Pipe laying through tunnels
Laying a socket pipe system through a tunnel involves:
– accommodation of thermal expansion,
– anchorage of components subjected to hydraulic thrust.
Ductile iron socket pipes provide a simple solution, particularly if cramped conditions do not permit the use of large joint assembly equipment.
– one per pipe,
– each support behind a socket,
– a support saddle (α = 120° is a good precaution),
– a fixing clamp with rubber lining.
The advantage of ductile iron mains is that expansion absorbers are not necessary.
Fixed points: every clamp must be sufficiently secured to constitute a fixed point (provide a clamp of sufficient width).
Expansion accommodation: the push-in joint between each support acts as an expansion absorber, taking up the expansion of the pipe length (within the permissible limits of ΔT).
Every component subjected to hydraulic thrust (bends, tees, isolating valves...) must be stabilized by an anchoring system (rigid welding to fixing plates is often a good method).
Directional changes involving large radius bends can be achieved simply by joint deflection (within the specified limits).
In this case, care must be taken to reinforce the support anchorage of the pipes involved, having assessed the hydraulic thrusts at the joint positions.
It is recommended to include a safety coefficient, to compensate the hydraulic forces due to a possible misalignment of the pipeline.