Unexpected Service Conditions

Fat contaminated the polyurethane floor at a margarine production factory causing it to break up. It is probable that the floor material manufacturer was not aware of the circumstances of use so that to him/her it would be unexpected service conditions, whereas considering the people who specified the floor it would be a case of incorrect choice of material. Yet again, it could be that the factory owner did not disclose the actual use of the floor area in question. Because the investigators were only required to prove damage from fat the actual human errors involved are not known. 

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Design error Inappropriate material Manufacturing fault Incorrect installation Unexpected service conditions Deliberate or accidental misuse. 

With the possible exception of unexpected service conditions, the root causes can all be attributed to human error, even if in some cases the error was very difficult to foresee. When the reasons for failures are spelt out like this it all seems obvious but the fact is that, however obvious the steps to prevention may seem, failures happen. 

Simple illustrations of the variety of service conditions are the difference in climates of Moscow, London and Phoenix, or the different chemicals that might come in contact with an engineering component. The implications are that uncertainty may mean designing for the worst case (or being unexpectedly caught out) and the variation potentially calls for testing (or making extrapolations) under many conditions. 

Firstly, it should be noted that predicted service life cannot take into account poor workmanship, incorrect use or maintenance, faults due to an assembly of components where each one is only tested individually, or unexpected operating conditions. 

Assessment starts with a general calculation based on assumed service conditions and identification of the critical parameters and components, with particular regard to risk. Although relatively crude, this ranking of components is probably correct. It is followed by assessment of the actual service conditions experienced - data that should be available for process plant. This can identify the accumulated exposure or dose , or confirm that parameters lie below a threshold level. It can also identify unexpectedly large values, due for example to rapid transient variations, which would not be found in the planned service history. Such large parameters can have an exceptional effect on service lifetime. This is followed by inspection (materials, dimensions, etc.) of the critical components either on the plant or, if allowed, of the dismantled component, to provide a more confident... 

Detection of process deviations detrimental to the service life of components Diagnosis of unexpected corrosive conditions Data collection in complex environments... 

The predictive models aim to produce real measurable parameters that can then be monitored. If the measured variable starts to diverge from the predicted value the life prediction can be amended. However, the monitoring may still identify unexpected changes in the operating parameters rather than in the material. Post-exposure testing of extracted specimens can be performed, but, as some level of acceleration is required, the conditions will never be the same as if the component or specimen had continued in service. 

Dynamic task allocation, on the other hand, makes decisions based on real-time information and is therefore more adaptive to changes. This chapter assumes a set of dynamically released tasks to be completed by a team of robots, and the conditions of the work process keep changing during task execution. This kind of dynamic working environment is ubiquitous in real-life applications, such as exploring and mapping by robots in unknown environments, unexpected adversarial targets in combats, stochastic pickups and delivery transport services, etc. [5]. 

This includes a complete examination and involves disassembly and inspection of each part and replacement where necessary. Conduct maintenance at least annually or more often if conditions warrant. Accomplish hydrostatic testing of portable fire extinguishers to protect against unexpected in-service failure. Failure can occur due to internal corrosion, external corrosion, and damage from abuse. Perform hydrostatic testing using trained personnel with proper equipment and facilities. OSHA Standard 29 CFR 1910.157 (Table 1) provides test intervals for extinguishers. 

Unforeseen events may occur during the execution of planned routing. These include unexpected traffic congestion, vehicle breakdown, blocked roads, and new customer orders. These events may cause disruptions in the scheduled routes and services of customers, and must be addressed appropriately. Dynamic routing facilitates incorporation of add and drop stops as needed, adjustments to traffic and weather conditions, and minimizing operating costs. 

Environmentally induced failures cost industries billions of dollars every year. A 1995 study reported that the cost impact of corrosion to the U.S. economy totaled nearly 300 billion annually, about 4% of the gross domestic product (Kuruvilla, 1999). Corrosion failures are usually caused by electrochemical reactions on the surfaces between the components and the environments. Typically, these corrosion failures occur way into their life cycles, otherwise defined by the loading conditions. They often occur unexpectedly in service. It is paramount to manage corrosion control and assess part corrosion resistance for a critical structural component of a machine. In automotive industries, corrosion management is part of the automotive... 

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