Lubricant design problem

The case study used to illustrate the concepts behind the strategy presented consist of a SC design problem that compares different technologies for the production of maleic anhydride (MA). MA is an important raw material used in the manufacture ofresins of phthalic-type and unsaturated polyester, co-polymers, surface coatings, plasticizers and lubricant additives (USEPA 1980). Two main technologies are available for its manufacturing by the catalytic oxidation of different hydrocarbons, benzene or butane (Chen and Shonnard 2004). Main process reactions are as follows ... 

The solution to Design Problem I is presented in this section. The lubrication approximation is used first to obtain a solution. This is followed by a numerical approach in which the die is broken into a series of annuli. 

Figure 16-16 shows the performance characteristic of a split-shaft turbine where the only power output limitation is the maximum allowable temperature at the inlet of the turbine section. In actual practice a torque limit, increased exhaust temperature, loss of turbine efficiency, aud/or a lubrication problem on the driven equipment usually preclude operating at very low power turbine speeds. The useful characteristic of the split-shaft engine is its ability to supply a more or less constant horsepower output over a wide range of power turbine speeds. The air compressor essentially sets a power level and the output shaft attains a speed to pnivide the required torque balance. Compressors, pumps, and various mechanical tinvc systems make very good applications for split-shaft designs. 

The installation of mixers on long shafts in tall tanks may become a problem if whip of the shaft develops. To reduce this possibility, a bearing support in the bottom of the tank will hold the shaft steady. Lubrication is by the tank fluid. Therefore this has limited application if abrasive particles are present. Normally the manufacturers designs avoid this extra bearing. Sometimes a guide bearing is installed about midway in the tanks to steady the shaft at this point. Again it is preferable to avoid this, if possible, and the manufacturer should make recommendations for the installation. 

The circulatory systems used in association with machine tools are generally conventional in nature, although occasionally their exceptional size creates special problems. The normal installation comprises a storage tank or reservoir, a pump and filter, suitable sprays, jets or other distribution devices, and return piping. The most recent designs tend to eliminate wick feeds and siphon lubrication. 

Corrosion resistance Although the equipment is designed to keep the water content at a minimum level, it is virtually impossible to eliminate it. The problem of rusting is therefore overcome by using corrosion inhibitors in the lubricant formulation. 

Pumps and compressors are designed per technical specifications and standards developed over years of operating and maintenance experience. Table lO-lO lists some of these standards for pumps and compressors and for related equipment such as lubrication systems and gearboxes which, if not properly specified, could lead to many operational and maintenance problems with the pumps and compressors. These standards specify design, construction, maintenance, and testing details such as terminology, material selection, shop inspection and tests, drawings, clearances, construction procedures, and so on. 

Seal design. In higher-pressure seals, more than one outboard (i.e., high differential) sleeve may be used. Generally, it is desirable to use a single sleeve because the inboard sleeve operates with up to 80 percent of the total pressure drop across it. The outer sleeve with the lower differential causes lubrication and cooling problems that can shorten the life of one or both sleeves. 

The most common scale-up problems are related to bulk density, powder flow, compactibility, and lubricant distribution. Therefore, any discussion of the issues of scaling-up capsule Ailing must take into account the design and operating principles of Ailing machines and their formulation requirements. 

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