• Bellcore Lighting
• Bellcore Manual Of Construction Procedures Free
• Bellcore Manual Of Construction Procedures Pdf

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Bellcore / Telcordia - Reliability Prediction ProcedureMaintaining reliability and providing reliability engineering is an essential need with modern electronic systems. Reliability engineering for electronic equipment requires a means for a quantitative baseline, or a reliability prediction analysis. The Bellcore procedure or standard was developed for the telecommunications industry and their applications; however, it has become widely used for industrial and commercial electronic equipment applications.

Using the Bellcore standard for reliability prediction produces calculated Failure Rate and Mean Time Between Failures (MTBF) numbers for the individual components, equipment and the overall system. The final calculated prediction results are based on the roll-up, or summation, of all the individual component failure rates.Published by Bell Communications Research, Inc., the standard is now maintained and updated by Telcordia Technologies, Inc. The purpose for developing this procedure was for use by Bellcore Client Companies (BCC) and other buyers of electronic equipment to establish and maintain consistent and uniform methods for estimating the reliability of electronic equipment and systems. The Bellcore procedure defines reliability as a measure of the frequency of equipment failures as a function of time.EquipmentThe Bellcore reliability prediction procedure refers to electronic systems as hierarchical assemblies constructed from device and unit level hardware. Device - Refers to a basic component such as a capacitor, integrated circuit, etc. Unit - Refers to any customer replaceable assembly of devices such as circuit packs, modules, plug-in units, racks, power supplies and ancillary equipment.

A unit will usually be the lowest level of replaceable assemblies or devices. Units are considered non-repairable. The Bellcore procedure is aimed primarily at the reliability prediction of units. Systems - The procedure refers to serial systems, which is any assembly of Units for which the failure of any single unit will cause a system failure.The Bellcore procedure's focus is predicting failure rates for electronic equipment, similar to the MIL-217 standard.

Bellcore Lighting

The procedure does not address other aspects of reliability such as downtime, repairable equipment, availability, redundancy and the impacts from failures.Part Stress AnalysisThe Bellcore procedure uses a part stress analysis similar to the MIL-217 standard. By component stresses, the standard is referring to the actual operating conditions such as environment, temperature, voltage, current and power levels applied, for example. The Bellcore standard groups components or devices by major categories and then has subgroups within the categories. An example is a 'Fixed, Tantalum, Solid' is a subcategory of the 'Capacitor' group. Each device or part category and it's subgroups have individual base failure rates that are applied to the model calculating the failure rate. The failure rate model also includes the various part stresses by applying pi factors in the model.Failure Rate and pi FactorsThe failure rate model referred to above include a base or generic steady-state failure rate, for the category and subgroup selected.

The base failure rates apply to components and parts operating under normal environmental conditions, with power applied, performing the intended function(s), using base component quality levels and operating at the design stress levels. The standard then applies many pi factors, or multiplying factors, to the base failure rates in order to factor in the actual operating conditions, environment and stress levels referred to above.

Base failure rates are adjusted by applying the pi factors, which range from 0 to 1.0, to the underlying equation or model provided for each component category.Bellcore Prediction MethodsThe above procedure calculates the predicted failure rate at the actual operating conditions for each component in the project. The Bellcore procedure provides three methods for predicting device and unit reliability. The method used is normally determined by the information that is available. Method I - The 'parts count' or 'Black Box' method is very similar to and was modeled from the MIL-217 standard.

Bellcore Manual Of Construction Procedures Free

This method assumes no reliability data is available on the devices and units included in the system. Predictions are based on the generic reliability parameters discussed. This is the simplest of the three methods and can be applied to devices or units. Method II - Use this method if laboratory failure rate data is available for some or all the devices or units.

This method allows the laboratory data to be combined with the generic data from Method I. The resultant prediction lies somewhere between Method I and Method II. Method III - Use Method III if field tracking reliability data is available for some or all the devices or units. As above, this method will allow actual field reliability data to be combined with the generic data to obtain predictions. This is obviously the most accurate of the prediction methods but requires considerable actual field data.The three methods are further broken down into three 'cases' based on stress values and if the unit or system has a 'burn-in' period.First-Year-MultiplierBellcore stresses the facts related to early life of electronic components and systems and the use of 'burn-in'. The Bellcore model applies a 'First-Year-Multiplier' factor in the failure rate prediction which factors in early life and the use of a 'burn-in' period.

Bellcore Manual Of Construction Procedures Pdf

Bellcore defines this multiplier to be the average failure rate during the first year of operation (8760 hours) expressed as a multiple of the Steady-State Failure Rate. The 'First-Year-Multiplier' together with the Steady-State Failure Rate provides a prediction of the expected number of failures in the first year of operation.Calculation FlowThe procedure to determine the overall system level or equipment failure rate is to sum, or roll up, the individually calculated failure rates for each device and then unit.