ISO 10928:2024 プラスチック配管システム | ページ 2

Foreword

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This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.

This fourth edition cancels and replaces the third edition (ISO 10928:2016), which has been technically revised.

The main changes are as follows:

• Annex B, “Non-linear relationships”, has been removed due to its complexity and highly specialized and limited application;
• Formula (B.3) [Formula (C.3) in ISO 10928:2016] has been corrected to include a factor 2 before Bx_L.

Introduction

This document describes the procedures intended for analysing the regression of test data, usually with respect to time, and the use of the results in the design and assessment of conformity with performance requirements. Its applicability is limited to use with data obtained from tests carried out on samples. Referring standards require estimates to be made of the long-term properties of the pipe for such parameters as circumferential tensile strength, long-term ring deflection, strain corrosion and creep or relaxation stiffness.

A range of statistical techniques that can be used to analyse the test data produced by destructive tests were investigated in the preparation of this document. Many of these simple techniques require the logarithms of the data to:

• a) be normally distributed;
• b) produce a regression line having a negative slope; and
• c) have a sufficiently high regression correlation (see Table 1).

Analysis of data from several tests showed that in the destructive test context, while conditions b) and c) can be satisfied, there is often a skew to the distribution and hence condition a) is not satisfied. Further investigation into techniques that can handle skewed distributions resulted in the adoption of the covariance method (method A, see 5.2) for the analysis of such data within this document.

The results from non-destructive tests, such as long-term creep or relaxation stiffness, often satisfy all three conditions. Therefore, a simpler procedure, using time as the independent variable (method B, see 5.3), can also be used in accordance with this document.

These two analysis procedures (method A and method B) are limited to analysis methods specified in ISO product standards or test methods. Other analysis procedures can be useful for the extrapolation and prediction of long-term behaviour of some properties of glass-reinforced thermosetting plastics (GRP) piping products. For example, a second-order polynomial analysis is sometimes useful in the extrapolation of creep and relaxation data. This is particularly the case for analysing shorter term data ここで, the shape of the creep or relaxation curve can deviate considerably from linear. A second-order polynomial analysis is included in Annex A.

1 Scope

This document specifies procedures suitable for the analysis of data which, when converted into logarithms of the values, have either a normal or a skewed distribution. It is intended for use with test methods and referring standards for glass-reinforced thermosetting plastics (GRP) pipes or fittings for the analysis of properties as a function of time. However, it can also be used for the analysis of other data.

Two methods are specified, which are used depending on the nature of the data. Extrapolation using these techniques typically extends a trend from data gathered over a period of approximately 10 000 h to a prediction of the property at 50 years, which is the typical maximum extrapolation time.

This document only addresses the analysis of data. The test procedures for collecting the data, the number of samples required and the time period over which data are collected are covered by the referring standards and/or test methods. Clause 6 discusses how the data analysis methods are applied to product testing and design.

2 Normative references

There are no normative references in this document.

3 Terms and definitions

No terms and definitions are listed in this document.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

Bibliography