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# Design of District Cooling Distribution System for Higher Availability, Reliability, Maintainability and Capability

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In this presentation, I discussed the components of effectiveness- Availability, Reliability, Maintainability and Capability. You shall find statistical data to understand the mathematical equations and examples to understand how these effectiveness components are applied in real world design.

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### Design of District Cooling Distribution System for Higher Availability, Reliability, Maintainability and Capability

1. 1. Design of District Cooling Distribution System for higher Availability, Reliability, Maintainability and Capability
2. 2. Contents 1. The Components of Effectiveness 2. Availability 3. Reliability 4. Maintainability 5. Capability
3. 3. A,R,M, and C Maintainability Capability Availability Reliability Effectiveness Effectiveness = Availability * Reliability * Maintainability * Capability
4. 4. Raw Data from Operating Logs Wall Clock Hours Start End Elapsed Time for Up Time Elapsed Time for Down Time 0 708.2 708.2 708.2 711.7 3.5 711.7 754.1 42.4 754.1 754.7 0.6 754.7 1867.5 1112.8 1867.5 1887.4 19.9 1887.4 2336.8 449.4 2336.8 2348.9 12.1 2348.9 4447.2 2098.3 4447.2 4452 4.8 4452 4559.6 107.6 4559.6 4561.1 1.5 4561.1 5443.9 882.8 5443.9 5450.1 6.2 5450.1 5629.4 179.3 5629.4 5658.1 28.7 5658.1 7108.7 1450.6 7108.7 7116.5 7.8 7116.5 7375.2 258.7 7375.2 7384.9 9.7 7384.9 7952.3 567.4 7952.3 7967.5 15.2 7967.5 8315.3 347.8 8315.3 8317.8 2.5 Total 8205.3 112.5 MTBM 683.8 MTTR 9.4 MTBM = mean uptime; this is the time between two maintenance periods MTTR= mean downtime due to maintenance; this is the time when system is down for repair
5. 5. • Deals with the duration of up-time for operations and is a measure of how often the system is alive and well. Availability = Uptime Uptime+Down Time Up-time ≡ not downtime A = A hardware*A software*A humans*A interfaces*A process Availability
6. 6. 98% availability for a continuous process says to expect • up-time of 0.98 * 8760 hours = 8584.8 hrs/year • down time of 0.02 * 8760 = 175.2 hrs/year, as Availability + unavailability = 1 Availability
7. 7. • Design looped network Availability LOOP
8. 8. • Design looped network Availability LOOP
9. 9. • Multiple Supply/Return at Plant Availability PLANT-1 PLANT-2 1 2 1 2
10. 10. • When high availability is of special importance, install standby “duty assist” pumps. Higher availability might be requested for commercial use than for residential buildings. • One control valve for each PHE • Multiple heat exchangers Availability
11. 11. • Deals with reducing the frequency of failures over a time interval and is a measure of the probability of failure-free operation during a given interval, i.e., it is a measure of success for a failure free operation Reliability
12. 12. R(t)= exp(− t MTBF ) MTBF (Mean Time Between Failures) is the time between system failures R = R utilities*R feed-plant*R processing*R packaging*R shipping • For a given mission time, to achieve high reliability, a long MTBF is required. Reliability
13. 13. • MTBF = 638.8 hours • Mission time = 1 year = 8760 hours Reliability = R(t)= exp − 8760 683.8 = 0.00027% • MTBF = 30 years • Mission time = 1 year Reliability = R(t)= exp − 1 30 = 96.72% 1 2 8760 683.8 =12.8 Reliability
14. 14. DCP Wadi DCP West DCP North DCP Marina Cooling plant • Four main plants : Total Market > 500,000 TR Reliability Multiple production sites around the city connected to DC grid
15. 15. Reliability • Pre-insulated • Welded end • Direct buried Eliminating flanges – a potential source of leaks
16. 16. Reliability
17. 17. • Deals with duration of maintenance outages or how long it takes to achieve the maintenance actions compared to a datum. M(t)= 1 − exp(− t MTTR ) MTTR is Mean Time To Repair Maintainability issue is to achieve short repair times for keeping availability high Maintainability
18. 18. • Maximum Repair Time 24 hrs • Maintenance Goal 99.9% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 1 25% 2 44% 3 58% 4 68% 5 76% 6 82% 7 87% 8 90% 9 92% 10 94% 11 96% 12 97% 13 98% 14 98% 15 99% 16 99% 17 99% 18 99% 19 100% 20 100% 21 100% 22 100% 23 100% 24 100% Hours Probability MTTR 3.48 Hours Maintainability
19. 19. • MTTR = mean down time due to maintenance = 9.4 hours • System Maintainability= ? If allowed Maximum Repair Time is 10 hours M(t)= 1 − exp(− 10 9.4 ) = 65.5% Probability of maintaining the system in allowed time of 10 hours is 65.5% Maintainability
20. 20. Maintainability Minimize need for maintenance; manufacture utilizing high quality material and components • Install leak detection system • Secure Joints: Do not let water/moisture enter the HDPE Jacket • Design pipe, works and components for high life-time; 40 years • 10 years warranty
21. 21. Maintainability Be Careful with Bends, Fittings and Valves
22. 22. Maintainability Condensation problems: LDS to monitor, detect and locate faults Building entry seal in concrete walls and floors
23. 23. • Deals with productive output compared to inherent productive output which is a measure of how well the production activity is performed compared to the datum. Capability = Efficiency * Utilization Efficiency = Productive Work output/ work input Utilization = Time spent on productive efforts / total time consumed Capability
24. 24. • For example; System efficiency 80% Utilization 82.19% (300/365 days) Capability = 0.8 * 0.8219 = 65.75% Capability
25. 25. Remember A,R,M, and C Maintainability Capability Availability Reliability Effectiveness Effectiveness = Availability * Reliability * Maintainability * Capability