OPERATIONAL HISTORY

The relay can be programmed to store the operating history of the cumulative service hours for each unit to obtain uniformity in ageing of each unit. 

Lillard, J. K. and Nieol, G., An Operating History of Turboexpanders in the Supereritieal Eluid Regime, 73rd Annual GPA Convention, New Orleans, Louisiana, Mareh 1994. 

Some of the more common problems are briefly discussed here. More detailed discussions, including unusual operating histories can be found in the references. ... 

Hower, T. C., and Kister H. Z.. Unusual Operating Histories of Gas Processing and Olefins Plant Columns, paper presented at A.I.Ch.E. Annual Meeting, November 2-7. 1986, Miami Beach, Florida. 

This is important information that describes the site and provides workers, visitors, and other personnel with pertinent site information. In addition to studying job specifications, contracts, and talking with project management, the author(s) should develop a detailed operating history of the site. The history is useful when determining potential site hazards. The type of information that can typically be located includes ... 

PRISIM embodies the IREP model of Arkansas 1. It includes extensive grapitivs of. simplified flow diagrams and relevant operating history from LERs (Licensee Event Reports required by Regulatory Guide 1.16) The plant model consists of 500 cutsets truncated by probabilities determined from normal operation. 

The tire analysis was assisted by SNL using methods described in NUREG/CR-4840 and the extensive operating history and fire experience. For 94 reactor-years from 1958 and 1987, 20 significant fire events were recorded. Hence, frequencies for the reactor building and the diesel generator buildings of 0.12 and 0.03 /y, respectively. A control room fire has never occurred at a SRS reactor. 

The number and severity of failures experienced by the equipment under study must be related to the operations of the facility. It would be inappropriate to assign the same operating histories to a continuously operating system and a system that operates intermittently. The number of hours in different operating modes (for example, 100% production versus shutdown) affect failure rate calculation and service description for taxonomy definition. 

It should be emphasized that qualitative consequence screening should only remove from further consideration those buildings where there is significant industry experience to support the assessment. In Example 5 cited above, a long and successful operating history exists to support the... 

If there is sufficient operating history to provide the labeled data and sufficient resources to label it, then it is desirable to rely on this information for data interpretation because it reflects the actual operation. With respect... 

If several processes require PrHAs, the PrHAs must be prioritized. A preliminary hazard analysis (PHA) may be used to determine and document the priority order for conducting PrHAs. At a minimum, the PSM Rule requires the prioritization to consider the potential severity of a chemical release, the number of potentially affected employees, and the operating history of the process, including the frequency of past chemical releases and the age of the process. 

In addition, conventional approaches assume that the only available information about the process is the known model constraints. However, a wealth of information is available in the operating history of the plant. In this case, together with spatial redundancy, there is also temporal redundancy, that is, temporal redundancy exists when measurements at different past times are available. This temporal redundancy contains information about the measurement behavior such as the probability distribution. The methods discussed in the first two sections of this chapter try to exploit these ideas by formulating the reconciliation problem in a different way. 

Large cogeneration units have had a long and successful operating history and are more durable than small-scale units. The larger systems operate at about 35% electrical conversion efficiency and 45% heat conversion efficiency. This means that 80% of the energy in the fuel is converted to heat or electricity. 

Persons familiar with the operation of the facility if the facility has no operating history, then operators from similar facilities may be included on the team. Frontline personnel are preferable, as they usually have the most accurate knowledge of the process equipment and procedures used during day-to-day operation, and are highly motivated to identify and eliminate hazards. 

OSHA/USEPA requires employers, such as the chemical industry service sector, to perform an initial process hazard analysis (PHA) on processes covered by PSM/RMP standards. The PHA must be appropriate to the complexity of the process and must identify, evaluate, and control the hazards involved in the process. Employers are required to determine and document the priority order for conducting process hazard analyses based on a rationale that includes such considerations as extent of the process hazards, number of potentially affected employees, age of the process, and operating history of the process. 

After the predefined tree has been used, a final generic cause test should be applied. The plant operating history, especially previous incidents, is considered to indicate if other generic management system problems exist. For example, repetitive failures may indicate generic causes that would not be apparent by only investigating the current incident. It is also an opportunity for a final overall review of the investigation to focus on the big picture, not just individual facts or causal factors. The team should ask, Are there any other causes that anyone has in mind that have not been included ... 

Finally, the investigation team considers generic causes that pertain to the overall management system for the process plant by considering the operating history and any other incidents that may have related causes. 

After the root causes have been identified from the predefined tree, a generic cause test should be applied. By considering the plant operating history, especially other incidents that may indicate repetitive failures, the investigator may identify other generic management system problems. 

Lee, S. Bacon, L. 2000. Operational history of the Ohaaki geothermal field, New Zealand. In Proceedings World Geothermal Congress 2000, Kyushu-Tohoku, Japan, 28 May-10 June 2000, 3211-3216. 

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