Level and Flow Applications for Biomass Gasifier Skid Systems

More and more owner/operators, OEMs and plant engineers throughout the process industry are fabricating their unit operations as modular skid systems. This post discusses instrumentation for biomass gasifier skid systems and is part of an occasional Magnetrol® blog series on level and flow control for skid system applications.

Biomass is cultivated and waste forms of biological material, including: crops, forest residue, waste from livestock, food processing, and municipal sources. When biomass is heated in the absence of oxygen, it decomposes into a mixture of hydrogen and carbon monoxide gases known as synthesis gas or “syngas”. Like natural gas, syngas is a valuable energy asset that can fuel boilers, generators, and furnaces, or serve as a feedstock.

BioMass-to-Syngas Skid

In this entrained-flow type of gasifier, the steam and oxygen reactants flow uni-directionally upwards through the gasifier until high temperature finished syngas exits the reactor.

The biomass feedstock enters the gasifier for conversion into synthesis gas. The syngas exits the gasifier and is routed to a gas cooler to recover useable thermal energy. The gas is then cleaned and routed to an application or to storage.

Level and Flow Applications


1.Hopper Level Solid biomass feedstock is ground into small particles and fed into a biomass hopper from where it is conveyed to the gasifier. High and low level detection in the hopper maintains correct hopper level.
Continuous Level: Eclipse® Model 706 Guided Wave Radar Transmitter

2. Input Air Flow Many gasification systems use nearly pure oxygen to facilitate the reaction in the gasifier. Typically, the oxygen is generated in an off-skid plant using cryogenic technology. The oxygen flow is monitored by mass flow transmitters.
Continuous Gas Flow: Thermatel® Model TA2 Thermal Dispersion Mass Flow Meter

3. Gas Cooler The raw syngas leaving the gasifier enters a gas cooling unit to reduce the gas’s temperature. Level controls monitoring the coolant within the cooler body serve as a leak detection system for the gas cooler.
Continuous Level: ECLIPSE Model 706 Guided Wave Radar Transmitter
Point Level: Model B35 External Cage Float Switch or Echotel® Model 961 Ultrasonic Switch

4. Scrubbers Impurities in the syngas—including trace minerals, particulates, sulfur, mercury, and unconverted carbon—are reduced to very low levels by using gas scrubbers. Accurate level monitoring maintains correct amounts of scrubber make-up water.
Continuous Level: ECLIPSE Model 706 Guided Wave Radar Transmitter
Point Level: Model B35 External Cage Float Level Switch or ECHOTEL Model 961 Ultrasonic Switch

5. Output Syngas Flow
Clean syngas is routed to storage or to its application, including: fuel for heat or electricity generation, or to serve as a chemical or petrochemical feedstock. The mass flow of the syngas is monitored by a mass flow transmitter.
Continuous Gas Flow: THERMATEL Model TA2 Thermal Dispersion Mass Flow Meter


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Level and Flow Solutions for Ammonia Skid Systems

Throughout the process industry, modular fabrication has increasingly become a viable option to field construction for owner/operators, OEMs, and plant engineers. From zero site disruption during fabrication to plug-and-play commissioning, single- and multiple-skid systems have become popular options in recent years.

Nearly any unit operation can be fabricated as a self-contained, modular skid system. While most skids are housed within an open structural framework, a skid maker can fabricate the skid system inside a standard shipping container.

This week’s blog post discusses instrumentation for ammonia skid systems and is part of an occasional series devoted to level and flow control for skid system applications.

Ammonia Skid: Aqueous Ammonia Vaporization

Anhydrous and aqueous ammonia are skid-configured for unloading, storage, transfer, vaporization, stripping, metering, injection, and urea-to-ammonia (U2A) conversion. Skids range from compact, single-process systems to multi-unit utility systems.

Ammonia vaporization changes the state of ammonia from a liquid to a gas. Vaporized ammonia is important for use in industrial refrigeration and in pollution abatement technology, such as selective catalytic reduction (SCR) systems used to neutralize nitrogen oxides from large electric utility and industrial boilers.

Aqueous ammonia vaporization uses heat to evaporate an ammonia and water mixture. The liquid is mixed with atomizing air and dispersed into the vaporization chamber as a fine mist where it is heated until it vaporizes. The air, ammonia, and water vapor mixture are then transferred to the injection grid.

