1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$.15!,)49G0G0/ these objectives should be well defined and documented at the outset.2 Fascicle II.3 - Rec. E.880The specific objectives of the field data collection and presen
2、tation are as follows:a) to provide for a survey of the actual performance level of the items monitored for information tomanagement, operation and planning, maintenance support, training of personnel, etc.;b) to indicate a possible need for the improvement of: items already installed and in operati
3、on, or further items to be delivered;c) to compare the specified or predicted characteristics of the item(s) with the actual field performance;d) to improve future designs;e) to improve predictions (data bases and procedures);f) to inform the provider about the performance of items on a regular or o
4、n a single occasion basis;g) to have a common reporting basis.4 Sources and means of data collectionIn the following, the various information sources are described and the methods for systematically collectinginformation are outlined.4.1 Sources of dataThe following sources of data may generally be
5、available: maintenance activities; repair activities (on site, repair and/or complaint centre); performance observation activities (e.g. anomaly reports, traffic measurements); existing information (e.g. stocklist, installation list, modifications, a regularly updated data base forconfiguration cont
6、rol purposes).4.2 Means of collecting dataIt is not intended to recommend any particular format for the recording medium (e.g. paper based orcomputer data base), however it should be recognized that early consideration of the format is necessary and importantin setting up an effective data collectio
7、n scheme and also aids subsequent successful processing.Frequently the recording of data will be by manual means but automated and interactive data collectionsystems may be also considered. The advantages to be gained from holding data in a form suitable for processing by anelectronic data processin
8、g system include easy and accurate updating of information and the possibility of performingnew extended analyses.Data may be collected by one or several of the following reporting means.4.2.1 Operation reportingData reporting should be supported by information on the use of the items. Where systems
9、 are in operationfor the reporting of all failures, it is necessary to collect data on the use of the whole population of items (the totalnumber of similar items under observation).4.2.2 Failure reportingAt any level, failure reporting is dependent on the fault coverage test resources used at the co
10、nsidered level:cases such as “fault not found” or “right when tested” should be clearly mentioned.Failure reporting should cover all failures that have been observed. They should also contain sufficientinformation to identify failures. Failures considered to be attributable to any maintenance action
11、 should be so noted.Fascicle II.3 - Rec. E.880 3The failure reporting should be sufficiently comprehensive to cover the requirements of detailed investigationof an individual failure and the resulting fault. Where economic reasons or lack of resources make it undesirable tocollect all of the failure
12、 data indicated, it may be desirable to agree upon a shortened form of report which can be usedto collect limited data on all relevant failures, with an option to call for the full report in specific cases.4.2.3 Maintenance reportingThe maintenance report should contain all information relevant to t
13、he manual or automatic action taken torestore the item.When there is need to distinguish between corrective maintenance and preventive maintenance reporting, ifno replacements or repairs are made, the action can be classified as a preventive maintenance report. If a preventivemaintenance action resu
14、lts in a replacement or repair, the report may be treated as a corrective maintenance report eventhough the item has in fact not failed in operation.4.3 Storage, updating and checking proceduresIndependently of the structure chosen for the data storage, data should be checked at the time of input so
15、 as toensure validity.It is evident that every data bank needs an in-depth study appropriate to its specific requirements, in order todefine the most suitable method of data checking, error correction, and updating.5 List of dependability measuresThe selection of the data to be collected is very dep
16、endent on the kind of performance measures to beevaluated/estimated.Field data reporting may have to be limited by economic necessity to the minimum necessary to meet therequirement, whilst recognizing that collection systems should be capable of future expansion.It is likely that certain data may b
17、e needed for more than one purpose, and careful consideration can thereforeresult in the most cost-effective data collection scheme.The dependability measures that might be taken into consideration are listed as follows.5.1 Reliability performanceFailure rateFailure intensityReplacement intensityMea
18、n operating time between failures.1)Up time.5.2 Maintainability performance5.2.1 Time related performance.1)Down time.1)Technical delay.1)Fault localization time.1)Fault correction time.1)Restart time_1). indicates according to specific applications a mean value or a fractile.4 Fascicle II.3 - Rec.
