Specification of duty

The first step in defining a selection problem is to specify the general requirements of the process environment. An initial specification can be quite limited and is essentially confined to the scale, mode of operation and overall objective of the separation. These objectives and unavoidable restrictions can be specified before any experiments are undertaken. Other specifications, such as the need for filter sterility or the possibility of toxic or flammable hazards, can be considered at a later stage in the selection process. 

---

A feeder that can cope with aU reasonable changes of duty is a more valuable asset than one marginally able to accommodate the narrow specification of duty originaUy laid down for the equipment There are many circumstances that screw feeders cannot be expected to handle, as described in the section on hazards. The effect of hard compaction of fine damp product in the working clearances is most easily overlooked, especially when caused by preferential condensation if the ambient temperature falls below dew point when handling a hygroscopic bulk product. 

Weld inspection duties of personnel responsible for judging the quahty of welding with regard to specifications have been treated (15). Some of these duties involve the visual inspection of welds to determine if they are of the proper size, location, and type and are free of defects. Specifications of materials used must be checked, as must equipment and procedures. 

To complete the specification, the duty (heat transfer rate) and the outlet temperature of the crude oil needed to be calculated. 

It is assumed that any East Coast site would obtain styrene from Puerto Rico or foreign sources. Any site located in the Midwest would obtain its styrene from Louisiana. To compare these sites the cost of styrene from these different sources must be known, as well as import duties and the specifics of the freeport laws which might be involved. A plant of this size would probably contract to receive styrene, and what special price concessions might be obtained would need to be investigated. Since information on this was not available it will be assumed that the only difference in the price of styrene at the site is due to the cost of transportation. The cost of shipping by sea from Puerto Rico to Philadelphia (- 1700 miles) is 4.51 ton=O.230/lb. The cost of shipping styrene from Baton Rouge, La. to Cincinnati, Ohio (-900 miles) is 1.7O/ton=O.O90/lb (see Fig. 2-5).29... 

In optimization using a modular process simulator, certain restrictions apply on the choice of decision variables. For example, if the location of column feeds, draws, and heat exchangers are selected as decision variables, the rate or heat duty cannot also be selected. For an isothermal flash both the temperatures and pressure may be optimized, but for an adiabatic flash, on the other hand, the temperature is calculated in a module and only the pressure can be optimized. You also have to take care that the decision (optimization) variables in one unit are not varied by another unit. In some instances, you can make alternative specifications of the decision variables that result in the same optimal solution, but require substantially different computation time. For example, the simplest specification for a splitter would be a molar rate or ratio. A specification of the weight rate of a component in an exit flow stream from the splitter increases the computation time but yields the same solution. 

In order to define such a system completely, the following six quantities must be specified. The first four relate to the quantities and compositions of the materials used. Quantity (e) specifies the manner in which each unit operates, and quantity (f) involves either the number of units or a specification of the duty required of the plant. 

The behavior-anchored rating scale (BARS) method of performance appraisal is designed more specifically to assess behaviors necessary for successful performance. Most BARS methods use the term job dimension to mean those broad categories of duties and responsibilities that make up a job, requiring development of unique scales for each dimension. Managers often develop BARS in collaboration with employees well versed in the job. An example of how a BARS may look for a community pharmacy technician in dealing with customers is illustrated in Table 10-4. The BARS system lends itself to providing quality feedback, particularly if supplemented with qualitative comments on how to improve. A drawback is the time and effort required to develop an effective BARS appraisal. 

Solvent recovery systems would also necessitate the specification of condenser duties, distillation tower sizes, holding tanks, piping, and valves. It is important to note that the engineering design of an adsorption system should be based on pilot data for the particular system. Information can usually be obtained directly from the adsorbent manufacturer. The overall size of the unit is determined primarily by economic considerations, balancing the operating costs against the capital costs. 

The above equation shows that for a given surface area A and constant L, specification of the duty leads to the average driving force. 

Again, there are a number of industrial chemistry posts for which second or third rate ability is sufficient, and generally speaking a man of second or third-grade is to be preferred to a woman of that mental calibre, because he can be used for a wider range of duties and he is not usually, though he may be, quite as inert mentally. Women are sometimes taken on for routine posts because they can be offered a lower salary than men and because they sometimes show a placid contentment in routine posts and do not crave for responsibility or any duties beyond those for which they are specifically appointed.18... 

According to Art. 2 of Annex I to PEPAT, the lEE shall contain at least two elements, namely i) a description of the proposed activity, including its purpose, location, duration and intensity and ii) consideration of alternatives to the proposed activity and any impacts that the activity may have, including consideration of cumulative impacts in the light of existing and known planned activities. The basic elements of any lEE are therefore directly established by PEPAT. This is a relevant difference in comparison with Recommendation XIV-2, which did not lay down any specific procedural duty. 

To identify scope of practice privileges for the clinical pharmacy specialist (CPS) at the VA Medical Center, and to define criteria for the qualifications for these privileges. The CPS will be qualified and authorized to perform specific clinical duties to assure high quality health care and appropriate pharmaceutical care is provided to the veterans. 

A 100 kmol/h stream containing 50% mole benzene and 40% mole toluene is sent to a 12-stage distillation column on the sixth stage from the top. The column pressure is 100 kPa, with a total condenser and a reboiler. The distillate is the benzene product with a specification of 6.0% mole toluene, and the bottom is the toluene product with a specification of 6.0% mole benzene. These specifications will be met by manipulating the reflux rate and the reboiler heat duty. It is required to determine the best pairing between the manipulated and controlled variables. 

These evaporators are necessarily precision machines and therefore are more expensive than other types, particularly so if compared strictly on equivalent heat transfer area. When the performance for a specific evaporation duty is the basis of comparison, the thin-film evaporator is often the more economical choice because the larger heat transfer coefficient and higher driving force mean much less surface is required than for other evaporators (A = Q/U AT). Thin-film evaporator cost per unit area decreases significantly with unit size, and the largest available unit has 430 square feet of active heat transfer surface. 

Although the temperatures and the L/F s are commonly selected as the independent variables in the IN Newton-Raphson method, a heating or cooling duty may be selected as an independent variable, and the L/V for that stage specified. For example, by specification of the reflux ratio LJVU the condenser duty QCI and the temperature Tt become the independent variables for the first stage of the main column. The variable Lj/Vj is replaced by the new variable 07-, which is defined by Eq. (4-8). 

---