ISO 3126:2005

INTERNATIONAL ISO
STANDARD 3126
Second edition
2005-03-01
Plastics piping systems — Plastics
components — Determination of
dimensions
Systèmes de canalisations en plastiques — Composants en
plastiques — Détermination des dimensions

Reference number
©
ISO 2005
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ii © ISO 2005 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 3126 was prepared by the European Committee for Standardization (CEN) in collaboration with Technical
Committee ISO/TC 138, Plastics pipes, fittings and valves for the transport of fluids, Subcommittee SC 5,
General properties of pipes, fittings and valves of plastic materials and their accessories — Test methods and
basic specifications, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
Throughout the text of this document, read “.this European Standard.” to mean “.this International
Standard.”.
This second edition cancels and replaces the first edition (ISO 3126:1974), which has been technically
revised.
C ontents           page
Foreword.v
1 Scope.1
2 Normative references .1
3 Terms, definitions and symbols .1
3.1 Terms and definitions.1
3.2 Symbols .1
4 Measuring devices .2
4.1 General requirements .2
4.2 Instruments .2
5 Determination of dimensions.3
5.1 General .3
5.2 Wall thicknesses .4
5.3 Diameters.5
5.4 Out-of-roundness .6
5.5 Pipe lengths .6
5.6 End squareness of pipes and fittings.7
6 Determination of other geometrical characteristics related to fittings .8
6.1 General .8
6.2 Bends .9
6.3 Branches .12
6.4 Reducers.14
7 Flanges, loose flanges and collar .15
7.1 General .15
7.2 Outside diameter of the flange, loose flange and collar.17
7.3 Bore diameter of the flange or collar.17
7.4 Bolt hole diameter .17
7.5 Bolt hole distribution.17
7.6 Concentricity of bolt circle diameter.17
7.7 Pitch circle diameter.17
7.8 Shoulder diameter of flange and collar .18
7.9 Flange and collar thickness .18
7.10 Length of the flange and collar.18
8 Other measurements .18
Bibliography .19

iv © ISO 2005 – All rights reserved

Foreword
This document (EN ISO 3126:2005) has been prepared by Technical Committee CEN /TC 155, "Plastics piping

systems and ducting systems", the secretariat of which is held by NEN in collaboration with Technical Committee
ISO/TC 138 "Plastics pipes, fittings and valves for the transport of fluids".
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by September 2005, and conflicting national standards shall be withdrawn at the
latest by September 2005.
This document is one of a series of standards on test methods, which support system standards for plastics piping
systems and ducting systems.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark,
Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

1 Scope
This document specifies methods for measurement and/or determination of the dimensions of plastics pipes and
fittings and the accuracy of the measurement.
It specifies procedures for measuring angles, diameters, lengths, squareness and wall thicknesses for the
purposes of checking conformity to geometric limits.
NOTE This document is using metric units. However the procedures and tolerances are applicable to other units by using
appropriate conversion factors.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including any
amendments) applies.
ISO/R 463, Dial gauges reading in 0,01 mm, 0,001 in and 0,0001 in.
ISO 3599, Vernier callipers reading to 0,1 and 0,05 mm.
ISO 3611, Micrometer callipers for external measurement.
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method.
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
accuracy
closeness of agreement between a test result and the accepted reference value
NOTE  The term "accuracy", when applied to a set of test results, involves a combination of random components and a
common systematic error or bias component (ISO 3534-1).
3.1.2
calibration
set of operations that establish, under specified conditions, the relationship between values of quantities indicated
by a measuring instrument or measuring system, or values represented by a material measure or a reference
material, and the corresponding values realised by standards
3.1.3
reference standard
internationally accepted definition of a given unit of measurement
3.2 Symbols
b : distance between the edge of a flange bolt hole and its bore
b : distance between the edge of a flange bolt hole and its outside diameter
b : distance between the centre of a flange bolt hole and its bore
b : distance between the centre of a flange bolt hole and its outside diameter
c : distance between the edges of two adjacent flange bolt holes
c : distance between the centres of two adjacent flange bolt holes
d : outside diameter of a (part of a) component
e
d : mean inside diameter of the main of a branch
i,m
d : outside diameter of a socket end
d : outside diameter of a spigot end
d : bore of a flange
d : diameter of a flange bolt hole
D : outside diameter of a flange
e : wall thickness of a component
k : pitch circle diameter of a flange
L : effective length of a branch
e,b
L : effective length of the main of a branch
e,m
L : effective length of a reducer
e,r
L : effective length of the socket end of a fitting
e,so
L : effective length of the spigot end of a fitting
e,sp
L : length of the straight part of a socket or a spigot end of a fitting
str
L : length of the tapered part of a reducer
t
L : maximum out-of-squareness distance from theoretical
L : measured distance from the root of the angle between a straight ruler and a reference surface to the
component along the surface
L : measured distance from the root of the angle between a straight ruler and a reference surface to the
component along the ruler
L : vertical distance from a reference surface to the nearest point of the upper end
L : socket insertion depth
L : overall length of a branch main
L : distance, measured in the centre-line plane of a branch, between the end of the branch spigot or socket to
the bottom of the main
L : overall length of a reducer
L : distance between the edges of two selected bolt holes of a flange
L : overall length of a flange in axial direction
γ : calculated angle of out-of-squareness
θ : angle of bend or branch
4 Measuring devices
4.1 Gen
...