Flanges and their joints - Gasket parameters and test procedures relevant to the design rules for gasketed circular flange connections

This European Standard specifies the gasket parameters required by EN 1591 1 and provides the test procedures for establishing the values of these parameters.
Gaskets which are wholly based upon elastomers, or based upon elastomers with only the inclusion of particulate fillers or particulate reinforcement, as opposed to gaskets combining elastomers, fillers and fibrous reinforcement, are beyond the scope of this document.
NOTE   The testing procedures given might be applicable to gaskets of other shapes and dimensions.

Flansche und ihre Verbindungen - Dichtungskennwerte und Prüfverfahren für die Anwendung der Regeln für die Auslegung von Flanschverbindungen mit runden Flanschen und Dichtungen

Dieses Dokument legt die nach EN 1591-1 geforderten Dichtungskennwerte fest und enthält die Prüf-verfahren zur Ermittlung der Zahlenwerte dieser Kennwerte.
Dichtungen, die gänzlich auf Elastomeren basieren oder die auf Elastomeren mit lediglich dem Einschluss feinteiliger Füllstoffe oder feinteiliger Verstärkungen basieren, liegen im Gegensatz zu Dichtungen, in denen Elastomere, Füllstoffe und Faserverstärkungen miteinander kombiniert werden, nicht im Anwendungs-bereich dieses Dokumentes.
ANMERKUNG Die enthaltenen Prüfverfahren können auch für andere Dichtungsformen und -maße angewendet werden.

Brides et leurs assemblages - Paramètres de joints et procédures d'essai relatives aux règles de calcul des assemblages à brides circulaires avec joint

Le présent document définit les paramètres de joints requis par l’EN 1591-1 et décrit les modes opératoires d’essai permettant de déterminer les valeurs de ces paramètres.
Les joints entièrement fabriqués en matériaux élastomères ou fabriqués à partir de matériaux élastomères additionnés uniquement de charges particulaires ou de renforts sous forme de particules, par opposition aux joints combinant des matériaux élastomères, des charges et des renforts fibreux, ne relèvent pas du domaine d’application du présent document.
NOTE Les modes opératoires d'essai indiqués peuvent s'appliquer à des joints ayant d'autres formes et dimensions.

Prirobnice in prirobnični spoji - Preskusni postopki in parametri tesnil, ki so potrebni za konstruiranje prirobničnih spojev, sestavljenih iz okroglih prirobnic in tesnil

General Information

Status
Published
Public Enquiry End Date
19-Nov-2019
Publication Date
02-Mar-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
25-Feb-2021
Due Date
02-May-2021
Completion Date
03-Mar-2021

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SLOVENSKI STANDARD
SIST EN 13555:2021
01-april-2021
Nadomešča:
SIST EN 13555:2014
Prirobnice in prirobnični spoji - Preskusni postopki in parametri tesnil, ki so

potrebni za konstruiranje prirobničnih spojev, sestavljenih iz okroglih prirobnic in

tesnil

Flanges and their joints - Gasket parameters and test procedures relevant to the design

rules for gasketed circular flange connections
Flansche und ihre Verbindungen - Dichtungskennwerte und Prüfverfahren für die
Anwendung der Regeln für die Auslegung von Flanschverbindungen mit runden
Flanschen und Dichtungen

Brides et leurs assemblages - Paramètres de joints et procédures d'essai relatives aux

règles de calcul des assemblages à brides circulaires avec joint
Ta slovenski standard je istoveten z: EN 13555:2021
ICS:
23.040.60 Prirobnice, oglavki in spojni Flanges, couplings and joints
elementi
23.040.80 Tesnila za cevne zveze Seals for pipe and hose
assemblies
SIST EN 13555:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 13555:2021
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SIST EN 13555:2021
EN 13555
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2021
EUROPÄISCHE NORM
ICS 23.040.60; 23.040.80 Supersedes EN 13555:2014
English Version
Flanges and their joints - Gasket parameters and test
procedures relevant to the design rules for gasketed
circular flange connections

Brides et leurs assemblages - Paramètres de joints et Flansche und ihre Verbindungen - Dichtungskennwerte

procédures d'essai relatives aux règles de calcul des und Prüfverfahren für die Anwendung der Regeln für

assemblages à brides circulaires avec joint die Auslegung von Flanschverbindungen mit runden

Flanschen und Dichtungen
This European Standard was approved by CEN on 27 December 2020.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13555:2021 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN 13555:2021
EN 13555:2021 (E)
Contents Page

European foreword ...................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 7

