prEN 1337-5
(Main)Structural bearings - Part 5: Pot bearings
Structural bearings - Part 5: Pot bearings
This document specifies rules for the design, testing and manufacture of fixed and sliding pot bearings.
It is applicable to pot bearings:
- with elastomeric pads made from natural rubber (NR) or chloroprene rubber (CR) up to 1 500 mm diameter,
- with pot and piston made from ferrous materials,
- with seals tested for different accumulated slide paths due to rotations between piston and pot of a) 500 m, b) 1 000 m or c) 2 000 m,
- with seals made from specific austenitic steel, brass, POM or carbon filled PTFE,
- subjected to operating temperature ranges between -25 °C and +50 °C or -40 °C and +50 °C,
- subjected to operating temperatures up to +70 °C for repeated periods of less than 8 h.
This document will be used in conjunction with prEN 1337-1:2018 and other relevant parts of the prEN 1337 series.
Lager im Bauwesen - Teil 5: Topflager
Dieses Dokument legt Regeln für die Bemessung, Prüfung und Herstellung von festen und gleitenden Topflagern fest.
Das Dokument gilt für Topflager:
- mit Elastomerkissen aus Naturgummi (NR) oder Chloroprengummi (CR) mit einem Durchmesser von bis zu 1 500 mm;
- mit Topf und Deckel aus eisenhaltigen Werkstoffen;
- mit für verschiedene akkumulierte Gleitwege aufgrund von Verdrehungen zwischen dem Deckel und dem Topf von a) 500 m, b) 1 000 m oder c) 2 000 m geprüften Dichtungen;
- mit Dichtungen aus speziellem austenitischem Stahl, Messing, POM oder PTFE mit Kohlefüllung;
- die Betriebstemperaturen zwischen −25 °C und +50 °C oder zwischen −40 °C und +50 °C ausgesetzt sind;
- die für wiederholte Zeiträume von weniger als 8 h Temperaturen von bis zu +70 °C ausgesetzt sind.
Dieses Dokument wird in Kombination mit prEN 1337-1:2018 und anderen relevanten Teilen der Normenreihe prEN 1337 verwendet.
Appareils d’appui structuraux - Partie 5 : Appareils d’appui à pot
Le présent document spécifie les règles de conception, d’essai et de fabrication d’appareils d’appui à pot fixe et glissant.
Il s’applique aux appareils d’appui à pot :
- dotés de coussins en élastomère en caoutchouc naturel (NR) ou en caoutchouc en chloroprène (CR) jusqu’à 1 500 mm de diamètre,
- dotés d’un pot et d’un piston en matériaux ferreux,
- dotés de joints ayant fait l’objet d’essais sur différentes distances de glissement cumulées en raison des rotations entre le piston et le pot de a) 500 m, b) 1 000 m ou c) 2 000 m,
- dotés de joints en acier austénitique spécifique, laiton, POM ou PTFE renforcé de carbone,
- soumis à des gammes de températures de service comprises entre –25 °C et +50 °C ou –40 °C et +50 °C,
- soumis à des températures de service jusqu’à +70 °C pendant des périodes répétées durant moins de 8 h.
Le présent document sera utilisé conjointement à la norme provisoire prEN 1337-1:2018 et les autres parties pertinentes de la série prEN 1337.
Konstrukcijska ležišča - 5. del: Lončna ležišča
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2018
.RQVWUXNFLMVNDOHåLãþDGHO /RQþQDOHåLãþD
Structural bearings - Part 5: Pot bearings
Lager im Bauwesen - Teil 5: Topflager
Ta slovenski standard je istoveten z: prEN 1337-5
ICS:
91.010.30 7HKQLþQLYLGLNL Technical aspects
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2018
ICS 91.010.30 Will supersede EN 1337-5:2005
English Version
Structural bearings - Part 5: Pot bearings
Lager im Bauwesen - Teil 5: Topflager
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 167.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1337-5:2018 E
worldwide for CEN national Members.
