Valve actuators provide force to move control valve trim. For precise positioning of a control valve, there…
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The Law of Continuity for fluids states that the product of mass density (\(\rho\)), cross-sectional pipe area…
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As we have seen, the concept of differentiation is finding the rate-of-change of one variable compared to…
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Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide…
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Imagine a liquid-level control system for a vessel, where the position of a level-sensing float directly sets…
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The advent of “smart” field instruments containing microprocessors has been a great advance for…
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One very convenient feature of waves is that their properties are universal. Waves of water in the ocean,…
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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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In the United States, the most common language used to program PLCs is Ladder Diagram (LD), also known as…
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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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One of the fundamental laws of electric circuits is Kirchhoff’s Current Law, which states the algebraic…
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Electrical Resistance Resistance (\(R\)) is the dissipative opposition to an electric current, analogous to…
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While 50 and 51 (instantaneous and time overcurrent) relay functions monitor line current magnitude and guard…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Regardless of valve type, all stem-actuated control valves require some form of seal allowing motion of the…
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A completely different way of measuring liquid level in vessels is to bounce a traveling wave off the surface…
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It is often useful to express the amplitude of an alternating quantity such as voltage or current in terms…
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Programmable logic controllers are essentially nothing more than special-purpose, industrial computers. As…
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In the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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In addition to directly performing logic functions, electromechanical relays may also be used as interposing…
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The transformer is one of the most important components in all of AC circuitry. Principally used to…
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A 4 to 20 mA current signal represents some signal along a 0 to 100 percent scale. Usually, this scale is…
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A pressure switch is one detecting the presence of fluid pressure. Pressure switches often use diaphragms or…
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Many liquid substances undergo a process whereby their constituent molecules split into positively and…
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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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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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Disturbances in the liquid tend to complicate liquid level measurement. These disturbances may result from…
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The efficient identification and correction of instrument calibration errors is an important function for…
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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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Few areas of mathematics are as powerfully useful in describing and analyzing the physical world as calculus:…
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Process analyzers measure the concentration of specific substances for the purpose of measuring and/or…
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Much has been written about the benefits of robust PID control. Increased productivity, decreased equipment…
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Linearity of Measurement Instruments The purpose of calibration is to ensure the input and output of an…
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Perhaps the most basic and necessary protective relay function is overcurrent: commanding a circuit breaker to…
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Weight-based level instruments sense process level in a vessel by directly measuring the weight of the vessel.…
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A great many precision instruments use the principle of balance to measure some quantity. Perhaps the simplest…
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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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A very common form of on/off valve used for pneumatic and hydraulic systems alike is the solenoid valve. A…
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An extremely important topic in engineering is that of transfer functions. Simply defined, a transfer function…
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An electric motor is often used as a discrete control element in a control system if driving a pump, conveyor…
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A machine in the broad sense of the word is any device designed to translate some form of energy into useful…
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When a high-energy photon strikes an atom, it may eject one of the lower-level electrons from its shell,…
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All masses require force to accelerate (we can also think of this in terms of the mass generating a reaction…
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In this section I will show screenshots from a process loop simulation program illustrating the effectiveness…
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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 the United States, the ANSI and IEEE organizations have standardized a set of numerical codes referring to…
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Constructing PID control systems using discrete components is a fairly simple method involving operational…
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All substances are comprised of various elements in various combinations and proportions. Elements may thus be…
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The next level of detail is the Process and Instrument Diagram, or P&ID. Here, we see a “zooming…
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(Will be addressed in future versions of this book)
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The following animation shows how the “rotating” magnetic field of a three-phase AC induction…
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As a general rule, high achievement only takes place in an atmosphere of high expectations. Sometimes these…
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An variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with…
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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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In reliability engineering, it is important to be able to quantity the reliability (or conversely, the…
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Perhaps the most valuable skill an instrument technician can possess is the ability to efficiently diagnose…
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Multiple accessories exist for pressure-sensing devices to function optimally in challenging process…
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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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Negative feedback systems, in general, tend to cause confusion for those first learning their fundamental…
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