trends in process field devices for automation

BY ARC ADVISORY GROUP DECEMBER 2001

Trends in Process Field Devices for Automation

Executive Overview ................................................................................3

New Field Measurements Needed ..........................................................4

Soft Sensors Stage a Comeback .............................................................6

Innovative Uses of Ultrasonic Waves.......................................................8

Old Measurements Go Mainstream......................................................10

Vertical Applications Key to Success of Model Based Systems..................11

Benefits and Drawbacks of Inferential Measurement ..............................13

Enterprise & Automation Strategies for Industry Executives

ARC Strategies � December 2001

2 � ARCweb.com � Copyright © ARC Advisory Group

TRADITIONAL MEASUREMENTS

Pressure

Analytical

TemperatureLevel

Flow

Soft Sensors

Interface

Model-basedVertical Solutions

Viscosity

Entrained AirReal-time Analytical

Product Quality

Multiphase Flow

Leak Detection

Real-time Corrosion

NEW MEASUREMENTS


Copyright © ARC Advisory Group � ARCweb.com � 3

Despite the high level ofcommonality of measurements in

process systems between industries,there are many unique processmeasurements needed in each.

Executive Overview

Demanding measurement applications are growing rapidly across all industries. Suppliers recognizing the enormous opportunity are developing new and enhanced measurements. New measurement solutions hitting the

market include viscosity, corrosion, and vertical solutions.

Soft sensors are a rapidly growing solution for measurement applications. Soft sensors are the only answer for many applications where hard

measurements are unavailable. Today’s soft sensors are widely used in the power industry to continuously monitor environmental dis-charges such as the emissions from combustion units to meet

federal, state, and local regulations. Soft sensors, however, are gaining acceptance across all the process industries in a wide va-riety of applications. Obstacles still remain, however, including

issues such as measurement validation.

Ultrasonic technology is findings its way into virtually every process measurement. Most commonly used to measure flow rate, level, and density,

ultrasonic techniques are now making inroads into temperature, and inter-face detection applications. Not only is ultrasonic technology capable of measuring these parameters, it often exceeds the performance of the current

mainstream technologies.

Corrosion measurement has been employed for decades to monitor corrosion rates of critical pipelines. Old corrosion instruments relied on off-line sample

techniques by measuring the reduction of weight of disposable coupons. The impracticality of making off-line measurements limited its use until Intercorr International met the challenge by releasing the first on-line real-time

corrosion monitor to measure localized corrosion of pipelines and equip-ment.

Despite the high level of commonality of measurements in process systems

between industries, there are many unique process measurements needed in each. Direct instrumentation, process analyzers or soft sensor sensors cannot measure many production specific parameters. Intangible parameters can be

very complex properties of a substance such as taste, creaminess, color or softness, which can only be subjectively defined. Comprehensive model based process applications are meeting the demand for industry specific



solutions. When adopting these solutions, however, drawbacks of the solu-tion must be considered from the onset to have a successful implementation.

New Field Measurements Needed

Traditional process control field devices commonly known as the “four

horsemen” provide four main categories of measurements: pressure, temperature, flow, and level. New faster response online analytical devices are providing near real-time measurements and increasingly have been used

as a mainstream process measurement however, as broad as these measure-ments are, collectively they still cannot provide the total insight needed for

today’s complex processes.

Demanding applications are growing rapidly in all industries particu-larly in the emerging biotech industry, which now has over 4000 companies world-wide up from just a few hundred less than 3 years

ago. This unprecedented growth offers an enormous opportunity for suppliers to develop new and enhanced measurements beyond the traditional four and analytical. Increasing cost reduction targets oc-

curring in all industries is compounding the situation and rendering once satisfactory measurements and processes obsolete in the quest to increase margins. Additionally, recent biological terrorist events have

renewed the push for faster development of vaccines and new drugs to combat the suddenly heightened worldwide threat.

