# BS EN 00705-1995

BRITISH STANDARD BS EN 705:1995 BS 2782-12: Methods 1220A to C: 1995 Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Methods for regression analyses and their use The European Standard EN 705:1994 has the status of a British StandardBSEN 705:1995 This British Standard, having been prepared under the directionof the Sector Board forMaterials and Chemicals, waspublished under the authorityof the Standards Boardand comes into effect on 15November1995 © BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference PRI/61 Draft for comment 92/41338 DC ISBN 0 580 24136 X Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/61, Plastics piping systems and components, upon which the following bodies were represented: British Gas plc British Plastics Federation British Plumbing Fittings Manufacturers’ Association British Valve and Actuator Manufacturers’ Association Department of the Environment (British Board of Agrément) Department of the Environment (Building Research Establishment) Department of the Environment (Property and Buildings Directorate) Department of Transport Electricity Association Federation of Civil Engineering Contractors Health and Safety Executive Institute of Building Control Institute of Materials Institution of Civil Engineers Institution of Gas Engineers Institution of Water and Environmental Management National Association of Plumbing, Heating and Mechanical Services Contractors Pipeline Industries Guild Plastics Land Drainage Manufacturers’ Association Society of British Gas Industries Society of British Water Industries Water Companies Association Water Services Association of England and Wales Amendments issued since publication Amd. No. Date CommentsBSEN 705:1995 © BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN 705 5BSEN 705:1995 ii © BSI 01-2000 National foreword This British Standard has been prepared by Technical Committee PRI/61, and is the English language version of EN705:1994 Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Methods for regression analyses and their use, published by the European Committee for Standardization (CEN). It is incorporated into BS2782 Methods of testing plastics — Part12. Reinforced plastics pipes, fittings and valves, as Methods1220A to C:1995 as follows. Method1220A corresponds to method A (Covariance method) of EN705:1994. Method1220B corresponds to method B (Regression with time as the independent variable) of EN705:1994. Method1220C corresponds to method C (Second order polynomial relationships) of EN705:1994. These methods are incorporated into BS2782 for association with related test methods for plastics materials and plastics piping components. This test method has been prepared for reference by other standards under preparation by CEN for specification of reinforced plastics piping systems and components. It has been implemented as a national standard to enable experience of the method to be gained and for use for other fresh applications. It is also for use for the revision or amendment of other national standards as practicable, but it should not be presumed to apply to any existing standard or specification which contains or makes reference to a different method until that standard/specification has been amended or revised to make reference to this method and adjust any requirements as appropriate. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN title page, pages2 to31 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN705 April1994 UDC 621.643.2-036.067.5:621.643.06:620.1:519.2 Descriptors: Pipelines, plastic tubes, pipe fittings, thermosetting resins, reinforced plastics, glass, data, statistical analysis, computation, design inspection English version Plastics piping systems — Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Methods for regression analyses and their use Systèmes de canalisations plastiques — Tubes et raccords plastiques thermodurcissable renforcés de verre (PRV) — Méthodes pour une analyse de régression et leurs utilisations Kunststoff-Rohrleitungssysteme — Rohre und Formstücke aus glasfaserverstärkten duroplastischen Kunststoffen (GFK) — Verfahren zur Regressionsanalyse und deren Anwendung This European Standard was approved by CEN on1994-04-11. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels ©1994 Copyright reserved to CEN members Ref. No. EN705:1994 E EN705:1994 © BSI 01-2000 2 Foreword This standard was prepared by CEN/TC155, Plastics piping systems and ducting systems. This standard is based on document N197 Glass-reinforced thermosetting plastics (GRP) pipes and fittings — Standard extrapolation procedures and their use, prepared by working group1 of Subcommittee6 of Technical Committee138 of the International Organization for Standardization (ISO). It is a modification of ISO/TC138/SC6/WG1 N197 for reasons of possible applicability to other test conditions and alignment with texts of other standards on test methods. The modifications are: — examples have been introduced to enable validation of alternative calculation facilities; — material-dependent requirements are not given; — editorial changes have been introduced. The material-dependent test parameters and/or performance requirements are incorporated in the referring standard. Annex A, which is informative, describes procedures for solving the given set of equations (see3.2.3) on a mathematical basis using the example shown in3.2.6. No existing European Standard is superseded by this standard. This standard is one of a series of standards on test methods which support System Standards for plastics piping systems and ducting systems. This standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October1994, and conflicting national standards shall be withdrawn at the latest by October1994. In accordance with the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, UnitedKingdom. Contents Page Foreword 2 Introduction 5 1 Scope 5 2 Principle 5 3 Procedures for determining the functionalrelationships 5 3.1 Linear relationships — Methods A and B 5 3.2 Second order polynomial relationships — Method C 14 4 Application of methods to product design and testing 16 4.1 General 16 4.2 Design 17 4.3 Examples for validation of calculation procedures for design 20 4.4 Procedures for verifying conformance toproduct design and