3.4 Application Modelling of Reliability and Performance in Engineering Design 263 Fig. 3.67 Hazards criticality analysis assembly condition portion of the FMEA results are very similar at both levels. Thus, in a hazards criti- cality analysis of the condition of selected components for inclusion in a design, the following component condition data illustrated in Fig. 3.68 are defined: • Failure description • Failure effects • Failure consequences • Failure causes. Figure 3.68 illustrates a h azards criticality analy sis of a common functional failure, “fails to open”, of a HIPS control valve. The condition worksheet in hazards criticality analysis is similar to the specifi- cations worksheet of selected equipment for consideration during the detail design phase of the engineering design process, in that it automatically integrates matched information pertain ing to the equipment condition and criticality, as illustrated in Fig. 3.69, with the necessary installation maintenance inform ation concerning the following: • Information from the equipment diagnostics worksheet relating to failure de- scription, failure effects, failure consequences and failure causes 264 3 Reliability and Performance in Engineering Design Fig. 3.68 Hazards criticality analysis component condition • Information relating to equipment criticality • Information relating to the necessary warranty maintenance strategy • Information relating to the estimated required maintenance costs • Information relating to the design’s installation logistical support The hazards criticality analysis—condition spreadsheet is a layout of selected com- ponents, based on the outcome of the condition worksheet of selected equipment for consideration during the detail design phase of the engineering design process. The condition spreadsheet (Fig. 3.70 ) is automatically generated, and serves as a FMEA pro-forma for electronically automated design reviews. The spreadsheet is vari- able, in that the data columns can be adjusted or hidden, but not deleted. These data columns include design integrity specificatio n information such as failure de- scription, failure mode, failure effects and consequences, as well as the relevant systems coding to identify the very many different elements of the systems break- down structure (SBS) for equipment and spares acquisition during the manufactur- ing/construction stages, and for operations and maintenance proceduredevelopment during the warranty operations stages of the engineered installation. This design in- tegrity specification information is automatically linked to the specific design pro- cess flow diagram (PFD) and pipe and instruments diagram (P&ID). 3.4 Application Modelling of Reliability and Performance in Engineering Design 265 Fig. 3.69 Hazards criticality analysis condition diagnostic worksheet The criticality worksheet in hazards criticality analysis automatically integrates matched informa tion pertaining to equipment criticality, with equipment condi- tion in formation and the necessary installation maintenance information of selected equipmentforconsideration duringthe detail design phase of the engineeringdesign process. The information illustrated in Fig. 3.71 relates to FMECA and includes: • Failure description • Failure severity • Consequence probability • Risk of failure • Yearly rate of failure • Failure criticality. The example in Fig. 3 . 71 is a typical hazards criticality analysis of a HIPS control valve showing failure severity and failure criticality. The hazards criticality analysis—criticality spreadsheet is a layout of selected components, based on the outcome of the criticality worksheet of selected equip- ment for consideration during the detail design phase of the engineering design pro- cess. The criticality spreadsheet (Fig. 3.72) is auto matically generated, and serves as a FMECA pro-forma for electronically automated design reviews. The spread- 266 3 Reliability and Performance in Engineering Design Fig. 3.70 Hazards criticality analysis condition spreadsheet sheet contains FMEA design integrity specification information such as the failure description, failure mode, failure effects and consequences, as well as the related failure downtime(including consequentialdamage), total downtime (repair time and damage), downtimecosts for quality/injurylosses, defectscosts (material and labour costs per failure including damage), economic or production losses per failure, the probability of occurrence of the failure consequence (%), the failure rate or nu mber of failures per year, the failure consequence severity, the failure consequence risk, the failure criticality, the total cost of failure per year and, finally, the overall failure criticality rating and the potential failure cost criticality rating. The hazards criticality analysis—strategy worksheet automatically integrates matched information p ertaining to the necessary warranty