Asset management solutions continue to be a hot topic due to its po-

tential savings in time and labor in the day-to-day operation of the plant. Coined Plant Asset Management (PAM), asset management solutions have become a critical strategy in many plants that are trying to squeeze that extra

bit of production from their plants. PAM applications have progressed sig-nificantly in recent years. Once used strictly to analyze trends using the automation system’s historian and identify abnormal trends, PAM ap-

plications have expanded to embedding artificial intelligent model based solutions to obtain more accurate health status and, in some cases, extend the useful life of the measurement by quantifying the problems, correcting the

output, and validating the signal while sending a low level alert highlighting potential issues with the unit.

Pressure, Temperature, Flow, and Level



Field device suppliers are taking up the slack by offering new innovative real-time hard sensors coupled with intelligent software to provide the

measurement of desired property. More sophisticated field device solutions are expected with the increasing adoption of fieldbus, which allows easy access to every online measurement on the bus. The rich data set offered by

Fieldbus, coupled with increased intelligence, will enable the local field de-vice to use model based techniques to infer the measurement of new parame-ters previously unavailable.

Field devices are following a natural product life cycle evolution as they ex-pand functionally. For example, ultrasonic level principle is being used in an increasing number of hard measurements ranging from flow, and tempera-

ture, to leak detection and nondestructive vessel testing. Field device suppliers are breaking away from traditional roles and using technology to broaden their appeal in the ever-tightening market.

By developing products to go beyond their traditional roles, vi-sionary field device suppliers are creating a strong launch pad into future markets and other lines of business. Expect to see in-

creasing growth in combined hardware and the software

solutions in this area.

Despite the improvements in analytical measurements, the lack of appropriate on-line instrumentation and reliability of on-line instruments have forced users to depend on laboratory analyses

resulting in infrequent and irregular and long analysis delays. Laboratory analyses may also be subject to reliability problems. On-line sensors may be available but suffer from long measure-

ment delays (e.g. gas chromatographs) or subject to factors that affect the reliability of the sensor (e.g. drifts and fouling). In either case, automatic control and optimization schemes cannot

be implemented and, as a result, process performance is de-graded.

Left unattended, the problems of delays and unreliable meas-

urement manifest themselves into critical problems that affect product quality and availability of production. Critical problems such as these can quickly devour the last bit of shrinking margin to drive en-

terprises into the red. Fortunately, field device suppliers have recognized this need and are working hard to provide new online real-time measure-ments. Progress in many areas, however, continues to be slow compared to

demand.

Needed Measurements

Viscosity

Entrained Air

Consistency

Measurement Validation

Leak Detection

Multi-Phase Flow

Real-time Analytical

Product Quality

Bio Cell Production

Corrosion

Pipe Coating



Soft Sensors Stage a Comeback

Automatic control enables and facilitates consistent production. To achieve these goals, however, controllers require regular and reliable measurements at the appropriate frequency. Some slow reacting processes can do with in-

frequent sample measurements but most demand continuous attention to maintain a narrow band of uncertainty for consistent product quality.

Processes are tough on instru-

mentation. Process pressure and temperature can exceed limits of field devices, high am-

bient temperature can cook electronics, and the inaccessibil-ity of the measurement location

may make physical measure-ments impractical. When hard measurements are unavailable,

soft sensors may be the only answer. Soft sensors, also known as inferential model-based analyzers, are programs that primarily use secondary measurements combined with mod-

eling methods to develop process input-output variable relationships. Soft sensors use mathematics to estimate either the value of product properties measured in the laboratory, properties measured infrequently on-line or that

take an inordinate amount of time to measure, or properties not measured at all. Soft sensors utilize easy to measure process variables such as pressure, flow, density, or temperature to estimate the value of an important property

and make the data immediately available to operators and control systems.

