LYING OF WATER SUPPLY PIPELINE:
The laying of water supply pipeline should be done according to the following steps
( 1) Marking of centre line and the width of the trench-
·
The centre line of the proposed
pipe line should be marked on the ground by means of stakes at an interval of
20m on straight line.
·
The width of general excavation
should be 30cm more than the external diameter of the pipe.
·
The excavation width is marked
on the ground.
·
At the place of joints the
width of excavation should be more than 30cm the normal trench width.
·
At joints the depth of
excavation should be 15cm more than the normal depth.
(2) Excavation of trench-
·
The excavation of the trench is
carried put according to the marking on the ground.
·
The excavated earth is dumped
on the both sides of the trench.
·
The depth of the trench should
not be less than 90cm to protect the pipeline from being damaged by external
loads.
·
The excavations should be done
carefully so that the underground cables may not be damaged.
(3) Side protection of trench-
·
When the excavation is done
along the hard soil, the side protection may not be provided.
·
When the excavation runs along
the loose soil, the side protection must be provided.
·
The side protection should be
done by wooden planks or iron sheets which are supported by timber blocks,
timber struts and wedges.
(4) Preparation of sub grade-
·
For small diameter pipes the
sub grade is prepared by simply ramming a layer of sand or clay to a thickness
of 15 to 30cm.
·
For large diameter pipes the
sub grade is prepared by cement concrete foundation (1:3:6) over a layer of
brick. Concrete benching should be provided to hold the pipeline in position
(5) Laying and jointing-
·
When the bed of trench is
prepared, the pipes are dropped in the trench carefully and placed side by
side.
·
Small diameter pipes may be
placed in the trench by manual labours
·
But the large diameter pipes
should be placed in the trench by crane or other mechanical device.
·
Then the operation of jointing
is done according to the recommended joints as pre pipe materials.
(6) Testing-
·
After laying the pipe in
position, they are tested for water leakage and pressure.
(7) Filling up the trench-
·
After testing, the soil which
was excavated is filled back in the trenches around the pipes and should be
well rammed.
(8) SETTING OUT ALIGNMENT OF PIPE LINE:
·
First of all detailed map of
whole area is prepared, where pipe line laying work is started.
·
Centre line of proposed pipe
line is declared on the map with consider the position of sewer line, telephone
line, electric poll, underground cables..
·
The process of marking the
proposed line is started from the reservoir tank side.
·
The pegs are entombing at a
distance of 30 meter in the center line of the pipe line with the help of
theodolite and compass.
But on the curves these pegs are entomb at a distance of approximately 7.5 meter to 15 meter.