maintenance strategy of selected equipment for consideration during the detail design phase of the engineer- ing design process, with equipmen t condition and criticality information, warranty maintenance costs and engineered installation logistical support information. The strategy information relates to FMECA and includes: • Maintenance procedure description • Maintenance procedure control • Scheduled maintenance description • Schedule maintenance control 3.4 Application Modelling of Reliability and Performance in Engineering Design 267 Fig. 3.71 Hazards criticality analysis criticality worksheet • Scheduled maintenance frequency • Schedule maintenance criticality. Figure 3.73 illustrates a maintenance strategy worksheet for the HIPS control valve showing a derived preventive maintenance strategy. The hazards criticality analysis—strategy spreadsheet is a layout of selected components, based on the outcome of the strategy worksheet of selected equip- ment for consideration during the detail design phase of the engineering design process. Similar to the criticality spreadsheet, the strategy spreadsheet (Fig. 3.74) is automatically generated, and serves as a FMECA pro-forma for electronically automated design reviews. The spreadsheet contains FMECA design integrity spec- ification information such as the failure description, the relevant maintenance task description,the required maintenancecraft type, the estimated frequencyof the task, the maintenance procedure description ( in which all the relevant maintenance tasks are grouped together, pertinent to the specific assembly and/or system that requires dismantling for a single task to be acco mplished), the procedure identification cod- ing, the grouped maintenance schedule (based on grouped tasks per procedure, and grouped proceduresper system shutdownschedule), the maintenanceschedule iden- tification coding for computerised scheduling, and the overall planned downtime. 268 3 Reliability and Performance in Engineering Design Fig. 3.72 Hazards criticality analysis criticality spreadsheet The hazards criticality analysis—costs worksheet automatically integrates matched information pertaining to the necessary warranty maintenance costs o f se- lected equipment for consideration during the detail design phase of the engineering design process, with equipment condition a nd criticality information, and the nec- essary warranty maintenance strategy and engineered installation logistical support information. The maintenance costs informationrelates to FMECA and includes the following: • Estimated to tal costs pe r failure • Estimated y early downtime costs • Estimated yearly maintenance labour costs • Estimated y early maintenanc e material costs • Estimated yearly failure costs. Figure 3.75 illustrates a maintenance costs for the HIPS control valve showing the derived corrective maintenance costs and losses. The hazards criticality analysis—costs spreadsheet is a layout of selected com- ponents, based on the outcome of the costs worksheet of selected equipment for consideration during the detail design phase of the engineering design process. The spreadsheet (Fig. 3.76) is automatically generated, and serves as a FMECA pro-forma for electronically automated design reviews. The spreadsheet contains 3.4 Application Modelling of Reliability and Performance in Engineering Design 269 Fig. 3.73 Hazards criticality analysis strategy worksheet FMECA design integrity specification information such as overall planned down- time, maintenance labour hours per task/procedure/schedule, the type of mainte- nance craft, the number of craft persons required, estimated maintenance mate- rial costs per task/procedure/schedule, the total maintenance downtime costs per task/procedure/schedule and, finally, the estimated total downtime costs per year, the estimated total maintenance labour costs per year, and the estimated total main- tenance material costs per year. The summation of these estimated annual costs are then projected over a period of several years (usually 10 years) beyond the war- ranty operations period, based on estimates of declining early failures in stabilised operation. The hazards criticality analysis—logistics worksheet automatically integrates matched informationpertaining to the necessary logisticalsupport of selected equip- ment for consideration during the detail design phase of the engineering design process, with equipment condition and criticality information, and the necessary warranty maintenance strategy and costs information. The logistical support infor- mation relates to FMECA and in cludes the fo llowing: • Estimated required spares description • Estimated required spares strategy • Estimated spares BOM description 270 3 Reliability and Performance in Engineering Design Fig. 3.74 Hazards criticality analysis strategy spreadsheet • Estimated spares category • Estimated spares costs. Figure 