Level and Flow Applications

ammonia skid

1. Ammonia Storage Tank Pure ammonia is stored in a pressure vessel rated at 250 to 300 psig. Aqueous ammonia (70 to 80% water) is stored in a tank rated at 25 to 30 psig.
Continuous Level: Eclipse® Model 706 Guided Wave Radar Transmitter or Atlas™ or Aurora® Magnetic Level Indicators
Point Level: Model A10/A15 Single Stage Displacer Switch

2. Mixing Tank The mixing tank uses an agitator for blending. Level controls trigger alarms in underfill and overfill incidents.
Continuous Level: Pulsar® Model RX5 Radar Transmitter or ATLAS or AURORA Magnetic Level Indicators
Point Level: Echotel® Model 961 Ultrasonic Switch or Model T20 Single Stage Float Switch

3. Pump Protection A flow switch along a pump’s discharge piping will actuate an alarm and shut down the pump when liquid flow drops below a minimum flow rate.
Flow Alarm: Thermatel® Model TD1/TD2 Thermal Dispersion Switch for low-flow cutoff

4. Air Flow Monitoring Flow meters help ensure efficient operation at rated SCFM output and detect air leaks. A flow meter with a totalizer provides an accurate measurement of compressed air consumption.
Flow Alarm: THERMATEL Model TD1/TD2 Thermal Dispersion Switch for low-flow cutoff
Flow Transmitter: THERMATEL Model TA2 Thermal Dispersion Mass Flow Meter

5. Vaporizer Liquid Level Functioning as an essential safety measure, a level switch in a vaporizer can provide high liquid level alarm, overfill tank alarm, leak detection alarm, or low level alarm.
Continuous Level: PULSAR Model RX5 Radar Transmitter; ECLIPSE Model 706 Guided Wave Radar Transmitter or ECHOTEL Model 355 Non-Contact Ultrasonic Transmitter
Point Level: THERMATEL Model TD1/TD2 Thermal Dispersion Switch for high/low alarm


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Flow Control Instrumentation for Industrial Steam Generation

Industrial steam generation creates useable steam for a wide variety of applications through a process known as the steam loop. First, water is treated so it can be converted into steam more efficiently. The feed water then undergoes deaeration. Boiler feed water is then further conditioned for greater efficiency. The boiler is heated and converts the water to steam. After the steam does its work, it condenses to water and is collected for reuse in the boiler plant. If you would like to learn more about level applications for the steam loop process, these are addressed in the Magnetrol® blog posts from September 1 and September 8.

Throughout the steam loop, it is necessary to monitor the flow of the water and the gas used for boiler fuel to maintain process efficiency and safety. This blog post identifies applications for flow instrumentation in industrial steam generation.

Pump Protection

industrial_steam_generationPumps are used in the steam loop for moving process fluids. Whether caused by a closed valve, a plugged line downstream or by pump cavitation, pumps operating in a reduced or no-flow condition can overheat and rupture the pump’s seal and cause a dangerous deviation in process pressure and temperature. A flow switch positioned along the pump’s discharge piping will actuate an alarm and shut down the pump when liquid flow drops below the minimum flow rate. Solid-state switches provide the highest level of pump protection in these instances by offering low flow sensitivity, wide temperature operation and high turndown.
Flow Alarm: Thermatel® TD1/TD2 Level/Flow/Interface Switch for High/Low Alarm.

Burner Fuel Gas Flow

Natural gas and biogas are the most common gaseous forms of boiler fuel. Natural gas is primarily methane, and biogas is typically 65% methane and 35% carbon dioxide. The flow of process gases in operations must be monitored for safety and efficiency. Flaring and venting as a management strategy for biogas is giving way to energy harvesting technologies with the economic advantage of creating heat, electricity, fuel or feed stocks while also reducing carbon emissions. Flow alarms and continuous flow controls monitor product streams and signal no-flow conditions caused by plugging or valve closure.
Continuous Flow: THERMATEL TA2 Mass Flow Meter.
Flow Alarm: THERMATEL TD1/TD2 Level/Flow/Interface Switch for High/Low Alarm.


