement requirements and challenges with a product application specialist. The combination of your process expertise and their product application skill will produce an effective solution.

Low Cost Radar Level Transmitter For Industrial Process Applications

Magnetrol Model R82 Radar Level Transmitter

With its ability to reliably detect tank liquid surface level under conditions that prove challenging to other methods, radar technology generally provides an operational advantage over other non-contact level measurement options. Historically, the cost of radar level transmitters for industrial process control applications has hindered their success as a unit of choice for some installations. Magnetrol has changed that imbalance with their recent introduction of a lower cost radar level transmitter for tough applications.

The Model R82 provides radar performance at a price point comparable to competitive ultrasonic units, but maintains the performance advantage inherent in a radar based device. The unit utilizes pulse burst radar technology at 26 GHz, employing advanced signal processing to filter out false echos produced by a range of in-tank conditions that can produce false readings from ultrasonic units.

The short video below provides a closer look at the R82 and its performance advantages. Technical data sheets and any application assistance you may need is available from product specialists. Share your level measurement and control challenges with them and work toward the best solution.

New Product - Model R96 Non-Contact Radar Level Transmitter

New Model R96 Non-Contact Radar
Level Transmitter
Courtesy Magnetrol International

Magnetrol is a well known manufacturer of level and flow measurement instrumentation for the industrial process control field. The company recently released the Model R96 Non-Contact Radar Level Transmitter for applications where continuous fluid level measurement is required.

The company's description of the product...

"Virtually unaffected by the presence of vapors or air movement within a vessel’s free space, the two-wire, loop-powered, 6 GHz Radar transmitter measures a wide variety of liquid media in process conditions ranging from calm product surfaces and water-based media to turbulent surfaces and aggressive hydrocarbon media."

 The new product offers features that combine to make a state-of-art instrument for accurate continuous level measurement. A product brochure is included below. Contact application specialists to formulate the right product configuration for your level measurement challenge.

Non Contact Radar for Level Measurement and Control from Miller Energy, Inc.

New Level Transmitter From Orion Instruments

Direct insertion and external mount versions of
Orion JM4 Magnetostrictive Level Transmitter
Courtesy Orion Instruments

Orion Instruments, a world class manufacturer of magnetic level indicators, level switches, and level transmitters, has released a new product for use in the industrial process measurement and control field. Their Jupiter Model JM4 magnetostrictive transmitter incorporates the company's many years of research, development, and field experience to provide a safer, simpler, and smarter transmitter for liquid level measurement and control.

The new model from Orion boasts level measurements with accuracy as high is +/-0.05" (1.27mm). The transmitter head can be rotated up to 310 degrees with an option for remote mounting. Variants are available for direct insertion or external mounting, with approvals for a number of area classifications. There are other valuable features to this series of level measurement instruments that reflect Orion's expertise in the field.

Browse the new product brochure included below. It provides illustrations of the product and its operating principle, along with dimensioned drawings and a listing of all the product options and variants. You can always obtain whatever information you need about Orion level measurement instruments from a product specialist. Share your liquid level measurement challenges and requirements with them for recommendations on the best solutions.

Orion Instruments Jupiter Magnetostrictive Level Transmitter 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.

Magnetic Level Indicators - Knowledge Base and Selection Guide

Magnetic Level Indicators
Courtesy Orion Instruments

Industrial process control frequently involves the storage of liquid in vessels or tanks. Continuous and accurate indication of liquid level within the tank is an essential data point for safety and process management. While there are a number of methods and instrument types utilized to provide tank level measurement, the instrument of choice is often a magnetic level indicator, also referred to as a magnetic level gauge. Its use for providing level indication has a number of positive attributes:

• Construction that is resistant to breakage.

• Measuring indicators, switches, and transmitters mounted externally, without contacting the medium being measured.

• Maintenance free operation. No regular cleaning needed.

• Readable level indication from greater distance than glass sight gauges.

• Magnetic level indicators can accommodate greater fluid level ranges without the need for multiple instruments.

Orion Instruments, a Magnetrol company and industry leader, has produced a comprehensive guide to magnetic level gauges, switches, transmitters, and related products. It delivers experts and newcomers an understandable and clear description of the technology and principals of operation behind magnetic level gauges and instruments. The guide also assists the reader in properly specifying and selecting the best instrument configuration for an application. A table of contents at the front of the document helps readers to quickly find the information they need.

Take a couple minutes to roll through the document and you are likely to find new and useful application tips and product information. Any questions about magnetic level indicators or your process measurement and control applications can be clearly addressed by a product specialist.

Orion instruments magnetic level gauge & instrument selection guide from Miller Energy, Inc.