Sometimes the Simple Solution Is the Best

This metal tube variable area flow meter is reliable,
accurate, and requires little maintenance
Photo courtesy Brooks Instrument

For process control and commercial or industrial applications, there are numerous methods of flow measurement from which to choose. Technologies range from very simple applications of physical principles to deployment of very specialized electronics and sensors. The available range of accuracy, response, and cost is quite broad, with a general expectation that higher cost will deliver better performance and accuracy.

Making the best instrument selection for a flow measurement application should include an assessment of what the operators really need in order to safely and effectively run the process or perform the task related to the measurement of fluid flow. Installing instrumentation with capabilities far beyond what is required is almost certainly a waste of financial resources, but may also have an unexpected impact on operators. Through the generation of data that, while accurate, does not provide any actionable information about process condition, operators can be misled, similar to the occurrence of a false or nuisance alarm. Some applications call for high accuracy, some do not. Define your informational needs and select instruments that will meet those needs.

There is a large array of applications that can be satisfied with simpler, less costly measurement technology. These devices often employ turbines or vanes to produce an indication of flow rate. Incorporated into some of the instruments is a means to visually observe the flowing liquid to verify color and clarity. Simple devices sometimes are intended only to indicate the presence of fluid flow, and whether the flow rate is high or low. Configurations are available that allow insertion into lines under pressure (hot tap) through a full port ball valve. Other variants with combinations of features and capabilities abound.

The selection range is enormous, so define your minimum needs first, then search for a compatible product. Your search can be enhanced by contacting an instrumentation specialist. Combining your process expertise with their broad product knowledge will produce effective solutions.

Metal Tube Variable Area Flow Meter from Miller Energy, Inc.

Heat Processing of Industrial Fluids

Steam produced by gas fired industrial boilers is a
commonly applied means of delivering heat energy

Heat, as an entity, was not always something seen as a partially visible potential indicator of changing weather patterns. The now outdated caloric theory portrayed heat as a measure of an invisible fluid called the caloric, typifying it as a solely physical property. Thermodynamics have surpassed the caloric theory and rendered it obsolete, but the understanding and manipulation of heat in industrial settings, especially pertaining to fluids, is a central part of some of the world’s most important industries. Specifically, the measurement and control of heat related to fluid processing is a vital industrial function, and relies on regulating the heat content of a fluid to achieve a desired temperature and outcome.

The manipulation of a substance’s heat content is based on the central principle of specific heat, which is a measure of heat energy content per unit of mass. Heat is a quantified expression of a system’s internal energy. Though heat is not considered a fluid, it behaves, and can be manipulated, in some similar respects. Heat “flows” from points of higher temperature to those of lower temperature, just as a fluid will flow from a point of higher pressure to one of lower pressure.

A heat exchanger provides an example of how the temperature of two fluids can be manipulated to regulate the flow or transfer of heat. Despite the design differences in heat exchanger types, the basic rules and objectives are the same. Heat energy from one fluid is passed to another across a barrier that prevents contact and mixing of the two fluids. By regulating temperature and flow of one stream, an operator can exert control over the heat content, or temperature, of another. These flows can either be gases or liquids. Heat exchangers raise or lower the temperature of these streams by transferring heat between them.

Recognizing the heat content of a fluid as a representation of energy helps with understanding how the moderation of energy content can be vital to process control. Controlling temperature in a process can also provide control of reactions among process components, or physical properties of fluids that can lead to desired or improved outcomes.

Heat can be added to a system in a number of familiar ways. Heat exchangers enable the use of steam, gas, hot water, oil, and other fluids to deliver heat energy. Other methods may employ direct contact between a heated object (such as an electric heating element) or medium and the process fluid. While these means sound different, they all achieve heat transfer by applying at least one of three core transfer mechanisms: conduction, convection, and radiation. Conduction involves the transfer of heat energy through physical contact among materials. Shell and tube heat exchangers rely on the conduction of heat by the tube walls to transfer energy between the fluid inside the tube and the fluid contained within the shell. Convection relates to heat transfer due to the movement of fluids, the mixing of fluids with differing temperature. Radiant heat transfer relies on electromagnetic waves and does not require a transfer medium, such as air or liquid. These central explanations are the foundation for the various processes used to regulate systems in industrial control environments.

The manner in which heat is to be applied or removed is an important consideration in the design of a process system. The ability to control temperature and rate at which heat is transferred in a process depends in large part on the methods, materials, and media used to accomplish the task. Selecting and properly applying the best suited controls, instruments and equipment is a key element of successful process operation. Share your challenges with application experts, combining your own process knowledge and experience with their product expertise to develop effective solutions.

Valves for LNG and CNG Operations

Valve specially designed for gas extraction operations
has integral bypass which equalizes pressure across the
valve prior to opening the main line, reducing torque
requirements and  piping stress.
Courtesy Habonim

The production and distribution of natural gas presents operators with substantial logistical, safety, and physical challenges. Maintaining flow control, containing, and dispensing of natural gas, CNG, and LNG are hazardous endeavors requiring special equipment configuration throughout the supply chain.