Contents Page
European foreword . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, symbols and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Symbols . 9
3.3 Abbreviations . 10
4 Types of pot bearings . 10
4.1 General . 10
4.2 Types of pot construction . 11
4.3 Types of internal seal. 12
4.3.1 General . 12
4.3.2 Seals type “a” . 12
4.3.3 Seals type “b” . 13
4.3.4 Seals type “c” . 15
4.4 Types of piston/pot contact surface . 17
5 Material properties . 18
5.1 Ferrous materials . 18
5.2 Elastomeric materials. 18
5.3 Seal materials . 18
5.3.1 Seal type “a” . 18
5.3.2 Seal type “b” . 18
5.3.3 Seal type “c” . 18
5.4 Lubricant . 19
6 Design . 19
6.1 General . 19
6.2 Internal seal system . 19
6.3 Behaviour under vertical load. 19
6.3.1 Contact pressure – elastomeric pad . 19
6.3.2 Deflection . 20
6.4 Behaviour under horizontal load . 20
6.4.1 General . 20
6.4.2 Piston/pot contact pressure . 20
6.4.3 Pot verification . 22
6.5 Behaviour under rotations . 27
6.5.1 General . 27
6.5.2 Restoring moment . 28
6.5.3 Working Life — Working life of seal due to sliding contact with pot wall. 29
6.5.4 Geometric criteria for required rotation . 29
6.6 Combination of vertical loads and rotations — Minimum thickness . 30
6.7 Combination with other bearings or elements . 31
6.7.1 Combination with sliding elements . 31
6.7.2 Load distribution through components . 31
6.7.3 Load transfer to the adjacent structure . 31
7 Testing . 31
7.1 Restoring moment . 31
7.2 Determination of compression stiffness . 31
7.3 Lubricant and rubber . 31
7.4 Surface roughness of steel parts . 32
8 Manufacturing, assembly, tolerances, marking and labelling . 32
8.1 General . 32
8.2 Elastomeric pad . 32
8.3 Parallelism of external surfaces . 32
8.4 Fit of components . 32
8.4.1 Piston in pot . 32
8.4.2 Elastomeric pad in pot . 32
8.5 Surface roughness . 33
8.6 Corrosion protection . 33
8.7 External seal . 33
8.8 Lubrication . 33
8.9 Sharp edges . 33
8.10 Marking and labelling . 33
9 Transport, storage and installation . 33
10 In-service inspection . 33
11 Maintenance . 33
12 Assessment and verification of constancy of performance . 34
12.1 General . 34
12.2 Type Testing . 34
12.3 Factory production control . 34
12.4 Assessment of the performance of the construction product . 34
Annex A (normative) Lubricant elastomer compatibility . 36
A.1 Test pieces . 36
A.1.1 Test pieces made of the elastomer . 36
A.1.2 Test pieces made of the internal sealing . 36
A.1.3 Conditioning of the test pieces . 36
A.2 Test liquid . 36
A.3 Interaction of the lubricant with the elastomer or other components of the pot
bearing . 37
A.3.1 Interaction of the lubricant with the elastomer . 37
A.3.2 Interaction of the lubricant with other components of the pot bearing . 37
A.4 Test Procedure and Details . 37
A.4.1 General . 37
A.4.2 Change of physical properties of elastomer and internal sealing material . 37
A.4.3 Change of mass . 38
A.4.4 Change of hardness . 38
A.4.5 Change of physical properties in tension . 38
A.5 Test report . 38
Annex B (informative) Determination of compression stiffness . 40
B.1 Determination by testing . 40
B.1.1 General . 40
B.1.2 Conditioning . 40
B.1.3 Testing . 40
B.1.4 Analysis of the test . 40
B.2 Determination by calculation. 41
Annex C (normative) Determination of restoring moment . 42
C.1 Introduction . 42
C.2 Preparation of test specimens . 42
C.3 Test procedure . 42
C.4 Evaluation of restoring moment factors . 43
C.5 Test report . 44
Annex D (normative) Test equipment . 46
D.1 Compression testing machine . 46
D.2 Rotation attachment . 46
D.3 Heating equipment (oven) . 47
D.4 Measuring instruments . 47
Annex ZA (informative) Relationship of this European Standard with Regulation (EU)
No. 305/2011 . 48
ZA.1 Scope and relevant characteristics . 48
ZA.2 System of Assessment and Verification of Constancy of Performance (AVCP) . 50
ZA.3 Assignment of AVCP tasks . 50
Bibliography . 55
European foreword
This document (prEN 1337-5:2018) has been prepared by Technical Committee CEN/TC 167
“Structural bearings”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1337-5:2005.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Regulation 305/2011.