Because many of the desired primary measurements are directly related to one or more secondary variables, measurement of previously unavailable

parameters is readily possible by using secondary variables to infer the state of a quality or primary variable. For example, liquid composition can be de-fined by pressure and temperature, concentration by density, and biomass

growth can be linked to CO2 evolution and feed rate.

The process of inferential measurement is quite common and has been in use by suppliers for decades to measure flow and level. For example, magmeters

measure electrical potential, orifices measure differential pressure, and ultra-sonic flowmeters measure transit time for both flow and level measurements.

Technology Function Inferential Measurement

Ultrasonic Flow & Level Transit Time & Frequency shift

Magnetic Flow Milli -Volts

Orifice/Venturi/Pitot/Nozzle Flow Differential Pressure

Radar Level Frequency

RTD Temperature Resistance

Turbine & PD Flow Rotor Speed

Common Inferential Field Devices



What is different in today’s solution is the complex modeling techniques ap-plied to standard measurements.

By modeling the relationship between a primary output and secondary out-put the response time can approach that of a typical online process meas-urement. Suppliers such as Pavilion, Aspen Technology, Optima PSE, and

Shell Global Systems are investing in this approach to provide soft sensors to replace analytical measurements. Instead of waiting 15-30 minutes for a gas chromatograph to complete its analysis, the inferential measurement

system could be returning estimates of compositions every few seconds.

Field device suppliers are also investigating the opportunities for these tech-niques to provide enhanced performance such as increasing the low range

measurement of vortex flow meters and modeling of fluid mixtures to enhance concentration measurements. Increasing sophistication of modeling techniques now make them sufficiently accurate to use inferential measure-

ment as direct feedback for automatic control. Despite their performance, many users continue to use inferential soft sensor measurement in conjunc-tion with traditional off line techniques to optimize measurements.

Soft sensors are widely used in the power industry to continuously monitor environmental discharges such as emissions from combustion units to meet federal, state, and local regulations. Typically software solutions extract data

from the process historian to build the model. Once built, the soft sensor will monitor and predict air emissions in real-time. Pavilion's Soft Sensor tech-nology for air emissions, CEM Software, is typical of these solutions.

Working with the EPA, Pavilion has installed 250 software solutions throughout the US. The documentation generated is a necessary step in the approval process that, in many cases, must be replicated for each local utility.

Using similar modeling techniques suppliers are developing measurement validation by employing rules at the lowest measurement level. To accom-plish this, automated program models are applied to key process variables

by taking advantage of redundant information contained in process instru-mentation. Predicted value is then compared against the actual measured key variable to determine if it is operating correctly or not. If the input is

suspect, an alarm is triggered; signaling for maintenance attention and con-trol action can be programmed for application specific action while preventing the use of suspect data.

Emissions Measurement



Despite their benefits, operators typically still do not totally trust the reliabil-ity of soft sensors. Many users point to the inability to quickly test, check,

and calibrate a soft sensor solution that is standard operating procedure rou-tinely performed on direct instrumentation. Previous initial solutions have also produced inconsistent readings and because instrumentation technicians

grew up with physical measurements, they are biased toward hard meas-urements and suspect the readings of soft. Bad memories are hard to erase and for soft sensors to continue their move into mainstream applications, ad-

ditional enhancements are needed to allow measurement checks to ease the fears of operators.

Innovative Uses of Ultrasonic Waves

Ultrasonic technology is findings its way into virtually every process meas-urement. Traditionally used to measure flow rate, level, and density,

ultrasonic techniques are now being applied to measure temperature, viscos-ity, and interface detection. Not only is ultrasonic technology capable of measuring these parameters, it often exceeds the performance of the current

mainstream technologies such as RTD temperature probes and vibration type viscometers.

Temperature can be measured with a multitude of sensors such as thermo-

couples, infrared, thermistors, and RTDs. Caldon, a niche ultrasonic supplier, utilizes ultrasonic technology in its LEFM meter to accurately measure feedwater temperature in nuclear power plants. Sound velocity of

a fluid is determined by the ratio of its compressibility and its density. For specific liquids such as pure water, compressibility and density are linked to various characteristics like temperature and pressure. As a result of this

interdependence, it is quite easy, with the right model, to infer temperature from the sound velocity through the fluid and pressure.