Source and pipeline operations are faced with high pressure and extreme working environments. At various points along the distribution path, valves will be needed to regulate or direct flow and isolate portions of the system for safety or service. Emergency shutdown valves must be configured and installed to provide failure-proof reliability when called upon to operate. Transportation containers and equipment will utilize specialized valves adapted for the pressure, temperature, and reliability requirements of the application and industry. Additionally, some may need to survive fire conditions without failure.

Fueling stations for compressed natural gas employ valves that will endure cold temperatures produced by gas expansion, plus dynamic pressure cycling. Bubble tight shutoff is necessary to maintain safety.

Liquified natural gas (LNG) presents many of the same application challenges as pressurized gas, with the added element of cryogenic temperatures.

All of these applications can be adequately served with a properly selected and configured valve and actuator. Share your fluid flow control and valve challenges of all types with application specialists. The combination of your process knowledge and experience with their product application expertise will produce an effective solution.

Industrial Valves for Gas Distribution, CNG, LNG from Miller Energy, Inc.

Water Quality Analysis – Constituent Survey Part 3

Water quality can be a concern for process input or effluent

What we know as “water” can consist of many non-H2O components in addition to pure water. This three part series has touched on some of the constituents of water that are of interest to various industrial processors. The first installment reviewed dissolved oxygen and chloride. The second article covered sulfates, sodium, and ammonia. 

To conclude the three part series on water quality analysis in process control related industrial applications we examine silica, another element which in sufficient quantities can become a confounding variable in water for industrial use. In natural settings, silica, or silicon dioxide, is a plentiful compound. Its presence in water provides a basis for some corrosion-inhibiting products, as well as conditioners and detergents. Problems arise, however, when high concentrates of silica complicate industrial processes which are not designed to accommodate elevated levels. Specifically, silica is capable of disrupting processes related to boilers and turbines. In environments involving high temperature, elevated pressure, or both, silica can form crystalline deposits on machinery surfaces. This inhibits the operation of turbines and also interferes with heat transfer. These deposits can result in many complications, ranging through process disruption, decreased efficiency, and resources being expended for repairs.

The silica content in water used in potentially affected processes needs to be sufficiently low in order to maintain rated function and performance. Silica analyzers provide continuous measurement and monitoring of silica levels. The analyzers detect and allow mitigation of silica in the initial stages of raw material acquisition or introduction to prevent undue disruption of the process. Additionally, a technique called power steam quality monitoring allows for the aforementioned turbine-specific inhibition – related to silica conglomerates reducing efficacy and physical movement – to be curtailed without much issue. The feedwater filtration couples with a low maintenance requirement, resulting in reduced downtime of analytic sequences and a bit of increased peace of mind for the technical operator.

While silica and the other compounds mentioned in this series are naturally occurring, the support systems in place to expertly control the quality of water is the most basic requirement for harvesting one of the earth’s most precious resources for use. As a matter of fact, the identification and control of compounds in water – both entering the industrial process and exiting the industrial process – demonstrates key tenets of process control fundamentals: precision, accuracy, durability, and technological excellence paired with ingenuity to create the best outcome not just one time, but each time.

New Pulsar R86 Non-contact Radar Level Transmitter From Magnetrol

Magnetrol's new non-contact radar level transmitter,,
Pulsar R86
Courtesy Magnetrol

Level measurement is a part of countless industrial processes and installations. Accurate measurement of contained solids or liquid enhances safety and operational efficiency, both of which contribute to the bottom line.

Magnetrol, globally recognized innovator in flow and level measurement, recently released its latest version of non-contact radar level measuring instruments. The Pulsar R86 transmitter operates in the 26GHz range, delivering a smaller wavelength with improved resolution, smaller antenna, and a narrower beam. Other unique innovations have been incorporated into the instrument to simplify installation and application.

The R86 is suitable for a broad range of applications across almost every industry. On board diagnostics are incrementally advanced to provide best performance and deliver the information needed to maintain proper operation.

The latest information on the Pulsar R86 is included below. Reach out to process measurement specialists and share your measurement challenges and requirements. Combining your own process knowledge and experience with their product application expertise will result in an effective solution.

Magnetrol Non-Contact Radar Level Transmitter Pulsar R86 from Miller Energy, Inc.

Water Quality Analysis – Constituent Survey (Part 2)

Water can contain many contaminants

It would be difficult to understate the role and importance of water in industrial processing, even our own biological existence. In the first installment of this series, the roles of dissolved oxygen and chlorides were covered.

Continuing the examination of water quality monitoring in municipal and industrial processes, another key variable which requires monitoring for industrial water use is sulfate. Sulfate is a combination of sulfur and oxygen, salts of sulfuric acid. Similarly to chlorides, they can impact water utilization processes due to their capability for corrosion. The power generation industry is particularly attuned to the role of sulfates in their steam cycle, as should be any boiler operator. Minerals can concentrate in steam drums and accelerate corrosion. Thanks to advancements in monitoring technology, instruments are available which monitor for both chlorides (covered in the previous installment in this series) and sulfates with minimal supervision needed by the operator, ensuring accurate detection of constituent levels outside of an acceptable range. Ionic separation technologies precisely appraise the amount of sulfate ions in the stream, allowing for continuous evaluation and for corrective action to be taken early-on, avoiding expensive repairs and downtime.

