PIPE CUTTING
For the installation of bends, branches and valves, pipelines require pieces of pipes of
varying lengths. The exact length can only be determined on the site and one must be able
to cut the pipes easily, quickly and safely. |
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CUTTING MACHINES
Today abrasive disc cutters with various kinds, of power supply are used to cut
ductile iron pipes. These cutters are powered by electric or compressed air connections or
they can be driven indirectly by internal combustion engines.
Many of the abrasive disc cutters in the market can be fitted with both abrasive cut of
discs for cutting and with roughing discs for rounding off the cut edges. If only one
machine is available on site then it should be suitable for both types of discs.
Stages in cutting operation
The pipe should be placed on level ground or on square timbers in such a way that
during cutting, the cutting disc does not become jammed and the remaining pipe wall does
not prematurely break away.
Marking : A line marked all around the pipe facilitates a
straight cut. The line is simply drawn along a steel band which is bent around the pipe.
Cutting : Using the cutting disc, the ductile iron and cement mortar lined pipe wall is cut through completely at one point. The pipe is then cut along the marked line in a single operation.
Rounding off : For jointing into sockets of the push – in
type, the new spigot end must be chamfered as the original spigot end. Only thus the spigot
end can be correctly inserted in the socket without damaging the gasket or pressing it out of it’s seat. A roughing disc is used for chamfering.
Re-coating : Subsequently, the bare metal surface should be
re-coated with zinc rich paint and a finishing layer of bitumen.
Marking the insertion depth : Before assembling the joint,
lines should be marked on the new spigot, showing the correct insertion depth of the spigot
end in the socket.
General
:
The external diameter of > DN 300 at the cut area should
conform to the following standards to ensure a satisfactory joint.
| E
x t e r n a l d I a m e t e r ( D E) |
DN (mm) |
Max (Tape) |
Min (Tape) |
Max (circum Tape) |
Min (circum Tape) |
350 |
1190.0 |
1177.0 |
379.0 |
374.6 |
400 |
1351.0 |
1337.0 |
430.0 |
425.5 |
450 |
1511.0 |
1497.0 |
481.0 |
476.4 |
500 |
1674.0 |
1660.0 |
533.0 |
528.2 |
600 |
1998.0 |
1983.0 |
636.0 |
631.0 |
700 |
2321.0 |
2306.0 |
739.0 |
733.7 |
800 |
2648.0 |
2631.0 |
843.0 |
837.5 |
900 |
2972.0 |
2953.0 |
946.0 |
940.2 |
1000 |
3295.0 |
3276.0 |
1049.0 |
1043.0 |
| 1100 |
3622.0 |
3600.0 |
1153 |
1146 |
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