Laying above ground
Laying of a main above ground involves determining:
- the support system,
- the accommodation of thermal expansion,
- the anchorage of components subjected to hydraulic thrust.
The following paragraphs give the general principles usually followed when laying STANDARD pipes above ground.
– 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 pipelines is that they do not require the installation of expansion absorbers.
Fixed point: every clamp must be sufficiently secured to constitute a fixed point (use a clamp of adequate 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).
Any component subjected to hydraulic thrust (bends, tees, tapers) must be stabilized.
Directional changes involving large radius bends can be negotiated simply by joint deflection (within the specified limits). In this case, care must be taken to reinforce the saddle anchorage of pipes involved, having assessed the hydraulic thrusts at the deflected joint positions.
Provision of an adequate safety margin on the support dimensions (saddles and clamps) is recommended, to compensate for hydraulic forces due to any misalignment of the pipes.