Project managment

Handling and jointing large pipes and fittings

All ductile iron or steel pipes and fittings must be handled with proper wide lifting slings to prevent damage to their sheathing or coating. The use of chains or wire ropes ‘blocked off’ pipes with pieces of wood should not be permitted by the resident engineer. Apart from possible damage to the coating, the packing pieces may slip out when the chain or wire rope slackens and the pipe may fall. Handling of heavy pipes and fittings must be done with every precaution.

The crane handling a heavy pipe must not slacken off until the pipelaying foreman is certain it is safe to do so, and no man would be put in danger if the pipe should move. Timber props, packings and wedges in adequate numbers should be available to secure the pipe before it is finally moved into position for jointing by slow jacking or barring to get it into position, the wedges being continuously adjusted to keep the pipe from moving unexpectedly.
Where large diameter pipes and fittings, such as bends, have to be fitted together there is often difficulty in getting them set so that their joints match accurately, especially when a bend must be fixed at an angle to the horizontal.
Before lowering such a bend into position it is worthwhile measuring it to find and mark, on the outside of the pipe at both ends, the diameters on the true axis of the bend and at 90 degrees to it. These should be accurately marked with a chiselled or indelible pencil line on white paint, not marked with chalk which will rub off. It is quite difficult to locate the axis of a bend accurately, even when the bend is above ground; and can be frustratingly difficult when the bend is laid in some trench or basement. It is also good practice to put a mark round the spigot end of a pipe showing how far it must be inserted into a socket. The relationship of this line to the socket face indicates whether the alignment is satisfactory.
Spigot and socket pipes need to be lined up within 1 degree to achieve a good joint; pipe flanges have to be lined up exactly parallel, with the bolt holes exactly matching, and as close as possible after insertion of the necessary joint ring before final drawing together of the flanges by progressive tightening of the bolts. To set a 1.2 m diameter 45 degree bend accurately to join a horizontal pipe at one end and an inclined pipe at the other may take a gang of four men and a crane driver two or three hours. If things do not go well it may take much longer.

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