Register Early for the Yokogawa Users Conference 2018

The Yokogawa Users Conference for North America will be held
on September 10 - 13 in Orlando, FL

Yokogawa is hosting its Users Conference in Orlando FL for 2018. This excellent event enables attendees to:

• Learn how to maximize the value of their measurement and control investment.
• View and learn about the latest products and solutions for process measurement and control.
• Interact with subject experts and Yokogawa partners.
• Network with industry peers.
• Build knowledge of best practices for particular industries and measurement and control in general.

There will be panel discussions, technical sessions, exhibits and more. The event is scheduled for September 10th through 13th, and early registration has started. Make plans to attend and build your knowledge base. You can find the registration information at the conference website, or reach out to a Yokogawa representative to find out more.

Magnetic Flow Meters

Magnetic flow meters can be easily applied in lined
pipe sections and those of substantial diameter.
Image courtesy Yokogawa

The measurement of fluid flow is a common process control function. Flow measurement can have a range of differing output requirements, depending upon the needs of the process operators. With many technologies and instruments from which to choose, knowledge of the principals behind each measurement technology and basic operation requirements can help in the selection of the best instrument for each application. 

Anywhere there are pipes, somebody wants to know how much fluid is passing through them. Industrial flow meters rely on their ability to measure the change in some physical characteristic of fluid moving within a pipe that can be related to fluid velocity or mass flow. Depending upon the nature of the raw measurement, additional information and processing may be necessary to convert the base measurement into a useful measurement of flow rate.

In the processing industries, differing technologies are used to measure fluid motion. Some common technologies include magnetic, ultrasonic, vortex shedding, Coriolis and differential pressure. This list is not exhaustive, and several other technologies will certainly be found in use. Each methodology survives within a competitive marketplace due to its unique combination of performance and value attributes. Let's look at magnetic flow meters, also referred to as magmeters.

The operational principle of a magnetic flow meter is based upon Faraday’s Law. This fundamental scientific principle states that a voltage will be induced across a conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure aspect of a conductive fluid to be expressed via the magmeter. In a magmeter application, the instrument produces the magnetic field referred to in Faraday’s Law. The conductor, moving at a right angle to the magnetic field, is the fluid. The actual measurement of a magnetic flow meter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with values of other fluid properties and the pipe cross sectional area. Magnetic flow meters enjoy some positive application attributes.

• Magnetic flow meters have no moving parts.
• The instrument, which often resembles a pipe section, can be lined with corrosion resistant material for use with aggressive media.
• With no sensor insertions or obstructions in the fluid path, the impact of the instrument on the flow is minimal.
• Accuracy, when compared to other technologies, is high.
• Application to laminar, turbulent, and transitional flow profiles is permissible.
• Generally, measurement is not adversely impacted by fluid viscosity, specific gravity, temperature and pressure.
• Magnetic flow meter technology can be applied to a very wide range of pipe sizes.
• Device responds rapidly to changes in fluid flow.
• Can be successfully applied to liquids containing heavy particulates.
• Generally long service life with little maintenance.

Though the roster of positive attributes is strong, magmeters are not universally applied. Consider some of these points with respect to your potential application.

• The fluid acts as the "conductor", as stated in Faraday's Law. Magnetic flow meters only work on liquids with conductivity above a certain threshold. They may be unsuitable for use with hydrocarbons and high purity water for this reason.
• Cannot be used to measure gas flow because gases are not sufficiently conductive.
• Piping must be grounded.
• Generally, rated accuracy requires the pipe cross section to be filled by the liquid being measured.

This listing of attributes is very general in nature. Some magnetic flow meter variants have adaptations that minimize or accommodate the impact of special process conditions. Share your flow measurement requirements and challenges with a process measurement specialist. Your own knowledge and experience will be leveraged into an effective solution by their product application expertise.

Best Temperature Control Performance Starts With a Match of Sensor Configuration to Application

A specially configured temperature sensor can improve
measurement response and process control.
Image courtesy Applied Sensor Technologies

There are more temperature controlled operations than any of us could count in a lifetime, each with a set of signature performance requirements and design challenges. Matching the means of temperature measurement, the control loop characteristics, and heat delivery method to the application are essential to achieving successful operation.

