Dave Harrold, CONTROL ENGINEERING

Articles

PID, APC November 2, 2018

Merging Mom’s Perceptive Power with Technology Creates Startling Results

KEYWORDS Process and advanced control Neural networks Multivariable sensors Sensing/measurement Analyzers What do the FBI (Federal Bureau of Investigation) and your mother have in common? Both use real measurements to reach an inferred outcome; are you telling the truth? Think about it, your mother would do a subtle interrogation all the while observing your body language—pupil dilation,...

By Dave Harrold, CONTROL ENGINEERING
Mechatronics and Motion Control January 1, 2006

Data Acquisition – 2006-01-01 – 2006-01-01

In its purest form, data acquisition (DAQ) is the process of gathering information in an automated fashion from analog and digital measurement sources and presenting that information in a meaningful way. Depending on your industry, DAQ means different things to different people. For example, to the utility industry, DAQ is part of the SCADA (supervisory control and data acquisition) system and ...

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors September 1, 2004

Custody transfer: getting what you pay for

When purchasing gasoline for your automobile, do you ever wonder if you are getting what you pay for? Have you ever stopped the pump at exactly 10 gallons to see if the price is correct? Verifying that an agreed-upon price per unit is being delivered is what custody transfer is all about. Whether it's between companies or between departments, ensuring custody transfers are accurate requires cal...

By Dave Harrold, CONTROL ENGINEERING
Energy, Power October 1, 2003

Turbine Flowmeters: Simple Elegance

Available in sizes to 12 in. (300 mm) and capable of handling process pressures to 10,000 psi (689 bar) and temperatures to 1,000 °F (538 °C), turbine flowmeters are versatile enough for many of the world's industrial, chemical, petrochemical, pharmaceutical, and food and beverage applications.

By Dave Harrold, CONTROL ENGINEERING
I/O Systems, I/O Modules September 1, 2003

Phased HMI and I/O Solution Boosts Productivity

Recently married and out of a job, Roy Costa applied for a safety coordinator position at the Michigan Waste Energy (MWE) facility in Detroit, Michigan. As the interview morphed into a discussion about obsolete control system problems, Costa articulated a phased solution that began by replacing the obsolete human-machine interface (HMI) with a new application built on National Instrument's (NI)...

By Dave Harrold, CONTROL ENGINEERING
Vision and Discrete Sensors August 1, 2003

Don’t Touch That Process!

Early adopters of non-contact level technologies were often disappointed with the installed results. However, significant technology advancements and installation know-how acquired by manufacturers and end-users over the past several years brush away past non-contact level measurement disappointments.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors July 1, 2003

New technologies make inroads

Magnetic flowmeters are most widely used, while mass and turbine flow technologies are gaining importance. Meanwhile, reliability and need for easy calibration rose significantly in importance with buyers from 2001 to 2003. These are among findings from Control Engineering and Reed Research Group surveys on flowmeters, designed to learn where reader/subscribers are using and what they are loo...

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors July 1, 2003

Flint Ink Steps Its Way to Success

Committed to increasing productivity, lowering costs, and reducing product variability at its New Albany, Indiana facility, Flint Ink began an automation journey that, like most journeys, included a number of unexpected bumps, twists, turns, and thrills along the way. Though the journey isn't complete, all the participants are positive the hardest parts are behind them and the rewards have alre...

By Dave Harrold, CONTROL ENGINEERING
Ethernet May 1, 2002

Users expect high quality, availability, competitive pricing

Despite all the hoopla about ways technology can enhance our lives at home and at work, none of the technology would have reason to exist without ac to dc power supplies. Oh sure, there are batteries, and solar and wind generators, but most technology relies on ac power, and thus the need for ac to dc power supplies.

By Dave Harrold, CONTROL ENGINEERING
Robotics January 1, 2002

Controllers: Heartbeat of Production

This is the first of a two-part series focused onindustrial controller capabilities. Part two will appear in the February 2002 issue of Control Engineering. Much of the controller capability information derives from an online questionnaire controller suppliers were invited to complete. The entire controller capability matrix is located at www.