4 Symbols .............................................................................................................................................................. 8

5 List of gasket parameters ............................................................................................................................. 9

6 Test equipment .............................................................................................................................................. 10

6.1 Design ................................................................................................................................................................ 10

6.2 Test platens ..................................................................................................................................................... 10

6.3 Metal Foils ....................................................................................................................................................... 10

6.4 Surface finish .................................................................................................................................................. 10

6.5 Measurement of gasket thickness ........................................................................................................... 10

6.6 Loading ............................................................................................................................................................. 11

6.7 Temperature................................................................................................................................................... 11

6.8 Leakage measurement ................................................................................................................................ 11

7 Test gaskets ..................................................................................................................................................... 11

7.1 Number of gaskets ........................................................................................................................................ 11

7.2 Procurement and identification of gaskets ......................................................................................... 11

7.3 Pre-conditioning of the gaskets ............................................................................................................... 11

7.4 Dimensions of test gaskets ........................................................................................................................ 12

7.5 Measurement of test gaskets as received ............................................................................................. 12

7.6 Influence of gasket dimensions ............................................................................................................... 12

8 Test procedures ............................................................................................................................................. 13

8.1 General.............................................................................................................................................................. 13

8.2 Testing Strategy ............................................................................................................................................. 13

8.3 Reference gasket thickness ....................................................................................................................... 13

8.4 Compression curve ....................................................................................................................................... 14

8.5 Determination of Q ............................................................................................................................ 14

Smax

8.6 Determination of the values of E .......................................................................................................... 18

8.7 Determination of P and Δe .............................................................................................................. 20

QR Gc

8.8 Determination of Q and Q ............................................................................................. 21

min(L) Smin(L)

8.8.1 General.............................................................................................................................................................. 21

8.8.2 Leakage diagram ........................................................................................................................................... 24

8.9 Determination of Q at elevated temperatures ................................................................... 24

Smin(L)

8.10 Determination of axial coefficient of thermal expansion ............................................................... 24

8.11 Determination of the coefficient of static friction ............................................................................. 25

9 Report details ................................................................................................................................................. 25

Annex A (informative) Generalized test rig schematic ................................................................................ 26

Annex B (informative) Test rig schematic for compression and compression creep tests ............. 27

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SIST EN 13555:2021
EN 13555:2021 (E)

Annex C (informative) Test rig schematic for ambient temperature leakage measurement ........ 28

Annex D (informative) Schematic of leakage rig allowing use of interchangeable face plate ....... 29

Annex E (informative) Transferability of measured leakage rates to service conditions .............. 30

Annex F (informative) The measurement of the sealing parameter Q after long
Smin(L)

term service simulating exposure to elevated temperature ........................................................ 31

Annex G (informative) Determination of the sealing characteristics of strip sealing

materials available in coil form ............................................................................................................... 33

Annex H (informative) Proposed method for the determination of the coefficient of static

friction, µ , of gaskets ................................................................................................................................. 34

Annex I (informative) Guideline for interpretation of test results and acceptable

modification of measured characteristics ........................................................................................... 36

Bibliography ................................................................................................................................................................. 40

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SIST EN 13555:2021
EN 13555:2021 (E)
European foreword

This document (EN 13555:2021) has been prepared by Technical Committee CEN/TC 74 “Flanges and

their joints”, the secretariat of which is held by DIN.

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 August 2021, and conflicting national standards shall

be withdrawn at the latest by August 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN 13555:2014.

In comparison with the previous edition, the following technical modifications have been made:

a) in Clause 2 the list of normative references has been revised;
b) in Clause 3 the list of definitions has been revised;
c) in Clause 5 the list of gasket parameters has been revised;
d) in 8.5 on the determination of Q has been revised;
Smax

e) a new informative Annex I on the guideline for interpretation of test results and acceptable

modification of measured characteristics has been added.

According to the CEN-CENELEC Internal Regulations, the national standards organisations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
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SIST EN 13555:2021
EN 13555:2021 (E)
Introduction

This document provides the test procedures to allow the generation of the gasket parameters to enable

the design formulas established in EN 1591-1 to be employed. The same test procedures may be used

for “Type Testing” of gaskets and gasket materials. These procedures are not for routine quality control

purposes.
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SIST EN 13555:2021
EN 13555:2021 (E)
1 Scope

This document specifies the gasket parameters required by EN 1591-1 and provides the test

procedures for establishing the values of these parameters.

