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TECHNICAL SOLUTIONS
HYDRAULIC CAPACITY
Since the sewerage pipelines operate intermittently,
with daily peaks, and in view of possible changes
of the demographic situation, network design must
cater for unexpected events.
In addition to the safety factor of ductile cast iron, the PAM system offers hydraulic advantages,
which represent a guarantee of trouble-free future:
• A perfectly smooth internal wall: epoxy or high alumina cement mortar applied
by spinning improves water flow.
• Inner diameter at least equivalent to the nominal diameter:
- extra capacity available for higher flows (e.g. peaks and urban growth),
- dimensions of the systeme can therefore be optimised.
• The pipes are straight and resistant to deformities: under stress,
the permitted ovalisation is limited to 4 % (extreme conditions).
The flow coefficient K in the Manning-Strickler formula is 105 for
cement lined ductile iron pipes, depending on the design of the
gravity network (number of manholes and connections, slope…).
K can be chosen between 80 and 90 in accordance with EN752.
The Colebrook-white formula is universally used for determining
the head losses in pipelines flowing full, with a coefficient
k = 0.1 mm for cement lined ductile pipes.
The water stream and the flow capacity
are always maintained.
Saint-Gobain PAM - SEWERAGE - 2012
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