Tolerance design

Rigorous design reviews must include the often highly complex resonance behavior of impellers and blading to ensure vibration-free or vibration-tolerant design of these critical turboexpander components. In other words, the manufacturer must perform comprehensive theoretical and experimental studies of the blade oscillations in the rotating system. 

Jeang, A. 1995 Economic Tolerance Design for Quality. Quality and Reliability Engineering International, 11, 113-121. 

Ross, P.J. (1988), Taguchi Techniques for Quality Engineering Loss Function, Orthogonal Experiments, Parameter and Tolerance Design, McGraw-Hill Book Company, New York, NY. 

To use the information gained from these types of experiments to model the process. The model can then be optimized and the tolerances set with the only requirement being computer time and confirmation experiments. The large number of experiments that would be required to perform the tolerance design study can be eliminated by this procedure. 

Tolerance design - if the parameter design step did not achieve the required results then this step can be used to decrease tolerances in the production, which involves however a cost increase... 

This chapter covers examples of system modifications made to prepare for maintenance. Each unwise modification created equipment damage. These incidents were simple changes intended to isolate, protect, clean, or clear equipment, and the methods chosen created problems. In some cases equipment was subjected to partial vacuum or positive pressure beyond the tolerable design limits. 

It is rarely possible to completely mitigate a risk other than by somehow taking action to avoid the associated hazard in the first place. Instead, risks need to be reduced so that they become As Low As Reasonably Practical (ALARP). Remedial project actions should be specifically documented — this is sometimes referred to as the Safety Case. Remedial actions may employ hazard avoidance strategies, introduce hazard tolerant design feamres, or apply specihc project management controls, or a combination. Further information on risk management for medical devices can be found in ISO 14971. ... 

Now that you ve minimized the impact of variation on your design, the last step in robust design is the tolerance design phase. Here you establish detailed tolerances or specifications that your design needs to operate within to meet expectations. For example, through our analysis of the skin patch design, we determined that expected variation, including noise, is approximately 0.033 mg/hr. This is more than acceptable if the required performance is 1.0 mg/hr it 0.2. 

This kind of plant design is also called single error forgiving or error tolerating design. For this purpose of identifying the error propagating pathways this qualitative use and evaluation of a fault tree analysis is especially suitable. 

Materials Algorithms Project Source of algorithms usefiil for modeling material behavior, http //www. msm.cam.ac.uk/map/rrrapmain.html Materials Properties Handbooks Operation Distributes the Aerospace Structural Metals Handbook, the Structural Alloys Handbook, the Damage Tolerant Design Handbook, and the Composite Failure Analysis Handbook, http // www.purdue.edu/MPHO... 

Incremental control, as described earlier, is a type of error-tolerant design technique. 

Taguchi differs between offline- and online-quality control. According to him, a sustainable and comprehensive system, parameter, and tolerance design, as part of the offline-quality... 

Tolerance Representation To be coherent, the tolerancing process has to use the same language based on a unified mathematical model to express tolerancing for each person involved during the process. To ensure this coherence between tolerance design and tolerance verification, there is a necessity of developing a complete tolerance model which should ... 

Simplification/Error Tolerance Designing facilities that make operating errors less likely, and that are forgiving of errors that are made... 

Human error is defined as an act outside the tolerance bounds. These are determined by the technical boundary conditions and may therefore be influenced— within limits— by the designer in the sense that the tolerance region becomes large (fault-tolerant design). This reduces the probability of human error. 

The fail-safe design concept implies the application of fault-tolerant design approaches... 

Previous research on software component failure dependencies seems to have been done primarily for parallel components, typically related to diverse and redrmdant components in fault tolerant designs such as N-version programming. These situations are characterised by components that are subject to the same input. We argue that failure dependencies must be viewed more generally, and that possible causes of dependent failure behaviour are more complex than current methods consider. 

The experience is that for I C systems approval the probabilistic goals are set and needs to be fulfilled. Reasonable consideration of software reliabihty is desired. This could lead to sometimes senseless way of involvement of software faults into Fault Trees and their quantification. The sensitivity analysis of system tolerance to software faults and their common cause aspects is much more meaningful and could reveal the weak points of the I C design. Even if this analysis is mostly quahtative unless we have applicable methodology to estimate particular basic events prob-abftistic parameters, the Fault Tree Analysis Method represents a good base to demonstrate a sound fault tolerant design. 

Wherever possible the design of SSCs should be a failure tolerant design. That is, should these items fail, their failure would tend to move the plant towards a safe plant condition. This technique has broader application to areas other than protection against internal hazards, but where vaUd it may help in mitigating the effects of postulated internal hazards. 

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