Gaskets which are wholly based upon elastomers, or based upon elastomers with only the inclusion of

particulate fillers or particulate reinforcement, as opposed to gaskets combining elastomers, fillers and

fibrous reinforcement, are beyond the scope of this document.

NOTE The testing procedures given might be applicable to gaskets of other shapes and dimensions.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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.

EN 1092-1, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN

designated - Part 1: Steel flanges

EN 1514-1, Flanges and their joints - Dimensions of gaskets for PN-designated flanges - Part 1: Non-

metallic flat gaskets with or without inserts

EN 1514-2, Flanges and their joints - Gaskets for PN-designated flanges - Part 2: Spiral wound gaskets for

use with steel flanges

EN 1514-3, Flanges and their joints - Dimensions of gaskets for PN-designated flanges - Part 3: Non-

metallic PTFE envelope gaskets

EN 1514-4, Flanges and their joints - Dimensions of gaskets for PN-designated flanges - Part 4:

Corrugated, flat or grooved metallic and filled metallic gaskets for use with steel flanges

EN 1514-6, Flanges and their joints - Dimensions of gaskets for PN-designated flanges - Part 6: Covered

serrated metal gaskets for use with steel flanges

EN 1514-7, Flanges and their joints - Gaskets for PN-designated flanges - Part 7: Covered metal jacketed

gaskets for use with steel flanges

EN 1591-1:2013, Flanges and their joints - Design rules for gasketed circular flange connections - Part 1:

Calculation

EN 1759-1, Flanges and their joint - Circular flanges for pipes, valves, fittings and accessories, Class

designated - Part 1: Steel flanges, NPS 1/2 to 24

EN 1779, Non-destructive testing - Leak testing - Criteria for method and technique selection

EN 12560-1, Flanges and their joints - Gaskets for Class-designated flanges - Part 1: Non-metallic flat

gaskets with or without inserts

EN 12560-2, Flanges and their joints - Dimensions of gaskets for Class-designated flanges - Part 2: Spiral

wound gaskets for use with steel flanges

EN 12560-3, Flanges and their joints - Gaskets for Class-designated flanges - Part 3: Non-metallic PTFE

envelope gaskets
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SIST EN 13555:2021
EN 13555:2021 (E)

EN 12560-4, Flanges and their joints - Gaskets for Class-designated flanges - Part 4: Corrugated, flat or

grooved metallic and filled metallic gaskets for use with steel flanges

EN 12560-5, Flanges and their joints - Gaskets for Class-designated flanges - Part 5: Metallic ring joint

gaskets for use with steel flanges

EN 12560-6, Flanges and their joints - Gaskets for Class-designated flanges - Part 6: Covered serrated

metal gaskets for use with steel flanges

EN 12560-7, Flanges and their joints - Gaskets for Class-designated flanges - Part 7: Covered metal

jacketed gaskets for use with steel flanges
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
Smax

maximum surface pressure that may be imposed on the gasket at the indicated temperatures without

collapse or “crash”, compressive failure or damage of the stressed area of the gasket such that failure is

imminent
3.2
min(L)

minimum gasket surface pressure on assembly required at the ambient temperature in order to seat the

gasket into the flange facing roughness and close the internal leakage channels so that the tightness

class is to the required level L for the internal test pressure
3.3
Smin(L)

minimum gasket surface pressure required under the service pressure conditions, (i.e.) after off-loading

and at the service temperature, so that the required tightness class L is maintained for the internal test

pressure
3.4
tightness classes that denotes maximum limit of defined leak rates (see Table 1)

Note 1 to entry: Additional, better, tightness classes can be introduced as required by continuing the series.

Table 1 — Tightness classes
Tightness class L L L L
N 1,0 0,1 0,01
–1 –1
≤ 1,0 ≤ 0,1 ≤ 0,01
Specific leak rate [mg s m ]
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SIST EN 13555:2021
EN 13555:2021 (E)
3.5

factor allowing for the effect on the imposed load of the relaxation of the gasket between the completion

of bolt up and long term experience of the service temperature
3.6

unloading modulus of elasticity that is determined from the thickness recovery of the gasket between

the initial compression surface pressure and unloading to a third of this initial surface pressure

3.7

coefficient of thermal expansion of the gasket under the service conditions of temperature and gasket

surface pressure in the axial direction
3.8

additional change in thickness of the gasket or sealing element due to creep between the completion of

the loading and the end of the test period
3.9

static friction factor between the gasket and the flange facing during service conditions and under

external loading
3.10
gasket surface pressure in the assembly condition
4 Symbols
For the purposes of this document, the following notations apply.