Another substance worthy of measurement and monitoring in process water is sodium. Pure water production equipment, specifically cation exchange units, can be performance monitored with an online sodium analyzer. Output from the cation bed containing sodium, an indication of deteriorating performance, can be diverted and the bed regenerated. Steam production and power generation operations also benefit from sodium monitoring in an effort to combat corrosion in turbines, steam tubes, and other components. Sodium analyzers are very sensitive, able to detect trace levels.

Ammonia is comprised of nitrogen and hydrogen and, while colorless, carries a distinct odor. Industries such as agriculture utilize ammonia for fertilizing purposes, and many other specializations, including food processing, chemical synthesis, and metal finishing, utilize ammonia for their procedural and product-oriented needs. An essential understanding of ammonia, however, includes the fact that the chemical is deadly to many forms of aquatic life. Removing ammonia from industrial wastewater is a processing burden of many industries due to the environmental toxicity.

Methods for removing ammonia from wastewater include a biological treatment method called ‘conventional activated sludge’, aeration, sequencing batch reactor, and ion exchange. Several methods exist for in-line or sample based measurement of ammonia concentration in water. Each has particular procedures, dependencies, and limitations which must be considered for each application in order to put the most useful measurement method into operation.

As water is an essential part of almost every facet of human endeavor and the environment in which we all dwell, the study and application of related analytics is an important component of many water based processes. The variety of compounds which can be considered contaminants or harmful elements when dissolved or contained in water presents multiple challenges for engineers and process operators.

The detection and measurement of water constituents can pose challenges to plant operators. Share your requirements with instrumentation experts, and combine your own process knowledge and experience with their product application expertise to formulate an effective solution.

Water Quality Analysis – Constituent Survey (Part 1)

Water quality analysis is utilized at sewage treatment plants,
but at many other industrial facilities, too.

Of all the raw materials available for human consumption – aside from the air we breathe – the most vital component of life on earth is water. In addition to the global need for humans to drink water in order to survive, the use of water is essential in a myriad of industries relating to process control. Whether the goal is the production or monitoring of pure water for industrial use, or the processing of wastewater, the ability to measure the presence and level of certain chemical constituents of water is necessary for success.

In order to use water properly, industrial professionals combine state of the art analyzers with technical expertise to evaluate water quality for use or disposal. Two essential values of process control are ensuring elements of a control system are accurate and secure, and, furthermore, that they are accurate and secure for each product every time. By properly vetting water in industry, engineers and other personnel in fields such as pharmaceuticals, chemical, food & beverage, brewing, power, and microelectronics are able to maintain standards of production excellence and conform with regulatory requirements related to water quality.

The amount of dissolved oxygen present in water can correlate with the degree of movement at an air-water interface, also being impacted by pressure, temperature, and salinity. Excessive or deficient dissolved oxygen levels in industrial process waters may have an impact on process performance or end product quality. Likely, the most common application for dissolved oxygen measurement is in the evaluation of wastewater for biological oxygen demand. The primary function of dissolved oxygen in wastewater is to enable and enhance the oxidation of organic material by aerobic bacteria, a necessary step in treatment.

To measure dissolved oxygen, specialized sensors and companion instruments are employed that require careful maintenance and trained technical operators. The level of measurement precision varies depending on the industry employing the technology, with numerous applications also being found in the food & beverage and pharmaceutical industries. In-line continuous measurement is used in wastewater processing to determine if the dissolved oxygen remains in a range that supports the bacteria necessary for biodegradation.

Chloride concentration in wastewater is strictly regulated. Industrial and commercial operation effluent can be regulated with respect to allowable chloride content. While commonly found in both streams and wastewater, chlorides, in large amounts, can present challenges to water utilization or processing facilities. Chloride levels impact corrosion, conductivity, and taste (for industries in which such a variable is paramount). In a process system, having an essential component marred due to elevated quantities of a substance could reverberate into any end-product being manufactured. Chloride analyzers, some of which can also detect and monitor other water characteristics, serve as important tools for water consuming facilities to meet regulatory standards for effluent discharge or internal quality standards for recycling.

There are other constituents of what we refer to as “water” that are subject to measurement and monitoring for a range of institutional, industrial, and municipal applications. Those will be explored in the next part of this article series.

Primary Flow Elements - Orifice Plate

A simple orifice plate
Courtesy Flow Lin

An orifice plate, at its simplest, is a plate with a machined hole in it. Carefully control the size and shape of the hole, mount the plate in a fluid flow path, measure the difference in fluid pressure between the two sides of the plate, and you have a simple flow measurement setup. The primary flow element is the differential pressure across the orifice. It is the measurement from which flow rate is inferred. The differential pressure is proportional to the square of the flow rate.

