Additional Information - Posters
Plastic Pipes Conference Association # 1998 Gothenburg
Leijstrom, Ifwarson
This paper presents experimental evidences and experiences obta~nedfrom the use of the so-called Miner's rule for determination of lifetime expectancies of plastic pipes subjected to varying testing conditions, i.e. altering temperatures and pressures. Results obtained from some unique long-term pressure tests of PE, PP, PB and PEX (Stage 111) performed at constant temperatures are presented as well as results obtained from cycling tests for validation of Miner's rule. The latter results show that Miner's rule is overestimating the lifetime in many cases for the investigated materials. In one case was just 57% of the lifetime observed compared to the one predicted with Miner's rule. This indicates that much too optimistic results may be predicted with Miner's rule if no care is taken in validating this method before usage. However, more work is needed in order to definitely confirm this conclusion. The paper also gives a background and an introduction to Miner's rule according to ISODIS 13760 and the Standard Extrapolation Method (SEM) according to ISOrTR 9080. Where the SEM is used to support the Miner's rule calculations of the lifetime at altering service conditions.
Related papers
Author(s) : Oertli, Ifwarson
While guaranteed lifetimes of pressure pipes in use is roughly 50 years, it is commonly accepted that a well designed and manufactured HDPE/MDPE pressure pipe would last as long as 100 years without failures. With ever-growing world population and intensifying pollution, it has become increasingly difficult supplying...
Author(s) : Ifwarson, Andersson
This paper presents experimental data for PEX, PEM, PP and PVC pipes exposed to different chemicals. More than 150 plastic pipes of PEX, PEM, PP and PVC have been pressure tested with different chemicals. The chemicals used are; 97% Sulfuric acid, 100% Acetic acid, 30% Sodium hydroxide and a solution of 50%...
Author(s) : Ifwarson, Aoyama
This paper presents experimental data for three Japanese polyolefin pipe grades exposed to chlorinated water. The chlorine concentrations used are 0.5, 1 and 3 ppm. Results are presented in creep rupture diagrams. The results are compared with hydrostatic pressure tests using 0 ppm of chlorine. Extrapolations using...
Author(s) : Leijstrom, Ifwarson
This paper presents results and experiences obtained at Studsvik Material AB from the use of the Standard Extrapolation Method (SEM) according to I S O n R 9080. Results obtained from SEM calculations are demonstrated in creep rupture curves for pipe materials of PE, PP and PEX. Attention is also given to problems...
Author(s) : Gedde, Smith, Ifwarson, Viebke
Polyolefin pipes subjected to extensive hoop stresses fail in a ductile manner (stage I). At lower stresses failure is brittle and may in certain cases be preceded by degradation of the polymer (stage 111). Reviewed in this paper are the changes in polymer structure and antioxidant concentration profiles preceding the...
Author(s) : Ifwarson, Leijstroem
The lifetime of plastic pipes has been studied at Studsvik for nearly 20 years. This paper presents results obtained from hydrostatic pressure testing of pipes made from polyethylene, crosslinked polyethylene and polypropylene. Examples of how different factors influence the lifetime of plastic pipes are explained in...
Author(s) : Eriksson, Ifwarson
Since 1978 STUDSVIK has been testing a PEMoD-grade from Unifos Kemi AB for applications in the temperature range 30 - 60 C. The aim has been to study the long term properties of the material and thus to enable its life to be determined. Pressure testing has show; that the material is expected to last for 50 years at...
Members of the Association
