Set-point control

Supply air conditions (set points, control strategy, limits)... 

Action Right action on wrong object Set point changed on wrong controller Same as above Same as above Clearly label controllers to distinguish among set point controls... 

The power source, relay, set-point controller and sensor need not be discussed here. However, the insulation, heating elements, and crucibles involve materials, and need to be examined in more detail. 

The startup checklist should also include a verification of the correct chamber set points, controller setup parameters, and compressor operating head pressure. 

A set-point control is mainly used to control process variables such as temperature and pH. For example, temperature is controlled by heating and cooling by cooling water, and pH is maintained by the addition of acid and alkali. The modification of a set-point will be done manually or by the DCS, which works as a supervisory system. 

The action of endogenous pyrogens on the hypothalamus produces fever, because of a readjustment ill the central set point controlling the body s internal temperature. Salicylates and other NSAIDs achieve their antipyretic effect by controlling the prostaglandin-induced release of pyrogens. 

This shorter sample time, in addition to giving better set point control, would permit a more rapid response to unexpected load upsets. 

PCs are fairly simple devices to operate. If they do not function properly all kinds of problems develop. A checklist for eliminating problems includes nonuniform processed plastic, heater element burnout, location and depth of sensor as related to response time, type of on/off control action such as proportional controller, set point control, and basic electrical component proper selection. It is important to have the proper depth of the sensor in a barrel in order to obtain the best reading for the melt the deeper the better. 

Fig. 5.5. (A) Scheme of a flow digestion system and the principle of pressure equilibration A pressure reactor, B heating zone, C cooling zone, D digestion coil, E cooling device, F connection for gas supply, G restrictor tube, H collector vial, I temperature sensor, J high-pressure pump, K injection valve, L sample loop, M sample, N and O peristaltic pumps. (Reproduced with permission of the American Chemical Society.) (B) Manifold for dynamic microwave-assisted extraction I solvent, 2 pump, 3 microwave oven, 4 extraction chamber, 5 temperature set-point controller, 6 thermocouple, 7 fluorescence detector, 8 recording device, 9 restrictor, 10 extractor. (Reproduced with permission of Elsevier.)...

Process control for animal cell fermentation should at least include a set point control of temperature, pH, pO and agitation rate. 

Figure 5.10.2 Level control by electronic flow meter with a set point control loop. OD = optical density.

Tatjewski P., Iterative optimizing set-point control-The basic principle redesigned , Proc 15thIFAC World Congress, Barcelona, 2002. 

Set-point control (see Servo problem) Set-point response with feedback controller, 260, 267, 271, 273, 276... 

What is material balance control for a complete plant In what sense is it different from the set point control we have seen in earlier chapters Discuss the two approaches for the implementation of material balance control. Which one is preferable, implementation in the direction of process flow or opposite to it Elaborate on your answer. Would you use steady-state or dynamic models for material balance control, and why (Note You will find Chapter 13 of Ref. 16 very useful in answering these questions.)... 

As explained in sub-section 2.5.3 it is possible to superimpose an integral controller on to the set point controls of the individual governors. The master integral controller will have a master frequency... 

Figure 5 Manifold for dynamic MAE. 1, Solvent 2, pump 3, microwave oven 4, extraction chamber 5, temperature set-point controller 6, thermocouple 7, fluorescence detector 8, recording device 9, restrictor 10, extractor. (Reproduced with permission from Luque de Castro MD and Luque-Garcia JL (2002) Acceleration and Automation of Solid Sample Treatment, Elsevier.)...

Steady state operations play a very important role in chemical engineering due to the easiness of material and energy recycling and the ability of set point control. Nevertheless it is very unlikely that steady state operations provide the best in conversion and selectivity. Since progress in automatic process control brings nowadays essentially ev forcing function within reach, there is no need to keep the process steady state from that point of view. Also the recyclability of mass and energy is still possible for non-steady operations if the time constant of the cycles is within reasonable bounds. 

Controller—device the primary purpose of which is to receive a signal from a transmitter, compare this signal to a setpoint, and adjust the (final control element) process to stay within the range of the set-point. Controllers come in three basic designs pneumatic, electronic, and electric. 

We have derived a new method for selecting controlled variables as linear combination of the available measurements, that from a linear point of view have perfect self-optimizing properties if we neglect implementation error. The idea is to calculate the optimal sensitivity function (Ayopt = FAd) and select controlled variables as linear combination of the measurements c = Hy, such that HF = 0. The method has been illustrated on a gas-lift allocation example. The example illustrate that in a constant set-point control structure, selecting the right controlled variables are of major importance. 

In general, based on operational requirements, process outputs can be classified into two broad categories (1) set-point controlled, outputs to be controlled at a desired value, and (2) set-interval controlled, outputs to be controlled within a desired range. For instance, production rate and product quality may fall into the first category, whereas process variables, such as level, pressure, and temperature in different units/streams may fall into the second category. In the following subsection, we shall focus on systems without extra degrees of freedom, that is... 

The objective function, J, would typically involve terms associated with the produced product but also with respect to the cost associated with the input use, such as their range, penalties to discourage wide ranges of certain inputs, etc. The constraints in M include equality constraints for the set-point controlled outputs, ysp, and the inequality constraints for the set-interval controlled outputs. Note that u, the solution of the optimization problem, is a function of ysp and d. Further, it will be worth pointing out that the DOS is defined only in terms of the set-point controlled variables. 

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