Where units are applicable, they are shown in brackets. Where units are not applicable, no indication is

given.
α the axial coefficient of thermal expansion of gasket –1
G [K ]
µ static friction factor between the gasket and the flange facing —
e gasket or sealing element thickness [mm]
Δe change in gasket or sealing element thickness due to creep [mm]
A area of gasket subjected to surface pressure 2
G [mm ]
d internal diameter of gasket [mm]
d internal diameter of area of gasket subjected to surface pressure [mm]
D external diameter of gasket [mm]
D external diameter of area of gasket subjected to surface pressure [mm]
E unloading modulus of elasticity of the gasket [MPa]
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SIST EN 13555:2021
EN 13555:2021 (E)
L tightness class — subscript N indicates the maximum specific leakage rate –1 –
N [mg s m
for that tightness class
P creep relaxation factor, the ratio of the residual and initial surface —
pressures
Q surface pressure [MPa]
Q gasket surface pressure at assembly prior to unloading [MPa]

Q the minimum level of surface pressure required for leakage rate class L on [MPa]

min(L)
assembly
Q the minimum level of surface pressure required for leakage rate class L [MPa]
Smin(L)
after off-loading
Q the maximum surface pressure that can be safely imposed upon the gasket [MPa]
Smax
at the service temperature without damage
Concordance with EN 1591-1:

Q , the gasket surface pressure at assembly is the gasket stress at the load situation 0 and is defined by

Q in EN 1591-1.
5 List of gasket parameters

The gasket parameters relevant to the calculation procedures for the design of bolted flange

connections as given in EN 1591-1 are shown in Table 2 together with the test procedures applicable

for determining the value of the parameter in each case.
Table 2 — Gasket parameters and test procedures
Gasket parameter Definition Test procedure(s)
Subclause Subclause
Q 3.1 8.5
Smax
Q 3.2 8.8
min(L)
Q 3.3 8.8 and 8.9
Smin(L)
P 3.5 8.7
E 3.6 8.6
α 3.7 8.10
Δe 3.8 8.7
µ 3.9 8.11
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SIST EN 13555:2021
EN 13555:2021 (E)
6 Test equipment
6.1 Design

Schematics of test rigs for compression, creep relaxation, and tightness measurement are shown in

informative Annexes A to D, Figures A.1, B.1, C.1 and D.1. Annex A is a generalized schematic with the

other figures providing further detail for specific aspects of the tests.
6.2 Test platens

The test platens, and heater assembly where appropriate, shall be sufficiently rigid so that any load

imposed on the gasket can be withstood and so that there is no platen deformation which results in

gasket surface pressure variation. This rigidity aspect can also be important when gasket elastic

recovery is being investigated.

The dimensions of the test platen raised faces shall be as given in EN 1092-1 for a DN 40/PN 40 gasket

and EN 1759-1 for an NPS 4 CLASS 300 gasket.

For testing in tongue and groove geometries the dimensions of the test platens should be in accordance

with EN 1092-1, Form C and Form D or EN 1759-1.
6.3 Metal Foils

Experience has shown that during hot compression tests, that is the P , Q and elevated

QR Smax

temperature tightness tests, some gasket materials are likely to adhere badly enough to the test platens

during the test to cause difficulty in the removal of the gasket after the completion of the test and

damage the platen surface finish.

To avoid such damage, stainless steel foils or shims of thickness of 0,05 mm placed between the test

gasket and the platens during P and Q tests may be used.
QR Smax

Where foils or shims are used the fact of their use shall be included in the test report.

Foils or shims shall not be re-used or used in tightness tests at any temperature nor in the Coefficient of

Static Friction determination defined in 8.11 and provisionally detailed in Annex H.

6.4 Surface finish

The platen surface finish shall be within the range specified by the relevant flange standards in the

EN 1092 series and EN 1759 series. For sheet materials where the standards are EN 1092-1 and

EN 1759-1 the finish should be as specified below.
The surface finish of the test platens shall conform to the following:
3,2 µm < R < 6,3 µm

Exceptions to this range are acceptable where the gasket is intended for use with a surface finish

outside of this range. In this case the surface finish used shall be recorded.

Before each test, the freedom from debris from the previous test and from scratch and impact damage

to the surface finish of the platens shall be checked visually.
6.5 Measurement of gasket thickness

For those procedures where the gasket thickness shall be monitored during the test there shall be

either three displacement transducers at 120° spacing around the circumference of the platens or one

displacement transducer placed on the central line.