An orifice plate is often mounted in a customized holder or flange union that allows removal and inspection of the plate. A holding device also facilitates replacement of a worn orifice plate or insertion of one with a different size orifice to accommodate a change in the process. While the device appears simple, much care is applied to the design and manufacture of orifice plates. The flow data obtained using an orifice plate and differential pressure depend upon well recognized characteristics of the machined opening, plate thickness, and more. With the pressure drop characteristics of the orifice fixed and known, the measuring precision for differential pressure becomes a determining factor in the accuracy of the flow measurement.

There are standards for the dimensional precision of orifice plates that address:

• Circularity of the bore
• Flatness
• Parallelism of the faces
• Edge sharpness
• Surface condition

Orifice plates can be effectively "reshaped" by corrosion or by material deposits that may accumulate from the measured fluid. Any distortion of the plate surface or opening has the potential to induce measurable error. This being the case, flow measurement using an orifice plate is best applied with clean fluids.

Certain aspects of the mounting of the orifice plate may also have an impact on its adherence to the calibrated data for the device. Upstream and downstream pipe sections, concentric location of the orifice in the pipe, and location of the pressure measurement taps must be considered.

Properly done, an orifice plate and differential pressure flow measurement setup provides accurate and stable performance. Share your flow measurement challenges of all types with a process measurement specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Wireless Transmitters In Process Measurement and Control

Wireless industrial temperature transmitter
Courtesy Yokogawa

In process control, various devices produce signals which represent flow, temperature, pressure, and other measurable elements of the process. In delivering the process value from the measurement point to the point of decision, also known as the controller, systems have traditionally relied on wires. More recently, industrial wireless networks have evolved, though point-to-point wireless systems are still available and in use. A common operating protocol today is known as WirelessHARTTM, which features the same hallmarks of control and diagnostics featured in wired systems without any accompanying cables. Other wireless standards are employed in industrial settings, as well.

Wireless devices and wired devices can cohabitate the same network. The installation costs of wireless networks are decidedly lower than wired networks due to the reduction in labor and materials for the wireless arrangement. Wireless networks are also more efficient than their wired peers in regards to auxiliary measurements, involving measurement of substances at several points. Adding robustness to wireless, self-organizing networks is easy, because when new wireless components are introduced to a network, they can link to the existing network without needing to be reconfigured manually. Gateways can accommodate a large number of devices, allowing a very elastic range for expansion.

In a coal fired plant, plant operators walk a tightrope in monitoring multiple elements of the process. They calibrate limestone feed rates in conjunction with desulfurization systems, using target values determined experientially. A difficult process environment results from elevated slurry temperature, and the associated pH sensors can only last for a limited time under such conditions. Thanks to the expandability of wireless transmitters, the incremental cost is reduced thanks to the flexibility of installing new measurement loops. In regards to maintenance, the status of wireless devices is consistently transmitted alongside the process variable. Fewer manual checks are needed, and preventative measures may be reduced compared to wired networks.

Time Synchronized Mesh Protocol (TSMP) ensures correct timing for individual transmissions, which lets every transmitter’s radio and processor ‘rest’ between either sending or receiving a transmission. To compensate for the lack of a physical wire, in terms of security, wireless networks are equipped with a combination of authentication, encryption, verification, and key management. The amalgamation of these security practices delivers wireless network security equal to that of a wired system. The multilayered approach, anchored by gateway key-management, presents a defense sequence. Thanks to the advancements in modern field networking technology, interference due to noise from other networks has been minimized to the point of being a rare concern. Even with the rarity, fail-safes are included in WirelessHARTTM.

All security functions are handled by the network autonomously, meaning manual configuration is unnecessary. In addition to process control environments, power plants will typically use two simultaneous wireless networks. Transmitters allow both safety showers and eyewash stations to trigger an alarm at the point of control when activated. Thanks to reduced cost, and their ease of applicability in environments challenging to wired systems, along with their developed performance and security, wireless industrial connectivity will continue to expand.

Share your process measurement and control challenges with knowledgeable professionals, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Trace Moisture Analyzer

Portable and fixed installation trace moisture analyzers
Courtesy Teledyne Analytical Instruments

Moisture, the presence of water molecules, can impact certain products and processes in undesirable ways. Trace moisture analysis of clean gases can be accomplished using aluminum oxide sensors, one of several technologies available.

Instruments are available for continuous monitoring of moisture levels, or spot checking. Aluminum oxide moisture sensors rely on the change in capacitance within the sensor, which varies with the moisture content.

A concern with aluminum oxide sensor technology is drift associated with temperature and aging. A great degree of this has been alleviated through changes in sensor structure. The technology and instrumentation is easily applied and requires little in the way of maintenance other then periodic calibration.

More detail and explanation of the technology and instruments can be found in the brochure included below. Share your process analytical measurement challenges with experienced product specialists, combining your own process knowledge and experience with their up to date product expertise to develop effective solutions.

