Regression analysis according to ISO 9080 of the pipe grade PB 4235
Client: Basell Polyolefins

Introduction
Bodycote Polymer (formerly Studsvik Polymer) offers accredited services according to ISO 9080, i.e. hydrostatic pressure testing followed by evaluation of the long-term hydrostatic strength.

Task
The aim of this work was to utilise the Standard Extrapolation Method (SEM) according to ISO 9080 in order to obtain a classification of the pipe grade PB 4235.
The work covers hydrostatic pressure testing at 20, 70 and 95°C. The hydrostatic pressure testing was followed by a SEM-evaluation according to ISO 9080.

Results obtained
Multiple linear regression analysis was performed on creep rupture data using the computer program delivered by Becetel SEM V 1.16t.

Hydrostatic pressure testing has also been performed at 110°C with water as the internal and air as the external test medium. The test results show that the pipe grade PB 4235 passes 8 760 h at 2.4 MPa.

Number of observations

20°C	70°C	95°C	110°C
30	46	48	46

Extrapolated strength values

Temp (°C)	Time (yrs)	σLPL (MPa)	σLTHS (MPa)
20	50	14.13	15.13
20	100	13.59	14.58
70	50	6.34	7.10
70	53.7	6.30	7.06
95	4.29	4.32	4.96
110	1.07	3.13	3.68

Classification: MRS = 14MPa
If you want more information please contact Mr. Mattias Svedberg, phone +46 155 22 14 56