By Dave Harrold, CONTROL ENGINEERING
Project Management December 1, 2001

‘Sensor-to-Boardroom’ Integration is Doable

In the 1970s the State of Qatar—a small peninsula nation jutting into the Persian Gulf—discovered what experts believe to be the world's largest single natural-gas reserve, estimated to be 500 trillion ft3.Despite Qatar's abundance of natural gas, until the early 1990s natural gas production was confined to domestic use.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors November 1, 2001

New and Improved: What’s that Mean?

Borrowing from the software programmer vernacular, writers of press releases, and advertisements frequently get caught in the dreaded "continuous loop," spewing forth descriptive adjectives until they run out of breath and have to insert a comma or period (Esc key) before they pass out. My eighth-grade English teacher used a red pencil to scribble "Run-on sentence" across these sorts of w...

By Dave Harrold, CONTROL ENGINEERING
PLCs, PACs September 1, 2001

Find the Right Engineering Tools

Most control and automation project planning and design methodologies follow a top-down define-and-design philosophy that begins with an overview and then uses an iterative process to add details until a thorough understanding of the control and automation requirements have been developed. The deliverable of this iterative process is the functional specification.

By Dave Harrold, CONTROL ENGINEERING
PLCs, PACs August 1, 2001

E-Manufacturing for Process Industries

This is the third in a series of articles on electronic- and collaborative-manufacturing. "E-manufacturing" appeared in the February issue, and "Control, MES Partner for C-manufacturing Solutions" appeared in the May issue.Harvard Business School's famous academician, professor Michael Porter crystallized the notion of competitive advantage when he said, "No company can earn above-average...

By Dave Harrold, CONTROL ENGINEERING
PLCs, PACs June 1, 2001

Tech Support is Standing By

KEY WORDS Process and advanced control Service Training Life-cycle planning Software and information integration Back in the "good old days," distributed control meant controllers were physically distributed throughout the plant or across the shop floor and the nearest thing to a control room was the break-room.

By Dave Harrold, CONTROL ENGINEERING
Workforce Development June 1, 2001

Users Speak Out On Support Services

User expectations about control and automation support services are clear, even if contradictory in some instances, according to the "2001 Control Engineering (CE) Control and Automation Support Services" survey. Hundreds of users responded to Control Engineering's in-depth questionnaire about control and automation support services and, generally, users are satisfied with the services they...

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors February 1, 2001

Push the Limits

A recent poll of advanced process control (APC) experts revealed unanimous agreement, users can expect APC applications to deliver sustainable, measurable benefits, but only when APC is built on a solid basic process control system (BPCS) foundation that:Wait a minute... if those three conditions are met, then the process would be as optimized as is possible, and APC wouldn't be needed! W...

By Dave Harrold, CONTROL ENGINEERING
PID, APC January 1, 2001

How Manufacturing Benefits by Understanding ERP and IT

During the '90s billions of dollars were spent by businesses that bought into the notion that ERP (enterprise resource planning) systems would lead to the "promised land" of gaining competitive advantage. Throughout the evaluation, design, implementation, and testing of ERP systems, the question "How do we tie in manufacturing?" was held at arm's length with the curt answer, "That's not ...

By Dave Harrold, CONTROL ENGINEERING
PLCs, PACs October 1, 2000

Look Beyond the Certification!

What you don't ask about products claiming to meet specified SIL requirements could hurt you.

By Dave Harrold, CONTROL ENGINEERING
PID, APC October 1, 2000

Virtual Reality Saves Money!

For a long time the resources and effort required to create complex simulations of manufacturing and process operations was avoided for all but the toughest problems, and when they were constructed, it was often a last resort. "Simulations? We can't afford that fancy stuff. That's just for the 'big boys,'" was heard for years throughout operational units around the world, but not any more.

