Abstract
The operating performance of deionized and water for injection (DI/WFI) distribution systems can be difficult to analyse due to the highly variable demand that is drawn from these systems, a situation compounded by schedule uncertainties. This paper presents a fuzzy logic (FL) model of a typical DI/WFI system simulating schedule uncertainties in the opening and closing events of the offtake valves based on operator behaviour, e.g. tiredness of the operators. The model utilises discrete-event simulation to calculate the demand profile of the distribution system and a continuous simulation to compute the variation of the level in the storage tank. It is shown that the FL model may be useful in the design of new DI/WFI systems if little historical data are available.
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Abbreviations
- acti,k :
-
Opening/closing event of valve i, k
- \( {\text act}_{{{\text{i}},{\text{k}}}}^{\text{Wait}} \) :
-
Opening/closing event of valve i, k waiting to be served
- fDiv :
-
Diversity factor
- i:
-
Integer parameter
- k:
-
Integer parameter
- n:
-
Integer parameter
- nop :
-
Number of operators
- nop, min :
-
Minimum number of operators
- Pri, k :
-
Priority rules for each acti, k
- t:
-
Time (h:m:s)
- tapi :
-
Valve of offtake point (tap) i along the distribution system
- \( {\text{t}}_{{2,{\text{ j}}}}^{\text{B}} \) :
-
Beginning of core break (h:m:s)
- \( {\text{t}}_{{3, {\text{j}}}}^{\text{B}} \) :
-
End of core break (h:m:s)
- \( {\text{t}}_{{{\text{i}}, {\text{k}}}}^{\text{close}} \) :
-
Scheduled closing time for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}},new}}^{\text{close}} \) :
-
New closing time for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}}}}^{\text{D}} \) :
-
Time delay for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}}}}^{{{\text{D}},De}} \) :
-
Defuzzified time delay for each acti, k (%)
- \( {\text{t}}_{{{\text{i}},{\text{k}}}}^{\text{Delay,1}} \) :
-
Time delay caused by operator for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}}}}^{{Delay,2}} \) :
-
Time delay caused by operator for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}}}}^{\text{Delay, No Op.}} \) :
-
Delay caused by no operator being available for acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}}}}^{\text{min,{\text{ D}}}} \) :
-
Minimum duration of each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{ k}}}}^{{open}} \) :
-
Scheduled opening time for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}},\text new}}^{\text{open}} \) :
-
New closing time for each acti, k (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}},\text new}}^{\text{open,R1}} \) :
-
New opening time due to influence of rule 1 (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}},\text new}}^{\text{open,R4}} \) :
-
New opening time due to influence of rule 4 (h:m:s)
- \( {\text{t}}_{{{\text{i}},{\text{k}},\text new}}^{\text{open,R5}} \) :
-
New opening time due to influence of rule 5 (h:m:s)
- tsim :
-
Simulated time (s)
- tmax :
-
Maximum allowable time (see rule 1) (h:m:s)
- tRule1 :
-
Sum defined as: tSim + tmax (h:m:s)
- t0 :
-
Time at start of simulated time (h:m:s)
- \( \Delta {\text{t}}_{{{\text{i}},{\text{ k}}}}^{\text{offtake}} \) :
-
Opening/closing interval for each acti, k (h:m:s)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{Design}}} \) :
-
Design flow rate (m3/h)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{Max}}} \) :
-
Maximum flow rate (m3/h)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{WFI,Blow}}} \) :
-
WFI generation blowdown (%)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{WFI,Gen}}} \) :
-
Volumetric flow rate WFI from WFI generation plant (m3/h)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{WFI,Gen,max}}} \) :
-
Maximum volumetric flow rate from WFI generating plant (m3/h)
- VWFI, L :
-
WFI volume in the WFI storage tank (m3)
- VWFI, L, C :
-
Temperature compensated water volume in WFI storage tank (m3)
- VWFI, L, max :
-
Maximum allowable water volume in WFI storage tank (m3)
- VWFI, L, min :
-
Minimum allowable water volume in the WFI storage tank (m3)
- VWFI, L, St :
-
Start volume in WFI storage tank at t0 (m3)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{WFI, off}}} \) :
-
Volumetric offtake from the WFI system (m3/h)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{WFI, off,{\text{ i}}}}} \) :
-
Volumetric offtake for each acti (m3/h)
- \( {\mathop{\text{V}}\limits^{ \bullet }_{\text{WFI,Pump}}} \) :
-
WFI Distribution pump delivery volume (m3/h)
- XD :
-
Defuzzified value
- \( {{\mu }}\mathop{{_{\text{B}}}}\limits_{\sim } ({\text{t}}) \) :
-
Membership function “operator break pattern” (h:m:s)
- \( {{\mu }}_{{\mathop{\text{D}}\limits_{\sim } }}^{{{\text{i}},{\text{k}}}}({\text{t}}) \) :
-
Membership function “duration of tasks” for each acti, k (h:m:s)
- \( {{\mu }}\mathop{{_{\text{S}}}}\limits_{\sim } ({\text{t}}) \) :
-
Membership function operator “shift pattern” (h:m:s)
- \( {{\mu }}\mathop{{_{\text{T}}}}\limits_{\sim } ({\text{t}}) \) :
-
Membership function “operator tiredness”
- \( {{\mu }}_{{\mathop{{Out}}\limits_{\sim } }}^{{0\% }}({\text{r}}), \ldots, {{\mu }}_{{\mathop{{Out}}\limits_{\sim } }}^{{100\% }}({\text{r}}) \) :
-
Membership function “output”
- ρ20 :
-
Water density at 20°C: ρ20 = 998.21 kg/m3 (kg/m3)
- ρ80 :
-
Water density at 80°C: ρ80 = 971.79 kg/m3 (kg/m3)
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Riedewald, F., Byrne, E. & Cronin, K. A Fuzzy Logic Model of Deionised and Water for Injection Systems for Sizing and Capacity Assessment Under Uncertainty. J Pharm Innov 6, 125–141 (2011). https://doi.org/10.1007/s12247-011-9108-4
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DOI: https://doi.org/10.1007/s12247-011-9108-4