1.
Design of District Cooling
Distribution System for higher
Availability, Reliability,
Maintainability and Capability

2.
Contents
1. The Components of Effectiveness
2. Availability
3. Reliability
4. Maintainability
5. Capability

3.
A,R,M, and C
Maintainability
Capability
Availability
Reliability
Effectiveness
Effectiveness = Availability * Reliability * Maintainability * Capability

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.
• 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.
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.
• Design looped network
Availability
LOOP

8.
• Design
looped
network
Availability
LOOP

9.
• Multiple Supply/Return
at Plant
Availability
PLANT-1
PLANT-2
1
2
1 2

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.
• 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.
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.
• 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.
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.
Reliability
• Pre-insulated
• Welded end
• Direct buried
Eliminating flanges – a
potential source of leaks

16.
Reliability

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.
• 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.
• 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.
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.
Maintainability Be Careful with
Bends, Fittings and
Valves

22.
Maintainability
Condensation
problems: LDS to
monitor, detect and
locate faults
Building entry seal
in concrete walls
and floors

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.
• For example;
System efficiency 80%
Utilization 82.19% (300/365 days)
Capability = 0.8 * 0.8219 = 65.75%
Capability

25.
Remember A,R,M, and C
Maintainability
Capability
Availability
Reliability
Effectiveness
Effectiveness = Availability * Reliability * Maintainability * Capability

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