Instrumentation drums

These are locations where condensation can accumulate. If allowed to accumulate, at some time it will enter the compressor as a slug of liquid and cause damage. If the piping configuration must contain a loop, the lower portion of the loop should be instrumented to detect the presence of liquid accumulation. Both for the drums and for the piping loops, pro vision must be made to drain any liquid that may be present. 

Sizing of the blowdown drum and location of the level instruments are based on the following guidelines. The reader should refer to Figure 2 while reviewing the following items. 

Instruments include pressure gauges to measure steam drum pressure, superheater outlet pressure, FW pressure, inlet and outlet draft pressure, and fuel supply and burner pressure. 

When the problem has been defined and needed background information has been studied, it is time to consider which analytical methods will provide the data you need to solve the problem. In selecting techniques, you can refer back to the other chapters in this book. For example, if you want to measure the three heavy metals (Co, Fe, and Ni) that were suspect in the Bulging Drum Problem, you might immediately think of atomic absorption or inductively coupled plasma atomic emission spectroscopies and reread Chapter 8 of this book. How would you choose between them Which would be more accurate More precise Does your lab have both instruments Are they both in working order What if you have neither of them What sample preparation would be needed ... 

The methods you select, whether instrumental or wet chemistry, must provide data that helps you answer a question related to the hypothesis. Ideally, the methods go right to the heart of the problem, to detect or measure an analyte central to the hypothesis. Ideally, the problem has a handle you can try to measure. (We use the term handle to describe the problem s key attribute. If a sample is offcolor, the color is the handle you want to use to solve the problem. If you have bulging drums, the gas causing the pressure is the handle. )... 

Limit of detection The method you choose must be able to detect the analyte at a concentration relevant to the problem. If the Co level of interest to the Bulging Drums was between 1 and 10 parts per trillion, would flame atomic absorption spectroscopy be the best method to use As you consider methods and published detection limits (LOD), remember that the LOD definition is the analyte concentration producing a signal that is three times the noise level of the blank, i.e., a S/N of 3. For real-world analysis, you will need to be at a level well above the LOD. Keep in mind that the LOD for the overall analytical method is often very different than the LOD for the instrumental analysis. 

Sample size and matrix Your choice of analytical method will also be dependent on the amount of sample you have, especially if the amount is limited and some of the methods under consideration are destructive to the sample. In the Bulging Drum Problem, sample size was not an issue. However, sampling the gas in the drum was challenging, since loss and contamination were quite likely. Getting the samples to the lab presented other challenges. Sample matrix is another important factor in method choice. As you know, some methods and instrumental techniques are not suitable for analysis of solids, without sample preparation. Table 21.8 lists some of the issues that must be considered for different sample matrices. 

These examples ask for the construction of flowsheets from the given process descriptions. Necessary auxiliaries such as drums and pumps are to be included even when they are not mentioned. Essential control instrumentation also is to be provided. Chapter 3 has examples. The processes are as follows ... 

In order for a process to be controllable by machine, it must represented by a mathematical model. Ideally, each element of a dynamic process, for example, a reflux drum or an individual tray of a fractionator, is represented by differential equations based on material and energy balances, transfer rates, stage efficiencies, phase equilibrium relations, etc., as well as the parameters of sensing devices, control valves, and control instruments. The process as a whole then is equivalent to a system of ordinary and partial differential equations involving certain independent and dependent variables. When the values of the independent variables are specified or measured, corresponding values of the others are found by computation, and the information is transmitted to the control instruments. For example, if the temperature, composition, and flow rate of the feed to a fractionator are perturbed, the computer will determine the other flows and the heat balance required to maintain constant overhead purity. Economic factors also can be incorporated in process models then the computer can be made to optimize the operation continually. 

A method of sizing reflux drums proposed by Watkins (1967) is based on several factors itemized in Table 18.1. A factor F3 is applied to the net overhead product going downstream, then instrument factors F, and labor factors F2 which are added together and applied to the weighted overhead stream, and finally a factor Ft is applied, which depends on the kind and location of level indicators. When L is the reflux flow rate and D the overhead net product rate, both in gpm, the volume of the drum (gal) is given by... 

Space needs to be provided for the auxiliaries, including the lube oil and seal systems, lube oil cooler, intercoolers, and pulsation dampeners. A control panel or console is usually provided as part of the local console. This panel contains instruments that provide the necessary information for start-up and shutdown, and should also include warning and trouble lights. Access must be provided for motor repair and ultimate replacement needs to be considered. If a steam turbine is used, a surface condenser is probably required with a vacuum system to increase the efficiency. All these additional systems need to be considered in the layout and spacing. In addition, room for pulsation dampeners required between stages has to be included. Aftercoolers may also be required with knockout drums. Reference 8 describes the requirements of compressor layouts and provides many useful piping hints. 

In lute 1941 Australian government researchers announced the development of a remote-controlled vehicle that can scout ahead of a rescue crew to locale missing and injured miners. Three stereo-video cameras permit the vehicle to operate in murky areas of a mine. The vehicle also includes gas analysis instrumentation. A fiber-optic cable, wound on a large drum, permits surface operators to convey instructions to the vehicle and to receive the results of gas analysis data and images of what the vehicle "sees. The vehicle is named after a burrowing marsupial, Numbat. 

With the widespread acceptance of the independently assessed ISO 9000 scheme, many companies will accept the analysis of the raw material supplier. Once the quality and consistency of the raw material are proven, only vital tests may be carried out. Because of the moisture sensitivity, opening and sampling of the drums may lead to faulty material if the drums are not properly resealed. The three vital control instruments are ... 

Density of the fluid whose level is to be measured can have a large effect on level detection instrumentation. It primarily affects level sensing instruments which utilize a wet reference leg. In these instruments, it is possible for the reference leg temperature to be different from the temperature of the fluid whose level is to be measured. An example of this is the level detection instrumentation for a boiler steam drum. The water in the reference leg is at a lower temperature than the water in the steam drum. Therefore, it is more dense, and must be compensated for to ensure the indicated steam drum level is accurately indicated. 

Heyrovsky s method, later called polarography, became an excellent analytical tool because it yielded qualitative and quantitative analyses of a solution in a single experiment. With Masuzo Shikata (1895-1964), Heyrovsky constructed the first polarograph, an instrument equipped with an electromotor that moved the Kohlrausch drum in accord with photographic paper rotating in a cylindrical cassette. It allowed the potential of the mercury-... 

Later, the uses for transparent sheet included rules and set-squares for geometrical drawing, while pearlescent materials were highly effective for show purposes—as in drum kits for dance bands, accordions, and other musical instruments. Some pearl finishes were produced much as veneers, for embellishing small items like the handles of pen-knives. 

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