Repair - meaning

For many substances the body s own mechanisms for de-toxification and repair mean that low doses of some chemicals can be tolerated without experiencing any adverse effects. However, once a certain threshold has been exceeded then the degree of adverse effect is related to the dose. The highest dose at which no adverse effects are observed in the most susceptible animal species is identified as the No Observed Adverse Effect Level (NOAEL). The NOAEL is used as the basis for setting human safety standards for food additive Acceptable Daily Intakes (ADIs)4... 

Looping of one strand or other of the DNA during copy or repair means that some genetic material may be gained or lost (Figure 5.3.10). 

For purposes of this section, the term emergency repair means a repair in a school building that was not planned and was in response to a sudden, unexpected event that threatens either-... 

In Eq. (9.98)is the failure rate. Analogously one describes repair by the repair rate [t, which is the reciprocal value of the mean duration of repair (mean time to repair MTTR), i.e. = 1/Tr... 

Smal, T. Stankiewicz, G. 2010. Devdopment trends of service and repair means in the Polish Armed Forces (In Polish). Logistykano. 6, CD-Room. ISSN 1231-5478. 

Cost of spare part during the inspection operation Mean time to repair Mean time between failures Non-Homogeneous Poisson Process Cumulative number of failures up to time t... 

Early failures may occur almost immediately, and the failure rate is determined by manufacturing faults or poor repairs. Random failures are due to mechanical or human failure, while wear failure occurs mainly due to mechanical faults as the equipment becomes old. One of the techniques used by maintenance engineers is to record the mean time to failure (MTF) of equipment items to find out in which period a piece of equipment is likely to fail. This provides some of the information required to determine an appropriate maintenance strategy tor each equipment item. 

Make maintenance planning more flexible, by providing, wherever possible, viable alternatives to unplanned shutdowns and to immediate component replace or repair actions. Increased flexibility of maintenance planning, by conditionally running under surveillance components with potential or incipient stmctural integrity problems, means improved plant availability, reduced energy replacement and maintenance costs. 

Insufficient information about the properties, layout pattern of small defects, potential for their growth in time, usually leads either to an unjustified rejection (repair) or to underestimation of the importance of the defect and, as aconsequence, construction failure. Use of automated computerised means of control allows safe service of the old constructions, periodically repeating the UT and monitoring the development of discontinuities in the metal. The main idea of such policy is periodical UT of development of discontinuities or, in a more general form, monitoring of the metal condition. 

The mean time between failures MTBF is used as a measure of system reflabiUty, whereas the mean time to repair MTTR is taken as a measure for maintainabihty. Eor example, a system with an MTBF of 1200 h and a MTTR of 25 h would have an availabihty of 0.98. Furthermore, if only an MTBF of 800 h could be achieved, the same availabihty would be realized if the maintainabihty could be improved to the point where the MTTR was 16 h. Such trade-offs are illustrated in Figure 3, where each curve is at a constant availabihty. 

Fig. 3. System availability trade-off curves. MTBF = mean time between failures MTTR = mean time to repair.

Since it is good practice to maintain a selected inventory of spare parts for drives, economy can be achieved by standardizing conveyor drives throughout the plant. For example, intermediate speed reduction by means of V belts, sheaves or chains, and sprockets can frequently permit using the same speed-reducer size for several drives. Thus, it may be necessary to keep only one repair-stock speed reducer for a number of conveyors. 

The difficulties of such operations on the research platform Nordsee are described in Ref. 9. The Murchison platform was provided with a combination of impressed current protection and galvanic anodes because there was a limit to the load to be transported [12]. The anodes for platforms are installed and provided with cables at the yard. They are installed with redundancy and excess capacity so that no repairs are necessary if there is a breakdown. The lower part of the platform up to the splash zone is usually placed in position in the designated location at least 1 year before the erection of the deck structure so that impressed current protection cannot initially be put in operation. This requires cathodic protection with galvanic anodes for this period. This also means that the impressed current protection is more expensive than the galvanic anodes. 

Equation 2.5-43 is a definition of availability." Since 1/p = MTTR (mean time to repair) and 1/A, = MTTF (mean time to failure) A more conventional definition is given by 2.5-44. 

