Unbalanced design

Another configuration, called an unbalanced design, has piston orientations that are neither in-phase nor 180° out-of-phase. In these configurations, the impact forces generated as each piston changes direction are not balanced by an equal and opposite force. As a result, the impact energy and the vibration amplitude are greatly increased. 

Another frequently overlooked design option in toxicology is the use of an unbalanced design, that is, of different group sizes for different levels of treatment. 

Unbalanced design for random effects. Suppose that the random effects model of Section 13.4 is to be estimated with a panel in which the groups have different numbers of observations. Let 7j be the number of observations in group i. 

To express as standard deviations, take the square root of each. The ANOVA estimates are applicable when the design is balanced and there are no missing data values using this method with missing data or an unbalanced design will result in misleading erroneous variance estimates. 

Because of the unbalanced design, the use of different laboratories for the isolation and determination, and the small numbers of laboratories involved with each type of sample, the data cannot be examined by conventional means and consequently cannot easily be compared with the interlaboratory variability of methodology for other contaminants. 

Unbalanced design highest SE among treatments is given. 

The modelling of phenomena related to severe accidents should be as realistic as possible to avoid unbalanced designs or unrealistic predictions of loads on the containment resulting in unrealistic predictions of doses outside the plant ... 

Dual-beUows assembhes, ie, universal-type expansion joints, are particularly vulnerable to squirm, and can experience elastic squirm at one-fourth the pressure of an individual bellows. When large amounts of offset are encountered, as is often the design basis, a pinwheel effect occurs because of unbalanced pressure forces. This effect tends to rotate the center-spool pipe which may lead to bellows mpture. Eor this reason the center spool should always be stabilized by hinges or tie-rod lugs to prevent such rotation. 

For tank internal pressures that do not exceed the weight of the roof plates, most tanks have conical roofs because these are the simplest and most cost-effective. When the pressure is increased beyond the weight of the roof plates, the roof-to-sheU area goes into hoop compression. A small portion of the roof, the roof-to-sheU angle, and the top few centimeters of the sheU act as a compression ring to resist the unbalanced forces from internal pressure on the conical roof. The internal design pressure for this case may be... 

Pre.s.sure. Pressure affects the choice of material and whether balanced or unbalanced seal design can be used. Most unbalanced seals are good up to 100 psig stuffing box pressure. Over 100 psig, balanced seals should be used. 

Nevertheless, unbalance is a major occurrence in either case and an unbalanced protection, in addition to short-circuit protection is imperative in all types of capacitor units. Hence it is also possible to design series protected capacitor units in larger sizes and for higher voltages, which are more economical, compared to smaller units. 

Designing a reactor for the middle phase to balance a large unbalanced current-carrying system... 

If the pump is put into service with a bent or unbalanced shaft assembly, its premature tailure can be traced to inadequate maintenance practices. The evidence does not lie. However, if the premature failure leaves evidence of a deflected shaft, this would be an operations or design failure. All too often, the mechanic is blamed. The two pictures above show how a deflected shaft appears when rotated 180 degrees (Figure 9-11 and Figure 9-12). 

The average unbalanced external seal is good for pressures of about 30 psig, while the balanced design will handle 150 psig. Special designs will handle much higher... 

Determining the number of theoretical and actual trays in a distillation column is only part of the design necessary to ensure system performance. The interpretation of distillation, absorption, or stripping requirements into a mechanical vessel with internal components (trays or packing, see Chapter 9) to carry out the function requires use of theoretical and empirical data. The costs of this equipment are markedly influenced by the column diameter and the intricacies of the trays, such as caps, risers, weirs, downcomers, perforations, etc. Calcvdated tray efficiencies for determination of actual trays can be lost by any unbalanced and improperly designed tray. 

Rotating machines subject to imbalance caused by turbulent or unbalanced media flow include pumps, fans, and compressors. A good machine design for these units incorporates the dynamic forces of the gas or liquid in stabilizing the rotating element. The combination of these forces and the stiffness of the rotor-support system (i.e., bearing and bearing pedestals) determine the vibration level. Rotor-support stiffness is important... 

Tolerance The penalty for having an unbalanced wall is the reduction of tolerance control. Tolerance limits are usually at least doubled. Also, with certain plastics it is more difficult to process them, such as those with low melt strength. Although the balanced wall is the ideal, having it is not always possible. Recognize that the unbalanced wall can be extruded with proper die design and control of the extruder line from upstream to downstream equipment. 

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