Measurement and Control Basics 3rd Edition (complete book)
.pdfAppendix C – Answers to Exercises |
365 |
Figure 10-5. Using this test setup, control valve manufacturers determine and publish Cv valves for their valves.
10.4The volumetric flow rate is 1060.2 cfm.
10.5The valve-sizing coefficient is 56.57 and a 3 in. valve should be selected.
10.6The valve will not cavitate and the valve-sizing coefficient is 253.
10.7If the pressure at the outlet of the valve is still below the vapor pressure of the liquid, bubbles will remain in the downstream system and result in flashing. If the downstream pressure recovery is sufficient to raise the outlet pressure above the liquid vapor pressure, the bubbles will collapse, or implode, producing cavitation.
10.8The torque constant is 0.143oz-in./v and damping constant is 4.8x 0-3 oz-in./rad/s.
10.9The torque (Kt) constant is 0.06 oz-in./v and damping constant (Dm) is 7.16 oz-in./rad/s.
10.10The parallel capacitance required to make the winding appear purely resistive is 16.6 microfarads.
10.11The total head developed is 19.03 ft.
10.12Rotary pumps function by continuously producing reducedpressure cavities on the suction side, which fills with fluid. The fluid is moved to the discharge side of the pump, where it is compressed and then discharged from the pump.
Chapter 11
11.1Some of the disadvantages of early centralized control computers were as follows: 1) very slow operating speed, 2) very small computer memory size (4K to 8K), 3) all programming had to be done in machine language, and 4) lack of programming experience by control vendors and users.
11.2The process data collected at level 1 is transferred to level 2. At this level, process operators and engineers use consoles with a keyboard, mouse, and video display to view and adjust the various processes being controlled and monitored by the system. At level 2, process and control engineers implement advanced control functions and strategies, and operations management members perform advanced data collection and analysis on process information. The various plant management systems—such as inventory management and control, billing and invoicing, and
366 Measurement and Control Basics
statistical quality control—exist at level 3. The highest level is used to provide extensive process and operations information to corporate management in large industrial plants.
11.3The functions and features of a typical DCS are control and monitoring, operations interface, and advanced applications software.
11.4The processor reads the inputs, executes logic as determined by the application program, performs calculations, and controls the outputs accordingly.
11.5The main purpose of the I/O system is to provide the physical connection between the process equipment and the PLC system.
11.6Some typical discrete input devices found in process industries are process switches for temperature, flow, and pressure.
11.7Some typical discrete output signals encountered in industrial applications are control relays, solenoid valves, and motor starters.
11.8Some typical analog signal values found in process control applications are 4 to 20-maDC current, 0 to 10 vDC, and 1 to 5 vDC.
11.9The difference between volatile and nonvolatile memory is that volatile memory will lose its programmed contents if all operating power is lost or removed. Nonvolatile memory will retain its data and program even if there is a complete loss of operating power.
11.10The common applications for personal computers in programmable controller systems are programming, graphical unit interfaces, and data collection.
11.11The personal computer is the most common device used to program PLCs.
11.12The three basic instructions used in ladder logic programs are the 1) normally open, 2) normally closed, and 3) coil output instructions.
11.13Power flow in a relay ladder diagram is the flow of electric current from the left side to the right side of a ladder rung.
11.14Logical power flow is obtained in a LAD program if there is logical continuity from the left side to the right side of a ladder logic rung.
11.15STL instruction statements have two basic structures. One, a statement made up of an instruction alone (for example, NOT) and another where the statement is made up of an instruction and an address.
Index 371
Wedge flow element |
257 |
Weight density 150 |
|
Wet-bulb temperature |
218 |
Wheatstone bridge circuit 190
Wide bands 54
Work 243
Ziegler-Nichols tuning method 58, 60–62, 64