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Thermatel® TA2 Flow Meter Wins Flow Control Innovation Award

Magnetrol® is excited to announce that our Thermatel® TA2 thermal dispersion mass flow meter has won a 2015 Flow Control Innovation Award. The THERMATEL TA2 was IALogo2015_winnerrecently updated with an innovative auto-switching option, which enables it to automatically switch between calibration tables. This provides the most value in applications in which turndowns can be substantially higher than 100:1. The calibration tables can apply to the same gas, such as natural gas, for a low flow range and a high flow range. They can also measure two different gases with distinct low flow and high flow ranges. The THERMATEL TA2 flow meter is one of just 9 products to win the 2015 Innovation Award.

The Flow Control awards program recognizes outstanding solutions for fluid movement, measurement and containment. Flow Control is a widely respected trade publication serving the fluid handling industry. MAGNETROL is honored to be recognized for our product innovation by Flow Control.

Thanks to all those who took the time to vote for us in the Flow Control Innovation Awards contest. We at MAGNETROL appreciate your support and help.

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Level Applications for the Steam Loop Process

The steam loop is the process by which useable steam is created for its various industry applications. Level instrumentation impacts virtually every aspect of the steam loop in order to ensure greater efficiency, safety and accuracy. In last week’s blog post, we discussed level solutions for the first three steps of the steam loop: make-up water treatment, feed water deaeration, and boiler feed water treatment. This blog post covers instrumentation for the final two steps: boiler steam generation and the condensate return system. 

STEAM LOOP: 4. Boiler Steam Generation

Feed water routed to the boiler is heated in an economizer before being chemically treated upon entering the boiler. After heat converts the water into steam, the steam is routed to its applications.

Boiler drum level control must maintain water level within critical set points. Ancillary boiler systems requiring level control include fuel storage, flash tanks and the boiler’s blowdown tank.


  1. Fuel Storage

A boiler can be fueled by natural gas, propane, fuel oil, coal, biomass or biogas. Storage of liquid fuel oils with low flash points requires safety-certified controls due to the hazardous location.

Continuous Level: Eclipse® Model 706 High Performance Guided Wave Radar Transmitter; Pulsar® R95 Thru-Air Radar Transmitter; Model R82 Thru-Air Radar Transmitter; Echotel® Model 355 Non-Contact Ultrasonic Transmitter.

Point Level: Model B10/B15 Dual Stage Displacer Level Switch.

  1. Boiler Drum

Low water level can cause severe, even catastrophic, damage. If necessary, level controls add feed water or shut down the burner operation. Excessive high level can cause damaging carryover and priming in which a large, rapidly applied load results in a sudden reduction in steam pressure that pulls boiler water into piping. In this event, the level control actuates a valve to throttle down feed water supply.

Continuous Level: ECLIPSE Model 706 High Performance Guided Wave Radar Transmitter; Digital E3 Modulevel® Displacer Transmitter; APM MODULEVEL Pneumatic Controller; Atlas™ or Aurora® Magnetic Level Indicators.

Point Level: Series 3 ASME 31.1 External Caged Level Switch; Model B40 HT/HP External Caged Level Switch.

  1. Blowdown Tank

Undesirable solids in boiler water can be reduced through a continuous purge or blowdown system. Blowdown tanks allow the blowdown to cool before it is discharged into the sewer system.

Continuous Level: ECLIPSE Model 706 High Performance Guided Wave Radar Transmitter; Digital E3 MODULEVEL Displacer Transmitter.

  1. Flash Tank

Boiler water blowdown can be used to heat process streams. Boiler water blowdown heat recovery systems use flash steam from the flash tank for deaeration. The blowdown from the flash tank is passed through an exchanger and used to preheat the boiler make-up water.

Continuous Level: ECLIPSE Model 706 High Performance Guided Wave Radar Transmitter; ATLAS or AURORA Magnetic Level Indicators.

STEAM LOOP: 5. Condensate Return System

After steam does its work it condenses to water and is collected in the condensate return system for reuse in the boiler plant. Since condensate has already been treated with chemicals and has been through the steam system, it will take far fewer resources to turn it back into steam than it would to make steam from an equal quantity of cold water. A condensate return unit thus provides a significant savings in make-up and the associated water treatment chemicals.


