chapter v – analysis and discussion

8/14/2019 Chapter v Analysis and Discussion

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CHAPTER VANALYSIS AND DISCUSSION

5.1 SupplyConveyance Analysis

A supply-conveyance analysis is an approximate method for evaluating whether the supply satisfies the

demand in a system. In this the actual demand being feed by the supply tanks will be compared to the

design demand of the system based from fixture unit values.

5.1.1 Supply from Underground Reservoir Tank to the Elevated Cylindrical Water Tank

Water will be pumped from the underground reservoir tank to the elevated water tank using 2 transfer

pumps. The riser pipe that will convey the water to the tank has a total length of approximately 140 m.

The water will passed in a number of elements of pipe fittings and pump as shown in the table below.

Elements Quantity diameter equivalent length total length

90 Elbow 21 75 1.3 27.3

Gate Valve 4 75 0.9 3.6

Tees 2 75 2.9 5.8

Flow Control

valve 2 75 0.9 1.8

Check Valve 2 75 1 2

Transfer Pump 2 75 - -

Total Additional Length 40.5

5.1.1.2 Water Level at the Elevated Cylindrical Water Tank

Using Bernoulli equation, the water level in the Elevated water tank will be approximate. Considering 2

points for the Bernoulli equation, first point was the water level in the underground reservoir tank and the

second point will be the water level at the elevated tank. The equation will be:


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Since both reservoirs was exposed to the atmosphere:

Where HA =

HL = hm + hf

Using equivalent length of pipes the minor loss in pipe fittings will be accounted as friction loss due to

pipe lengths. Therefore HL = hf, where hf= 0.00826 x

Then the equation will be

- 0.00826 x

Using the pump properties and assuming 95% efficiency of the pump, the computed value for was

359.577m. Comparing the computed head to the actual elevation of the water tank of 90.069m

from the bottom of the reservoir tank, it was shown that the 2 transfer pump at the pump room

can deliver water trice as much the water system needed. Therefore at 95% efficiency of the 2

pumps, the system is assured that it can maintain its water level even in peak loads of demand.

5.1.2 Supply from the Elevated Cylindrical Water Tank to the Outlet Pipes on Each Floor

The water will be supplied from the elevated water tank in two ways; 1. Pressurized Flow for 20th

to 23rd

floor and 2. Gravity Flow for the rest of the system. Separate down feeds were provided for each type of

flow. Down feeds for gravity and pressurized flow has a diameter of 100 mm and 75 mm respectively.


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5.1.2.1 Flow rate Distribution in the Gravity Flow Zone

Floor Level Elevation Roughness DesignPressure

Diameter Friction lossCoefficient

Discharge

Ground 21680 120 372.8685 100

2nd Floor 24680 120 343.4968 100

3rd Floor 27680 120 314.1251 100

4th Floor 30680 120 284.7535 100

5th Floor 33680 120 255.3818 100

6th Floor 36680 120 226.0101 100

7th Floor 39680 120 196.6385 100

8th Floor 42680 120 167.2668 100

9th Floor 45680 120 137.8951 100

10th Floor 48680 120 396.5175 100

11th Floor 51680 120 367.1458 100

12th Floor 54680 120 337.7741 100

14th Floor 57680 120 308.4025 100

15th Floor 60680 120 279.0308 100

16th Floor 63680 120 249.6592 100

17th Floor 66680 120 220.2875 10018th Floor 69680 120 190.9158 100

19th Floor 72680 120 161.5442 100

5.1.2.2 Flow rate Distribution in the Pressurized Zone

Floor Level Elevation Roughness Design

Pressure

Diameter Friction loss

Coefficient

Pump head Discharge

20th Floor 75680 120 270.0676 100

21st Floor 78680 120 235.8007 100

22nd Floor 81680 120 201.5337 100

23rd Floor 84680 120 167.2668 100

5.1.2.3 Comparison between the Design Demand and the Actual Discharge

Floor Level Elevation Design Demand Actual Discharge


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5.2 Pressure Analysis of the System

The system will be subjected to pressure testing, its reliability will be analyzed according to its capacity to

carry large amount of pressure. In a high-rised condominium large pressures are expected due to its

elevation, these pressures may cause failure in the system if not sophisticatedly addressed in the design.

