Above ground
Above ground

For above ground installations the pipes are laid on supports or cradles and fastened with straps to ensure stability. The supports are usually concrete or steel; the fastening straps are made of steel.

Both thrust-bearing pipe systems and non-thrust bearing systems can be installed above ground.

Non-thrust bearing pipes and joints
Non-thrust bearing pipe systems carry the fluid pressure, but are not designed to transfer thrust forces and therefore require thrust blocks or other supports to resist unbalanced thrust. The unbalanced thrust will be generated at any change in direction of the pipeline, or change in geometry or cross sectional area, i.e. at elbows, reducers, valves, branches, bifurcations etc. Thrust blocks are usually made of concrete and shall encase the fitting completely and transfer the thrust safely to solid ground. In most cases the thrust blocks must be reinforced in order to transfer the load. The water pressure in the system will generate hoop stresses in the pipes, but axial stresses will be secondary.

For analysis of non-thrust bearing pipes and joints, care needs to be taken to include water pressure when stability is checked. FLOWTITE Technology has designed and analysed the most common of installations. More information at FLOWTITE Installation Guide Above Ground with non-restrained Joints.

Thrust-bearing pipes and joints
Thrust-bearing pipe systems carry the fluid pressure and are also able to transfer longitudinal forces or bending moments resulting from end-thrust. Both the pipe and the joints have axial load bearing capacity. Unbalanced thrust can thus be resisted by the piping system and thrust blocks are not necessary; careful placement of support will ensure that the axial stresses is under the allowable limits. [Various terminology has been used for such systems by the piping industry: biaxial pipes and joints, restrained joints, self-anchoring system, with end-thrust, tied joints, tensile joints etc.]

Thrust-bearing piping systems require a rigorous three dimensional structural analysis. The piping engineer uses specialised computer software to determine all stresses and displacements, as well as support forces. To minimize stresses the piping system may need to be analysed several times with varying configurations and support placement. Because of axial stresses generated in the system the pressure class of the pipes and joints usually need to be higher than the operating pressure. Because FLOWTITE pipes have lower E-moduli than e.g. steel, the force on components are often lower.