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Design of District Cooling
Distribution System for higher
Availability, Reliability,
Maintainability and Capability
Contents
1. The Components of Effectiveness
2. Availability
3. Reliability
4. Maintainability
5. Capability
A,R,M, and C
Maintainability
Capability
Availability
Reliability
Effectiveness
Effectiveness = Availability * Reliability ...
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
...
• Deals with the duration of up-time for
operations and is a measure of how often
the system is alive and well.
Availabili...
98% availability for a continuous process says to
expect
• up-time of 0.98 * 8760 hours = 8584.8 hrs/year
• down time of 0...
• Design looped network
Availability
LOOP
• Design
looped
network
Availability
LOOP
• Multiple Supply/Return
at Plant
Availability
PLANT-1
PLANT-2
1
2
1 2
• When high availability is of special
importance, install standby “duty assist”
pumps. Higher availability might be reque...
• Deals with reducing the frequency of failures
over a time interval and is a measure of the
probability of failure-free
o...
R(t)= exp(−
t
MTBF
)
MTBF (Mean Time Between Failures) is the time
between system failures
R = R utilities*R feed-plant*R ...
• MTBF = 638.8 hours
• Mission time = 1 year = 8760 hours
Reliability = R(t)= exp −
8760
683.8
= 0.00027%
• MTBF = 30 year...
DCP Wadi
DCP West
DCP
North
DCP
Marina
Cooling plant
• Four main plants :
Total Market >
500,000 TR
Reliability
Multiple
p...
Reliability
• Pre-insulated
• Welded end
• Direct buried
Eliminating flanges – a
potential source of leaks
Reliability
• Deals with duration of maintenance outages
or how long it takes to achieve the
maintenance actions compared to a datum.
...
• 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%...
• MTTR = mean down time due to
maintenance = 9.4 hours
• System Maintainability= ?
If allowed Maximum Repair Time is 10 ho...
Maintainability
Minimize need for maintenance; manufacture
utilizing high quality material and components
• Install leak d...
Maintainability Be Careful with
Bends, Fittings and
Valves
Maintainability
Condensation
problems: LDS to
monitor, detect and
locate faults
Building entry seal
in concrete walls
and ...
• Deals with productive output compared to
inherent productive output which is a
measure of how well the production
activi...
• For example;
System efficiency 80%
Utilization 82.19% (300/365 days)
Capability = 0.8 * 0.8219 = 65.75%
Capability
Remember A,R,M, and C
Maintainability
Capability
Availability
Reliability
Effectiveness
Effectiveness = Availability * Rel...
Thank you
Muhammad Ali
Phone: 00974 55293436
Email: muhammad.ali@Marafeq.com.qa
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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.

Published in: Engineering
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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
  26. 26. Thank you Muhammad Ali Phone: 00974 55293436 Email: muhammad.ali@Marafeq.com.qa

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