Plastic Pipes are classified by their ring stiffness. The preferred stiffness classes as described in several product standards are: SN2, SN4, SN8 and SN16, where SN is Nominal Stiffness (kN/m2). Stiffness of pipes is important if they are to withstand external loadings during installation.
The higher the figure, the stiffer the pipe! After correct installation, pipe deflection remains very limited but it will continue to some extent for a while.
In relation to the soil in which it is embedded, the plastic pipe behaves in a 'flexible' way.
This means that further deflection in time depends of the settlement of the soil around the pipe. Basically, the pipe follows the soil movement or settlement of the backfill, as technicians call it.
This means that good installation of pipes will result in good soil settlement.Further deflection will remain limited. For flexible pipes, the soil loading is distributed and supported by the surrounding soil.Stresses and strains caused by the deflection of the pipe will occur within the pipe wall.
However, the induced stresses will never exceed the allowed limit values. The thermoplastic behavior of the pipe material is such that the induced stresses are relaxing to a very low level.It has to be noted that induced strains are far below the allowable levels. This flexible behaviour means that the pipe will not fail.It will exhibit only more deflection while keeping its function without breaking. However, rigid pipes by their very nature are not flexible and will not follow ground movements.
They will bear all the ground loadings, whatever the soil settlement.
This means that when a rigid pipe is subject to excessive loading, it will reach the limit for stress values more quickly and break. It can therefore be concluded that the flexibility of plastic pipes is such that it offers an extra dimension of safety.Buried Pipes need flexibility9Źródło: https://en.wikipedia.org/wiki/Plastic_pipework#Flexibility
Within a week, they are repaired by a team of plumbers employed in cooperatives.In contrast, during the holiday season, or in the case of sudden death during the night, residents will be able to call the emergency water and sanitation and ask to come to the block where the accident occurred.
In some situations it may become necessary to purify the basement flooded by the sewage system before the tenants will be able again to enter it.
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow ? liquids and gases (fluids), slurries, powders and masses of small solids.
It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members. In common usage the words pipe and tube are usually interchangeable, but in industry and engineering, the terms are uniquely defined.
The term "tube" is also commonly applied to non-cylindrical sections, i.e., square or rectangular tubing.
For materials that are inflexible, cannot be formed, or where construction is governed by codes or standards, tube assemblies are also constructed with the use of tube fittings.Źródło: https://en.wikipedia.org/wiki/Pipe_(fluid_conveyance).