3.77 illustrates spares requirements planning (SRP) for the HIPS control valve showing the derived spares strategy, spares category for stores replenishment, and recommended bill of spares (spares BOM). The hazards criticality analysis—logistics spreadsheet is a layout of selected components, based on the outcome of the logistics worksheet of selected equip- ment for consideration during the detail design phase of the engineering design process. The spreadsheet (Fig. 3.78) is automatically generated , and serves as an FMECA pro-forma for electronically auto mated design reviews. The spreadsheet contains FMECA design integrity specification in formation such as the critical item of equipment requiring logistic support, the related spare parts by part description, the part identification number (according to the maintenance task code), parts spec- ifications, parts quantities, the proposed manufacturer or supplier, the relevant man- ufacturer/supplier codes, the itemised stores description (for spare parts required for operations), the related bill of material (BOM) description and code for required stock items, the manufacturer’s BOM description and code for non-stock items, the relevant manufacturer/supplier catalogue numbers and, finally, the estimated price per unit for the required spare parts. 3.4 Application Modelling of Reliability and Performance in Engineering Design 271 Fig. 3.75 Hazards criticality analysis costs worksheet 3.4.2 Evaluation of Modelling Results a) Failure Modes and Effects Criticality Analysis A case study FMEA was conducted on the environmentalplant several months after completion of its design and installation where initially, prior to the design and construction of the plant, the process of sulphur dioxide to sulphuric acid conversion from a non-ferrous metal smelter emitted about 90 tonnes of sulphur gas into the environment per day, resu lting in acid rain over a widespread area. The objective of the study was to determine the level of correlation between the d esign specifications and the actual installation’s operational data, particularly with respect to systems criticality. The RAMS model initially captured the environmental plant’s design criteria during design and commissioning of the plant, and was installed on the organisation intranet. After a hierarchical structuring of the as-built systems into their assemblies and components, an FMEA was conducted, consisting mainly of identifying compo- nent failure descriptions, failure modes, failure effects, consequences and causes. Thereafter, a FMECA was conducted, which included an assessment of: the proba- bility of occurrence of the consequences of failure, based on the relevant theory and 272 3 Reliability and Performance in Engineering Design Fig. 3.76 Hazards criticality analysis costs spreadsheet analytic technique s previously considered,relating to uncertainty and probability as- sessment; the failure rate or number of failures per year, based on an extract of the failure records maintained by the installation’s distributed control system (DCS; cf. Fig. 3.79); the severity of each failure consequence,based on the expected costs/loss of the failure consequence; the risk of the failure consequence, based on the prod- uct of the probability of its occurrence and its severity; the criticality of the failure, based on the failure rate and the failure’s consequence severity; and the annual aver- age cost of failure. From these FMEA and FMECA assessment values, a failure crit- icality ranking and potential failure cost criticality were established. Th e results of the case study presented in a failure modes and effects analysis (FMEA) and failure modes and effects criticality analysis (FMECA) ar e given in Tables 3.24 and 3.25. The results using the RAMS analysis model are shown in Figs. 3.80 through to 3.83. Only a very small portion (less than 1%) of the results of the FMEA is given in Ta- ble 3.24, Acid plant failure modes and effects analysis (ranking on criticality) and Table 3.25 , Acid plan t failure mode s and effects criticality an alysis, to serve as il- lustration. Figure 3.79 illustrates a typical data sheet (in this case, of the reverse jet scrubber weak acid demister sprayers) in notepad format of the data accumulated by the installation’s distributed control system (DCS). . during the detail design phase of the engineering design process, in that it automatically integrates matched information pertain ing to the equipment condition and criticality, as illustrated in Fig operations stages of the engineered installation. This design in- tegrity specification information is automatically linked to the specific design pro- cess flow diagram (PFD) and pipe and instruments. layout of selected components, based on the outcome of the criticality worksheet of selected equip- ment for consideration during the detail design phase of the engineering design pro- cess.