Trace Moisture Analyzer For Industrial Use from Miller Energy, Inc.

Myths About Process Switches

Example of a general purpose switch for industrial use
Courtesy United Electric Controls

We may have developed an obsession with data and information. Understatement, right? Whether a process variable is high or low no longer is satisfactory. We want to know how high, how low, how long, how fast is it changing, and more. In many cases, this is useful information that can be applied toward goals of safety and efficiency. Let us not, however, overlook the possibility that some facets of an operation are best served by that old soldier, the process switch.

Process switches are readily available for temperature, pressure, and differential pressure in ranges to suit almost any application. They are rugged time and field proven devices designed to do one thing extremely well. Process switches will reliably and instantly change the state of their mechanical switch when the process value reaches their setpoint. Once properly installed and set, process switches require little, if any, maintenance and can provide extended periods of reliable service.

United Electric Controls, globally recognized leader in the manufacture of process switches for temperature, pressure, and differential pressure, authored an informative piece that debunks some myths about process switches. The piece is included below and makes interesting reading.

Establishing the best instrumentation and control layout for a process benefits from careful consideration of many factors. Share your requirements and challenges with process measurement and control specialists, combining you own process knowledge and experience with their current product application expertise to develop effective solutions.

Myths About Process Switches from Miller Energy, Inc.

Standalone Industrial Process Controllers

Standalone process controller with
integrated input processing, display,
and outputs.
Courtesy Yokogawa

The regulation of temperature is a common operation throughout many facets of modern life. Environmental control in commercial, industrial, and institutional buildings, even residential spaces, uses the regulation of temperature as the primary measure of successful operation. There are also countless applications for the control of temperature found throughout manufacturing, processing, and research. Everywhere that temperature needs to be regulated, a device or method is needed that will control the delivery of a heating or cooling means.

For industrial process applications, the temperature control function is found in two basic forms. It can reside as an operational feature within a programmable logic controller or other centralized process control device or system. Another form is a standalone process temperature controller, with self-contained input, output, processing, and user interface. A temperature switch could be considered as a rudimentary, yet very effective standalone temperature controller. Depending upon the needs of the application, one may have an advantage over the other. The evolution of both forms, integrated and standalone, has resulted in each offering consistently greater levels of functionality.

There are two basic means of temperature control, regardless of the actual device used. Open loop control delivers a predetermined amount of output action without regard to the process condition. Its simplicity makes open loop control economical. Best applications for this type of control action are processes that are well understood and that can tolerate a potentially wide variation in temperature. A change in the process condition will not be detected, or responded to, by open loop control. The second temperature control method, and the one most employed for industrial process control, is closed loop.

Closed loop control relies on an input that represents the process condition, an algorithm or internal mechanical means to produce an output action related to the process condition, and some type of output device that delivers the output action. Closed loop controllers require less process knowledge on the part of the operator than open loop to regulate temperature. The controllers rely on the internal processing and comparison of input (process temperature) to a setpoint value. The difference between the two is the deviation or error. Generally, a greater error will produce a greater change in the output of the controller, delivering more heating or cooling to the process and driving the process temperature toward the setpoint.

The current product offering for standalone closed loop temperature controllers ranges from very simple on/off regulators to highly developed products with multiple inputs and outputs, as well as many auxiliary functions and communications. The range of product features almost assures a unit is available for every application. Evaluating the staggering range of products available and producing a good match between process requirements and product capabilities can be facilitated by reaching out to a process control products specialist. Combine your own process knowledge and experience with their product application expertise to develop effective solution options.

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.

Q&A for Ultrasonic Level Switches

Ultrasonic level switches with single
and multiple level measurement points
Courtesy Magnetrol International

Ultrasonic level switches appear, at first glance, to be a renamed version of a vibrating tuning fork level switch. They have a similar appearance and tank mounting scheme, but a closer look at the technology of the two instruments reveals that they rely on different operating principles to indicate when liquid level reaches their fixed switch point.

A previous article , with an accompanying video, provided some comparison between the two detection methods. Here is the operational difference summarized. A vibrating tuning fork device monitors the resonant frequency of the vibrating fork and responds when the frequency shifts due to immersion of the fork in liquid. An ultrasonic level switch transmits an ultrasonic pulse across a gap, measuring the intensity of the received signal and determining whether the signal passed through liquid (high level received signal) or air (low level received signal). While both technologies are effective, the ultrasonic level switch can be applied over a wider range of liquid density and does not require recalibration or adjustment for a change in media density.

Magnetrol International, globally recognized innovator in level measurement technology and instruments, recently answered a few application questions in their blog about their Echotel ultrasonic switches. The questions, along with answers penned by Magnetrol's product manager Tom Kemme, are shared here.

Question: Can ECHOTEL be used in applications that have entrained air?