Step one is to measure the process temperature. This sounds simple until you start researching products and technologies for measuring temperature. Like the temperature controlled operations mentioned previously, they are numerous. To filter the possible candidates for temperature sensing devices, consider these aspects of your application and how well a particular sensor may fulfill your requirement.

• Response Time - How rapidly the sensor will detect a change in process temperature is a function of how the sensor is constructed and how it is installed. Most temperature sensors are enclosed or encapsulated to provide protection for the somewhat vulnerable sensing element. Greater mass surrounding the sensing element, or a shape that inhibits heat transfer from the process to the sensor, will slow sensor response. Whether the slower response time will adversely impact process operation needs to be considered. More consideration is due to the manner in which the temperature sensor assembly is installed. Not all applications involve a fluid in which the sensor assembly can be conveniently immersed, and even these applications benefit from careful sensor placement.
• Accuracy - Know what your process needs to be effective. Greater levels of accuracy will generally cost more, possibly require more care and attention to assure the accuracy is maintained. Accuracy is mostly related to the type of sensor, be it RTD, thermocouple, or another type.
• Sensitivity - Related to the construction, installation, and type of sensor, think of sensitivity as the smallest step change in process temperature that the sensor will reliably report. The needs of the process should dictate the level of sensitivity specified for the temperature sensor assembly.

Take a simple application as an illustration. Heat tracing of piping systems is a common function throughout commercial and industrial settings experiencing periods of cold weather. Electric heat trace installations benefit from having some sort of control over the energy input. This control prevents excessive heating of the piping or applying heat when none is required, a substantial energy saving effort. A temperature sensor can be installed beneath the piping's insulation layer, strapped to the pipe outer surface. A specially designed sensor assembly can improve the performance of the sensor and the entire heat trace control system by enhancing the response time of the temperature sensor. A right angled sheath permits insertion of the sensor beneath the piping insulation while orienting the connection head upright. A surface pad at the tip of the sheath increases the surface contact with the pipe to provide faster sensor response. The surface pad is a metal fixture welded to the sensing end of the temperature sensor assembly. It can be flat, for surface temperature measurements, or angled for installation on a curved surface, like a pipe. The increased surface contact achieved with the surface pad promotes the conduction of heat to the sensor element from the heated pipe in our illustration. This serves to reduce and improve the response time of the sensor. Adding some thermally conductive paste between the pad and the pipe surface can further enhance the performance. While the illustration is simple, the concepts apply across a broad range of potential applications that do not allow immersion of the temperature assembly in a fluid.

A simple modification or addition of an option to a standard sensor assembly can deliver substantially improved measurement results in many cases. Share your temperature measurement requirements and challenges with a process measurement specialist. Leverage your own process knowledge and experience with their product application expertise.

Special RTD Temperature Sensor Configuration for Heat Trace Applications from Miller Energy, Inc.

Diaphragm Seals For Protection of Process and Pressure Instruments

One of many diaphragm seal variants
Courtesy Wika

Pressure measurement is a common element industrial operations or control systems. Fluid processing can often involve media that is potentially harmful to pressure sensing devices. The media may be corrosive to the sensor material, or other media properties may impact the performance or usable life of the instrument. In process control environments, diaphragm seals play a role in protecting items like pressure sensors from damage by process fluids. The diaphragm seal is a flexible membrane that seals across the connecting path to a sensor and isolates the sensor from the process media. System pressure crosses the barrier without inhibition, enabling accurate measurement, but the process fluid does not. Typical materials composing diaphragm seals are elastomers, with a wide variety of specific materials available to accommodate almost every application.

In the operating principle of the diaphragm seal, the sealed chamber created between the diaphragm and the instrument is filled with an appropriate fluid, allowing for the transfer of pressure from the process media to the protected sensor. The seals are attached to the process by threaded, open flange, sanitary, or other connections.  Diaphragm seals are sometimes referred to as chemical seals or gauge guards. Stainless steel, Hastelloy, Monel, Inconel, and titanium are used in high pressure environments, and some materials are known to work better when paired with certain chemicals.