By Dave Harrold, CONTROL ENGINEERING
Machine Safety September 1, 2000

Digital Paper

Looking for a quick payback? Digital paper's an investment stacked in your favor. When the Pennsylvania Treasury's Bureau of Unemployment Compensation Disbursements learned the computer system they were using to process benefit checks was not Y2K compliant, they were forced to replace the system with a more efficient document management and imaging system.

By Dave Harrold, CONTROL ENGINEERING
Workforce Development August 1, 2000

Developing Intellectual Capital

Rare is the annual report that doesn't somewhere state, "Our employees are our most valuable asset", or something like that. However, you can read every word in most of those annual reports and not find any explanation of how the company intends to preserve, use, and grow its proclaimed most valuable assets, its intellectual (human) capital.

By Dave Harrold, CONTROL ENGINEERING
PLM, Control Design May 1, 2000

Project Success Requires Vision and Attention to Detail

Many companies talk about needing flexibility, agility, repeatability, and tight integration in highly automated processes, but far fewer actually achieve such lofty goals. One exception is Genentech's (South San Francisco, Calif.) new pharmaceutical manufacturing campus located in Vacaville, California.

By Dave Harrold, CONTROL ENGINEERING
PID, APC April 1, 2000

Going Fast with Wireless Technology

At 220 mph you inch your Indy Racing League (IRL) racecar away from the wall and head for the apex of turn number four. Your driving line brings your left side wheels just above the white line. You press the accelerator pedal and your 4.0-liter, 700 hp, Oldsmobile Aurora engine moves you smoothly onto the main straightaway.

By Dave Harrold, CONTROL ENGINEERING
Diagnostics, Asset Management February 1, 2000

Monitor Quality Performance Online to Improve Customer Satisfaction

Meeting business objectives requires manufacturing managers to identify key process performance indicators, institute online measurements of those indicators, and present the results to the right people, while the product is being produced.For two decades, industrial manufacturing has looked longingly to computer-based control and automation systems as a solution to manufacturing problems.

By Dave Harrold, CONTROL ENGINEERING
Workforce Development February 1, 2000

Enterprise Integration Requires Understanding the Plant Floor

Weaving enterprise optimization from the plant floor to glass house and through the supply chain requires sorting through difficulties, weighing options, and eliminating confusion. Related solutions and user and vendor recommendations are included in AMR Research's (AMR, Boston, Mass.) Oct. '99 Report On Manufacturing titled "Variability: The Cure is Out There," written by AMR's research...

By Dave Harrold, CONTROL ENGINEERING
PID, APC January 1, 2000

Next Generation Control System Technologies Promote Solutions

"Americans have done an outstanding job of inventing and documenting how their inventions work, but have tended to put those inventions on a shelf and go off to invent something new," says Dick Morley, inventor of the programmable logic controller and entrepreneur.Support for that proclamation is the change in philosophy and mission goals of the U.

By Dave Harrold, CONTROL ENGINEERING
Diagnostics, Asset Management January 1, 2000

Developing and Using a Risk Assessment Model

Consistency in evaluating and quantifying risk begins with documented definitions.

By Dave Harrold, CONTROL ENGINEERING
Machine Safety January 1, 2000

Where control systems have been, and where they are going

Here We Go Again.

By Dave Harrold, CONTROL ENGINEERING
Machine Safety November 1, 1999

Incomplete Combustion Burns Money

Those plant managers continuously seeking ways to increase profits could benefit by visiting the boiler house. (It's that building tucked near the back of the property with the big coal piles around it). Once there they need to ask one question: "What has been the average percentage of O2 in each boiler's stack over the past 24 hours?"Burning coal (or natural gas, fuel oil, wood, or gar...