Using mean pulsed time from its meter combined with an external pres-

sure input Caldon’s LEFM meter precisely calculates the temperature of high temperature feed water exceeding 450 deg Fahrenheit. Sound velocity can be determined within 1 part in 1000 yielding an accuracy of +/- .3 percent,

which is a significant improvement over the typical RTD performance of +/-2.6 percent in this application. Other suppliers are investigating the use of high speed 22 bit software in a multi-input transmitter to approach fast re-

Ultrasonic Technology



sponse highly accurate temperature measurement to within .0005 degrees Celsius for the semiconductor industry in the production of the next genera-

tion of processors.

Viscosity can be determined in a similar way by measuring the attenuation of ultrasonic signals as they pass through the viscous liquid. Despite the

simplicity of the concept for both temperature and viscosity measurement a number of parameters such as distance of travel, sonic velocity, pressure measurement and the allowance for transmission delays in the liquid must

be accurately determined. Ultrasonic technology is one of the fastest re-sponding measurement methods, which makes this technology ideal for determining the interface between two different fluids transported through

pipelines carrying finished petroleum products coast to coast.

Caldon’s Sountrack measures viscosity, density and interface using one or multiple ultrasonic transducers mounted in a simple ring that is simply in-

stalled between a pair of process pipe flanges. Interface can be detected within one second and kinematic viscosity can be determined within +/-.04 centistokes (cSt).

Caldon, best known for pioneering approval from the Nuclear Regulatory Commission (NRC) for power up rates in nuclear power plants based on im-proved feedwater flow measurement, introduced a new eight-path transit

time flowmeter for custody transfer applications that may prove to be one of the most accurate meters in the world. Multipath ultrasonic technology gained user mass acceptance in the natural gas industry after approval by the

American Gas Association in 1998. Krohne, Daniels, FMC and Instromet all have released products utilizing multipath technology. The combination of no moving parts with high reliability and high performance is hard to ignore.

Ultrasonic technology is increasingly the technology of choice for leak detec-tion of long pipelines. Krohne, Panametrics, and Controlotron offer leak detection systems. Caldon’s new LineWatch dynamic leak detection systems

is a prime example of these solutions, which can be used on existing pipe-lines to cost-effectively comply with environmental guidelines and regula-tions. LineWatch can determine the location of a sudden break or leak in the

pipeline by measuring and timing the pressure waves created by such an event. Caldon also manufactures a static leak detection system used princi-pally for jet fuel delivery lines in commercial and military airports, which

requires significantly less down time than other technologies.

Nuclear Power Applications



Old Measurements Go Mainstream

Corrosion is not new and has been employed for decades to measure corro-sion rates of critical pipelines, the main artery of the oil & gas industry. Traditional instruments, however, relied on the reduction of weight of dis-

posable coupons. The impracticality of making this off-line measurement limited its use to the detriment of equipment and the safety of the personnel running the plant. The increasing popularity of equipment condition moni-

toring and plant asset management indirectly pushed corrosion monitoring into the spotlight. Intercorr International met the challenge by releasing the first on-line real-time corrosion monitor to measure general corrosion and,

more importantly, the localized corrosion that represents the bulk of corro-sion failures.