Unavailability = I availability. If p >A, it is, asymptotically, found from equation 2.5-43 to be equation 2.5-45, where t -- 1/p is the mean time between repairs. 

With the Industrial Revolution, life became more complex but it was not until World War II that reliability engineering was needed to keep the complex airplanes, tanks, vehicles and ships operating. Of particular concern was the reliability of radar. Prior to this time equipment was known qualitatively to be reliable or unreliable. To quantify reliability requires collecting statistics on part failures in order to calculate the mean time to failure and the mean time to repair. Since then, NASA and the military has included reliability specifications in procurements thereby sustaining the collection and evaluation of data build statistical accuracy although it adds to the cost. 

The GIDEP Reliability-maintainability Data Bank (RMDB) has failure rates, failure modes, replacement rates, mean time between failure (MTBF) and mean time to repair (MTTR) on components, equipment, subsystems and systems. The RMDB includes field experience data, laboratory accelerated life test data, reliability and maintainability demonstration test results. The... 

EPRI NP-2433 addresses diesel generator reliability at nuclear power plants. The sources include plant records, utility records, and LERs. The report gives frequency of failure to start, failure. o continue running, and mean repair times. 

Since dependency analysis is not needed, we can go on to the BUILD program. Go to FTAPSUIT and select 5 "Run Build." It asks you for the input file name including extender. Type "pv.pch," It asks you for name and extender of the input file for IMPORTANCE. Type, for examle, "pv.ii . It next asks for the input option. Type "5" for ba.sic event failure probabilities. This means that any failure rates must be multiplied by their mission times as shown in Table 7.4-1. (FTAPlus was written only for option 5 which uses probabilities and error factors. Other options will require hand editing of the pvn.ii file. The switch 1 is for failure rate and repair time, switch 2 is failure rate, 0 repair time, switch 3 is proportional hazard rate and 0 repair time, and switch 4 is mean time to failure and repair time.)... 

Accident progression scenarios are developed and modeled as event trees for each of these accident classes. System fault trees are developed to the component level for each branch point, and the plant response to the failure is identified. Generic subtrees are linked to the system fault trees. An example is "loss of clcciric power" which is analyzed in a Markov model that considers the frequencies of lo,sing normal power, the probabilities of failure of emergency power, and the mean times to repair parts of the electric power supply. 

Customer supplied products that are issued for incorporation into supplies don t often require maintenance however, items for use in conjunction with the contract may be retained for such a duration that maintenance is necessary. If the products require any maintenance you should be provided with a maintenance specification and the appropriate equipment to do the job. Maintenance may include both preventive and corrective maintenance but you should clarify with your customer which it is. You may have the means for preventive maintenance, such as lubrication and calibration, but not for repairs. Always establish your obligations in the contract regarding customer supplied product, because you could take on commitments for which you are not contractually covered if something should go wrong. You need to establish who will supply the spares and re-certify the equipment following repair. 

The term approval can be taken to mean certification or qualification, the difference being that certification is performed each time the equipment is repaired and qualification only when the equipment is introduced into service. The standard only refers to the term qualification in connection with special processes, but this clause does not distinguish between special and ordinary processes and equipment. However, there are two levels of approval that apply to processes and equipment initial qualification approval and periodic setting-up approval. 

It should also not be assumed that these requirements are only intended for implementation by a department with the title Inspection or Test. Whenever a product is supplied, produced, or repaired, rebuilt, modified, or otherwise changed, it should be subject to verification that it conforms with the prescribed requirements and any deficiencies corrected before being released for use. That is what control means. Control is not just the inspection part of the process and hence quality control , which for years was the name given to inspection departments, was misunderstood. Inspection and test don t control quality. Inspection and test merely measure the quality achieved and pass the results to the producer for remedial action. 

Disposition means to dispose of or decide what to do with the nonconforming item whether to use it, repair it, scrap it, etc. The options available are discussed later. By providing for the disposition of product you need to determine the action to take and notify... 

Repair and maintenance records were analyzed to determine failure rates and distribution of failure modes. Preliminary findings are reported which include the Weibull distribution characteristics. Failure mode distributions are approximate. Overall mean-time-between-failure is given for the kiln, leach tank, screwfeeder, tank pump, tank gearbox, and kiln gearbox. The study was confined to an analysis of unscheduled repairs and failures. 

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