By Dave Harrold, CONTROL ENGINEERING
Workforce Development October 1, 1999

ISA’s SP75.25 Control Valve Dynamic Testing Subcommittee Update

A ccording to Cullen Langford, chairman of the SP75.25 sub-committee, progress has been outstanding with a high level of professional interaction among committee members. In some cases data and charts brought to sub-committee meetings have been so similar they are nearly interchangable. Mr.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors October 1, 1999

Select and Size Control Valves Properly to Save Money

This is the second of a two-part article on control valves. Part one appeared in the September 1999issue of Control Engineering.There is a saying, "When momma ain't happy, nobody's happy." A parallel could be said about control valves, "When control valves aren't working, the whole loop's not working.

By Dave Harrold, CONTROL ENGINEERING
HMI, OI September 1, 1999

Control valve characteristic guidelines

Liquid Level Control System Control valve pressure drop Best inherent characteristic Constant delta pressure Linear Decreasing delta pressure with increasing load, delta pressure at maximum load > 20% of minimum load delta pressure. Linear Decreasing delta pressure with increasing load, delta pressure at maximum load & 20% of minimum load delta pressure. Equal percentage Increasing delta pressure with increasing load, delta pressure at maximum load & 200% of minimum load delta pressure. Linear Increasing delta pressure with increasing load, delta pressure at maximum load > 200% of minimum load delta pressure. Quick opening Source: Control Engineering with data from Fisher Controls Flow Control Processes Best inherent characteristic Flow measurement signal to controller is: Location of control valve in relation to measuring element is: Wide range of flow setpoint Small range of flow but large delta pressure change at valve with increasing load Proportional to flow In series Linear Equal percentage In bypass * Linear Equal percentage Proportional to flow squared In series Linear Equal percentage In bypass * Equal percentage Equal percentage * When control valve closes, flow rate increases in measuring element.Source: Control Engineering with data from Fisher Controls Pressure Control System Application Best inherent characteristic Liquid process Equal percentage Gas process, small volume, less than 10 ft (3 m) of pipe between control valve and load. Equal percentage Gas process, large volume [process has a receiver, distribution system, or transmission line exceeding 100 ft (30.5 m) of nominal pipe volume], decreasing delta pressure with increasing load, delta pressure at maximum load >20% of minimum load delta pressure. Linear Gas process, large volume, decreasing delta pressure with increasing load, delta pressure at maximum load &20% of minimum load delta pressure. Equal percentage Source: Control Engineering with data from Fisher Controls Comments?E-mail dharrold@cahners.com.

By Dave Harrold, CONTROL ENGINEERING
Vision and Discrete Sensors September 1, 1999

Control Valves Match Size with Application

Big dividends in reduced maintenance cost can be obtained when control valves are engineered to match requirements of the application, and this is especially true for severe service applications. Though less than 10% of all control valves are installed in severe service applications, applying the information in this article will ensure every control valve is correctly engineered to meet t...

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors September 1, 1999

Seat leakage classifications

Seat Leakage Classifications (In accordance with ANSI B16.104-1976) Leakage class designation Maximum leakage allowable Test medium Test pressure Testing procedures required for establishing rating I --- --- --- No test required provided user and supplier agree. II 0.5% of rated capacity Air or water at 50 to 125 45 to 60 psi (3.1 to 4.1 bar) or maximum operating differential whichever is lower Pressure is applied to valve inlet, with outlet open to atmosphere or connected to a low head-loss measuring device, full normal closing thrust provided by actuator. III 0.1% of rated capacity As above As above As above IV 0.01% of rated capacity As above As above As above V 0.0005 liters per minute of water per inch (mm) of port diameter per psi (bar) differential. Water at 50 to 125 Maximum service pressure drop across valve plug, not to exceed ANSI body rating. 100 psi (6.9 bar) pressure drop minimum. Pressure applied to valve inlet after filling entire body cavity and connected piping with water and stroking valve plug closed. Use net specified maximum actuator thrust, but no more, even if available during test.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors August 1, 1999

How to Get Control and Automation Projects Approved

Gaining approval for control and automation projects and seeing them succeed requires tight integration with business goals and diligent resolution of specific problems.Fundamental motivators driving manufacturers to invest in control and automation systems include a desire to reduce costs and improve:Although few would argue with the logic of these common-sense motivators, they're rarely...