Intercorr’s SmartCET is a cost-effective electrochemical multi-technique

corrosion monitoring instrument that measures corrosion using tech-niques such as electrochemical noise, Linear Polarization Resistance (LPR), Harmonic Distortion (HD), Galvanic Current (GC), and Hydrogen Per-

meation Current (HP). The system consists of a wetted 2- or 3- electrode probe with a companion transmitter/computer to compute corrosion rate. By releasing the first online monitor, Intercorr has provided users a means

to perform low cost corrosion measurements with information immedi-ately available whether onshore or offshore, local or remote. SmartCET also provides users the opportunity for direct interfacing between corro-

sion, chemical injection, process control, and maintenance management sys-tems to allow personnel to take appropriate remedial action

Yamatake’s Smart Plus One gas chromatograph is the world’s smallest natu-

ral gas analyzer that fits in the palm of your hand. Previous products needed large amounts of real estate and were typically the size of a small refrigera-tor. SmartPlus is one of the first introductions of the new trend of

miniaturized analyzer on a chip. The small size of future field devices will expand measurement possibilities and include variables that were previously inconceivable.

Real-Time Corrosion Monitoring



Vertical Applications Key to Success of Model Based Systems

Despite the high level of commonality of measurements in process systems

between industries, there are many unique process measurements needed in each. Some of these go unattended and left for the operator to control the best they can with limited knowledge by juggling seemingly contradictory

needs. The resulting inefficiency wastes raw materials, finished products and time that can never be recovered.

Direct instrumentation, process analyzers, and soft sensor sensors cannot

measure many production specific parameters. These intangible parameters can be found in virtually every industrial segment with many concentrated in the oil & gas industry. Intangible parameters can be very complex proper-

ties of a substance such as taste, creaminess, color or softness, which can only be subjectively defined. Although an intangible parameter can be tied to physical properties of the substance, there is typically no known definition.

Typically, intangible parameters must be measured without having any de-tailed knowledge of the parameter.

Comprehensive model based process applications are meeting the demand to

measure intangible parameters with industry specific solutions. Using infer-ential modeling techniques, industry specific systems takes soft sensor technology to a much higher level that many times is a semi-customized so-

lution for an industrial process or particular plant.

Final product quality isn’t the only quality assurance necessary to meet customer standards and regulatory requirements, interim product qual-

ity in the production is increasingly needed to allow time to take action on off-spec products. With the high production rates mandated by effi-cient production, time is of the essence, making online real-time

continuous measurements necessary.

Complex non-linear models can be built using neural networks, genetic pro-gramming, partial least squares, algebraic, hybrid neural, and regression

technologies. PSE Optima offers Product Quality Estimator solutions an em-pirical modeling tool to develop on-line models for estimating product quality from process measurements in real-time or with engineering correla-

tions or user engineering correlations. This approach has proven to be a very effective means for on-line estimation of polymer properties. Typically, his-

Model Based Software



torical process data is used to develop models of key process and quality variables to be placed on-line. These models are updated online with lab re-

sults (or analyzers if available). Virtually all performance optimization companies are offering non-linear model solutions today for use in oil & gas, refining, food processing, petrochemical, power, chemicals, mining, and pulp

& paper industries.

Specific process parameters and quality measure-ments inferred on-line are very dependent on the

specific process and product requirements. Today’s excellent examples of solutions include: Melt index, Tray Temperature, Mooney, Naphtha 95% point,

Catalyst Mileage, Polymer residence time and Sheet color and opacity.

Because these parameters can drastically change

with process operational changes it may be neces-sary to use an adaptive inferential measurement scheme by augmenting the estimated parameter

with slow off-line measurements. This will correlate values generated by the parameter estimator with

measured values and compensate the measurement model to more represen-

tative values. In this adaptive framework, the slower measured primary output is fed to the faster parameter estimator, which updates the inferential measurement model when available.

An excellent example of a model based vertical application solution is ABB’s OptimizeIT Well Monitoring System for estimating the flow rates of oil, gas, and water from individual wells in an oil field. OptimizeIT Well may be

used as a software multiphase flowmeter, as a Reliability Tool, and as a Pro-duction Allocation System. OptimizeIT Well can also detect water or gas breakthrough, predict the production rate with high accuracy, provide re-

dundancy, and validate specific measurements from the well’s instrumentation.

