Assembly errors

The high power density and narrow flow channels could cause fuel hot spots and flow starvation. Fuel experts at ORNL and ANL identified five types of defects three fuel IIIhomogeneities and two assembly errors to arrive at 4D, for fuel defects is 2.1 x 10-. / i... 

Two major sources of vibration due to mechanical imbalance in equipment with rotating parts or rotors are (1) assembly errors and (2) incorrect key length guesses during balancing. 

Even when parts are precision balanced to extremely close tolerances, vibration due to mechanical imbalance can be much greater than necessary due to assembly errors. Potential errors include relative placement of each part s center of rotation, location of the shaft relative to the bore, and cocked rotors. 

Assembly errors are not simply the additive effects of tolerances, but also include the relative placement of each part s center of rotation. For example, a perfectly balanced blower rotor can be assembled to a perfectly balanced shaft and yet the resultant imbalance can be high. This can happen if the rotor is balanced on a balancing shaft that fits the rotor bore within 0.5 mil (0.5 thousandths of an inch) and then is mounted on a standard cold-rolled steel shaft allowing a clearance of over 2 mils. 

Other assembly errors can cause vibration. Variances in bolt weights when one bolt is replaced by one of a different length or material can cause vibration. For setscrews that are 90° apart, the tightening sequence may not be the same at final assembly as during balancing. To prevent this, the balancer operator should mark which was tightened first. 

Cheung J, Estivill X, Khaja R, MacDonald JR, Lau K, Tsui LC, Scherer SW. Genome-wide detection of segmental duplications and potential assembly errors in the human genome sequence. Genome Biol 2003 4 R25. 

Measurement of internals is particularly important for those dimensions that change from one section of the column to another. Assembly errors can often result in internals being interchanged. If these are not detected, severe hydraulic problems can arise. One experience has been described (295) in which the rectifying trays were interchanged with the stripping trays. 

Mass accuracy is affected mainly by the precision of machining and assembly of the electrodes of mass analyzers as well as the stability of their electronic systems. Imperfections in the construction of mass analyzers originate from mechanical errors during manufacturing and assembly of components. It is difficult to ensure an overall machining and assembly error of <10 pm even for a small mass analyzer, such as IT. Assuming one dimension of a mass analyzer is roughly 6 cm, a 10 pm error corresponds to 0.017% relative error. The... 

Leakage rates can be estimated by assigning nominal leakage rates to system components. This method can be cumbersome and is not readily adapted to predict leaks resulting from fabrication and assembly errors. 

Figure 2. Partides selectively placed at designated traps on dedicated assembly templates by capillary assembly a) 200-nm particles in small traps, b) 350-nm particles in medium traps, c) 500-nm in large traps. Traps other than the designated ones remained empty. The assembly of 200-nm paiticle dimers in d) medium and e) large traps, and f) 350-nm particle dimers in large traps constitute assembly errors. The assembly direction is from right to left. Samples were o)ated with 10 nm gold for imaging enhancement using SEM. The scale bars are 2 pm.

Consequently, the symmetry may be lower and the structural characterization can be a challenge. As we show, MS contributes its share here, but the focus is again on the solution-phase reactivity. Self-sorting includes the possibility that assembly errors occur, which need to be corrected. MS is able to detect these errors and follow the error correction steps. 

Perhaps the most Important consideration In the design of oil lubricated bearings Is that of minimum oil film thickness. This decides the tolerance of the bearing to angular misalignment resulting from assembly errors or shaft deflections. It also Influences the wear arising from oil... 

The failure rate/time curve for most items is shaped like a bath, the failure rate being plotted vertically and the time horizontally. The higher failure rate soon after commissioning is due to assembly errors and premature failure of defective components. For the more important items, at least, it is prudent to increase the number of inspections during this time. After this teething period, the failure rate should fall to a minimum until the apparatus nears the... 

There are other assembly errors that can cause vibration. Variances in bolt weights when one bolt is replaced by one of a different length or material... 

Figure 4.78 HR system assembly errors causing loss of leak proofing Reproduced with permission from Dynisco HotRunners)...

Use Poka-Yoke (mistake-proofing) techniques to help reduce operator assembly errors by prescribing component features and/or assembly procedures to aid correct assembly. 

Assembly errors increase if components/sub-assemblies are complex, difficult to align, insert or if there is restricted access for insertion. 

The causes of i failure mode (potential causes of failure) are the physical or chemical processes, design defects, quality defects, part misapplication, or others, which are the reasons for failure (Military Standard (1980)). The causes listed should be concise and as complete as possible. Typica causes of failure are incorrect material used, poor weld, corrosion, assembly error, error in dimension, over stressing, too hot, too cold, bad maintenance, damage, error in heat treat, material impure, forming of cracks, out of balance, tooling marks, eccentric, etc. It is important to note that more than one failure cause is possible for a failure mode all potential causes of failure modes should be identified, including human error. 

The lathe spindle was assembled in the following manner with the adhesive. The bearings were first installed on the spindle and the sleeves bonded. The spindle nut was then tightened to apply appropriate pressure on the bearings. Then the whole spindle unit was inserted into the spindle box with the adhesive on its sleeves. The spindle location was adjusted during the pot-life of the adhesive, so that assembly errors in the parallelism between the spindle and the carriage motion, and difference between the heights of the head and tail stocl, were reduced to tolerable levels. 

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