Sanitary processes, such as food, beverage, and pharmaceuticals, use diaphragm seals to prevent the accumulation of process fluid in pressure ports, a possible source of contamination. If such a buildup were to occur, such as milk invading and lodging in a port on a pressure gauge, the resulting contamination compromises the quality and purity of successive batches. Extremely pure process fluids, like ultra-pure water, could be contaminated by the metal surface of a process sensor. Some pneumatic systems rely on the elimination of even the smallest pressure fluctuations, and diaphragm seals prevent those by ensuring the separation of the process materials from the sensors.

Diaphragm seals are not without some application concerns, and devices are now built to address and counter many potential issues related to the use of diaphragm seals with process monitoring instruments and equipment. Products seek to eliminate any and all dead space, allow for continuous process flow, and are self-cleaning thanks to continuous flow design. Some high pressure seals come equipped with anti-clogging features, accomplished by the elimination of internal cavities while protecting gauges. Multi-purpose seals reduce temperature influence and improve instrument performance while pinpointing and diffusing areas of high stress. These pre-emptive measures result in longer instrument life-cycles and improved performance while ensuring protection from corrosion.

There are numerous options and available diaphragm seal variants. Share your application specifics with a product specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Quick Reference Guide for Pressure and Flow Instrumentation

Mass Flow Controller
Courtesy Brooks Instrument

Brooks Instrument is a globally recognized manufacturer of flow and pressure instrumentation for scientific and industrial use. The company's product line ranges through:

Variable Area Flowmeters - Armored metal, glass tube and plastic for reliable measurement of liquids and gases

Mass Flow Controllers - Coriolis and thermal mass flow technology for precision fluid measurement and control

Pressure Controllers - Digital and mechanical pressure regulators and controllers deliver high precision gas control

Pressure and Vacuum Products - Pressure transducers, gauges, and capacitance manometers

Vaporization Products - Deliver controlled high purity vapor to processes from source liquid

There are many products and variants. The company developed a summary document that provides an overview of the various product types, enabling potential users to focus quickly on the instruments that will meet their requirements. The document is included below.

Share your pressure, vacuum, and flow measurement and control challenges with product application specialists, combining your process knowledge and experience with their product application expertise to develop effective solutions.

Flow, Pressure & Vapor Instrumentation from Miller Energy, Inc.

Summary of Technologies Used For Continuous Liquid Level Measurement in Industrial Process Control

Non-contact radar liquid level transmitter
Courtesy Magnetrol

Automated liquid processing operations in many fields have requirements for accurate and reliable level measurement. The variety of media and application criteria demand continuous improvement in the technology, while still retaining niches for older style units utilizing methods that, through their years of reliable service, inspire confidence in operators.

Here is a synopsis of the available technologies for instruments providing continuous liquid level measurement. All are generally available in the form of transmitters with 4-20 mA output signals, and most are provided with additional outputs and communications. What is notably not covered here are level switches or level gauges that do not deliver a continuous output signal corresponding to liquid level.

Whether considering a new installation or upgrading an existing one, it can be a good exercise to review several technologies as possible candidates for a project. None of the technologies would likely be considered the best choice for all applications. Evaluating and selecting the best fit for a project can be facilitated by reaching out to a product application specialist, sharing your applications challenges and combining your process knowledge with their product expertise to develop an effective solution.

Displacer – A displacer is essentially a float and a spring that are characterized for a particular liquid and range of surface level movement. The displacer moves in response to liquid level, changing the location of a core connected to the displacer by a stem. The core is within a linear variable differential transformer. The electrical output of the transformer changes as the core moves.

Guided Wave Radar – A radar based technology that uses a waveguide extending into the liquid. The radar signal travels through the waveguide, basically a tube. The liquid surface level creates a dielectric condition that generates a reflection. Calculations and processing of the emitted and returned signals provide a measure of distance to the liquid surface. No moving parts.

Magnetostrictive – A method employing measurement of the transit time of an electric pulse along a wire extending down an enclosed tube oriented vertically in the media. A magnetic float on the exterior of the tube moves with the liquid surface. The float’s magnetic field produces the return signal to the sensor. Processing the time from emission to return provides a measure of distance to the liquid surface.

