Control system components

3 final control elements (usually control valves) 

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Control-System Components The three principal elements of a control system are the sensing device which measures the error as the deviation from the set point, means for transmission and amphfi-cation of the error signal, and the control output device in the form of a seivo-operated valve. In the case of the direct-acting flyball governor (Fig. 29-18) these three elements are combined in the flyball element and the linkage that connects to the valve. 

The elements of a PM plan include periodic inspection, cleaning, and service as warranted, adjustment and calibration of control system components, maintenance equipment and replacement parts that are of good quality and properly selected for the intended function. Critical HVAC system components that require PM in order to maintain comfort and deliver adequate ventilation air include a outdoor air intake opening, damper controls, air filters, drip pans, cooling and heating coils, fan belts, humidification equipment and controls, distribution systems, exhaust fans. 

Heater and air conditioner control system components, functional parts in the heating, ventilation and coolant sectors. .. 

On the other hand the synthetic problem is the design of the whole control system, including in its broadest implication the design of process, as well as the specification of, control instruments. Before the synthetic problem can be tackled intelligently, the criteria of satisfactory control must be identified. These criteria are different for different systems, but most usually they are described in terms of the response of the system to certain stimuli. Having established the criteria of control, the problem of synthesis is one of optimizing the selection of control system components and their disposition in the control loop, so that the criteria are met. 

At the time this report was being prepared, the control system included some equipment that could be considered obsolete, but was stiU functional. To ensure continuing support for control system spares, a control system spares management contract has been negotiated with Rockwell Automation, the present owner of the Allen Bradley operations that provided the original control system components. 

Separation of Protection and Control Systems. The protection system shall be separated from control systems to the extent that failure of any single control system component or channel, or failure or removal from service of any single protection system component or channel which is common to the control and protection system leaves intact a system satisfying all reliability, redundancy, and independence requirements of the protection system. Interconnection of the protection and control systems shall be limited so as to ensure that safety is not significantly i mpa i red. 

Figure 5.4 shows a typical sequential setup for the control system components. 

Green - Normal heat removal Orange - Control system components... 

The purification subsystem has been analyzed for seismic withstand the methods and criteria used for the seismic analysis are similar to those used for seismic Category II pipe. The chemical and volume control system components are located inside the containment, which is itself a seismic Category I structure. 

Emission control system components ElectricaPelectronic components Engine covers Fuel cells... 

In earlier chapters, Simulink was used to simulate linear continuous-time control systems described by transfer function models. For digital control systems, Simulink can also be used to simulate open- and closed-loop responses of discrete-time systems. As shown in Fig. 17.3, a computer control system includes both continuous and discrete components. In order to carry out detailed analysis of such a hybrid system, it is necessary to convert all transfer functions to discrete time and then carry out analysis using z-transforms (Astrom and Wittenmark, 1997 Franklin et al., 1997). On the other hand, simulation can be carried out with Simulink using the control system components in their native forms, either discrete or continuous. This approach is beneficial for tuning digital controllers. 

The code includes many generic component models from which general systems can be simulated. The component models include pumps, valves, pipes, heat releasing or absorbing structures, reactor point kinetics, electric heaters, jet pumps, turbines, separators, accumulators, and control system components. In addition, special process models are included for effects such as form loss, flow at an abrupt area change, branching, choked flow, boron tracking, and non-condensable gas transport. 

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