Answer: Yes, ECHOTEL ultrasonic switches can be used in applications that have entrained air. All ECHOTEL gap switches feature a tip-sensitive transducer that provides superior performance over side gap transducers that are offered by other companies. Side gap transducers allow gas bubbles to adhere to the upper surface of the gap, which cause false dry gap alarms. Tip sensitive transducers allow these bubbles to pass through the gap. Applications with severe turbulence or entrained air should use the Model 961 switch, which offers a time delay adjustment. Up to 10 seconds of delay can be used to disregard entrained air and reliably detect the true liquid level.

Question: We are considering adding level alarm switches to our process to provide high-high level indication in several tanks. Instead of switches with relay outputs, we are considering the current shift output. What are the advantages of a current shift output?

Answer: Current shift electronics simply shift the current output from 8 mA when the level switch is in the normal operation, to 16 mA to indicate a level alarm. ECHOTEL Model 961 also has a user selectable fault signal of 3.6 or 22 mA. Current shift switches are 2-wire loop powered, which allows them to be offered with intrinsically safe approvals. This allows these switches to be put into hazardous area locations at a lower cost since rigid conduit is not necessary. Since current shift switches provide constant indication of either a normal (8 mA), alarm (16 mA), or a fault (3.6 or 22 mA) condition, they are sometimes referred to as a transmitter for the price of a switch.

Share your level measurement requirements and challenges with process measurement specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Industrial Control Valves

Cutaway view of industrial control valve
Courtesy Cashco

Control valves are at the heart of almost every fluid based industrial control process. Understanding their basic operation and function is essential for the process engineer, operator, or other stakeholder. A previous blog provided a good information source for those wishing to learn about control valves or review and hone their technical knowledge. The applications for which control valves are used seem uncountable in their variety, but common operating traits of control valves enable their use in every one.

Cashco, globally recognized manufacturer of industrial control products including control valves, regulators, controllers, pressure/vacuum relief vents, and flame and detonation arrestors, will be exhibiting at Interphex in Booth 3464 on March 21 through March 23 at the Jacob Javits Center in New York City. Knowledgeable personnel will be on hand to discuss your industrial control applications and challenges. If your plans include attendance at Interphex this year, take advantage of the opportunity to speak face to face with representatives of an industry leader.

E-Book on Fired Heaters and Combustion Efficiency

Modern high power boiler room

Yokogawa, globally recognized leader in a number of process control fields, has authored an e-book which provides useful insight into how operators of combustion based equipment and systems can improve efficiency and enhance safety by employing modern technology.

[All quoted passages in this article are from the Yokogawa e-book]

The Yokogawa e-book Combustion & Fired Heater Optimization offers “an analytical approach to improving safe & efficient operations” related to the use of combustion & fired heaters in the process industries. Through presenting an overview of combustion sources, such as furnaces and fired heaters, the book states that while “fired heaters pose a series of problems from safety risks to poor energy efficiency,” those problems “represent an opportunity for improved safety, control, energy efficiency and environmental compliance.” Fired heaters “account for 37% of the U.S. manufacturing energy end use.” Tunable Diode Laser Spectrometer (TDLS) technology helps mitigate safety concerns by “measuring average gas concentrations across the high temperature radiant sections.”

The book states that the four main concerns applicable to fired heaters are asset sustainability, inefficient operations, the operator skillset, and safety and compliance. Outdated diagnostics and controls have placed unnecessary stress on operator response, making sustainability of fired heaters difficult. The emissions of fired heaters are generally higher than designed, and can be coupled with control schemes for firing rates little changed over the past 40 years. Operators, generally, lack a clear understanding of design, and even engineering principles of heat transfer are not typically included in education related to fired heaters. Confounding the situation further, “many natural draft heaters do not meet this [safety regulation] guideline with existing instrumentation and control systems.” These complications combine to form a noticeable problem Yokogawa’s technology hopes to address. The company notes how the fired heater relies on natural draft instead of forced air, meaning the heaters “typically lack the degree of automation applied to other process units in the plant.” Offering a full detail of both the control state of most fired heaters and their systems defines the process situation currently considered common in the field, while emphasizing high excess air as providing a “false sense of safety.”

The proposed TDLS system allows for the measurement of “both the upper and lower conditions in a fired heater” by “simultaneously controlling the fuel and air supply based on fast sample intervals.” Safer burner monitoring and heater efficiency results from the TDLS measurements of CO, CH₄, and O₂. The optimization of air flow control reduces “O2 concentration … from 6% to 2%” and increases the furnace’s thermal efficiency. Combustion control is achieved by managing fuel flow and the arch draft. The TDLS integrated system works in tandem with already established logic solver systems in the plant. The TDLS technology works as a non-contacting measurement with “full diagnostic capability” and offers “distinct advantages over single point in situ analyzers” via reduction of false readings. Specific gas measurements, fast response time, optical measurement technology, and “high and variable light obstruction” are featured components of the TDLS system highlighted to show the technology’s durability and flexibility. The longevity and reliability of the system is showcased by how the TDLS combustion management system has been operational in a major refinery since 2010. The percentage of excess O₂ in sample fired heaters has decreased by 1% to 1.5%. Measurements by the TDLS system have been verified by other gas analyzers. The furnace conditions in the plant are more efficiently monitored and controlled. As a result, the furnace in the functional environment is “now near its optimum operating point, using minimum excess air.”