For relationship with EU Regulation 305/2011, see informative Annex ZA, which is an integral part of
this document.
prEN 1337, Structural bearings, consists of the following 8 parts:
— Part 1: General;
— Part 2: Sliding elements;
— Part 3: Elastomeric bearings;
— Part 4: Roller bearings;
— Part 5: Pot bearings;
— Part 6: Rocker bearings;
— Part 7: Spherical and cylindrical PTFE bearings;
— Part 8: Guide bearings and Restraint bearings.
The major technical changes are listed below:
— Complete technical and editorial revision of the document; it is not possible to list all implemented
changes to this edition of EN 1337-5.
1 Scope
This document specifies rules for the design, testing and manufacture of fixed and sliding pot bearings.
It is applicable to pot bearings:
— with elastomeric pads made from natural rubber (NR) or chloroprene rubber (CR) up to 1 500 mm
diameter,
— with pot and piston made from ferrous materials,
— with seals tested for different accumulated slide paths due to rotations between piston and pot of
a) 500 m, b) 1 000 m or c) 2 000 m,
— with seals made from specific austenitic steel, brass, POM or carbon filled PTFE,
— subjected to operating temperature ranges between –25 °C and +50 °C or –40 °C and +50 °C,
— subjected to operating temperatures up to +70 °C for repeated periods of less than 8 h.
This document will be used in conjunction with prEN 1337-1:2018 and other relevant parts of the
prEN 1337 series.
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.
prEN 1337-1:2018, Structural bearings — Part 1: General
prEN 1337-2:2018, Structural bearings — Part 2: Sliding elements
EN 1991-2, Eurocode 1: Actions on structures — Part 2: Traffic loads on bridges
EN 1993-1-1:2005, Eurocode 3: Design of steel structures — Part 1-1: General rules and rules for
buildings
EN 1993-2:2006, Eurocode 3 — Design of steel structures — Part 2: Steel Bridges
EN 1993 (all parts), Eurocode 3: Design of steel structures
EN 10025 (all parts), Hot rolled products of structural steels
EN 10083-3, Steels for quenching and tempering — Part 3: Technical delivery conditions for alloy steels
EN 10088-2:2014, Stainless steels — Part 2: Technical delivery conditions for sheet/plate and strip of
corrosion resisting steels for general purposes
EN 10113-1, Hot-rolled products in weldable fine grain structural steels — Part 1: General delivery
conditions
EN 10204:2004, Metallic products — Types of inspection documents
EN 12167:2016, Copper and copper alloys — Profiles and bars for general purposes
EN ISO 527-1, Plastics — Determination of tensile properties — Part 1: General principles (ISO 527-1)
EN ISO 527-2, Plastics - Determination of tensile properties — Part 2: Test conditions for moulding and
extrusion plastics (ISO 527-2)
EN ISO 1133 (all parts), Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow
rate (MVR) of thermoplastics (ISO 1133, all parts)
EN ISO 1183 (all parts), Plastics — Methods for determining the density of non-cellular plastics (ISO 1183,
all parts)
EN ISO 2039-1, Plastics — Determination of hardness — Part 1: Ball indentation method (ISO 2039-1)
EN ISO 4287, Geometrical product specifications (GPS) — Surface texture: Profile method — Terms,
definitions and surface texture parameters (ISO 4287)
EN ISO 4288, Geometrical product specifications (GPS) — Surface texture: Profile method — Rules and
procedures for the assessment of surface texture (ISO 4288)
EN ISO 7500-1:2015, Metallic materials — Calibration and verification of static uniaxial testing
machines — Part 1: Tension/compression testing machines — Calibration and verification of the force-
measuring system (ISO 7500-1:2015)
ISO 37, Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties
ISO 48, Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between 10 IRHD
and 100 IRHD
ISO 1083, Spheroidal graphite cast irons — Classification
ISO 1817, Rubber, vulcanized or thermoplastic — Determination of the effect of liquids
ISO 3755, Cast carbon steels for general engineering purposes
ISO 6446, Rubber products — Bridge bearings — Specification for rubber materials
ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test
methods
3 Terms, definitions, symbols and abbreviations
3.1 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 http://www.iso.org/obp
3.1.1
accumulated slide path
sum of the relative movements between the internal seal and the pot wall resulting from variable
rotations
3.1.2
elastomeric pad
circular component which provides the rotational capability by deformation
3.1.3
external seal
component or material which is used to exclude moisture and debris from the gap between the piston
and the pot
3.1.4
internal seal
component which prevents escape of the elastomeric material through the gap between the wall of the
pot and the piston when a compressive force is applied
3.1.5
lubricant
special grease used to reduce the friction between the pad and the metallic components for the purpose
of reducing wear and the rotation stiffness
3.1.6
piston
component which closes the open end of the recess in the pot and bears on the elastomeric pad
3.1.7
pot
component with a machined circular recess which contains the elastomeric pad, piston and internal seal
3.1.8
pot bearing
structural bearing consisting of an elastomeric pad (rotational element) confined in a recess by means
of a close fitting piston and an internal seal
Note 1 to entry: The orientation of the bearing is not restricted.
