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How to avoid PVC-U tube caused by thermal expansion and contraction of the fault

Update:05 Dec 2017
Summary:

PVC-U pipe thermal expansion coefficient of 0.07mm / (m […]

PVC-U pipe thermal expansion coefficient of 0.07mm / (m · ℃), larger than the traditional pipe. Therefore, we should pay attention to the longitudinal deformation caused by the temperature difference, especially the surface water as the water supply system. As the rubber ring connecting pipe interface with scalability, may not consider this issue, but for the adhesive pipe connection, especially bright pipe, because the interface after bonding is rigid, can not expand and contract, if no expansion joints, The huge stress caused by expansion or contraction will act on the pipe itself or on the pipe. After calculation, for 75 ~ 200mm diameter water pipe, negative temperature difference of 12 ~ 15 ℃ makes the pipe subjected to longitudinal tensile stress which is equivalent to the inner water pressure of 1.18 ~ 3.04MPa in the pipe, which is very large stress, , The correct approach is to add in the design of flexible joints. The number of telescopic sections should be calculated according to the closed temperature difference in pipeline operation using the following formula.

ΔL = 0.07 L · Δt

Where: ΔL-longitudinal deformation due to temperature difference, mm

0.07-PVC-U pipe linear expansion coefficient (mm / m · ℃)

L-pipeline length, m

Δt-laying and use of medium temperature difference between inside and outside, ℃

In general, the telescopic section of the distance should not be greater than 150 meters, the amount of expansion should not be less than 12cm, when the telescopic tube is small, the number of expansion joints should be added. It is noteworthy that the connection to the flanged stubs should be made with a flexible connection because PVC-U flanges are the most easily damaged by longitudinal tension among the numerous PVC-U fittings.

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