However, for a leak test, the use of an axial transducer is not recommended as it introduces a sealing

complication to the rig design.
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SIST EN 13555:2021
EN 13555:2021 (E)
6.6 Loading

Any loading means may be used that allows the gasket to be loaded and unloaded at a required and

consistent rate. The rate of loading and unloading to be used is fixed as:

0,5 MPa/s for all types of gasket except for PTFE based gaskets when 0,1 MPa/s shall be used.

The loading shall be recorded as a function of time.
6.7 Temperature

The rate of increase of temperature in all elevated temperature tests shall be 2 K/min.

6.8 Leakage measurement

EN 1779 gives the limits that can be achieved by various method of leakage measurement. The

information given in that document shall be taken into account when selecting a measurement system.

For modern, high performance, sealing materials and gasket styles, the most appropriate method of

measurement is very likely to be mass spectrometry.
7 Test gaskets
7.1 Number of gaskets
At least two gaskets for each type of test shall be tested.

NOTE More rigorous guidance on the number of repeat tests required for each test type will be available for

the next revision of this document.
7.2 Procurement and identification of gaskets

The gaskets to be tested shall be selected at random from production gaskets or shall be cut from sheet

representative of normal production. Prior to selection for test the gaskets or sheet shall have been

stored in accordance with the recommendations of the manufacturer and the time since manufacture

should be within any time limit set by the manufacturer.

Some basic checks shall be made in order to ensure that the gaskets or sheet are acceptable by the

normal quality assurance criteria before the tests to this document are carried out. The results of these

checks shall be recorded.
In all cases, full traceability to production shall be maintained.
7.3 Pre-conditioning of the gaskets

For every gasket type where the sealing element is not solid metal the gasket shall be conditioned as

indicated below before any of the tests of this document are carried out.

The test gasket shall be held for at least 48 hours in air with a relative humidity of (50 ± 6) % at ambient

temperature.

The required relative humidity can for example be generated and maintained by the use of a saturated

solution of magnesium nitrate hexahydrate, Mg (NO ) 6H O. The test gaskets that are to be held at the

3 2 2

required relative humidity should be stored above a saturated solution of the salt, containing an excess

of the solid salt, in a glass container fitted with a ground glass lid and held in an area at ambient

temperature.

The test gaskets shall be removed from the conditioning atmosphere no more than 30 min before the

test is carried out.
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SIST EN 13555:2021
EN 13555:2021 (E)
7.4 Dimensions of test gaskets
The test gasket dimensions shall be either of those specified in Table 3.
Table 3 — Test gasket dimensions for Raised Face Flanges
Raised face dimensions
Flange description Gasket dimensions according to
according to
DN 40/PN 40 EN 1092-1 EN 1514-1 to EN 1514-7 (according to the type of gasket)
EN 12560-1 to EN 12560-7 (according to the type of
NPS 4 CLASS 300 EN 1759-1
gasket)
For convenience for sheet materials the gasket dimensions are given below:
EN 1514-1 ID 49 mm OD 92 mm
EN 12560-1 ID 115 mm OD 181 mm

Where the intended service is in tongue and groove flanges, the test gasket size is specified in

EN 1092-1 or in EN 1759-1, and the test shall be carried out with test platens which have a tongue and

groove configuration. Some required adjustments to the test parameters for gasket tapes are

summarised in Annex G.

Tolerance of the platens for tongue and groove configurations shall be as given below:

— negative tolerance for tongue width;
— positive tolerance for groove width.
If this mode of testing is used it shall be clearly stated in the report.
7.5 Measurement of test gaskets as received

The internal and external diameter of the gasket or sealing face shall be measured with an appropriate

device such as micrometer, caliper or circometer (π tape) at ambient temperature.

Except where a circometer is used, the measurement shall be taken at not less than four positions

around the gasket and the mean diameter shall be reported.

The mean values shall conform to the theoretical values within the tolerances given in the appropriate

document or the supplier's information.

The as received thickness of the gasket or sealing element shall be measured by a micrometer or other

suitable device with contact faces wide enough to provide a measurement without penetration. The

value of the reference gasket thickness is obtained by measuring the gasket thickness under a 1 MPa

surface pressure at ambient temperature and after a one minute stabilization period. The

measurements of thickness shall be taken at not less than four positions around the gasket or ring and

the mean reported. The measured thickness shall be within the tolerances given in the appropriate

document or the supplier's information if no document exists.

Where the gasket has centering or locating rings associated with the sealing element then the thickness

of the rings shall also be measured and reported.
7.6 Influence of gasket dimensions
For gaskets the tes
...

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