Another category of control strategies involves the use of signal relays or function blocks with the ability…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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Self-balancing mechanisms consisting solely of a baffle/nozzle detector coupled to a feedback bellows, while…
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As discussed at the beginning of this chapter, instrumentation safety may be broadly divided into two…
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Finally, we arrive at the loop diagram (sometimes called a loop sheet) for the compressor surge control system…
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Perhaps the most important rule of controller tuning is to know the process before attempting to adjust the…
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The disadvantages of pneumatic instruments are painfully evident to anyone familiar with both pneumatic and…
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Disconnect Switches Disconnects are switches designed to isolate sections of a power system in case of damage…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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A Safety Instrumented Function, or SIF, is one or more components designed to execute a specific…
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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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The following collection of photographs chronicles the complete disassembly of a Fisher E-body globe valve…
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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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There are many process control applications in the industry where it is desirable to have multiple control…
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Creative Commons Attribution 4.0 International Public License By exercising the Licensed Rights (defined…
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To show a practical process example, let’s examine three diagrams for a compressor control system,…
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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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As we have seen, the concept of integration is finding the accumulation of one variable multiplied by another…
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An on/off valve is the fluid equivalent of an electrical switch: a device that either allows unimpeded flow or…
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Most of these formulae appear in molecular chemical form rather than structural form. For example, ethanol…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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The final element of PID control is the “D” term, which stands for derivative. This is a calculus…
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This section shows some of the many instrument symbols found in different types of technical diagrams used to…
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At the next OSI Reference Model layer (layer 4) is a set of protocols specifying how reliable communication…
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A variety of problem-solving techniques have been presented for students over the years which are all helpful…
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A quantitative PID tuning procedure is a step-by-step approach leading directly to a set of numerical values…
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A flow switch is one that detects the flow of some fluid through a pipe. Flow switches often use…
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Feedback Control System Components Before we begin our discussion on process control, we must define a few key…
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Many years ago, when I was first learning about electricity, I happened to discover a length of coaxial…
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(Will be addressed in future versions of this book)
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An important type of “accessory” relay, especially for legacy electromechanical protective relays,…
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A hand switch is exactly what the name implies: an electrical switch actuated by a person’s hand motion.…
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A sliding-stem valve body is one where the moving parts slide with a linear motion. Some examples of…
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A bridge circuit is basically a pair of voltage dividers where the circuit output is taken as the difference…
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A special type flowmeter suited for powdered or granular solids is the weighfeeder. One of the most common…
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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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Any conductor possesses a characteristic called inductance: the ability to store energy in the form of a…
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Area refers to the size of two-dimensional surface. Volume refers to the size of a three-dimensional space. To…
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Capacitance Any two electrical conductors separated by an insulating medium possess the characteristic called…
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A limitation inherent to pneumatic valve actuators is the amount of air flow required to or from the actuator…
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Layer 1 of the OSI Reference Model is where we define the “physical” elements of a digital data…
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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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As described earlier in this chapter, calibration refers to the adjustment of an instrument so its output…
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The purpose of a control valve actuator is to provide the motive force to operate a valve mechanism. Both…
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This section does not describe a particular type of flowmeter, but rather a design that may be implemented for…
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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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The vast majority of PID controllers in service today are digital in nature. Microprocessors executing PID…
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Given the ability of pressurized fluids to transmit force over long distances, it is not surprising that many…
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A pneumatic controller receives a process variable (PV) signal as a variable air pressure, compares that…
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Nearly every technical course teaches and tests students on definitions, basic concepts, and at least some…
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Valves can experience a number of problems, most of them either preventable or repairable. These problems can…
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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-sensing elements include the bellows, the diaphragm, and the bourdon tube. Each of these…
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Data-processing modules within FF systems are known as function blocks. Sometimes these blocks serve merely to…
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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 is the accounting of atoms before and after a chemical reaction. It is an expression of the Law…
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One of the most common, and most useful, pressure measuring instruments in industry is the differential…
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The very purpose of physics is to quantitatively describe and explain the physical world in as few terms as…
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