By Dave Harrold, CONTROL ENGINEERING
Control Systems August 1, 1999

Process Controller Tuning Guidelines

This material addresses numerous reader inquiries asking how to calculate tuning parameters. Users should understand this material is not a substitute for formal training on process control loop analysis and tuning, but rather as an introduction or refresher. Control Engineering provides this information as a service and makes no guarantees of its usefulness for a particular application (See also, summary, in August 'News.' ). R ecent articles in Control Engineering have addressed methods to improve control loop performance (see Feb.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors July 1, 1999

Asset Management: Predictive Maintenance

Not that long ago, maintenance was the corporate black hole-the cost center one couldn't ignore, escape, or seemingly control. Capturing, analyzing, and sharing meaningful maintenance costs is key to lowering operational costs, improving efficiency, and effectively managing assets.A look at the balance sheet of most manufacturing companies reveals the biggest dollar assets are plant, prop...

By Dave Harrold, CONTROL ENGINEERING
Machine Safety June 1, 1999

Ethernet Everywhere

The goal of enterprise-wide networking is to tie all computers, applications, printers, control systems, intelligent devices, and the Internet/intranet together to achieve real-time communications throughout the corporation.Long the network of choice at business levels of an enterprise, recent reports insist Ethernet works for industrial networking and permits a single network architectur...

By Dave Harrold, CONTROL ENGINEERING
I/O Systems, I/O Modules May 1, 1999

Network Terms

# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 32-bit - Refers to number of bits used by an operating system to perform an operation. Is based on the microprocessor that the OS is designed to run on. access method - Technique for moving data between main storage and input/output devices. In a Systems Network Architecture (SNA) environment, it is the software that controls the flow of information in a network. adapter - Hardware installed in a PC or other computer and used to connect the computer to other hardware. address - Identifier assigned to networks, stations and other devices so that each device can be separately designated to receive and reply to messages. Address Resolution Protocol (ARP) - Internet protocol that dynamically maps Internet addresses to physical (hardware) addresses on local area networks.

By Dave Harrold, CONTROL ENGINEERING
PID, APC April 1, 1999

Estimating Process Control Implementation Made Easier

When ISA's S88 committee released ANSI/ISA S88.01 Batch Control: Models and Terminologythe process control industry received a method that allowed project planning and estimating to move from an art to a science. The standard creates basic modules that never loose their independent identity, functionality, and interconnectivity.

By Dave Harrold, CONTROL ENGINEERING
Machine Safety April 1, 1999

Sample Batch Reactor for Time Estimating

This sample was developed by Control Engineering and sent to 14 control system supplier companies with batch product focus requesting participation in this article. The sample application was developed from material provided in Guidelines for Safe Automation of Chemical Processes published by Center for Chemical Process Safety of the American Institute of Chemical Engineers (New York, N.Y.). This sample was written and presented in a manner similar to what many service estimators receive from users.

By Dave Harrold, CONTROL ENGINEERING
HMI, OI March 1, 1999

Summarized Guide to Variable Control Chart Selection

Generally, selection of a control chart and rational subgroup must be balanced between needs, costs, and acceptable risks. Larger sample sizes may make the chart more sensitive in detecting changes, but usually will cost more to operate. X-bar & R charts are usually effective, but in some situations they are not as effective as other chart types.

By Dave Harrold, CONTROL ENGINEERING
System Integration March 1, 1999

Examples of Common Nonrandom Patterns Occurring in Shewhart-type Charts

E valuating chart patterns is part of Six Sigma training. The following are some common nonrandom patterns that may occur on Shewhart-type control charts. These nonrandom patterns may be used as a basis for control chart interpretation and/or establishing test runs to determine out-of-control conditions. Source: Control Engineering with data from Motorola Mixture patterns: This pattern is indicated when the plotted points tend to fall near the control limits, with relatively few points near the center line. A mixture pattern is caused by two or more overlapping distruibutions generating the process output.

