Superior technical guide For precision moulded seals continuous, aggressive improvement in the...
Transcript of Superior technical guide For precision moulded seals continuous, aggressive improvement in the...
We have not designed it to be a catalogue,
but a reference to guide you through the
relevant selection and design processes.
It will become clear as you use the
guide that we are not in the business
of commodity production. Superior
manufactures precision components
from specialised high performance
rubber compounds.
As a result, we actively seek the most
demanding customers. We relish involvement at
the earliest point in their product development
cycle. It is the customer who benefits most:
more effective application of seals means
better product design – everyone wins.
To this end, we have committed to a culture
of continuous, aggressive improvement in the
design, manufacture and supply of precision
o-rings and special mouldings.
We like to exceed expectations. Innovation
and investment are the keys to this.
Natural curiosity and the desire to find better
processes and methodologies feed the
Superior promise to innovate.
Re-investment in state-of-the-art facilities
and valued, accountable people increases our
ability to convert ideas into production reality.
This guide is a part of that investment.
Use it with confidence. It is fully backed by
both our Engineering and Technical Service
teams who are on hand to offer advice and
support: we strongly recommend using this
service as part of your design development
process. You will find the contact number
at the foot of each page.*
Superior technical guide We believe that this latest edition of the guide will become an invaluable resource for anyone involved in the specification and application of elastomer seals.
*This service has been developed with you in mind. If you have any issues or comments arising from it, please contact us in the first instance.
Material Science Department +44 (0)1202 854300 | 1
Your guide
ContentsSuperior technical guide
Research, development and partnership A relevant approach to design for today’s manufacturing.01
01
Consultation 3
Testing
Optimising
Tooling
Staying ahead
02Temperature 4
Media compatibility rating 5
Approvals
Superior elastomer grades 6
Materials reference guide 7
Elastomer properties 8
Hardness
Compression set
Tensile strength
Elongation at break
Tear strength
Gas permeability
Abrasion 9
Colour
Ageing
Low temperature flexibility
Media table 10
Producing an order specification 12
03
Precision o-rings 13
O-ring size and compound
selection program
Groove layouts 14
General housing guidelines 15
Housing diametrical tolerances
Lead chamfers Z
Surface finish or texture
Coefficient of thermal expansion
Coefficient of friction
Static sealing – axial and triangular 16
Static axial face housing
Static triangular housing
Static/dynamic sealing – radial 17
O-ring stretch in piston sealing
Reduction of cross-section due to stretch
Guidelines
Gough-Joule effect
Typical compression range 18
Typical o-ring housing data for piston
and rod sealing applications
Pressure 19
04
Superior engineering 22
Seal integrity
Seal performance
Development of a seal profile
Precision mouldings / bespoke seals 23
Lip seals / U-seals / V-seals
Symmetrical seals
Quad rings
Moulded gaskets
Custom radial seals
Tolerances for moulded parts 24
A heritage of excellence 25
Our tool room
The service we offer to our customers
05
O-ring size range standards 26
Quality acceptance criteria ISO 3601-3 27
Quality control: documentation 28
Seal surface inspection levels
Special moulding tolerances
Certification
Environmental compliance
06
O-ring stretch during assembly 29
Fitting aids and sharp edges
Housing chamfers 30
Traversing cross drilled ports
Rolling
Cleanliness / cleaning materials
Storage 31
Light
Humidity
Contaminants
Stress
Temperature
Oxygen and ozone
Shelf life
Customer Service lies at the heart
of everything we do at Superior.
Our philosophy is based upon three
key constituents:
• Material science and technology
• Seal engineering
• State-of-the-art manufacturing
The combination of these three factors
provides the high integrity of our precision
o-rings and seals, and in turn, provides the
long term performance and high integrity in
our customers products. Our ‘fast response’
culture is applied to each individual factor to
help reduce our customers’ overall project
lead time.
ConsultationWe actively encourage and cultivate early
involvement in customer projects. This helps
to ensure that the seal element is optimised
within the environment demanded by the
customer. This ensures that our products are
reliable, fit for purpose, correctly specified with
all critical features identified, controlled and
costed at an appropriate and agreed level.
TestingWe work closely with our customers on
all aspects of seal testing and development
programs. All testing procedures are carried
out to international standards, BS ISO, DIN,
ASTM, or to customer specific requirements.
We offer a diverse range of compounds
to satisfy the majority of market needs.
If a customer has a specific need that
cannot be met within our existing elastomer
range, we will develop new compound
grades at our in-house laboratory.
We are able to conduct extensive test
programs to fully validate specific
elastomers to customer parameters
(e.g. temperature/media exposure
and mechanical property testing).
We will also validate to specific accreditation
standards (e.g. EN681, WRAS, DVGW, ACS,
KIWA, NSF, EN 549).
Optimising
Through the customer partnership exchange,
we can assist with optimised seal profile
design and application.
Tooling
Our Tooling Manufacture department designs
and machines precision prototype and
production moulds to exceed conventional
tolerancing. Pilot tooling can be provided
economically and rapidly to further expedite
customer test programs.
With our extensive tooling expertise, we can
optimise critical surface features to facilitate
reliable function with mating parts.
Staying aheadOur continuous capital investment program
allows us to remain at the leading edge of
our field.