Pulse Burst Radar - A radar based technology employing emissions in precisely timed bursts. The emission is reflectex from the liquid surface and transit time from emission to return is used to determine distance to media surface.  Not adversely impacted by changes in media conductivity, density, pressure, temperature. No moving parts.

Frequency Modulated Continuous Wave Radar – Another radar based technology that employs a radar signal that sweeps linearly across a range of frequencies. Signal processing determines distance to media surface.  Not adversely impacted by changes in media conductivity, density, pressure, temperature. No moving parts.

RF Capacitance - As media rises and falls in the tank, the amount of capacitance developed between the sensing probe and the ground reference (usually the side metal sidewall) also rises and falls. This change in capacitance is converted into a proportional 4-20 mA output signal. Requires contact between the media and the sensor, as well as a good ground reference. No moving parts.

Ultrasonic Non-Contact – Ultrasonic emission from above the liquid is reflected off the surface. The transit time between emission and return are used to calculate the distance to the liquid surface. No contact with media and no moving parts.

Differential Pressure – Pressure sensor at the bottom of a vessel measures the pressure developed by the height of the liquid in the tank. No moving parts. A variation of this method is often called a bubbler, which essentially measures hydrostatic pressure exerted on  the gas in a tube extending into the contained liquid. It has the advantage of avoiding contact between the measuring instrument parts, with the exception of the dip tube, and the subject liquid.

Laser - Probably one of the latest arrivals on the liquid level measurement scene, laser emission and return detection is used with time interval measuring to accurately determine the distance from the sensor source to the liquid surface.

Load Cell - A load cell or strain gauge can be incorporated into the support structure of the liquid containing vessel. Changes in the liquid level in the vessel are detected as distortions to the structure and converted, using tank geometry and specific gravity of the liquid.

All of these technologies have their own set of attributes which may make them more suitable to a particular range of applications. Consulting with a product specialist will help determine which technologies are the best fit for your application.

Basic Guide to Understanding Pressure

One style of absolute pressure transmitter
Courtesy Yokogawa

The impact of pressure on industrial processes would be difficult to understate. Pressure is an element of process control that can affect performance and safety. Understanding pressure concepts and how to effectively measure pressure within a process are key to any operator's success.

Yokogawa, a globally recognized leader in process measurement and control, has made available a handbook on pressure that covers a range of useful topics. The content starts with the very basic concepts and moves quickly to practical subjects related to process measurement and control.

The handbook will prove useful to readers at all levels of expertise. Share your process measurement challenges with application specialists, combining your process knowledge with their product application expertise to develop effective solutions.

Pressure Handbook for Industrial Process Measurement and Control from Miller Energy, Inc.

Comparison of RTD and Thermocouple for Process Measurement

Industrial Temperature Sensor
Courtesy Wika

Proper temperature sensor selection is key to getting useful and accurate data for maintaining control of a process. There are two main types of temperature sensors employed for industrial applications, thermocouple and resistance temperature detector (RTD). Each has its own set of features that might make it an advantageous choice for a particular application.

Thermocouples consist of a junction formed with dissimilar metal conductors. The contact point of the conductors generates a small voltage that is related to the temperature of the junction. There are a number of metals used for the conductors, with different combinations used to produce an array of temperature ranges and accuracy. A defining characteristic of thermocouples is the need to use extension wire of the same type as the junction wires, in order to assure proper function and accuracy.
Here are some generalized thermocouple characteristics.

• Various conductor combinations can provide a wide range of operable temperatures (-200°C to +2300°C).
• Sensor accuracy can deteriorate over time.
• Sensors are comparatively less expensive than RTD.
• Stability of sensor output is not as good as RTD.
• Sensor response is fast due to low mass.
• Assemblies are generally rugged and not prone to damage from vibration and moderate mechanical shock.
• Sensor tip is the measuring point.
• Reference junction is required for correct measurement.
• No external power is required.
• Matching extension wire is needed.
• Sensor design allows for small diameter assemblies.