The Pressure test and Leak test are done in the system; the contractor must accomplish a Quality

Assurance Inspection Checklist after installation. This checklist will be the basis of the system reliabilityin terms of pressure capacity. A sample of Quality Assurance Checklist is attached in this study (See

Appendix)

5.2.1 Pressure Testing for Waterlines

Ground 21680

2nd Floor 24680

3rd Floor 27680

4th Floor 30680

5th Floor 33680

6th Floor 36680

7th Floor 39680

8th Floor 42680

9th Floor 45680

10th Floor 48680

11th Floor 51680

12th Floor 54680

14th Floor 57680

15th Floor 60680

16th Floor 63680

17th Floor 66680

18th Floor 69680

19th Floor 72680

20th Floor 75680

21st Floor 78680

22nd Floor 81680

23rd Floor 84680


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Pressure Testing shall be done in accordance to the technical specifications for Plumbing layouts, where

in after installation of pipes, the pipe and any valve section shall be subjected to hydrotastic pressure of 1

of the designed working pressure of the system 200 psig, but in the project the hydrotastic pressure that

was used for testing varies but the most commonly used was 180 psi, depending on what was specified by

the Contractor (JCI) and approved by the Designer (NBFCE).

The sections of the pipelines were solely filled by water and had been subjected to the testing pressure by

means of a pump connected to the pipe. All valves were opened during the testing.

Figure 5.1 Opening of valves before the hydro testing


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The result of testing for each floor is

summarized at the Table below.

Table 5.1- Pressure Test Report for Pipe and Pipe Fittings of HWL and CWL lines

Floor Elevation (m) Test Pressure (psig) Design Pressure (psig) Remarks

Ground 15.500 180 54.08 System passed the requirements

2nd Floor 19.000 180 49.82 System passed the requirements

3rd Floor 22.000 180 45.56 System passed the requirements

4th Floor 25.000 180 41.3 System passed the requirements




8th Floor 37.000 180 24.26 System passed the requirements9th Floor 40.000 180 20 System passed the requirements






16th Floor 58.000 180 36.21 to be subjected for testing





21st Floor 73.000 180 34.91 to be subjected for testing

22nd Floor 76.500 180 29.94 to be subjected for testing

23rd Floor 80.000 180 24.97 to be subjected for testing

From 16th to 23rd floors pressure testing are not yet done because the installation of pipe and fittings are

not yet finished. But based from the results shown from the ground floor to the 15 th floor it is shown that

the pipe material used in the system can carry up to 180 psi of pressure load. Compared to the computed

pressure load that the pipe will be experienced in actual operation it shows that the system is adequate in

terms of pressure capacity.

5.2.2 Leak Test

Figure 5.2 Hydro Testing


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During Hydro testing leaks in the system is also examined, leaks are determined by the leak test. The

pipes are filled with water and the pressure in the pipe sections is recorded. After the test duration of 2

hours the pressure reading will be examined. If there is a pressure drop in the reading, therefore there

were leaks in the system; the personnel handling the testing will now start to locate the leaks. Leaks are

properly addressed and the pipe section will be subjected for retesting.

The result of leak test is summarized in the Table below.

Floor Initial Reading(psig) Final Reading(psig) Remarks

Ground 180 180 No pressure drop

2nd Floor 180 180 No pressure drop

3rd Floor 180 180 No pressure drop

4th Floor 180 180 No pressure drop











16th Floor 180 - to be subjected for testing





21st Floor 180 - to be subjected for testing

22nd Floor 180 - to be subjected for testing

23rd Floor 180 - to be subjected for testing

The results show that the system was reliable in terms of quality of work in the installation of the

pipelines. Since no leaks are recorded during the testing of each floor, it is expected that there will be no

loss in the system during actual operation due to leaks.


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5.3 System Reliability against Problems Encountered in a Water Distribution System

Since no water distribution system is perfect, the system will always encounter problems especially

during actual operations. It must be noted that if we want to measure the reliability of a system we must

examine its capability to avoid failures. These failures might occur in pipes, appurtenances and fittings,

pumps and even in tanks. In the design of the system some of these failures must be considered.

5.3.1 Water Hammer Failure

Water hammer is large fluctuations develop in the system that produce pounding noises and vibration.

This force is capable of bursting the pipe fittings and pipe lines, may cause leaks and may shorten the life

span of the system.

To avoid this damages due to excessive pressure the designer provide a means of regulating the pressure,

that is by installing a pressure reducing valve in the system. The PRV is installed in the 10 th floor of the

building where in it reduce the accumulated pressure from the top zone to a gage of 20 psi, which is the

actual minimum pressure required for a water closet.

The location of the installation of PRV is computed based from the maximum pressure criterion of 70 psi.

The maximum pressure zone height is 115.5 ft or 9.6 floors. Therefore the desired location for the PRV is

in the 10th floor based from the computed pressure zone height. (See Appendix for computation)

chapter v – analysis and discussion

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