By Dave Harrold, CONTROL ENGINEERING
HMI, OI March 1, 1999

Summarized Guide to Attribute Control Chart Selection

G enerally, selection of a control chart and rational subgroup must be balanced between needs, costs, and acceptable risks. Larger sample sizes may make the chart more sensitive in detecting changes, but usually will cost more to operate. X-bar & R charts are usually effective, but in some situations they are not as effective as other chart types.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors March 1, 1999

Optimize Existing Processes to Achieve Six Sigma Capability

This is the second of a two part series. Part one appeared in the January issue and addressed designing processes to achieve Six Sigma capability.A well-designed, well-executed system keeps a process under control at an existing performance level. Control charts of the process can identify, and even predict, when the process is becoming unstable.

By Dave Harrold, CONTROL ENGINEERING
HMI, OI February 1, 1999

Valve characteristics selection guidelines

Control valves are called to handle all kinds of fluids at temperatures from the cryogenic range to well over 1,000F (538selecting a control valve to ensure satisfactory operation without undue initial expense. Reputable control valve manufacturers are dedicated to helping customers select the control valve best suited for the existing service conditions. Frequently several correct choices may be available, thus it is important for customers to provide control valve manufacturers the following information. Type of fluid to be controlled. Temperature range of fluid. Viscosity range of fluid. Specific gravity range of fluid. Minimum and maximum flow required. Minimum and maximum inlet pressure at the control valve. Minimum and maximum outlet pressure at the control valve. Pressure drop across the valve expected during normal flowing conditions. Pressure drop across the valve at zero flow. Maximum permissible noise level, if pertinent, and the measurement reference point. Degrees of superheat or existence of flashing across the valve, if known. Inlet and outlet pipeline size and schedule of pipe. When conducting an audit of existing processes, the control valve is already installed. The following guidelines can be useful in determining if the control valve installed, is suitable for the application. Flow control processes Flow measurement signal to controller Location of control valve in relation to measuring element Wide range of flow setpoint Proportional to flow In series Linear In bypass (see note) Linear Proportional to flow squared In series Linear In bypass (see note) Equal percentage Small flow range with large changes in pressure drop across the valve In series In bypass (see note) Equal percentage characteristics should be used for applications with a small range of flow setpoint, large delta pressure at the valve, and increasing loads. Note: When control valve closes, the flow rate as measured by the sensing element increases. Pressure control processes Liquid process Equal percentage Gas process with small volume and less than 10 ft (3 m) of pipe between control valve and load valve. Equal percentage Gas process with large volume (process has a receiver, distribution system, or transmission line exceeding 100 ft (30.5 m) of pipe).

By Dave Harrold, CONTROL ENGINEERING
Mechatronics and Motion Control February 1, 1999

Understanding control valve bench set

C ontrol valves are frequently reused, disassembled for maintenance, or 'stroke tested' before installation. A key factor to ensuring that control valves perform as expected, is understanding how operating conditions, changes in packing material, spring compression, and other influences contribute to overall control valve performance. During control valve and actuator sizing, several factors must be considered to ensure the actuator can move and maintain the valve plug in place while operating at process conditions. Factors influencing control valve performance under operating conditions include: Diaphragm loading pressure , which is frequently 3-15 psi, but may be significantly higher, especially when a positioner is being used. Diaphragm effective area is defined by the size of the actuator. Most manufacturers offer a variety of actuator sizes. Valve plug stroke and travel is determined by sizing the valve body to meet flow requirements. Secondary forces acting on the valve plug in order of importance include static unbalance, dynamic unbalance, packing friction, stem size, and diaphragm hysteresis. Spring characteristics are the most active of all influences and should be determined after all other factors have been considered. A control valve and actuator assembly is tested on a bench, not under actual operating conditions.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors February 1, 1999

Turn Problem Loops Into Performing Loops

Understanding the five essential pieces of a control loop contributes to process performance and can turn problem loops into performing loops.

