6.7.3 Pipe Joints

There are two types of joints forAC pipes.

-Cast iron detachable joint, and
- AC coupling joint.

(a) Cast iron detachable Joints

This consists of two cast iron flanges, a cast iron central collar and two rubber rings along with a set of nuts and bolts, for a particular joint. For this joint of the AC pipes should have flush ends. For jointing a flange, a rubber ring and a collar are slipped to the first pipe in that order; a flange and a rubber ring being introduced from the jointing of the next pipe. Both the pipes are now aligned and the collar centralised and the joints of the flanges tightened with nuts and bolts.

(b) A.C Coupling Joint

This consists of an A.C Coupling and three special rubber rings. The pipes for these joints have chamfered ends. These rubber rings are positioned in the grooves inside the coupling, then grease is applied on the chamferred end and the pipe and coupling is pushed with the help of a jack against the pipe. The mouth of the pipe is then placed in the mouth of the coupling end and then pushed so as to bring the two chamfered ends close to each other. Wherever necessary change over from cast iron pipe to AC pipes or vice versa should be done with the help of suitable adapters IS 6530- 1972 may be followed for laying A.C pipes.

6.7.4 Pressure Testing

The procedure for the test as adopted generally is as follows

(a) At a time one section of the pipe line between two sluice valves is taken up for testing. The section usually taken is about 500 meters long.

(b) One of the valves is closed and the water is admitted into the pipe through the other, manipulating air valves suitably.

(If there are no sluice valves in between the section, the end of the section can be sealed temporarily with an end cap having an outlet which can serve as an air relief vent or for filling the line as may be required. The pipe line after it is filled, should be allowed to stand for 24 hours before pressure testing).

(c) After filling this sluice valve is closed and the pipe section is isolated.

(d) Pressure gaugages are fitted at suitable intervals on the crown into the holes meant for the purpose.

(e) The pipe section is then connected to the delivery side of the pump through a small valve.

(f) The pump is then worked till the pressure inside reaches the designed value which can be read from the pressure gauges fixed.

(g) After the required pressure has been attained, the valves is closed and the pump disconnected.

(h) The pipe is then kept under the desired pressure during inspection for any defect i.e. leakages at the jionts etc. The test pressures will be generally as specified in 6.7.1 and Appendix 6.4. The water will then be emptied through scour valves and defects observed in the test will be rectified.