Pipe Support for Roof


Ken Dodson

= 34. 2 ft/s^2

The Modulus of Elasticity of PVC 1120 at 73. 4° F is 400 000 psi, while that for HDPE 3408 is usually 115 000 psi. The table below summarizes your surge pressures expected for any 1 ft/s instantaneous velocity change in both PVC together with HDPE. For velocities besides 1 ft/s, the surge will be equal to the values in the table multiplied by the actual velocity in ft/s (we. e. if V = 3 ft/s, surge = 3 times the table value for any given material and DOCTOR).

Table 3 – One Ft/s Spikes


(E=400 000 psi) (E=115 000 psi)


DRPs (psi)DRPs (psi)

5110. 8218. 8

4111. 4179. 9

32. 512. 813. 511. 3

2514. 71112. 7

2116. 0914. 3

1817. 47. 316. 3

1419. To investigate a typical situation, a pressure pipeline is usually buried 10 feet in soil which includes a density of 120 lb/ft^3 and subjected to a momentary negative 10 psi vacuum due to a transient shockwave. A comprehensive negative load of (-)18. 3 psi would be created. As can be observed from the above kitchen table, this negative pressure would exceed some of the Pcr values of PVC (DR41 and 51) and HDPE (DR17, twenty one, 26 and 32. 5). You\’re eliminating minimum soil stiffness associated with 500 psi, the values of Pb for any DR\’s of both supplies will easily exceed the total negative load and buckling will not occur.

If any of these pipes happened to have significant voids in their backfill, it is conceivable that buckling failure may well occur. It is imperative that will lower pressure rated thermoplastic pipe be installed to be able to have a minimum soil stiffness, E\’, of 500 psi. Voids inside haunch support zone may be prevented by using adequate bedding material and gentle compaction. This point is especially relevant if ever considering assembling thermoplastic pipe previously mentioned the trench and going it in before backfilling. Buckling can be a situation far less apt to occur if the pipe is installed using a conventional open trench with moderate compaction next to the pipe as the brand installation progresses.


To do a thorough comparison with PVC and HDPE, many other factors must be considered such since: material cost, installation charge, connection methods, and manufacturing test requirements. The designer should also ensure that each material has a successful track record for the application being considered.

This report has offered a snapshot comparison with the 2 thermoplastic materials used quite often for pressure pipe in The united states – PVC and HDPE. The capacity of each material was illustrated with regard to their pressure ratings, surge performance and buckling resistance allowing designer an equal comparison between PVC and HDPE.


Qualitypipe fabrication is an important prerogative of all industry sectors. And also to achieve perfection there are plenty of steps involved like melting, forging, machining, welding and numerous others. Every single one these steps are equally important and all the manufacturers involved in fabrication of pipes should include the following in their scope of work for pipe support fabrication. They are:

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