By Dave Harrold, CONTROL ENGINEERING
I/O Systems, I/O Modules January 1, 1999

Designing for Six Sigma Capability

This article is the first of a two part series. The second part will appear in the March issue and will address optimizing existing processes to achieve 6 capability. The ultimate in optimization is called Six Sigma (6σ), and its practitioners are known as Black Belts. It may sound like a mystical art, but it is in fact a data driven method for achieving near-perfect quality.

By Dave Harrold, CONTROL ENGINEERING
Control Systems November 1, 1998

Flexible Batch Proven in First Week

Mead Johnson Nutritionals (Evansville, Ind.), a world leader in adult and infant nutritional products, sought to become flexible and quick in adapting new products at its 32 oz. processing center. Engineers there needed to replace an obsolete control system with technology capable of supporting global enterprise integration and reduce process variability caused by manual interventions.

By Dave Harrold, CONTROL ENGINEERING
Machine Safety October 1, 1998

4-20 mA Transmitters Alive and Kicking

Because they've been around so long, everyone already knows all there is to know about 4-20 mA transmitters and how to install them. But, if so much is known about selecting and installing 4-20 mA transmitters, why do the same questions keep coming up? Questions like:Transmitter classificationsUnderstanding differences between two-, three- and four-wire devices will help clear up several ...

By Dave Harrold, CONTROL ENGINEERING
PID, APC October 1, 1998

Pressure Regulators Simplicity May Suffice

Pressure regulators are very simple control devices, taking necessary operating energy from the process. In contrast, control valves require transmitters, controllers, and external energy sources.Value engineering strives to implement simple solutions that meet requirements. The simplicity of pressure regulators is reason enough to consider them.

By Dave Harrold, CONTROL ENGINEERING
Process Instrumentation and Sensors September 1, 1998

Master Disaster How to Avoid Abnormal Situations

In early mining applications, cages of birds were placed throughout shafts to alert miners of abnormal situations—too much methane gas. Later, birds were replaced with sensors and annunciator panels that alerted workers of abnormal conditions.In the 1980s programmable control systems such as distributed control systems, programmable logic controllers, and supervisory control and dat...

By Dave Harrold, CONTROL ENGINEERING
Project Management September 1, 1998

Automation Objectives Lower Cost and Improve Time-to-Market

At Eli Lilly and Co. (Indianapolis, Ind.), a leader in the development and manufacture of pharmaceutical products, process automation has played a key role for over 20 years. So in 1994 when Lilly's management challenged the manufacturing units to cut unit operating costs by 25% over the next three years, process automation was an acknowledged key element in meeting the challenge.

By Dave Harrold, CONTROL ENGINEERING
Energy, Power August 1, 1998

Do You Know What’s Leaking?

In 1990 leaks on the launch pad necessitated grounding of the Space Shuttle fleet until the leak source could be identified, a process costly in monetary and scheduling disruptions. The U.S. Navy continuously monitors for toxic hydrogen sulfide build-ups in wastewater containment areas aboard sea-going vessels.

By Dave Harrold, CONTROL ENGINEERING
PID, APC July 1, 1998

New ‘Soft DCS’ Reaches the Market

PCSoft (Braintree, Mass.) set a goal to build an open distributed control system (DCS)—one that provides features and functions of a traditional DCS, utilizes a defacto-standard operating system, makes extensive use of open standards, and resides on a single hardware platform.WizDCS is the result of its efforts and indications are PCSoft has exceeded its goal.

By Dave Harrold, CONTROL ENGINEERING
Energy Efficiency May 1, 1998

HP Vantera Helps Companies with Deregulation

As electric utilities become deregulated or privatized, they will have a much greater need for fast and efficient access to information about their operations and how customers use their services.At the same time, deregulation will increase user awareness of the need to review and understand consumption histories, usage characteristics, and the ability to manage load curves.

By Dave Harrold, CONTROL ENGINEERING