3.1.9
restoring moment
moment generated from the elastomeric pad caused by the rotation deformation
3.1.10
sliding pot bearing
pot bearing combined with a sliding element to accommodate translational movements
3.1.11
slide path
relative movements of internal seal to pot wall
3.2 Symbols
For the purposes of this document, the following symbols apply:
Latin upper case letters
A cross section area 2
mm
d internal diameter of pot mm
int
d outer diameter of pot ring mm
ext
E modulus of elasticity
k factor in restoring moment formula for zero rotation
k factor in restoring moment formula for lubricated pad
k factor in restoring moment formula for unlubricated pad
R resistance of weld 1
w N/mm
V resultant applied horizontal load N
xy
h depth of the cylindrical recess mm
M restoring moment from pad and internal seal in test Nmm
rt;exp
M restoring moment from pad and internal seal Nmm
rt
M additional moment from friction between piston and pot Nmm
fric
M total resistance moment from rotation Nmm
tot;r
N axial force N
r radius of contact surface mm
t thickness of the pot base mm
base
V total transverse or shear force N
1 total transverse or shear force per unit length N
V
tot
V shear force due to elastomer pressure N
el
T temperature
Latin lower case letters
a additional clearance for rotation
b width of piston face mm
b calculated piston/pot contact width mm
cal
c factor used in slide path expression
d diameter of elastomeric pad mm
el
d internal diameter of pot mm
int
d outer diameter of pot ring mm
ext
f ultimate strength of material 2
u N/mm
f yield strength of material 2
y N/mm
f design contact strength of the elastomer 2
el;d N/mm
s accumulated slide path
A,d
t nominal thickness of elastomeric pad mm
el
w Vertical deflection mm
Greek letters
γ partial material factor
m
α rotation angle rad
α resultant rotation angle due to permanent actions rad
g
α resultant rotation angle due to traffic loads rad
Q
α rotation angle in restoring moment test rad
rt
Subscripts
bot lower, bottom
d design, design value
k characteristic
R resistance
fric resulting from friction
rt restoring
top upper
tot total
E internal forces and moments from actions N, Nmm
u ultimate limit state
w weld
el elastomer
3.3 Abbreviations
PTFE polytetrafluoroethylene
POM polyoxymethylene (acetal)
4 Types of pot bearings
4.1 General
The components of a pot bearing are shown in Figure 1.
Key
1 internal seal
2 piston
3 external seal (in this area)
4 elastomeric pad
5 pot
Figure 1 — Components of a pot bearing
The pot may be formed in various ways as shown in Figure 2. Different types of internal seal can be
used. The piston can be shaped in two ways in the area of contact with the pot wall. The bearing can be
used in inverted position also.
Pot bearings may be combined with sliding elements in accordance with prEN 1337-2:2018.
4.2 Types of pot construction
There are four construction types for pots (see Figure 2):
— Type a): made of a monolithic plate,
— Type b): made from a ring with a base plate welded inside,
— Type c): made from a ring welded to a base plate.
— Type d): made from a ring connected to a base plate with a recess and bolts.
