Muhammad Ali

Design of District Cooling Distribution System for higher

Availability, Reliability, Maintainability and Capability

Contents

1. The Components of Effectiveness2. Availability3. Reliability4. Maintainability5. Capability

A,R,M, and C

Maintainability

Capability

Availability

Reliability

Effectiveness

Effectiveness = Availability * Reliability * Maintainability * Capability

Raw Data from Operating LogsWall Clock Hours

Start End Elapsed Time for Up Time

Elapsed Time for Down Time

0 708.2 708.2 708.2 711.7 3.5711.7 754.1 42.4 754.1 754.7 0.6754.7 1867.5 1112.8

1867.5 1887.4 19.91887.4 2336.8 449.4 2336.8 2348.9 12.12348.9 4447.2 2098.3 4447.2 4452 4.84452 4559.6 107.6

4559.6 4561.1 1.54561.1 5443.9 882.8 5443.9 5450.1 6.25450.1 5629.4 179.3 5629.4 5658.1 28.75658.1 7108.7 1450.6 7108.7 7116.5 7.87116.5 7375.2 258.7 7375.2 7384.9 9.77384.9 7952.3 567.4 7952.3 7967.5 15.27967.5 8315.3 347.8 8315.3 8317.8 2.5

Total 8205.3 112.5MTBM 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

• Deals with the duration of up-time for operations and is a measure of how often the system is alive and well.

Availability

Up-time ≡ not downtimeA = A hardware*A software*A humans*A interfaces*A process

Availability

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

• Design looped network

Availability

LOOP

• Design looped network

Availability

DN 1200

DN 800

DN 1

200

LOOP

• Multiple Supply/Return at Plant

Availability

PLANT-1

PLANT-2

12

1 2

• 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

• 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

R(t)

(Mean Time Between Failures) is the time between system failuresR = 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

• MTBF = 638.8 hours• Mission time = 1 year = 8760 hoursReliability = R(t)

• MTBF = 30 years• Mission time = 1 year Reliability = R(t)

1

2

=12.8

Reliability

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

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.

M(t)

MTTR is Mean Time To RepairMaintainability issue is to achieve short repair times for keeping availability high

Maintainability

• Maximum Repair Time 24 hrs

• Maintenance Goal 99.9%

0 5 10 15 200%

10%20%30%40%50%60%70%80%90%

100%

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

Prob

abili

ty

MTTR 3.48 Hours

Maintainability

• MTTR = mean down time due to maintenance = 9.4 hours

• System Maintainability= ?

If allowed Maximum Repair Time is 10 hoursM(t) = 65.5%

Probability of maintaining the system in allowed time of 10 hours is 65.5%

Maintainability

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

Maintainability Be Careful with Bends, Fittings and

Valves

MaintainabilityCondensation

problems: LDS to monitor, detect and

locate faults

Building entry sealin concrete walls

and floors

• 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 inputUtilization = Time spent on productive efforts / total time consumed

Capability

• 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 * Reliability * Maintainability * Capability

Thank you

Muhammad AliPhone: 00974 55293436Email: muhammad.ali@Marafeq.com.qa