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Reliability block diagram templates

RBD — Municipal Water Treatment Works

Annual potable-output reliability of a treatment works: 3-of-4 raw water pumps, duplicated filter trains, UV, and a warm-standby chlorine dosing pair with an explicit dormancy factor.

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Municipal water treatment works — potable outputMission 8 760 h · 1.00 yr · 12 blocks · 3 redundant arrangements · R 0.121890Raw water intake screensR 0.713964 · A 0.999543 of 4 · R 0.403566Raw water pump 1R 0.557663 · A 0.99840Raw water pump 2R 0.557663 · A 0.99840Raw water pump 3R 0.557663 · A 0.99840Raw water pump 4R 0.557663 · A 0.99840Coagulation and clarificationR 0.815690 · A 0.99981parallel · R 0.874206Rapid gravity filter train AR 0.645326 · A 0.99920Rapid gravity filter train BR 0.645326 · A 0.99920UV disinfection reactorR 0.746769 · A 0.99980warm standby · switch 0.980 · R 0.808465Chlorine dosing, dutyR 0.481909 · A 0.99967Chlorine dosing, standbyR 0.481909 · A 0.99967Contact tank and final waterR 0.982633 · A 0.99990System reliability0.121890Unreliability0.8781System MTTF4 588 h · 191 dAvailability0.999034Reliability importance — Birnbaum ∂R/∂Rᵢ, with criticality share1Raw water intake screens0.170723crit 5.56%2UV disinfection reactor0.163223crit 4.71%3Coagulation and clarification0.149432crit 3.14%4Raw water pump 10.124644crit 6.28%5Raw water pump 20.124644crit 6.28%6Raw water pump 30.124644crit 6.28%7Raw water pump 40.124644crit 6.28%8Contact tank and final water0.124044crit 0.25%+4 more blocks not shownWeakest link: Raw water intake screens — R 0.713964, Birnbaum 0.170723, 5.56% of system failure. Improving this one block moves the system number further than improving any other.Redundancy check: removing any one of the 7 branches makes its own group measurably more likely to fail — the least of them by 39%. Every one of them is earning its place.

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title "Municipal water treatment works — potable output"
mission 8760h

block intake  "Raw water intake screens"      mtbf: 26000h  mttr: 12h
block pump1   "Raw water pump 1"              mtbf: 15000h  mttr: 24h
block pump2   "Raw water pump 2"              mtbf: 15000h  mttr: 24h
block pump3   "Raw water pump 3"              mtbf: 15000h  mttr: 24h
block pump4   "Raw water pump 4"              mtbf: 15000h  mttr: 24h
block coag    "Coagulation and clarification" mtbf: 43000h  mttr: 8h
block filtA   "Rapid gravity filter train A"  mtbf: 20000h  mttr: 16h
block filtB   "Rapid gravity filter train B"  mtbf: 20000h  mttr: 16h
block uv      "UV disinfection reactor"       mtbf: 30000h  mttr: 6h
block cl2     "Chlorine dosing, duty"         mtbf: 12000h  mttr: 4h
block cl2s    "Chlorine dosing, standby"      mtbf: 12000h  mttr: 4h
block contact "Contact tank and final water"  mtbf: 500000h mttr: 48h

# Three of four pumps carry design flow. The standby doser is warm rather
# than cold: it is kept primed, so it degrades at about 15% of duty rate.
series {
  intake
  kofn 3 of 4 { pump1; pump2; pump3; pump4 }
  coag
  parallel { filtA; filtB }
  uv
  standby warm { primary: cl2; spare: cl2s; switch: 0.98; dormancy: 0.15 }
  contact
}