Failures, engineering causes

Centralized Reliability Data Organization Input Guide Nuclear 1800 Component failure events causing abnormal operation engineering data for 20,000 components found in liquid metal reactors (e.g., LMRs). Gives generic data lor 45 equipment items (valves, pumps, etc.) Liquid metal reactor sites and test facility systems and components 62. 

Corrosion of most common engineering materials at near-ambient temperatures occurs in aqueous (water-containing) environments and is electrochemical in nature. The aqueous environment is also referred to as the electrolyte, and, in the case of underground corrosion, it is moist soil. Corrosion is a common form of structure degradation that reduces both the static and cyclic strength of a pipeline. There is always the chance that pipelines could leak or rupture, and a pipeline failure can cause serious human, environmental, and financial losses [3-5]. 

May 5,1973, Miami, FL. All three engines in an Eastern Airlines L-1011 jumbo jet failed because 0-ring seals were missing. The failure nearly caused the pilot to ditch the plane and its 172 passengers in the Atlantic Ocean. During the investigation of this incident, mechanics for the airline testified that it was too dark in the service area to see if the very small seals were in place. ... 

Troubleshooting pumping difficulties is a job that operating engineers face every week. Count the number of pumps on your unit the total will likely exceed 100. A major part of a unit s mechanical budget is allocated to pump maintenance. Many pumps sent to the shop are just disassembled, reassembled, and returned to the unit. The shop machinists have found nothing wrong with them. Also, many pump mechanical failures are caused by operator errors. 

Failure mode describes how the component can fail. All credible failure modes and their causes should be listed. Since a failure mode may have more than one cause, all probable independent causes for each failure mode should be identified and described. Three failure mode causes are shown in the sample worksheet. Some engineers will create a separate failure cause column tied to each failure mode so that causes are more easily tracked. Here, the two are combined for ease of understanding. Typical failure modes (conditions) that should be considered are... 

Optional standby power systems are for systems whose failure could cause effects such as damage to process equipment, interruption of manufacturing processes, loss of airflow to maintain cleanliness conditions, etc. Although not required by code, process engineers may want selected production equipment on optional standby power. Loads which are not related to life safety, yet are desired to be connected to the emergency power system, must be separated and controlled by their own transfer switches. The nonlife-safety loads must be able to be shed, if necessary, due to a generator malfunction. 

Hammond, Rolt. Engineering Structural Failures The Causes and Results of Failure in Modern Structures of Various Types. New York Philosophical Library, 1956. 

Fail-safe is a system characteristic whereby any malfunction affecting safety will cause the system to revert to a state that is known to be within acceptable risk parameters. Fail-safe provides the ability to sustain a failure and retain safe control of the system or operation, or revert to a state which will not cause a mishap. A fail-safe design should be provided in those areas where failure can cause catastrophic damage to equipment, injury to personnel, or inadvertent operation of critical equipment (source MIL-STD-1472E Human Engineering, Design Criteria Standard, 1998). 

Control of quality and state of engine parts, components of electric, pneumatic, hydraulic systems, load-bearing elements Investigations of parts and units failure causes... 

Evidence of localized corrosion can be obtained from polarization methods such as potentiodynamic polarization, EIS, and electrochemical noise measurements, which are particularly well suited to providing data on localized corrosion. When evidence of localized attack is obtained, the engineer needs to perform a careful analysis of the conditions that may lead to such attack. Correlation with process conditions can provide additional data about the susceptibility of the equipment to locaHzed attack and can potentially help prevent failures due to pitting or crevice corrosion. Since pitting may have a delayed initiation phase, careful consideration of the cause of the localized attack is critical. Laboratory testing and involvement of an... 

The accuracy of absolute risk results depends on (1) whether all the significant contributors to risk have been analyzed, (2) the realism of the mathematical models used to predict failure characteristics and accident phenomena, and (3) the statistical uncertainty associated with the various input data. The achievable accuracy of absolute risk results is very dependent on the type of hazard being analyzed. In studies where the dominant risk contributors can be calibrated with ample historical data (e.g., the risk of an engine failure causing an airplane crash), the uncertainty can be reduced to a few percent. However, many authors of published studies and other expert practitioners have recognized that uncertainties can be greater than 1 to 2 orders of magnitude in studies whose major contributors are rare, catastrophic events. 

The original steam generators were simple pressure vessels that were prone to caiasirophic failures and loss of life. Due to better boiler design, tube-fired boilers, and boiler inspections, the incidence of catastrophic failure is now to a rare event (about once every 100,000 vessel-years). In Great Britain in 1866, there were 74 steam boiler explosions causing 77 deaths. This was reduced to 17 explo.sions and 8 deaths in 1900 as a result of inspections performed by the Manchester Steam User Association. In the United States, the American Society of Mechanical Engineers established the ASME Pressure Ves.sel Codes with comparable reductions. 

The first perspective is the traditional safety engineering approach (Section 2.4). This stresses the individual factors that give rise to accidents and hence emphasizes selection, together with motivational and disciplinary approaches to accident and error reduction. The main emphasis here is on behavior modification, through persuasion (motivational campaigns) or pimishment. The main area of application of this approach has been to occupational safety, which focuses on hazards that affect the individual worker, rather than process safety, which emphasizes major systems failures that could cause major plant losses and impact to the environment as well as individual injury. 

Many data collection systems place the primary emphasis on the technical causes of accidents. There is usually a very detailed description of the chemical process in which the accident occurred, together with an in-depth analysis of the technical failures that are seen as the major causes. The human or system failures that may have contributed to the accident are usually treated in a cursory manner. Technically oriented reporting systems are very common in the CPI, where engineers who may be unfamiliar with human factors princi-... 

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