A different strategy for controlling the flow of fluid is to insert a rotary element into the flow path.…
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An important design parameter of a control valve is the position it will “fail” to if it loses…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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Those familiar with industrial instrumentation will find much within the electric power industry remarkably…
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So far we have just looked at instruments that sense, control, and influence process variables. Transmitters,…
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The digital multimeter (DMM) is quite possibly the most useful tool in the instrument technician’s…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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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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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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A form of protection against faults on long-distance power lines is called distance relaying, so named because…
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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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A simple control system drawn in block diagram form looks like this: Information from the measuring device…
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The reason why a pneumatic control valve’s stem position corresponds linearly to the amount of air…
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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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Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century…
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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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Another category of control strategies involves the use of signal relays or function blocks with the ability…
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Control strategies such as cascade, ratio, feedforward, and those containing limit and selector functions can…
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A very simple device used to measure pressure is the manometer: a fluid-filled tube where an applied gas…
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In contrast to quantitative tuning procedures where definite numerical values for P, I, and D controller…
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Learning how to tune PID controllers is a skill born of much practice. Regardless of how thoroughly you may…
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A laser is a light source emitting waves of light that not only share the exact same frequency (color)…
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Many traditional flowmeter technologies respond to the volumetric flow rate of the moving fluid.…
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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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A positive displacement flowmeter is a cyclic mechanism built to pass a fixed volume of fluid through with…
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Coy, John J. et. al. (December 2012) Sampled graphic illustrations from his NASA Reference Publication…
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Any physical location in an industrial facility harboring the potential of explosion due to the presence of…
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Nearly every technical course teaches and tests students on definitions, basic concepts, and at least some…
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DC electric motors generate torque by a reaction between two magnetic fields: one field established by…
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Diagnostic ability is arguably the most difficult skill to develop within a student, and also the most…
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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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In November of 2007 a new computer virus was submitted to a virus scanning service. The purpose of this new…
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The Law of Mass Conservation states that matter can neither be created nor destroyed. The Law of Energy…
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Labwork is an essential part of any science-based curriculum. Here, much improvement may be made over the…
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Developed by the Modicon company (the original manufacturer of the Programmable Logic Controller, or PLC) in…
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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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One of the marks of a successful problem-solver is a habit of applying general principles to every new problem…
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Level gauges are perhaps the simplest indicating instrument for liquid level in a vessel. They are often found…
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Like so many other industrial data networks, FOUNDATION Fieldbus is an “unswitched” or…
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The simple PLC ladder diagram (LD) commands consist of contacts and coils, arranged in sequences that mimic…
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First, let us review some of the properties of differentials and derivatives, referencing the expression and…
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Two extremely important principles in electric circuits were codified by Gustav Robert Kirchhoff in the year…
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Instrument technicians should not have to concern themselves over the programming details internal to digital…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float sets the…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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A fundamental principle in instrumentation system troubleshooting is that every instrument has at least one…
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Fluid pressure exerts force on any surface area it contacts, as described by the formula \(F = PA\). One…
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In some process applications, it is important that the control valve be able to completely stop fluid flow…
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Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in…
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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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A very common method for directly controlling low flow rates of fluids is to use a device known as a metering…
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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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In a manually-controlled process, a human operator directly actuates some form of final control element…
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As we have seen, feedforward control is a way to improve the stability of a feedback control system in the…
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Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by…
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Flow, by definition, is the passage of material from one location to another over time. So far this chapter…
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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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Sample sizes of chemical substances are often measured in moles. One mole of a substance is defined as a…
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An exciting development in industrial instrumentation is the WirelessHART radio communication standard,…
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