  1. Condensate Receiver Tank

Level controls in receiver tanks ensure that water is returned to the boiler house for reuse. When the control senses the upper level in the receiver tank it will actuate a pump to route the condensate to the deaerator. Typically, these tanks range from 65 to 1,800 gal. (250 to 7,000 L).

Continuous Level: ECLIPSE Model 706 High Performance Guided Wave Radar Transmitter; Digital E3 MODULEVEL Displacer Transmitter; ATLAS Magnetic Level Indicator.

Point Level: Thermatel® TD1/TD2 Flow/Level/Interface Switch; ECHOTEL Model 961 Single Point Ultrasonic Level Switch; Sealed External Caged Level Switch; Model B40 External Caged Liquid Level Switch.


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Level Instrumentation for Steam Generation Process Applications

Steam is today’s utility player in the industrial energy arena. It cleans and sterilizes, dries and concentrates, separates and evaporates. In cookery, it preserves flavor, texture, and retains nutrients. In chemistry, it fosters reactions by controlling process pressure and temperature. In biotechnology, it’s essential for growing production organisms. Steam ranges in purity from boiler grade for routine tasks, to culinary grade “clean steam” for food and dairy, and graduates up to super pure, pyrogen-free steam for biopharmaceutical use.

Generated steam is ubiquitous because it’s industry-friendly. It’s intrinsically safe, flexible, economical, aseptic, and environmentally benign. Steam can arise from fossil fuels, biomass or biogas. Its high efficiency is due to its ability to return a significant portion of condensate to the generation cycle. With proper maintenance, a steam plant can last for decades.

Magnetrol® has produced a special applications brochure on level instrumentation for the steam generation process. This brochure focuses on the industrial steam boiler. If you are interested in steam applications for power generation, the massive electricity-generating utility boilers are addressed in our Power Gen and Nuclear brochures. This blog post, the first in a three-part series, will discuss three aspects of the steam loop: make-up water treatment, feed water deaeration, and boiler feed water treatment. Future posts in the series will cover the rest of the steam loop as well as flow control applications.

STEAM LOOP: 1. Make-Up Water Treatment
It all begins with water, the essential medium for the steam generation process. Conditioning water properly can increase boiler efficiency and extend the boiler’s operating life. Improper or nonexistent feed water treatment is the major cause of boiler failure.

All natural sources of fresh water require varying degrees of treatment prior to boiler use. Boiler feed water treatment prevents scale and deposits, removes dissolved gases, protects against corrosion, eliminates water and steam carry-over, and optimizes boiler efficiency and minimizes maintenance costs.
Feed water is treated and conditioned in three phases:
1. Raw make-up water is treated before entering the deaerator
2. Treated make-up water and return condensate merge in the deaerator for removal of dissolved gases
3. De-oxygenated and heated feed water enters the boiler where it is further treated with chemicals

Feed water treatment requirements vary greatly. In rare cases, raw make-up water only needs filtering. More commonly, some form of external treatment is needed, as in the typical process units listed below.

Raw water with sediments may require a settling tank with the addition of chemicals to foster precipitation of the suspended matter. Clarified water is then drawn off at a surface outlet.
Continuous Level: Eclipse® 706 Guided Wave Radar (GWR); Echotel® Model 355 Non- Contact Ultrasonic Transmitter

Coarse and Fine Filtration
Suspended solid impurities are reduced or eliminated by passing make-up water through a filter. If the suspended solids are very fine, a flocculation step may be required.
Continuous Level: ECHOTEL Model 355 Non-Contact Ultrasonic Transmitter; Pulsar® R95 Thru-Air Radar Transmitter; Model R82 Thru-air Radar Transmitter

Water Softening
Calcium and magnesium are hard scale forming minerals that build up on boilers and steam-related equipment resulting in costly repairs, increased energy consumption, and plugged equipment. Softening occurs as hardness minerals attach to the softening resin and “exchange” for sodium.
Continuous Level: PULSAR R95 Thru-Air Radar Transmitter; ECLIPSE 706 Guided Wave Radar; Atlas™ or Aurora® Magnetic Level Indicators (MLIs).