Yokogawa presents a process-related problem, then details the key points of the problem while unpacking the causes. The e-book introduces Yokogawa’s technology, explains the mechanics, and demonstrates how TDLS acts as a solution to the problem, supported by a tangible example. The book offers great insight for both the operational principles of fired heaters and a new technology designed to maximize efficiency in the control process.

The e-book is included below. More detail is available from product applicationspecialists, with whom you should share your combustion and fired heater related challenges. Combining your own facilities and process knowledge and experience with their product application expertise will lead to effective solutions.

Fired Heater and Combustion Optimization From Yokogawa from Miller Energy, Inc.

Consolidated Tool Kit for Sensor Maintenance

Configured repair kit contains everything needed
Courtesy United Electric Cotnrols

Keeping things going, working, no matter your industry, is a continuous challenge. In process measurement and control operations, sensors and transmitters perform an essential function that often calls for immediate repair upon failure. Being properly prepared by having any needed parts on hand empowers technicians to quickly and effectively return sensor assemblies or transmitters to operation.

United Electric offers their "Sensor Box™" a kit that is preloaded with everything needed to effect temperature sensor and transmitter repairs in the field. The kit keeps everything needed in one spot, ready to go.

The video shows the convenience with which a technician can use the kit to make field repairs. Share your temperature measurement and process control challenges with product application experts, combining your own process knowledge with their product expertise to develop effective solutions.

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.

Case Study From CSB: Industrial Plant Heat Exchanger Explosion

Shell and tube heat exchangers

Industrial accidents, whether minor or catastrophic, can serve as sources of learning when analyzed and studied. Operators, owners, and technicians involved with industrial chemical operations have a degree of moral, ethical, and legal responsibility to conduct work in a reasonably and predictably safe manner without endangering personnel, property, or the environment. Part of  a diligent safety culture should include reviewing industrial accidents at other facilities. There is much to learn from these unfortunate events, even when they happen in an industry that may seem somewhat removed from our own.

The U.S. Chemical Safety Board, or CSB, is an independent federal agency that investigates industrial chemical accidents. Below, find one of their video reenactments and analysis of an explosion that occurred at a Louisiana chemical processing plant in 2013. A portion of the reenactment shows how a few seemingly innocuous oversights can combine with other unrecognized conditions that result in a major conflagration.

Check out the video and sharpen your senses to evaluate potential trouble spots in your own operation.

Accurate Level Measurement Contributes to Heat Rate Reduction

Industrial steam turbine

Steam production is a costly operation in any facility, but is of paramount importance in power generation plants. The bottom line of a combustion based power generation facility is sensitive to the cost of input fuel. Measures that can be taken to reduce fuel input for a unit of power output (called heat rate) can translate directly into profitability. An additional benefit of reducing heat rate is a commensurate reduction in emissions.

A major contributor to heat rate reduction is the recovery of heat from the process and transference of that heat into the boiler feedwater. A sizable feedwater preheater of the shell and tube type is used to recover the heat. Shell and tube heat exchanger efficiency can be maximized with accurate control of liquid level.

Magnetrol, globally recognized leader in level measurement technology, makes the case for using guided wave radar level measurement technology as the most advantageous means for this application. The video below describes the process and how the guided wave radar level transmitter can provide the best performance.

Magnetrol has an information kit devoted to heat rate reduction. Share your steam system and level measurement challenges with a product specialist, and ask how you can get the Heat Rate Reduction Kit. Combining your facility and process knowledge with the product application expertise of a specialist will result in effective solutions.

Applying Coriolis Flowmeters

Coriolis Flowmeter
Courtesy Yokogawa

Coriolis mass flow meters are widely used throughout the process measurement and control field. Their basic operating principle, combined with modern sensor and signal processing technology, provide a list of potential application advantages.

• Directly measure mass flow based on the principle of measurement.
• No "moving" parts (except the slightly vibrating sensor tubes).
• Coriolis sensors have the ability to measure flow of non-conductive fluids.
• Measure the mass flow rate with high accuracy.
• Instruments can be applied across a wide usable measurement range.
• Deliver density measurement based on oscillating frequency.
• Not materially impacted by fluid viscosity or density.
• Coriolis flow meters also do not need lengthy straight pipe sections upstream or downstream of the sensing unit.

