6.4.4 Testing of the pipe Line

6.4.4.1 GENERAL

After laying and jointing the pipe line be pressure tested to ensure that pipe joints are sound enough to withstand the maximum pressure likely to be developed working conditions.

6.4.4.2 TESTING OF PRESSURE PIPES

The field test pressure to be imposed should be not less than the greatest of the following.
(a) 1 1/2 times the maximum sustain operting pressure
(b) 1 1/2 times the maximum pipe linstatic pressure
(c) Sum of the maximum sustained operating pressure and the maximum surge pressure.
(d) Sum of the maximum pipe line static pressure and the maximum surge pessure, subject to a maximum equal to the works test pressure for any fittings incorporated.

The field test pressure should whereever possible be not less than 2/3rd work test pressure appropriate to the class of pipe except in the case of spun iron pipes and should be applied and maintained for atleast four hours. If the visual inspection satisfies that there is no leakage the test can be passed.

Where the fields test pressure is less than 2/3 the works test pressure, the period of test should be increased to atleast 24 hours. The test 1kg/cm2/min. If the pressure measurement are not made at the lowest point of the section an allowance should be made for the difference in static head between the lowest point and the point of measurement to ensure that the maximum pressure is not exceeded at the lowest point. If a drop in pressure is not exceeded at the lowest point. If a drop in pressure occurs the quantity of water added in order to re-establish the test pressure should be carefully measured. This should not exceed 0.1 liter per mm of pipe diameter per KM of pipe line per day for each 30 meter head of pressure applied.

In case of gravity pipes maximum working pressure shall be 2/3 works test pressure.

The hydrostatic test pressure at works and at field after installation and the working pressure for the difference classes of C.I Pipes are given in Appendix 6.4.

The allowable leakage during the maintenance stage of pipes carefully laid and well tested during construction, however should not exceed.

qL=ND \/P
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115 (6.11)

where,
qL = Allowable leakage in cm3/ hour
N = No of joints in the length of pipe line
D = Diameter in mm
P = the average test pressure during the leakage test in kg/cm2.

Where any test of pipe laid indicates leakage greater than the specified as per the above formula, the defective pipe (s) or joint(s) shall be repaired/ replaced until the leakage is with in the specified allowance.

The above is applicable to spigot and socket Cast Iron pipes and A.C pressure pipes whereas twice this figure may be taken for steel and prestressed concrete pipes.

6.4.4.3 TESTING OF NON-PRESSURE CONDUITS

In case of testing of non pressure conduits the pipe line shall be subject to a test for of 2.5 meters head of water at the height point of the section under test for 10 minutes. The leakage or quantity of water to be supplied to maintain the test pressure during the period of 10 minutes shall not exceed 0.2 liters/ mm dia of pipes per kilometer length per day.