OptimizeIT Well is based on data from standard well instrumentation that is

designed to handle any configuration of well instrumentation, making the solution easily transferable from region to region and, therefore, suitable for any user around the globe. Calculations are based on a mechanistic model

for multiphase flow and a full, compositional model of the fluid. ABB’s ap-proach to calculating all fluid properties using the full model is superior to

Suppliers Product

AspenTech AspenIQ

Gensym NeurOn-line

Pavilion Technologies Property Predictor

Shell Global Solutions RQE

Honeywell Profit Sensor

Emerson Process Management

Intelligent Sensor Toolkit

Invensys/Pacific Simulations

FACTNET

Typical Soft Sensor Solutions



methods based on interpolation of tabulated data most commonly used in commercially available multiphase fluid simulation programs.

Model-based measurement products typically come from software optimiza-tion companies that take reams of data to predict the measurement without direct knowledge of the sensor making the measurement. Direct involve-

ment of sensor manufacturers such as ABB helps to expand this technique further. With collaboration of sensor and software suppliers, development of new innovative measurements may result.

Benefits and Drawbacks of Inferential Measurement

Despite the relatively simple concept of inferential measurement and the straightforward inferential model building techniques given the abundance

of computer-aided tools, there are a number of important things to bear in mind when adopting inferential model based solutions.

Benefits Here are some of the benefits that you can expect from successful inferential measurement and control scheme:

• Faster return of information. Process upsets can be detected quicker and

remedial action can be taken before it is too late.

• Increasing standard “shrink wrapped” vertical solutions reduce model-ing time and lowers implementation cost.

• The inferential estimates carry a fair degree of 'feedforward' in-formation. For example, disturbances affecting tray temperatures in a distillation column in a refinery may show up much later in the product

compositions but will immediately be reflected in the composition esti-mates.

• Reducing human involvement in the control loop increases consistent

production.

• Better process control can be achieved.

Validation Key For Continued Adoption



• Increased scope for process optimization leading to higher profit-ability.

Drawbacks Drawbacks are few. Here are the major issues that need consideration for successful implementation:

• High cost model based solutions will not replace on-line field de-vices

any time soon. They can, however, provide the only real alternative.

• Data conditioning can be time consuming - Delete data with abnormali-ties since the old adage rubbish in, rubbish out applies.

• Selection of appropriate secondary inputs can be difficult – Select the least number of variables to develop a model of sufficient accuracy.

• Estimator testing must be rigorous- test model over a broad range and

account for changing process conditions.

• Measurement mistrust from operators and the inability to calibrate or to check the measurement. This, however, is becoming less of an issue now

with measurement validation enhanced solutions.



Analyst: Wil Chin

Editor: David Clayton

Distribution: All MAS-P & MAS-H Clients

Acronym Reference:Acronym Reference:Acronym Reference:Acronym Reference: For a complete list of industry acronyms, refer to our web page at www.arcweb.com/arcweb/Community/terms/indterms.htm

AI Artificial Intelligence ANSI American National Standards Institute API Application Program Interface APS Advanced Planning & Scheduling B2B Business-to-Business B2C Business-to-Consumer BPR Business Process Reengineering CAGR Compound Annual Growth Rate CAN Controller Area Network CMM Collaborative Manufacturing

Management CNC Computer Numeric Control CPG Consumer Packaged Goods CRM Customer Relationship Management EAI Enterprise Application Integration EAM Enterprise Asset Management EC Electronic Commerce

EPA Environmental Protection Agency ERP Enterprise Resource Planning GC Galvanic Current HD Harmonic Distortion HP Hydrogen Permeation Current MRP Materials Resource Planning OLE Object Linking & Embedding OPC OLE for Process Control NRC Nuclear Regulatory Commission PAM Plant Asset Management PD Positive Displacement RTD Resistance Temperature Detector SCE Supply Chain Execution SPC Statistical Process Control TMS Transportation Management System WAH Web Application Hosting WMS Warehouse Management System

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