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Limit, Selector, and Override Controls

Limit, Selector, and Override Controls

Another category of control strategies involves the use of signal relays or function blocks with the ability…


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Sliding-stem Valves

Sliding-stem Valves

A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…


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Pilot Valves and Pneumatic Amplifying Relays

Pilot Valves and Pneumatic Amplifying Relays

Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…


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High-reliability Control Systems

High-reliability Control Systems

As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…


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Loop Diagrams (Loop Sheets)

Loop Diagrams (Loop Sheets)

Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…


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Self-regulating, Integrating, and Runaway Process Characteristics

Self-regulating, Integrating, and Runaway Process Characteristics

Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…


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Advantages and Disadvantages of Pneumatic Instruments

Advantages and Disadvantages of Pneumatic Instruments

The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…


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Circuit Breakers and Disconnects

Circuit Breakers and Disconnects

Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…


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Fluid Power Systems

Fluid Power Systems

Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…


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Actuator Bench-set

Actuator Bench-set

Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…


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Safety Instrumented Functions and Systems

Safety Instrumented Functions and Systems

A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…


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Solenoid Valves

Solenoid Valves

A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…


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Disassembling a Globe Valve

Disassembling a Globe Valve

The following collection of photographs chronicles the complete disassembly of a Fisher E-body globe valve…


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What is Hydrostatic Pressure?

What is Hydrostatic Pressure?

A vertical column of fluid generates a pressure at the bottom of the column owing to the action of gravity on…


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Split-Range Control

Split-Range Control

There are many process control applications in the industry where it is desirable to have multiple control…


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Legal Code

Legal Code

Creative Commons Attribution 4.0 International Public License By exercising the Licensed Rights (defined…


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Process Flow Diagrams

Process Flow Diagrams

To show a practical process example, let’s examine three diagrams for a compressor control system,…


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Fluid Mechanics

Fluid Mechanics

A fluid is any substance having the ability to flow: to freely change shape and move under the influence of a…


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Numerical Integration

Numerical Integration

As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…


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On/off Shut-off Valves

On/off Shut-off Valves

An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…


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Formulae for Common Chemical Compounds

Formulae for Common Chemical Compounds

Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…


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Digital Multimeter (DMM) Tips and Tricks

Digital Multimeter (DMM) Tips and Tricks

The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…


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Derivative (Rate) Control

Derivative (Rate) Control

The final element of PID control is the “D” term, which stands for derivative. This is a calculus…


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Instrument and Process Equipment Symbols

Instrument and Process Equipment Symbols

This section shows some of the many instrument symbols found in different types of technical diagrams used to…


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Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)

At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…


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General Problem-solving Techniques

General Problem-solving Techniques

A variety of problem-solving techniques have been presented for students over the years which are all helpful…


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Quantitative PID Tuning Procedures

Quantitative PID Tuning Procedures

A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…


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Flow Switches

Flow Switches

A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…


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Basic Feedback Control Principles

Basic Feedback Control Principles

Feedback Control System Components Before we begin our discussion on process control, we must define a few key…


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Open-ended, Shorted, and Properly Terminated Transmission Lines

Open-ended, Shorted, and Properly Terminated Transmission Lines

Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…


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Instruction List (IL) Programming

Instruction List (IL) Programming

(Will be addressed in future versions of this book)


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Auxiliary and Lockout (86) Relays

Auxiliary and Lockout (86) Relays

An important type of “accessory” relay, especially for legacy electromechanical protective relays,…


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Hand Switches and Stackable Switches

Hand Switches and Stackable Switches

A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…


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Sliding-stem Valves

Sliding-stem Valves

A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…


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Basics of Bridge Circuits

Basics of Bridge Circuits

A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…


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Weighfeeders

Weighfeeders

A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…


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Controller Output Current Loops

Controller Output Current Loops

The simplest form of 4-20 mA current loop is the type used to represent the output of a process controller,…


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Introduction to Inductors and Inductance

Introduction to Inductors and Inductance

Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…


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Understanding Area, Volume and Common Geometry

Understanding Area, Volume and Common Geometry

Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…


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Introduction to Capacitors and Capacitance

Introduction to Capacitors and Capacitance

Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…


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Pneumatic Actuator Response

Pneumatic Actuator Response

A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…


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FOUNDATION Fieldbus H1 Protocol Physical Layer

FOUNDATION Fieldbus H1 Protocol Physical Layer

Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data…


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Ladder Diagram (LD) Programming Contacts and Coils

Ladder Diagram (LD) Programming Contacts and Coils

In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…


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Calibration Procedures in Linear, Non-Linear and Discrete Instruments

Calibration Procedures in Linear, Non-Linear and Discrete Instruments

As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…


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Control Valve Actuators

Control Valve Actuators

The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…


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Insertion Flowmeters

Insertion Flowmeters

This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…


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Level Sensor Accessories

Level Sensor Accessories

Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…


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Examples of PLC Systems

Examples of PLC Systems

Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…


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Digital PID Controllers

Digital PID Controllers

The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…


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Fluid Power Systems

Fluid Power Systems

Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…


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Pneumatic PID Controllers

Pneumatic PID Controllers

A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…


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Practical Topic Coverage

Practical Topic Coverage

Nearly every technical course teaches and tests students on definitions, basic concepts, and at least some…


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Common Control Valve Problems

Common Control Valve Problems

Valves can experience a number of problems, most of them either preventable or repairable. These problems can…


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Radio-energy Pulse in Guided-wave Radar Level Measurement

Radio-energy Pulse in Guided-wave Radar Level Measurement

The following animation shows how a radio-energy pulse travels down and then up the waveguide of a guided-wave…


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Mechanical Pressure Elements

Mechanical Pressure Elements

Mechanical pressure-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…


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FOUNDATION Fieldbus Function Blocks

FOUNDATION Fieldbus Function Blocks

Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…


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Tube and Tube Fittings

Tube and Tube Fittings

Tube, like pipe, is a hollow structure designed to provide an enclosed pathway for fluids to flow. In the case…


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Stoichiometry and the Law of Mass Conservation

Stoichiometry and the Law of Mass Conservation

Stoichiometry is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…


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Differential Pressure Transmitters

Differential Pressure Transmitters

One of the most common, and most useful, pressure measuring instruments in industry is the differential…


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The International System of Units

The International System of Units

The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…


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