performance values 23 4.5 Examples for validation of calculation procedures for design or product performance verification 26 Annex A (informative) Mathematical procedures 30 A.1 Matrix system 30 A.2 Substitution system 30 Figure 1 — Regression line from the results inTable 4 11 Figure 2 — Regression line from the results inTable 7 16 Figure 3 — Derived values 18 Figure 4 — Extrapolated values 19 Figure 5 — Example on pressure 21 Figure 6 — Example for ring stiffness 24 Figure 7 — Property test values 25 Table 1 — Minimum values for the squared, r 2 ,andlinear coefficient of correlation, r, for acceptabledata from n pairs of data 7 Table 2 — Percentage points of Student’s t distribution (upper2,5% points; two sided5% levelof confidence; t vfor97,5%) 8 Table 3 — Basic data for example calculation andstatistical analysis validation 10 Table 4 — Estimated mean values, V m , for V 11 Table 5 — Basic data for example calculationandstatistical validation 13 EN705:1994 © BSI 01-2000 3 Page Table 6 — Estimated mean values, V m , for V 13 Table 7 — Estimated mean values, V m , for V 16 Table 8 — Initial burst test results 20 Table 9 — Initial ring stiffness test results 22 Table 10 — Initial burst test failure pressuresforthe sample 26 Table 11 — Times to failure of burst tests of thesample 27 Table 12 — Initial ring stiffness results for thesample 28 Table 13 — Stiffness results at1 000h for thesample 28 4 blank EN705:1994 © BSI 01-2000 5 Introduction This standard has been prepared to describe the procedures intended for analysing the regression of test data, usually with respect to time, and the use of the results in design and assessment of conformity with performance requirements. Its applicability has been limited to use with data obtained from tests carried out on samples. The referring standards require estimates to be made of the long-term properties of the pipe for such parameters as circumferential tensile strength, deflection and creep. The committee investigated a range of statistical techniques that could be used to analyse the test data produced by tests that were destructive. Many of these simple techniques required 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 (seeTable 1). Whilst the last two conditions can be satisfied, analysis has shown that there is a skew to the distribution and hence this primary condition is not satisfied. Further investigation into techniques that can handle skewed distributions resulted in the adoption of the covariance method for analysis of such data for this standard. The results from non-destructive tests, such as creep or changes in deflection with time, often satisfy these three conditions and hence simpler procedures, using time as the independent variable, can also be used in accordance with this standard. 1 Scope This standard 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 the test methods and referring standards for glass-reinforced plastics pipes or fittings for the analysis of properties as a function of, usually, time. However it can be used for the analysis of any other data. For use depending upon the nature of the data, three methods are specified. The extrapolation using these techniques typically extends the trend from data gathered over a period of approximately10000h, to a prediction of the property at50 years. 2 Principle Data are analysed for regression using methods based on least squares analysis which can accommodate the incidence of a skew and/or a normal distribution and the applicability of a first order or a second order polynomial relationship. The three methods of analysis used comprise the following: — method A: covariance using a first order relationship; — method B: least squares with time as the independent variable using a first order relationship; — method C: least squares with time as the independent variable using a second order relationship. The methods include statistical tests for the correlation of the data and the suitability for extrapolation. 3 Procedures for determining the functional relationships 3.1 Linear relationships — Methods A and B 3.1.1 Procedures common to methods A and B Use method A (see3.1.2) or method B (see3.1.3) to fit a straight line of the form where y = a + bx (1) y is the logarithm (lg) of the property being investigated; a is the intercept on the y axis; b is the slope; x is the logarithm (lg) of the time, in hours. EN 705:1994 6 © BSI 01-2000 3.1.2 Method A — Covariance method 3.1.2.1 General For method A calculate the following variables as necessary in accordance with3.1.2.2 to3.1.2.5: where NOTEIf the value of Q xyis greater than zero the slope of the line is positive and if the value of Q xyis less than zero then the slope is negative. 3.1.2.2 Suitability of data Calculate the squared, r 2 , and the linear coefficient of correlation, r, using the following equations: If the value of r 2or r is less than the applicable minimum value given inTable 1 as a function of n, consider the data unsuitable for analysis. 3.1.2.3 Functional relationships To find a and b for the functional relationship line first set then calculate a and b using the following equations: 3.1.2.4 Calculation of variances If t uis the applicable time to failure, then set Using equations(11),(12) and(13) respectively, calculate for i =1 to n the following sequence of statistics: — the best fit x i ‰ for true x i ; — the best fit y i ‰ for true y i ; and (2) (3) (4) Q y is the sum of the squared residuals parallel to the y axis divided by n; Q x is the sum of the squared residuals parallel to the x axis divided by n; Q xy is the sum of the squared residuals perpendicular to the line, divided by n; Y is the arithmetic mean of the y data, i.e. X is the arithmetic mean of the x data, i.e. x i , y i , are individual values; n is the total number of results (pairs of readings for x i , y i ). (5) (6) y = a + bx (1) (7) b = – (¿) 0,5 (8) a = Y – bX (9) x u– lg t u (10)EN705:1994 © BSI 01-2000 7 — the error variance, ‚ 2for x. Calculate the following quantities: Calculate the variance C of the slope b using the following equation: Table 1 — Minimum values for the squared, r 2 , and linear coefficient of correlation, r, for acceptable data from n pairs of data 3.1.2.5 Check for the suitability of data for extrapolation If it is intended to extrapolat