SELECTION AND INSTALLATION RECOMMENDATIONS

Some considerations for product selection and installation of Coriolis mass flow meters:

• Rapid temperature changes within the measured medium can impact measurement accuracy.
• Wide ranges of connection types are available, specify the best match for your system.
• Select sensor tube construction material to accommodate media characteristics.
• For liquid measurement, the sensor tube will extend downward from a horizontal pipe run. 
• As with most industrial products, there may be restrictions on where the device may be used. For example, not for use in aircraft. Assure that your application conforms with the intended usage of the instrument.
• Install at least one tight shutoff valve adjacent to the instrument for purposes of zeroing. Isolation valves for inlet and outlet are preferred.
• Follow manufacturer recommendations for pipe supports, if required, at inlet and outlet sides of the unit
• Avoid installation at locations with high levels of vibration or strong electrical fields.
• Locate the sensor unit at the lowest practical level in the piping system. This helps avoid collection of gas bubbles in the sensor tubes.
• Sensor tubes need to be completely filled with subject medium to obtain accurate measurement.
• Avoid the use of flexible connections and reducers at the unit connection points, unless in accordance with specific manufacturer guidelines.

The Coriolis flow meters of different manufacturers may have some particular recommendations, all of which should be followed to insure the best available performance, safety, and longevity of the unit.

Share your process instrumentation challenges and requirements with process measurement specialists, combining your process knowledge and expertise with their product application experience to develop effective solutions.

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.

Thermal Mass Flow Meter Q&A From Magnetrol

Thermatel® thermal mass flow meter
Courtesy Magnetrol®

Sometimes you discover that others do something better than you. When that happens, watch and listen.

Tom Kemme, from Magnetrol®, expertly fielded some questions about thermal mass flow meters in a recent blog post. Mr. Kemme's responses were so useful and clear that I decided, with all the credit flowing his way, to share them here for those of you that may not closely follow the Magnetrol® Blog.

Question: What is the difference between the flow units Nm3/h, Sm3/h, and actual m3/h?

Answer: Actual m3/h is a flow rate at operating temperature and pressure. Normal or standard m3/h (Nm3/h = Sm3/h) is a flow rate at standard temperature and pressure (STP). I tend to reference the natural gas industry, where it is not possible to compare flow rates at every operating condition, so it is preferable to reference all flow rates back to a set of base conditions, such as 60°F and 1 atm. STP is not universal so it may be unique based on the region or industry.

Most flow meters output a flow rate at operating conditions and need to correct this measurement. This may be accomplished with a multivariable transmitter or external to the device. A few examples that do not need to correct the measurement are thermal mass flow meters, such as the ones produced by MAGNETROL, and Coriolis flow meters.

Question: Do you have any certified failure rate data on your units to perform an SIL verification?

Answer: A Failure Modes, Effects, and Diagnostics Analysis (FMEDA) is completed during development to determine failure rates and Safe Failure Fraction (SFF). The SFF is utilized to determine Safety Integrity Level (SIL), which is often the published value.

Question: What should my meter be reading with no air flow in the pipe?

Answer: At zero flow and a dry pipe, a thermal mass flow meter should measure zero. Different thermal meters may have varying stability at no flow due to differences in operation.

There are two different types of operation: constant temperature (CT) and constant power (CP). CT devices start with a low power and this power increases with the flow rate to maintain the constant temperature difference (ΔT) between the RTDs. CP devices start with a high ΔT between RTDs at low flow and the ΔT decreases as the flow rate increases. CP may lack stability at zero flow due to possible convection currents associated with the high ΔT. CT will hold zero better, particularly devices that add less heat. For example, the maximum surface temperature of a TA2 probe is 4 C above process temperature. This is extremely low heat, eliminating convection currents due to the sensor. Convection currents could also occur through the pipe due to temperature variations.

It is also possible for a thermal meter to measure above zero during a no flow condition when there is pressure buildup in the line (typically a valve closed downstream). There may be low flow cutoff settings that can be changed to ignore nuisance measurements.

You can easily tap into Magnetrol® expertise to solve your flow measurement challenges. Reach out to a product specialist and combine your process knowledge with their flow measurement expertise to develop effective solutions.

Mounting Options For DP Transmitters With Universal Mounting Bracket

This short video illustrates the ease with which numerous mounting configurations of DPharp transmitters can be accomplished in new and existing operations. The DPharp line of pressure transmitters utilize Yokogawa's top flight digital sensing technology for accurate process measurement of pressure and differential pressure in a multitude of applications.

Share your process measurement challenges with application experts, combining your process knowledge with their product application expertise to develop effective solutions.

Dynamic Compensation for Static Pressure Effects in Differential Pressure Measurement

DPharp Gauge Pressure Transmitter
Courtesy Yokogawa

Attaining the best available performance and accuracy from any measuring device utilized in an industrial process is always advantageous. The scale of most industrial processes is such that even small inaccuracies in process measurement produce financially tangible impact. Differential pressure measurement, with wide application in the industrial process sphere, can be improved with the addition of a means to compensate for the real world effects of static pressure upon instrument performance.

Yokogawa Corporation has developed a means to dynamically compensate for static pressure effects in field measurements. The brief technical presentation below will help you understand how static pressure effects can impact your field measurements, as well as how Yokogawa’s Real-time Dynamic Compensation works to offset its impact.

More detailed product and application information is available from your Yokogawa specialist.

Dynamic Compensation for Static Pressure Effects in Differential Pressure Measurement from Miller Energy, Inc.