Demineralization is typically an ion exchange process whereby minerals or mineral salts are removed from water. Chemical treatment or a feed water evaporator can be used as alternative methods, the latter using extraction steam to remove impurities in raw water.
Point Level: ECHOTEL 961 Ultrasonic Level Switch; Model T20 Single Stage Float Level Switch.
Continuous Level: ECLIPSE 706 GWR; Digital E3 Modulevel® Displacer Transmitter. Point Level: Models T5x and T6x Float-Based Level Switches.

Header Tank
The treated make-up water is routed for storage in a cold-water header tank. From there the water passes on demand through a flash tank for heating and on to the deaerator for degassing.
Continuous Level: Model R82 Non-contact Radar Transmitter; ECLIPSE 706 GWR; PULSAR R95 Thru-Air Radar Transmitter.

STEAM LOOP: 2. Feed Water Deaeration
Because boiler and steam systems are made primarily of steel and the heat transfer medium is water, the potential for corrosion is very high. Dissolved oxygen is the major cause of boiler system corrosion. Oxygen and other gases are removed from both feed water streams—treated make-up water and return condensate feed water—when they merge in the deaerator. Deaerators remove non-condensable gases from feed water streams by steam heating and by aggressively agitating incoming water. The deaerator’s storage section is typically designed to hold enough water for ten minutes of boiler operation at full load.


Level control on a deaerator typically measures the level in the storage tank and modulates a control valve on feed water streams to maintain tank level at the desired set points.
Continuous Level: ECLIPSE 706 Guided Wave Radar; ATLAS or AURORA Magnetic Level Indicators.
Point Level: Series 3 ASME B31.1 External Caged Liquid Level Switch.

STEAM LOOP: 3. Boiler Feed Water Treatment
For higher boiler efficiencies, the feed water is further conditioned prior to and upon entering the boiler. First, the water is preheated by an economizer using the boiler’s hot exhaust gas streams. Next, water treatment inside the boiler reduces foaming, eliminates adherence of suspended matter to boiler internals, further prevents corrosion and scaling by eliminating residual oxygen. Chemical feed systems are employed for both internal boiler treatment and in the make-up water treatment unit.


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Understanding Tank Bridle Level Measurement

A bridle is a vertical pipe connected to the side of a storage tank or process vessel, typically with side/side or side/bottom connections. Because the fluid inside the bridle will rise and fall equally with the level of fluid inside the tank or vessel, the bridle has been adapted for
level measurement on a broad scale.

The Magnetrol® use of the term “bridle” refers to a bypass chamber on a larger process vessel on which the level instrumentation for that vessel is mounted. Bridles usually do not have level equipment extending into the bridle itself. Level equipment is typically placed in its own cage or nozzle attached to the bridle.

Bridle Advantages

 Tank bridle level measurement has provided industrial users with distinct advantages:

Isolation: Because a level instrument mounted in a bridle is isolated from the process it can be calibrated or maintained without disturbing the process.

Fewer Connections: A bridle reduces the number of connections necessary on the process vessel. This is especially important on boiler code vessels that require qualified welders and procedures.

Prudent Design: Level instrumentation is often the last consideration on a project. Mounting the instrumentation on a bridle eliminates the need for planning multiple instrumentation connections on the vessel.

Saves Time: Because instrumentation is typically left until the end, ordering a bridle with all the level instrumentation cuts down on the time necessary to add connections and install the instrumentation at the project deadline.

Avoids Obstructions: When a tank has mixers, agitators, aerators, ladders, or structural bracing, a bridle avoids any interference between these objects and the level controls.

Reduces Turbulence, Foam: In a highly agitated vessel, a bridle calms the surface to be measured and reduces foam to improve measurement accuracy.

Isolation: Because a level instrument mounted in a bridle is isolated from the process it can be calibrated or maintained without disturbing the process.

Bridle Instrumentation

Here are a few of the most common level instrument technologies used for tank bridle measurement:

Guided Wave Radar GWR mounted in a cage is well suited for bridle measurement. Configuration is fast, no calibration is required, and accuracy isn’t affected by changing densities, dielectrics, high temperatures or high pressures. MAGNETROL Eclipse®  transmitters are available with a wide range of probes, materials and options.

