Time between overhaul

Performance based total productive maintenance aims to maximize equipment efficiency and time between overhaul, (overall performance effectiveness)... 

The motivation level for incorporating desalination plants into plant i nfrastructure varies. The Middle East has fuel resources in abundance— natural gas, clean oil, and residual oil—and technology available that will help it bum each of these options with acceptable efficiency. Desalination technology also helps the Middle East achieve its major operational objective, which is to extend the time between overhauls (TBOs) and therefore parts life [as defined by Kfe-[Pg.225]

Parameter adjustment for extension of TBOs (time between overhauls)... 

The preceding operational description indicates that fuel choice radically affects the required daily maintenance, overhaul, time between overhauls, and therefore effective life cycles of components. Undoubtedly, fuel choice can radically affect life-cycle assessment results. 

The implications for turbine maintenance are that if the shops use their new technology well, the longevity of parts can be extended, as can time between overhauls. Properly used, sophisticated repair technology can be used to promote the on-condition philosophy that end users are learning to value increasingly. This fact is best illustrated by looking at the nature of some of these repair processes. 

High availability and reliability are the most important parameters in the design of a gas turbine. The availability of a power plant is the percent of time the plant is available to generate power in any given period. The reliability of the plant is the percentage of time between planed overhauls. 

They can possibly extend the time between valve overhauls. 

Heavy industrial gas turbines are usually to be found in refineries, chemical plants and power utilities. They are chosen mainly because of their long and reliable running times between major maintenance overhauls. They are also capable of burning most types of liquid and gaseous fuel, even the heavier crude oils. They also tend to tolerate a higher level of impurities in the fuels. Heavy industrial machines are unsuitable for offshore applications because -... 

Where Cpx = the diagnostic coverage of the proof test and LT = the lifetime of the instrument. This period is often the time between major overhauls where an instrument is removed from service and completely renewed. 

Overhaul process units thoroughly by adding better catalyst, clean heat exchangers, filters, absorption towers, repair refractory lining, and ETP. Reduce idle time between batches and convert batch operation to continuous operation. 

For a repairable highly reliable system, the question is often when to replace or overhaul an old system. Replacing (orrenewing) the system too often is expensive, but an old deteriorating system may fail often requiring many repairs. The objective is to choose the time between renewals to minimize the cost. There are many possible cost models for this scenario, but we will suppose a simple linear cost model. 

Companies in all three case study industries undertook major reprioritizations of their corporate investments and expenditures on capital, maintenance, and labor. For example, one study of aviation maintenance found that airlines increased the amount of time between engine overhauls after deregulation, but did not experience a higher rate of engine failures as a result. This is presumably because the airlines successfully focused their maintenance efforts on the most significant problems. 

Reliability and maintainability analysis, based on breakdown, repair, and periodic maintenance statistics obtained for each plant item (or even on sensible guesses from experienced people). In conjunction with economic data, the model is used to predict plant availability and economic performance while taking into account the probability of failure of individual components and the repair time. The model may be used to make optimum choices on the provision of standby equipment, equipment enhancement, operational flexibility enhancement (including optimizing the period between overhauls), maintenance facilities, intermediate tankage or stockpile capacity, and capacity margins for individual equipment items. 

Continuous valve performance is based on long-term valve quality, which is achieved through a timely comprehensive valve maintenance programme. The maintenance programme is based on both performance experience (preventive maintenance) and expected behaviour (predictive maintenance). The interval between overhauls of safety related MOVs is 4 years. 

Traditional PM is keyed to failure rates and times between failures. It assumes that these variables can be determined statistically, and that one can therefore replace a part that is due for failure shortly before it fails. The availability of statistical failure information tends to lead to fixed schedules for the overhaul of equipment or the replacement of parts subject to wear. PM is based on the assumption that the overhaul of equipment by disassembly and replacement of parts restores it to a like-new condition with no harmful side effects. 

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