Measuring and control devices

Humidistat A measuring and control device used to control the humidity of a space. 

Laboratory furnaces. Several types of furnaces are used in the laboratory these are often available as commercial rigs, generally equipped with more or less sophisticated temperature measurement and control devices. As an alternative, a lab-made or commercial furnace and its temperature measuring devices may be connected to a multi-channel data acquisition/actuator/switch unit, to be programmed by a personal computer, in order to plan and carry out thermal treatments, to collect and retrieve measured thermal data, etc. 

Descriptive of a substance, the physical characteristics of which arc appreciably altered by effects of water vapor. The hygroscopicity of certain materials has been advantageously utilized ill humidity measurement and control devices for example, the hair clement of a hair hygrometer. 

Practical application of advanced process control for chromatographic processes is still at the beginning. Optimal operation of large-scale production should also include the adaptation and optimization of thermo- and fluid-dynamic properties, which might vary during extended operation. Progress in this field is very closely linked to improved detectors and other measurement and control devices. 

SOPs for use, maintenance, calibration, and cleaning of the plant must be developed during the OQ process, as well as schedules for maintenance and calibration. Each OQ document contains a list of required SOPs for the use of the plant. At this point, training of the technical staff of the plant should take place. The training must be documented and checked using prepared forms. Within the OQ process, the calibration of measuring and controlling devices must be checked. Critical parameters and circumstances identified in the risk analysis (RA) must be checked for conformity to the acceptance criteria. 

The first calibration of measurement and control devices must be checked. 

The fundamental scheme of arrangement as applied in the first edition has been retained. Section 5.1.3 has been extended to cover pilot plant distillation. Section 4.2 now deals with fluid and interface dynamics. Chapter 8 could be drastically shortened as there are a variety of components of distillation apparatus and the pertaining measuring and control devices commercially available. The nomograms, which were presented separately, have been inserted in the text. The references for the various chapters have been rearranged and important new items added to them. A great number of review articles serve to provide comprehensive lists of references for a longer period. 

The extent to which measuring and control devices are employed in batch and continuous distillation depends on the nature of the work and, to a considerable degree, on financial considerations [12]. In practice a distinction can be made between semi- (or partly) automatic and fuUy automatic apparatus. In the latter all operations except starting up are performed automatically in partly automatic apparatus only some of the functions are governed by regulating devices. 

Chemical reactors and pressure vessels must be protected against an intolerable pressure rise by the installation of safety devices. If measuring and control devices are not sufficient to control a runaway reaction, then the only remaining protective measure is, as discussed in the previous section, to provide a pressure relief system, such as a bursting disk or safety valve. 

Fig. 2.8-16 Meaning of symbols on a measurement point. The combination of letters describes the type of measurement and control device (Table 2.8-2). The dash indicates that the Q value is transmitted to the control room (no dash = no transmission, processing in situ). The number is the number of the measuring point.

Separation processes typically consist of hrmdreds of elements (pipes, vessels, heat exchangers, columns, pumps, compressors, engines, measuring and control devices, etc.) that are too complex for exact graphical depiction. Therefore, the process structures are depicted in a very abstract and geometrically nonsimilar manner in the form of flow sheets. Flow sheets show the process structure with symbols for the essential process elements according to international standards (e.g., DIN, ISO). 

The flow sheet of a process for the production of absolute alcohol by pressure swing distillation is shown in Fig. 11.0-1. The process consists, in essence, of two distillation columns, several heat exchangers, several vessels, and a complex network of pipelines (see Sect. 11.3.2). Also shown are measuring and control devices. According to international standards (e.g., DIN 19227, ISO 3511) these devices are illustrated by thin circles with a letter code indicating the function of the device, for instance, first letters F = flow, L = liquid level, P = pressure, T = temperature subsequent letters A = alarm, C = control, F = fraction, etc. 

Intrinsic safety ia, ib, ic (note 2) EN 60079- 11 The equipment used in the explosion hazard zone only contains intrinsically safe circuits. A circuit is intrinsically safe if neither a spark nor a thermal effect can cause the ignition of a standard explosible atmosphere. The corresponding tests are carried out under standardized conditions, which comprise both normal operation and certain faulty states. Measurement and control devices, communication devices, sensors, actors... 

A variety of other configurations and modifications of the basic design shown in Figures 3-6 and 3zZ are possible. Valve trays (see Chapter lOi are popular. Downcomers can be chords of a circle as shown or circular pipes. Both partial and total condensers and a variety of reboilers are used. The column may have multiple feeds, sidestream withdrawals, intermediate reboilers or condensers, and so forth. The column also usually has a host of temperature, pressure, flow rate, and level measurement and control devices. Despite this variety, the operating principles are the same as for the sinple distillation column shown in Figure 3-6. 

Batteries and capacitors Corrosion prevention Measuring and controlling devices... 

As mentioned above, this category includes all those measuring and controlling devices whose operation is based on electrochemical principles. The shipments figures for this component of the electrochemical industry are the result of a mail survey of the major... 

Table 12 The Major Measuring and Controlling Devices Which Operate Electrochemically O 0 1 1 a o s... 

Standard and Poor s Industry Studies. Interviews played an important role in determining the major firms in the batteries and capacitors, measuring and controlling devices, and corrosion prevention components. 

The fastest growing components of the electrochemical industry were water treatment, surface finishing, measuring and controlling devices, and batteries and capacitors, in that order. 

All neutron flux measurement and control devices, both vertical and horizontal, are located in the low-pressure calandria, perpendicular to and between the horizontal fuel channels. 

Process instrumentation—transmitters, controllers, transducers, primary elements and sensors, and so on all the measurement and control devices used to monitor and control a process. 

Measurement and control devices in flow schemes of chemical plants are denoted by a combination of up to four letters ... 

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