Magnetic Level Indicators Developed for the most demanding industrial applications, MLIs provide local visual indication and remote indication when combined with a transmitter. Highly visible flags magnetically coupled to the moving float provide local level indication. Aurora® (float and GWR transmitter redundancy) and Atlas™ (float-based MLI) can be customized for unique application solutions.

Magnetostrictive Transmitters Designed to attach quickly and easily to magnetic level indicators, magnetostrictive transmitters offer high accuracy and high linearity when combined with MLIs. The MAGNETROL Jupiter® magnetostrictive transmitter is available with an innovative dual compartment design.

External Cage Float Switches A wide range of float switches suitable for bridle applications with flanged and sealed cage designs include ASME B31.1 construction for boiler and power plant use and B31.3 construction for petrochemical use. HP and HT versions and a selection of switch styles and material options are available.

Displacer Controllers Displacer Controllers utilize simple buoyancy principles to detect and convert liquid level changes into a stable output signal. Modern displacer controllers serve most liquid level measurement and control applications including those with varying dielectric, vapors, turbulence, foam, buildup, bubbling or boiling and high fill/empty rates. The MAGNETROL Digital E3 Modulevel® is an advanced, intrinsically safe, two-wire controller that comes in a variety of configurations and pressure ratings for varied applications.

Ultrasonic Contact Point Sensors Nozzle-mounted ultrasonic switches are mounted horizontally on bridles for high or low level alarm applications. The MAGNETROL Echotel® Model 961 Level Switch offers advanced transducer designs, extensive hazardous location approvals, and self-test technology. Pulsed signal technology for superior performance in difficult conditions and excellent immunity from electrical noise interference are also featured.

Thermal Dispersion Point Sensors Nozzle-mounted thermal dispersion switches provide a high level of performance for level and interface applications on bridles. MAGNETROL Thermatel® Model TD1/TD2 switches feature continuous diagnostics with fault indication, temperature compensation, narrow hysteresis, and fast response time.

MAGNETROL has created a pamphlet on tank bridle level measurement that provides even more information about bridle instrumentation, specification, and torque tube replacement. Download the pamphlet today to learn more.


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Guided Wave Radar Instrumentation in Steam Drum and Feedwater Heater Applications

With the addition of non-conventional, renewable generation to the energy mix, many operators have questions and concerns about level technology and how it can improve the efficiency of their power plants. Magnetrol® expert Donald Hite recently answered questions about guided wave radar level control instrumentation as part of a power Optimizing Level Control Webcastindustry-focused webinar, “Optimizing Level Control to Meet New Generation Demands.” This week’s blog post shares some of that Q&A.

Question: What is the standard mounting for a guided wave radar instrument in a feedwater heater and in a steam drum? Should the instruments be mounted externally or internally?

Answer: The standard mounting for both a feedwater heater and a steam drum is an external chamber. Level instrumentation on feedwater heaters are never directly inserted – the internal construction of a heater prevents top entry of level sensing devices; thus, limiting them to external mount only. Historically, guided wave radar is also mounted externally on a steam drum. However, recent research and testing has explored the possibility of internal installation. MAGNETROL has proven that direct insertion of guided wave radar into a steam drum is not only a viable, but also a more effective and less complicated method of measuring the level. As of right now, all of our direct insertion GWR installations in steam drums are being done internationally due to the fact all of the R&D and testing was accomplished in that market space. On the domestic front, direct insertion is a new concept and will catch on as plants are made aware of the cost and performance benefits, which I should say are significant.

Question: One of the claims made about guided wave radar is that it requires no external input to achieve and maintain accuracy. What does this mean?