RTD sensors are comprised of very fine wire from a range of specialty types, coiled within a protective probe. Temperature measurement is accomplished by measuring the resistance in the coil. The resistance will correspond to a known temperature. Some generalized RTD attributes:

• Sensor provides good measurement accuracy, superior to thermocouple.
• Operating temperature range (-200° to +850°C) is less than that of thermocouple.
• Sensor exhibits long term stability.
• Response to process change can be slow.
• Excitation current source is required for operation.
• Copper extension wire can be used to connect sensor to instruments.
• Sensors can exhibit a degree of self-heating error.
• Resistance coil makes assemblies less rugged than thermocouples.
• Cost is comparatively higher

Each industrial process control application will present its own set of challenges regarding vibration, temperature range, required response time, accuracy, and more. Share your process temperature measurement requirements and challenges with a process control instrumentation specialist, combining your process knowledge with their product application expertise to develop the most effective solution.

Thermal Dispersion Flow Meter For Compressed Air and Nitrogen Measurement

Thermal Dispersion Flow Meter
Magnetrol

Monitoring compressed air usage in a factory or other operation where it is consumed is essential for proper system maintenance and attainment of energy efficiency goals. The ability to track down leaks and monitor compressed air usage enables stakeholders to work toward maximizing the return on an asset with substantial initial and operating costs.

Easy installation and simplicity of operation are advantages for any instrument applied in this manner, making compressed air flow measurement a good application for a thermal dispersion flow meter. With no moving parts and a simple operating principal, a thermal dispersion flow meter can be quickly installed and put into operation. A digital display of the flow measurement provides local information, and a networking connection or other signal output can provide for remote or centralized monitoring and data collection.

A cut sheet is included below that provides detail on technological, operational, and installation aspects of this simple and effective instrument. Share your flow measurement challenges with application experts, combining your own process knowledge with their product application expertise to develop cost effective solutions.

Thermal Dispersion Mass Flow Measurement from Miller Energy, Inc.

"Bubbler Method" Liquid Level Measurement

An accurate pressure transmitter
is an integral part of  a liquid level
measurement system using the
"Bubbler Method"
Courtesy Brooks Instrument

Measuring liquid level in a tank or vessel can be accomplished in a number of ways, all of which require some arrangement of instrumentation to either infer the liquid level from the measurement of a related physical property, or directly deliver the liquid level visually using a scaled gauge arrangement. One indirect method of level measurement is often referred to as the bubbler method, so named because it employs a purging gas that continually vents from the bottom of a tube extending into a tank of liquid. Through a simple apparatus, the level of a liquid can be inferred by the amount a back pressure exerted upon the gas flowing through the tube.

Probably the greatest advantage of this method of liquid level measurement is that the liquid does not contact the sensing instrumentation. The only portion of the apparatus in contact with the liquid is a tube immersed into the tank. Basically, a purge gas flows through the immersion tube and may bubble out the immersed end of the tube, which is open to allow the contained liquid to exert a hydrostatic pressure on the purge gas. The back pressure on the gas that is exerted by the liquid contained within the tank will vary directly with the depth of the liquid. The back pressure can be correlated to a liquid level. Further calculations, which would include the tank shape, dimensions, and the liquid density can provide an indication of the volume and mass of the liquid. Here is an illustration of the setup, provided courtesy of Brooks Instrument, globally recognized leader in flow and pressure measurement and control. The illustration is from Brooks' January blog article.

Bubbler Method Tank Level Measurement Apparatus, showing application of some Brooks Instrument devices.

Below are data sheets detailing the components used in the system to control and measure the gas flow, and measure the back pressure on the immersion tube. There are other components needed for a complete system, but they are fairly generic in nature and easily obtainable. Contact a flow and level measurement specialist with your application challenges and work with them to produce effective solutions.

Bubbler Method Liquid Tank Level Measurement Instruments from Miller Energy, Inc.

Welcome to the Process Measurement, Instrumentation and Control Blog, sponsored by Miller Energy

Welcome! We hope (over time) you find this blog interesting to visit and it becomes a trusted resource for process measurement and control. We plan on weekly educational and informative blog posts innovative process control solutions, insight to how industrial controls work, and new products that solve tough engineering challenges. Please come back often!