Figure 7 shows that for the same amount of crack growth/extension ([DELTA]a), the variations of SIF with crack growth in the PENT and SENT and whole-pipe tensile specimens are different.
From earlier investigations (9) it was found that the SCG test failure time using SENT tests on parent material could be correlated to the 10k or 2k PENT failures on the compounded resin materials.
Nomenclature BPV Boiler and Pressure Vessel DR dimensional ratio (DR = OD/thickness) FEA finite element analysis HDPE high-density polyethylene ID inner diameter of pipe OD outer diameter of pipe PE polyethylene PENT Pennsylvania edge notch tension SCG slow crack growth SENT single edge notch tension SIF stress intensity factor ([K.
The above calculation was repeated for the case of a 100-year lifetime and a PENT value of 500 hr.
Note that the above results depend on the ratio of lifetime to PENT value and not on unique values of life time or PENT.
This is obviously a poor criterion since the notch which causes a certain lifetime is strongly nonlinearly related to thickness and strongly depends on the PENT value.
The answer depends on the hoop stress, the average ground temperature, and the PENT value of the resin.
t(pipe) = 118,000 t(PENT) hours or 13 years of pipe life time corresponds to 1 hr of PENT.
The primary control of the life time of the pipe depends on the choice of the resin with respect to its PENT value.
85 241 copolymer (low naphthalate content) PENT
M & G, Hipertuf 86017- 0.