Answer: The fundamental principle of Guided Wave Radar technology does not rely on specific gravity or inference as the basis for the measurement. Consequently, parameters which normally affect such devices have relatively little impact on the measurement. It doesn’t require any external input to compensate for process conditions that affect the specific gravity of the material being measured. This is in contrast to how many other level instruments function. Take a displacer, for instance. A displacer is designed to be most accurate at the specific gravity of the material being measured at operational conditions. Any fluctuations from the design criteria relative to specific gravity have a negative impact on the accuracy. A similar statement can be made about differential pressure technology. These vulnerabilities, if uncorrected, reduce accuracy during critical startup and cycling conditions where swings in specific gravity are commonplace. Guided wave radar gets its return signal from the surface of the material being measured. As a consequence, its accuracy is not contingent on correcting for fluctuations in specific gravity. The key is ensuring the material being measured is of sufficient dielectric value during all application conditions to return a signal that can be tracked.   Although the saturated steam in the vapor space does affect the propagation speed of microwave energy, the correction is self contained and accomplished internally in the unit, completely transparent to the end user. When you use guided wave radar in any given steam application, you no longer need to introduce other measurements, which could be sources of additional error, to determine the true level.

Question: How does guided wave radar work with foaming applications?

Answer: There are essentially three scenarios when using guided wave radar on foaming applications. In the worst case scenario, the foam absorbs all of the microwave energy eliminating GWR as a level solution. Although rare, it does occur from time to time. Another possibility is that it has no impact at all. The microwave energy passes through the foam unchallenged and the level is easily acquired. In a third scenario, the foam is of sufficient dielectric value to create a reflection which can be tracked as level while low enough to allow the energy to pass through creating a second reflection from the actual liquid surface. In this scenario the instrument can be configured to track either the foam or liquid level.

Question: Is guided wave radar now the industry’s preferred option for drum level control?

Answer: At the moment, it is not. The most common technologies you see used on drum level applications are differential pressure and conductivity. Up until recently, the process isolation seal material used in GWR probes for saturated steam applications could not tolerate the temperature common on high-pressure drums. GWR has always been a viable level solution on the LP and IP drums. Most customers prefer to standardize on a single technology for all drums. Since GWR could not handle the HP drum it did not see much service for this reason.

To learn more about guided wave radar technology and optimized level control in steam drum and feedwater heater applications, view the webcast “Optimizing Level Control to Meet New Generation Demands.”

Heat Rate Webcast

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Orion Instruments® Acquires ASME U Stamp Certification

Orion Instruments® was recently certified as an ASME Section VIII, Division 1 Boiler and Pressure Vessel Code facility. This achievement verifies that ORION’s engineering, manufacturing, and quality systems meet the stringent requirements of ASME Sec. VIII, Div. 1. As a result, our capabilities now include the construction of code stamped chambers to meet end user specifications.

Adding ASME Sec. VIII, Div. 1 certification to our construction code offerings gives ORION the ability to offer custom engineering, design, and manufacturing at any level the process application may require. Customers can be assured that their magnetic level indicators (MLIs) are manufactured with the highest quality and craftsmanship regardless of construction code.

There are a limited number of MLI manufacturers with ASME Sec. VIII, Div. 1 certification.

This certification allows ORION Instruments to provide the following:

  • ASME Sec. VIII, Div. 1 U stamp (full implementation of code with stamp, National Board Registration, 3rd party inspection, and supporting documentation)
  • Construction in accordance with ASME Sec. VIII, Div. 1
  • Designed to code calculations
  • Documentation to customers’ specifications
  • No 3rd party inspection
  • No National Board registration
  • No “U” stamp designator
  • Construction in an ASME Sec. VIII, Div. 1 certified facility
  • Ensures the highest level of quality and manufacturing processes

For more information on ASME Boiler and Pressure Vessel Code (BPVC) Section VIII, Division 1, or to acquire a copy of the certification, please contact the ORION Instruments factory or visit our website.

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Technologies for Liquid Interface Level Measurement

The need for interface level measurement arises whenever immiscible liquids–those incapable of mixing—reside within the same vessel. The lighter material rises to the top and the heavier material settles at the bottom. In oil production, for example, water or steam is used to extract oil from a well. Well fluids then route to production separators where they settle into their primary constituent parts as a water-hydrocarbon interface. Water may also be used as a transport medium or a cleaning agent and forms an interface with an allied material which is later extracted.

Interfaces are most commonly found in the diverse separation processes that are essential to every industry. Separation recovers additives, catalysts or solvents, extracts impurities, and routes media into different processing channels.