Figure 2 — Types of pot construction
4.3 Types of internal seal
4.3.1 General
The internal seals are classified with regard to the standard accumulated slide path as follows:
— Seals with accumulated slide path “a”, 500 m (see 4.3.2);
— Seals with accumulated slide path “b”, 1 000 m (see 4.3.3);
— Seals with accumulated slide path “c”, 2 000 m (see 4.3.4).
4.3.2 Seals type “a”
The stainless steel seal is classified for an accumulated sliding movement S = c × 500 m in the
R
structure
The sealing ring shall be made from stainless steel strip formed into an equal or unequal angle section
inserted between the elastomeric pad and the pot wall with the ends overlapping. The top surface may
have notches, see Figure 3.
Figure 3 — Typical notched stainless steel seal
The sealing ring shall be made from stainless steel strip formed into an equal or unequal angle section
inserted between the elastomeric pad and the pot wall.
The leg length and thickness of the section shall meet the following.
a) with notches:
where diameter d ≤ 700 mm — leg length 5 mm to 10 mm, thickness 1 mm minimum; where
el
diameter d > 700 mm leg length 15 mm to 17 mm, thickness 1,5 mm minimum; the minimum
el
overlap of the ring ends shall be 20 mm; where the thickness > 1 mm, the ends shall be reduced in
thickness at the overlap position.
b) without notches:
minimum leg length 3 mm;
minimum thickness 1 mm;
minimum overlap 5 mm;
where the thickness > 1 mm, the ends shall be reduced in thickness at the overlap position.
4.3.3 Seals type “b”
The brass seal is classified for an accumulated sliding movement S = c × 1 000 m in the structure.
R
Internal brass seals shall be fitted into a recess formed in the edge of the upper surface of the
elastomeric pad and shall consist of a number of split rings formed to the internal diameter of the pot.
When fitted, the gap between the ends of the ring shall not exceed 0,5 mm. The gaps in adjacent rings
shall be equally disposed around the perimeter of the pot. Where possible no gap should coincide with
the point of maximum rotation movement on the pot wall.
Rings with a minimum cross-section of 10 mm × 2 mm may have slits 7 mm deep, cut 0,5 mm wide
spaced at 5 mm around the internal diameter to facilitate forming. Rings with a smaller cross-section
shall not have slits.
Dimensions in millimetres
Figure 4 — Typical Brass seal
The internal brass seal (see Figure 4) shall be fitted into a formed recess in the upper edge of the
elastomeric pad and shall consist of a number of split rings formed to the internal diameter of the pot.
When fitted, the gap between the ends of the ring shall not exceed 0,5 mm and the gaps in adjacent
rings shall be equally disposed around the perimeter of the pot. Where possible no gap should coincide
with the point of maximum rotation movement on the pot wall.
Rings with a minimum cross-section of 10 mm × 2 mm may have slits 7 mm deep by 0,5 mm wide
spaced at 5 mm around the internal diameter to facilitate forming. Rings with a smaller cross-section
shall not have slits.
The allowable solid brass sealing ring configurations are given in Table 1.
Table 1 — Allowable solid brass sealing ring configurations
Diameter
Minimum
d
cross-section
el Slits Number of rings
mm
mm
d ≤ 330
6 × 1,5 Not permitted 2
el
330 < d < 715
10 × 1,5 Not permitted 2
el
715 ≤ d ≤ 1 500
10 × 1,5 Not permitted 3
el
7 mm × 0,5 mm
d ≤ 1 500
10 × 2 3
el
5 mm spacing
4.3.4 Seals type “c”
4.3.4.1 POM Seal
Dimensions in millimetres
Figure 5 — Typical small POM seal element (a)
Dimensions in millimetres
Figure 6 — Typical large POM element (b)
The POM seal is classified for an accumulated sliding movement S = c × 2 000 m in the structure
R
The POM seal shall consist of individual interlocking elements in the form of a chain, which can adapt
easily to deformation.
Overall width and height of the individual elements shall be:
a) elastomer diameter d ≤ 550 mm: 10 mm ± 0,5 mm;
b) elastomer diameter d > 550 mm: 15 mm ± 1,0 mm.
The POM sealing chain shall be moulded as an integral part of the elastomeric pad during the
vulcanisation process to ensure correct functioning, see Figures 5 and 6.
