Pipes are typically laid within trenches and extreme caution must be exercised when working in trenches. Collapse of trenches can be very harmful, and has resulted in moderate to severe injuries.
Any trench deeper than 1200mm (4 feet) MUST be properly shored up.
Do NOT take risks!
- Do not to have trenches open for any longer than necessary.
- Use barrier fencing and/or security barriers to keep children and members of the public out of excavations.
- Try not to have trenches open in inclement weather.
- Try not to have trenches open too far in advance of pipe-laying.
- Keep trench width to a minimum (generally pipe diameter plus 300mm).
- Always stand at least 600mm back from the edge of open trenches.
- Never work alone in a trench – always have a ‘buddy’ or preferably a banksman.
AIC TIPS ON HOW TO PROFESSIONALLY LAY VITRIFIED CLAY PIPES
1- Unloading Trucks: Pipes are to be checked on unloading. Possible damages must be reported immediately. Checking can be done by using white powder.
Use a Crane or Excavator: When removing, lifting belts must be placed outside around the pallets & outside of the base timber.
Carefully, Steer the pallets manually to prevent them colliding with anything. Pallets should not be moved using any levers or crowbars while on the truck. Pipes should not be subjected to any hard impact.
Use a Forklift: The pallets of pipes should be placed transversely on the forks & the forks should be positioned sufficiently widely apart.
When placing the pallets on the forklift, a protective piece of timber should be between the parcel and the forks base for a smooth transition.
2- Storage on Site: Pipes should not be placed on hard ground with force. There must be sufficient space between individual pallets. Sealing elements can be saved from damage by setting them down on a leveled surface and off the floor by using a piece of wood.
3- Transportation to Pipe Trench: It is preferred to move the whole pallets to the point of destination where they will be laid before opening or dismantling the pallets.
The parcel of pipes must be carefully place on a flat surface so that the pipes don’t slip or have a damaging impact when unloading.
Transport individual pipes with belts (mark on crown – yellow or white spot = center of gravity– pipe hangs level).
Individual pipes must not be transported in excavator shovel; belts are a more secure method.
4- Installation: Both ends of the pipe should be checked optically and internally with white talcum powder to find any cracks that might have occurred before they pipe are laid in the ground.
The paint mark must always point upwards.
The pipe inverts will be at level (any steps that might arise between two pipes will be within the permissible tolerance)
A possible small variance between two jointed pipes in the axial line will not lie in the flow zone (any small deviation of straightness will lay aside)
The shape of the seals enables pre-centering to be carried out. First lubricant should be applied to the spigot and to the socket seal.
Short lengths of the pipes should be used at points where differences in settling are to be expected, e.g. in the region of the shafts or at the wall breakthroughs, to produce flexible connections.
Pushing the pipes together with the crane bucket and a belt (≥ DN 400mm).
Pushing the pipes together with a crowbar – always have a piece of timber between the pipe and the crowbar.
It’s not recommended to push against the pipe with the excavator shovel to make any corrections in the axial line.
In a normal practice, the sockets will point in the upside direction and the pipes should be installed in the center-line of the trench.
5- Excavation & Compaction:
For the minimum required width of the trench (on accordance with nominal size and depth of laying), refer to EN 1610 for the laying of sewer pipes.
A trench that is too narrow makes it difficult to compact the bedding zone properly. A trench that is too wide increases the laying costs and both increase the loading on the pipe.
Minimum trench width for security reasons are mentioned in the table below. To reach good compaction results the specifier might precise larger trench widths.
Minimum trench width, in relation to DN and in relation to depth.
Socket holes must be made so that the sockets do not lie on a compacted bottom; this would result in point loading. Support must be provided over the whole barrel length.
Between the trench bottom and pipe a bedding angle of at least 90˚ must be realized with materials that can be compacted well.
The backfilling directly above the pipe and to a width equal to the outside diameter of the pipe should be compacted by hand where need be.
Mechanical compaction of the main backfill directly above the pipe should not be commenced until there is a total depth of cover of at least 300 mm above the top of the pipe. This layer must consist of stone-free soil.
The selection of the compacting device, the number of passes and the thickness of the layer to be compacted should match the back material.
If the layer above the pipe is inadequately thick (less than 30 cm), do not move the compactor over the pipeline.
When compacting at the sides of the trench, kindly ensure that the compactor does not contact the pipes. Similarly, do not run the compactor over the pipes.