Principal Interface Applications

Here are a few of the most common industries and processes where interfaces are found:

Petroleum and Gas

  • Separators
    • LPG Dehydrators
    • Heater Treaters
    • Crude Desalters
    • Free-water Knock-out
  • Regenerators
    • Coalescers
    • Crude Dewatering
    • Acid Settling Tanks
    • Alkylation Tanks
    • Coking Drums

Water & Wastewater

  • Settlement Tanks
    • Clarifiers
    • Sludge Thickeners
    • Filtration Systems
    • Final Effluent Monitoring

Other Industrial

  • Liquid Oxygen and Nitrogen production
  • Digester Vessels
  • Extractors & Separators
  • Grease Traps
  • Pulp and Paper
  • Mining and Quarrying
  • Food and Beverage
  • BioPharmaceutical
  • Chemical Plants
  • Storage Facilities

Though our emphasis is on liquid/liquid interface, interfaces also form between liquid and solids, liquid and foam, or liquid and a gas—such as gases (other than air) that are used in tank blanketing.


Immiscible liquids meet along an interface layer where they undergo some amount of emulsification. This emulsion layer (also called a rag layer) may form a narrow and precise boundary; but more frequently it is a broader gradient of mixed liquids—or liquids mixed with particles that form a slurry. Generally, the thicker the emulsion layer, the greater will be the measurement challenge. Knowing the position of a process interface is necessary for maintaining product quality and operations efficiency. The interface is measured and controlled by precision level switches and transmitters. Though at least 20 different types of liquid level measurement devices are in service today, only a very few are suitable for accurate and reliable interface level measurement.

Level Measurement Technologies

Here are three of the most reliable technologies for interface level measurementThe information presented describes the technologies as they pertain to Magnetrol® level instrumentation:

Displacer Controllers and Transmitters- Modulevel®
Measurement Principle: Movement of the interface level along the length of the displacer causes the precision range spring to extend or compress. This causes the movement of the core within a linear variable differential transformer in the Digital E3 Electronic MODULEVEL resulting in a digital or analog output. In the Pneumatic MODULEVEL, this causes the movement of a magnetic ball which guides the magnet carriage resulting in a pneumatic output change.
Interface Measurement: This technology is widely used for interface service because it is unaffected by emulsions and will accurately track the middle of the emulsion layer.

Thermal Dispersion- Thermatel®
Measurement Principle: Switches using thermal dispersion technology detect heat transfer which reduces the temperature difference between the switch’s two sensors; one sensor is for reference and the other is heated to a temperature above the process temperature. The temperature difference is greatest in air, then decreases when cooling occurs due to a change in media. The electronics compare the electrical signal from the sensor against the set point and provide a relay actuation.
Interface Measurement: The THERMATEL TD1/TD2 and TG1 switches have been designed and engineered for level, flow or interface detection. When used as an interface detection switch, the set point can be adjusted to detect the difference in media between two fluids that have different thermal conductivity. Water has a very high thermal conductivity while organic materials (oil) have a much lower thermal conductivity. THERMATEL detects the difference in media due to the temperature difference which will be greater in the organic layer than in the oil layer.

Guided Wave Radar- Eclipse®
Measurement Principle: ECLIPSE is based on Time Domain Reflectometry. TDR transmits pulses of electromagnetic energy down the wave guide, or probe. When a pulse reaches a liquid surface that has a higher dielectric constant than the air in which it is traveling (dielectric constant of 1), the pulse is reflected. Ultra high-speed timing circuitry provides an accurate measure of liquid level. Even after the pulse is reflected from the upper surface, some of the energy continues along the length of the probe through the upper liquid. The pulse is again reflected when it reaches the higher dielectric lower liquid.
Interface Measurement: The dielectric constant (ε) of the interface media is critically important for GWR. As shown in the illustration at right, the upper dielectric should be between 1.4 and 5, and the lower dielectric should be greater than 15. The typical oil and water interface application shows the upper, nonconductive oil layer being 2, and the lower, very conductive water layer being 80. ECLIPSE measurement is suitable where the interface is clean and distinct and the depth of the emulsion layer is shallow.

MAGNETROL has produced a special applications brochure featuring these and more interface level measurement technologies, with an overview of technology specs, process capabilities, and transmitter options. Download the brochure today and learn more about the benefits and applications of each technology.


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