19、E.880.2)Checkout time.2)Repair time.2)Active corrective maintenance time.5.2.2 ProbabilitiesProbability of fault coverageProbability of false alarmProbability of fault nondetectionProbability of alarm detectionProbability of a failure being localized within a given number of replaceable units.5.3 Ma
20、intenance support performance5.3.1 Time related performance.2)Logistic time.2)Administrative delay.5.3.2 ProbabilitiesSpare parts shortage probabilityTest resource shortage probabilityHuman resource shortage probability.5.4 Availability performanceSteady state availability.2)Accumulated down time.6
21、Data requiredConsideration of the foregoing objectives defines the need for a system which provides for the collection ofdocumented data covering:a) the identity of items or population of items under observation;b) operational conditions;c) maintenance support conditions;d) performance monitoring.Fo
22、r each individual item, sufficient information has to be recorded to clearly identify the item itself and itsoperating environment.Depending on the item under consideration (e.g. equipment, printed circuit board, component, personnel),and on the depth and kind of analysis of collected data, the nece
23、ssary item identification data shall be used, on a caseby case basis.The item identification should also allow the analysis of the relationships between the items for which data iscollected.In relation to the particular analysis to be done, some items may be considered as equivalent, thereforesepara
24、te small items need not to be collected in such cases._2). indicates according to specific applications a mean value or a fractile.Fascicle II.3 - Rec. E.880 5The following information may be needed and could be collected or will be available from existing sources: type of item manufacture/provider
25、item configuration individual No. or serial No. date of manufacture supplier delivery date installer (company) installation date customer (name) site (geographic) system.Consideration should be given to possible limitations due to non-completeness of collected data or possibledifficulties in data co
26、llection or particular assumptions made for the collection itself.The choice of the kinds of data to be collected and the design of the related collection procedure depend onmany factors, some of which are: the required end-result; the diversity of components or systems; the duration of the data col
27、lection project; the data handling method (manual or computer based); a sufficient knowledge of the capability to collect the required quantity of information and theaccessibility to data to be gathered.6.1 Number of items to be consideredThe number of items to be considered depends mainly on the ch
28、aracteristics to be dealt with, the statisticalaspect of the evaluation to be made and the cost involved.6.2 Information on items being considered6.2.1 Operating conditions6.2.1.1 Environment classesa) Fixed (outdoors, indoors, underground, undersea, off-shore, etc.);b) Portable (item specially buil
29、t for easy transportation by one man only);c) Mobile (in motor vehicle, in ship, in aircraft);d) Other (specify).6.2.1.2 Specific environment dataa) Climatic conditions weather-protected, not weather protected, air temperature, air pressure, humidity;b) Electrical environment (EMC);c) Mechanical con
30、ditions (vibration, shocks, bumps);d) Mechanically active substances (sand, dust, etc.);6 Fascicle II.3 - Rec. E.880e) Chemically active substances;f) Biological conditions.6.2.1.3 Mode of operationa) Continuous;b) Intermittent (give cycle);c) Stand-by;d) Single operation (e.g. one shot devices);e)
31、Storage.6.2.1.4 Load conditionsa) Overload;b) Other (specified).6.3 Failure and fault description Fault recognition: symptoms and indications, fault detected, fault not detected, false alarm. Item fault mode (identification of functions affected). Failure causes:a) Inherent to item under observation
32、;b) Misuse failure;c) Induced by maintenance or administrative action;d) External to item under observation;e) Secondary (caused by related item);f) Other.In cases where the failure immediately follows a period of transport, storage or stand-by, the relevantconditions shall be stated. Fault conseque
33、nces List (identification) and physical location of faulty replaced parts:a) quantity of suspected replaceable items;b) quantity of replaced items. Fault evidence and documentation (printouts, photograph, etc.). Action taken: Replacement, repair, adjustment, modification, lubrication, etc. Active ma
34、intenance time (diagnostic + repair + tests + . . .). Downtime, including, where applicable: undetected fault time, fault localization time, reconfiguration time3), technical delay, logistic delay, administrative delay, fault correction time, checkout time, restart time._3)Time required for automati
35、c reconfiguration (if manual operations are needed, they are integrated into technical delay).Fascicle II.3 - Rec. E.880 76.4 Maintenance support data: spare resources shortage, test resources shortage, resources shortage.7 Data presentation for evaluationWhen collected data is offered for subsequen
36、t evaluation by using approximate statistical methods, allconditions for their correct use and understanding should be clearly stated.These conditions should encompass the purpose of the data gathering especially with respect to type andvariation of the data chosen. Information on the circumstances
37、should also be provided such as when (e.g. busy hourconditions), where (e.g. geographic considerations) and for how long the collection took place. Specific situations,which may limit the data application and use, should be indicated, e.g. difficulties encountered, particular assumptionsmade, non-co
38、mpleteness.Considerations should also be given to the form of presentation: where appropriate, a condensed form (e.g.diagrams, histograms) may prevail over a detailed raw data presentation.8 Statistical methods for data treatmentIn most cases the need for data treatment appears in connection with on
39、e of the following activities: estimation, compliance evaluation, monitoring of performances, comparison of performances.For each performance of interest, estimations, hypothesis tests, control charts and comparison techniques areused for evaluating.The application of a given statistical procedure u
40、sually requires the fulfilment of some general conditions andassumptions which have to be carefully investigated. Some of these preliminary investigations relate directly to theproperties and the characteristics of the (stochastic) process generating the collected data, some other relate to thedistr
41、ibution underlying the collected data.Both preliminary investigations and data treatment may require statistical procedures not dealt with in thisRecommendation. International organizations other than CCITT, e.g. IEC, have produced valuable material in this field1.Reference1 International Electrotechnical Commission Catalogue of Publications, Ed. 1987.