4.3.4.2 Carbon filled PTFE seal
Dimensions in millimetres
Key
1 brass angle
2 sealing ring
Figure 7 — Typical joint in carbon filled PTFE seal
The carbon filled PTFE seal is classified for an accumulated sliding movement S = c × 2 000 m in the
R
structure
Internal carbon filled PTFE seals shall be fitted into a recess formed in the edge of the upper surface of
the elastomeric pad and shall consist of a single split ring with stepped joint formed to the internal
diameter of the pot, see Figure 7.
4.4 Types of piston/pot contact surface
There are two types of piston/pot contact surface (see Figure 8):
— Type e): cylindrical,
— Type f): toroidal.
Key
1 broken edges
Figure 8 — Types of piston contact surface
5 Material properties
5.1 Ferrous materials
The pot and piston shall be manufactured from ferrous materials in accordance with
EN 10025 (all parts), EN 10083-3, EN 10113-1, EN 10088-2, ISO 3755 or ISO 1083.
The specification of the material selected shall correspond to the requirements for resistance and
durability, weldability, if applicable, and the operating temperature.
5.2 Elastomeric materials
The elastomeric material used for the elastomeric pad shall be natural or polychloroprene rubber in
accordance with ISO 6446.
5.3 Seal materials
5.3.1 Seal type “a”
The material used for the stainless steel seal shall be as specified in EN 10088-2:2014, 1.4401 or
1.4311.
5.3.2 Seal type “b”
The material used for the brass seal shall be grade CuZn37 or CuZn39Pb3, as specified in
EN 12167:2016 respectively, in the metallurgical condition used in the type tests.
5.3.3 Seal type “c”
5.3.3.1 POM seal
The material used for the moulded seals shall be polyoxymethylene (POM) and shall have the
properties shown in Table 2.
Table 2 — Physical and mechanical properties of POM
Property In accordance with Requirements
Density EN ISO 1183 series 3 3
1 410 kg/m ± 20 kg/m
Melt flow index MFI 190/2, 16 EN ISO 1133 (all parts) 10 g/min ± 2,0 g/min
Ultimate tensile strength EN ISO 527-2 2
≥ 62 N/mm
Ultimate strain EN ISO 527-2 ≥ 30 %
5.3.3.2 Carbon filled PTFE seal
The material composition shall consist of PTFE +25 % carbon.
The material properties shall be in accordance with the requirements of Table 3 below.
Table 3 — Mechanical and physical properties of carbon filled PTFE seal
Properties In accordance with Requirements
3 3
Density EN ISO 1183 series
2 100 kg/m to 2 150 kg/m
Ultimate tensile strength EN ISO 527-2 ≥ 17 N/mm
Ultimate strain EN ISO 527-1 ≥ 80 %
Ball hardness EN ISO 2039-1 ≥ 40 N/mm
The material properties shall be verified on samples taken from finished tubes at 23 °C and 50 %
humidity.
The ultimate tensile strength and the ultimate strain shall be determined with a speed C = 50 mm/min
on test samples with a PTFE thickness of 2 mm ± 0,2 mm in accordance with EN ISO 527-2.
The ball hardness shall be determined on samples with a minimum thickness of 4,5 mm.
5.4 Lubricant
The lubricant shall not be damaging to the elastomeric material of the elastomeric pad nor other
components with which it is in contact.
It shall not cause swelling or shrinkage of the elastomer which results in a relative change in
weight ≥ 8 %. The change of the determined values for tensile strength at break, the elongation at break
and the stress at an elongation of 100 % of conditioned and not conditioned test pieces shall not
exceed ± 20 %. The change of the determined values for the hardness for the conditioned and not
conditioned test pieces shall not exceed ± 5 IRHD.
6 Design
6.1 General
prEN 1337-1:2018 applies.
The design rules are based on the assumption that the elastomeric material of the elastomeric pad acts
as a fluid carrying the vertical loads. Rotations generate restoring moments due to the fact that the
elastomeric material does not act entirely as a fluid.
For fixed or internally guided sliding pot bearings horizontal loads are transferred through the piston
pot contact surface. For externally guided sliding pot bearings the horizontal loads are transferred
directly from the guide to the pot.
