Failure prevention techniques

In addition, freezing and corrosion due to water accumulation in pipes, dead pockets, and instruments have caused numerous pipe failures. Some of these led to gas releases and fatal accidents. A detailed discussion on preventing water accumulation in column piping is presented elsewhere (210). Extensive discussions of winterization and freeze-prevention techniques are also available (120, 266). 

Specific health problems associated with the workplace have contributed to (he development of the modem safety and health movement. These problems include lung diseases in miners, can-c s caused by contact with various industrial chemicals, and lung cancer tied to asbestos. Widely used accident prevention techniques include failure minimization, fail-safe designs, isolation, lockouts, screening, personal protective equipment, redundancy, and timed replacements. 

As one reviews the early history of criticality safety there is good evidence that standard industrial accident prevention techniques served well. Where there were failures, the evidence was not obscure that Simple, straUd>tforward multiple techniques of procedural control would produce the level of accident control required even by a changing social climate. 

In the use of protective techniques, the basic procedure is to take some form of action, after an initial failure or malfunction, to prevent additional or secondary failures. By reducing the number of failures, such techniques can be considered as enhancing product reliability, although they also affect availability and product effectiveness. Another major consideration is the impact of maintenance, repair, and part replacement. If a fuse protecting a circuit is replaced, what is the impact when the product is re-energized What protective architectures are appropriate for postrepair operations What maintenance guidance must be documented and followed when fail-safe protective architectures have or have not been included ... 

Once identified the basic events analyzed for the occurrence of deviation (as an example no flow), it can observe that the basic events correspond to the failure mode of a component for that reason the FMEA technique is applied in order to identify the causes of failure that lead to the occurrence failure mode and consecutively select maintenance policies. As an example, the failure modes and effects analysis for the Electric Motor A.C. considering the failure Motor A.C. won t start is shown in Table 5. Those systems are submitted, according to manufacturer s recommendation, to a detailed maintenance policy based on predictive or preventive techniques. 

Thus, a visual assessment of the fracture surfaces of a joint which has been subjected to environmental attack does not indicate exactly the locus of failure and techniques such as Auger and X-ray photoelectron spectroscopy are needed to identify precisely the locus of failure. However, it does indicate that we should concentrate our attention on the interfacial regions if we are to understand and prevent such environmental failure of adhesive joints. 

We have only to look at the introductory clauses of ISO 9001 to find that the aim of the requirements is to achieve customer satisfaction by prevention of nonconformities. Hence quality management is a means for planning, organizing, and controlling the prevention of failure. All the tools and techniques that are used in quality management serve to improve our ability to succeed in our pursuit of excellence. 

Several techniques have evolved to identify potential sources of failure in designs and process. These techniques serve to prevent nonconformity and hence are preventive action measures. One such technique is Failure Mode and Effects Analysis (FMEA). 

This section discusses normal failure modes, monitoring techniques that can prevent premature failures, and the measurement points required for monitoring common machine-train components. Understanding the specific location and orientation of each measurement point is critical to diagnosing incipient problems. 

While preventive maintenance is concerned with regularly testing, and reconditioning equipment to prevent failures in service and premature deterioration, it follows that predictive maintenance procedures are concerned with the ability to predict when the equipment will fail and then developing schedules to implement timely repairs. Predictive maintenance does not imply that with the use of these techniques, failure modes in equipment can be prevented rather, it suggests that the occurrence of failure can be predicted and thus planned for. An appropriate example would be the inspection and change of a major compressor face-type oil seal where random heat checking (FM) has been observed over the years. 

Whereas HF theory is good for isolated, gas-phase molecules, some potential problems should be noted. One is the failure of a calculation to reach an SCF. There is no guarantee every SCF run will converge to a stable solution, without which all subsequent analyses of energies, charge distribution, and other molecular properties are precluded. Most calculations run okay, but sometimes electron density will oscillate between the two sides of a molecule, thereby preventing the achievement of an SCF. Techniques are available in many MO programs to damp down on the oscillation if it arises and to otherwise help reach a satisfactory endpoint, i.e., the SCF... 

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