Mechanical considerations

Weld configuration in capillary type (left) and pushrod type transducer 

In the stress plane weld configuration, the area of the diaphragm under maximum stress coincides with the weld. This can create problems because the weld is different from the other parts of the diaphragm. The weld and the area right around it will be more susceptible to stress corrosion and brittleness problems. This is particularly true of Type 304 stainless steel because of embrittlement from carbide precipitation at the weld zone. 

The integral weld places the weld zone in a non-stressed location. This configuration is typical of the force-rod design and can readily be recognized by the lack of weld bead at the circumference of the diaphragm. Some newer pressure transducers do not employ the welded diaphragm construction but use a non-welded, one-piece diaphragm and tip assembly. 

The transducers with hydraulic coupling between the diaphragm and the strain gauge often use mercury see Fig. 4.5 (left). The amount of mercury is very small. The channel between the diaphragm and strain gauge is a small capillary. This transducer, therefore, is sometimes referred to as a capillary-type transducer. Mer- 

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An expression for the short-range repulsive force (which arises from the interpenetration of the electron clouds of the two atoms) can also be derived from quantum-mechanical considerations" as... 

Mechanical Considerations. The mechanical design of a fan and the various forces that fan parts must withstand are discussed ia Reference 14. The forces result from a combination of fluid, iaertial, and vibrational effects. 

Upper working temperatures (Mechanical considerations only)... 

Mechanical Considerations and Fiber Dimensions. The hoUow fiber is self-supporting, and is actuaUy a thick waU cylinder. The ratio... 

The large variety of displacement-type flmd-transport devices makes it difficult to list characteristics common to each. However, for most types it is correct to state that (1) they are adaptable to high-pressure operation, (2) the flow rate through the pump is variable (auxiliary damping systems may be employed to reduce the magnitude of pressure pulsation and flow variation), (3) mechanical considerations limit maximum throughputs, and (4) the devices are capable of efficient performance at extremely low-volume throughput rates. 

The choice of size, shape, and type of electrode is based on economic considerations and is usually determined by the characteristics of the gas and suspended matter and by mechanical considerations such as flue arrangement, the available space, and previous experience with the electrodes on similar problems. The spacing between collecting electrodes in plate-type precipitators and the pipe diameter... 

Safety Relief Valves Conventional safety relier valves (Fig. 26-14) are used in systems where built-up backpressures typically do not exceed 10 percent of the set pressure. The spring setting or the valve is reduced by the amount of superimposed backpressure expecied. Higher built-up backpressures can result in a complete loss of continuous valve capacity. The designer must examine the effects of other relieving devices connected to a common header on the performance of each valve. Some mechanical considerations of conventional relief valves are presented in the ASME code however, the manufacturer should be consulted for specific details. 

Induction motor mechanical considerations. If the motor is plaeed between the eompressor and the expander its shaft ends must be eapable of full torque transmission. Unit torque requirements are generally well above those required by the motor rating. The result is speeially designed motors. 

It is important to note that back pressure affects balanced PR valve capacities in the same way as for conventional valves, and appropriate factors are included in the sizing procedures. They are subject to the same recommended limits of maximum total back pressure (superimposed plus built-up) as conventional valves. In the case of balanced bellows valves, mechanical considerations must also be evaluated, since they may limit the maximum permissible back pressure. 

The foundation of shock-compression science is based upon observations and analyses of the mechanical responses of solid samples to shock-loading pulses. Although the resulting mechanical framework is necessary, there is no reason to believe that a sufficiently complete scientific picture can be based on mechanical considerations alone. Nevertheless, the base of our knowledge rests here, and it is essential to recognize its characteristics, and critically examine the work. 

Rukovena, F. and T. D. Koshy, Packed Distillation Tower Hydraulic Design Method and Mechanical Considerations, Ind. and Eng. Chem. Res., Vol. 32, No. 10 0993) p. 2400 (Used by permission. The American Chemical Society. All rights reserved.)... 

While glass can provide many of the desirable features of an ideal inert material, fabrication difficulties prevent its use for large-diameter chemical process equipment, and mechanical considerations would in any case make it necessary to treat any such equipment with great care. 

Iebo90a] Lebowitz, J.L., C.Maes and E.R.Speer, Probabilistic cellular automata some statistical mechanical considerations, pages 401- 414 in [jen90a],... 

In the preceding sections it has been shown that in a large number of crystals containing covalent bonds, cited as examples, the number and distribution of the bonds are in good agreement with a classification deduced from quantum mechanical considerations, and, moreover, there exist regularities in the observed interatomic distances which may be expressed by assigning covalent radii to the atoms, dependent in a... 

Quantum mechanical considerations predict that a jr-electron system containing six electrons should be particularly stable.205 Examples of conspicuously stable six electron systems are benzene and the cyclopentadienyl anion. The cycloheptatrienylium cation is also stable, presumably for the same reason.206-207... 

Hollow-fiber permeators, 26 22 Hollow fibers, 13 389-390 cellulose ester, 26 19 cellulosic, 26 18-20 ion-exchange, 26 15 mechanical considerations and dimensions for, 26 5-7 natural polymer, 26 23 polyacrylonitrile, 26 23 polyamide, 26 21-22 post-treatment of, 26 13-14 preparation of, 26 3 production of, 19 757 with sorbent walls, 26 26 technology of, 26 27 wet spinning of, 25 816, 817-818 Hollow-fiber spinning processes, 26 7-12 Hollow fiber spinning technology,... 

In Equations 4.51 and 4.52 k is Boltzmann s constant, T is the absolute temperature and the Eis s are the energy states of the molecules i. The statistical mechanical considerations in this book will refer to an ideal gas unless explicit mention is made to the contrary. For an ideal gas, a gas of non-interacting molecules, one can express the partition function Q of a collection of N molecules of species i in terms of the single molecule partition functions q as follows1... 

If, as above, the potential-energy barrier height is E, statistical mechanical considerations indicate that the atom will have sufficient thermal energy to pass over the barrier a fraction exp(— E/k T) of the time. If/is a characteristic atomic vibrational frequency, the probability p that during unit time the atom will pass the potential-energy barrier is given by... 

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