The selected material shall be verified in accordance with the principles given in the relevant parts of
the EN 1993 series, e.g. EN 1993-1-10.
6.2 Internal seal system
An internal seal system in accordance with 5.3 shall be used.
6.3 Behaviour under vertical load
6.3.1 Contact pressure – elastomeric pad
The elastomeric pad is assumed to have hydrostatic characteristics under pressure. This means that the
elastomeric pad contact pressure acts in all directions. This influences all adjacent components.
Under the fundamental combination of actions the condition as given in Formula (1) shall be satisfied.
N ≤ N (1)
Ed Rd
With N as given in Formula (2).
Rd
N
Rk
N = (2)
Rd
γ
m
where
N is the design value of compressive resistance of the elastomeric pad;
Rd
N is the characteristic value of compressive resistance of the elastomeric pad;
Rk
γ is the partial material factor.
m
The minimum value of γ = 1,30.
m
The characteristic value of the resistance N shall be determined with Formula (3):
Rk
π
N =××df (3)
Rk el e,k
where
d is the diameter of elastomeric pad in mm;
el
f 2
e,k = 60 N/mm .
NOTE f is the pressure in the elastomer in pot bearings to be considered for the characteristic resistance
e,k
N , which is limited by the effectiveness of the seal preventing the elastomer from extruding between the piston
Rk
and the pot wall.
6.3.2 Deflection
If the elastic compression stiffness of the bearing is of relevance to the design of the adjacent structure
it shall be determined by means of testing (see Annex B).
6.4 Behaviour under horizontal load
6.4.1 General
The partial material factor γ is given in EN 1993-2:2006, 6.1.
M0
6.4.2 Piston/pot contact pressure
6.4.2.1 General
The mechanical resistance of the contact surface shall be verified in accordance with 6.4.2.2 or 6.4.2.3
for the fundamental combination of actions.
6.4.2.2 Cylindrical contact surface
The contact surface of the piston may be cylindrical in accordance with 4.4 provided that the width of
the piston contact surface, b, is less than 15 mm (see Figure 8).
The cylindrical contact surface shall be verified for the weakest of the contact materials as given in
Formula (4).
V ≤ V (4)
Ed Rd
where
V is the design value of the transverse force.
Ed
is the design resistance of the surfaces in contact as given in Formula (5).
V
Rd
fd×× b
y int
V = (5)
Rd
1,5×γ
m9
where
d is the internal diameter of the pot (mm);
int
f 2
y is the yield strength of material (N/mm );
b is the width of piston face (mm);
The recommended value for γ = 12, . This value covers the combination of contact pressure, shear
m9
stress and concurrent movements.
NOTE The pressure between piston and pot walls resulting from external horizontal actions is assumed to be
parabolically distributed over half of the perimeter and the maximum value is taken as 1,5 times the mean value.
The combination of the materials in contact shall be such as to avoid cold welding.
6.4.2.3 Toroidal contact surface
The toroidal contact surface shall have a radius r (see Figure 8), of not less than 0,5 × d or 100 mm,
int
whichever is the greater.
The toroidal contact surface shall be verified for the weakest of the contact materials, so that:
V ≤ V (6)
Ed Rd
Where
V is the design value of the transverse force.
Ed
is the design resistance of the surfaces in contact as given in Formula (7).
V
Rd
f
u
dr⋅⋅
int 1
γ
m9
V = 15, 4 (7)
Rd
E
where
r is the radius of contact surface (mm); see also Figure 3;
f 2
u is the ultimate strength of material (N/mm );
E 2
is the modulus of elasticity (N/mm );
d is the internal diameter of the pot (mm).
int
The recommended value for γ = 12, . This value covers the combination of contact pressure, shear
m9
stress and concurrent movements.
V determined with Formula (7) shall not exceed V determined with Formula (5).
Rd Rd
NOTE 1 The ability of curved surfaces and plates to withstand deformation under load is dependent upon the
hardness of the material from which they are made. There is not a constant relationship between hardness and
yield stress of steel but there is between hardness and ultimate strength. Consequently the above expressions are
based on the ultimate strength of the material.
NOTE 2 Formula (7) is a simplification of a Hertzian contact pressure distribution on the pot wall. The pressure
between
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