We continually implement latest technology
systems, ensuring batch-to-batch consistency
throughout the manufacturing process.
With such broad customer support facilities,
Superior will always strive to provide added
value with our customer programs.
Indeed, we find that each new project
challenges our thinking and creates a
springboard to increasingly enlightened
manufacturing practices.
Research, development and partnershipSuperior technical guide
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Research, development and partnership
Specifying compounds
Seal design Quality
Custom seal design
Assembly
Media compatibility ratingVirtually all elastomers exhibit a physical or
chemical change when exposed to working
media, whether gas or fluid.
The degree of change depends upon
media composition in combination with
the elastomer exposed. Aggressive media
become more active with subsequent
increase in temperature. Physical changes
become apparent in two ways and can
occur simultaneously;
• the elastomer absorbs the media
– creating a volume increase or swell
• a base constituent (such as plasticiser)
is extracted – creating a volume decrease
or shrinkage.
The degree of volume change is
dependant upon:
• the media type
• the elastomer chemical structure
• the geometric shape of the seal
(section thickness)
• the stressed condition of the seal
• temperature
• time.
A rubber will swell significantly less when
compressed in the working envelope than
in the free state (up to 50% less).
Chemical changes tend to affect the
cross-linking structure of the elastomer
(e.g. embrittlement).
Any application where the media can create
high shrinkage changes to the elastomer
should be avoided, due to squeeze reduction
and resultant leakage risk.
Approvals We are able to develop and provide
a comprehensive range of elastomers
specific for;
Water Industry:
WRAS, NSF, DVGW, KTW, ACS,
KIWA, UL
Gas Industry:
EN549, EN682 Compliance
Food and Beverage Industry:
FDA, AAA, NSF51
Pharmaceutical:
USP Class VI
Please consult our Technical Service
department for specific accreditations.
Specifying compoundsSuperior technical guide
Specifying compounds Important environmental parameters.02
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Temperature At Superior we are able to develop and
manufacture the majority of elastomer
compounds used in most market sectors.
Awareness of specific limitations on each
elastomer is fundamental, in terms of both
mechanical and chemical characteristics.
The most relevant influential working
criteria should then be carefully matched
to elastomer parameters.
Only then is it possible to achieve accurate
selection of the most suitable elastomer
for any given environmental condition.
Please refer to the materials reference
guide on page 7.
Terms and environmental aspects related
to working with compounds are highlighted
in the following pages.
Each elastomer type has a specific
working temperature range, however this
will be influenced by many factors: media
compatability, dynamic or static operation
and seal design being several of these.
Many factors affect the service temperature
of elastomers. All dynamic and shock loads
should be avoided at temperatures below the
minus limit of a given compound. However,
elastomers stored in static conditions,
below the low temperature flexible range,
will recover full physical properties during the
warm-up period. At elevated temperatures,
consideration must be given to the long term
running limit and the short term peak limit of
each elastomer.
Elastomers exposed to the extreme limit
can suffer an accelerated loss of flexibility,
resulting in excessive compression set.
This can dramatically shorten effective sealing
life. Also there is an influence in volume swell
and age hardening at high temperatures,
dependent on compound type.
The temperature guide below is generic for
each elastomer type. We have developed
particular compounds which exhibit improved
upper or lower temperature performance.
Please consult our Technical Service
department on +44 (0)1202 854300
NBR Nitrile rubber MN/HN
NBR Low temperature Nitrile rubber LN
IIR Butyl rubber BB
ECO Epichlorohydrin EC
ACM Polyacrylate rubber PA
EPDM Ethylene-Propylene-Diene rubber EP
HNBR Hydrogenated Nitrile rubber TH
AEM Ethylene Acrylate VA
FVMQ Fluorosilicone rubber FSIL
FPM Fluorocarbon rubber VF/VP
VMQ Silicone rubber SIL
FFPM Perfluorinated elastomer
°C -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300F -148 -112 -76 -40 -4 32 68 104 140 176 212 248 284 320 356 392 428 464 500 536 572S
uper
ior
des
igna
tion
Recommended temperature range: guide only Extended temperature range: guide only
Rating
••• Very Good
•• Good
• Fair
x Unsuitable
It should be noted that the parameters specified in this table illustrate the typical working band of commercially available elastomers. Material development is constant and we are able to assist for parameters outside of the stated values if required.
Specifying compoundsSuperior technical guide
Materials reference guideSuperior elastomer grades
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Principal properties
EPDM: EP Ethylene Propylene Terpolymers
• outstanding resistance to water
and steam
• excellent weathering resistance
• general temperature use -40°C to +130°C
• can be designed to meet DW Approvals
and food approvals
• can be designed to give specific
chemical resistance (mineral acids
and phosphate esters)
• low compression set in water and air
• not suitable for use in mineral oils.
NBR: LN, MN, HN, WN, FN Acrylonitrile Butadiene (Nitrile)
• very good resistance to petroleum
based fluids
• good flexibility at low temps,
-50°C for LN grades
• upper temperature limit of 100°C
• can be designed to meet DW
approvals – WN grades
• can be designed to meet gas approvals.
HNBR: TH Hydrogenated Nitrile
• extend the temperature range
of NBR’s to 150°C
• excellent mechanical properties:
high strength and wear resistance
• good dynamic properties and
weathering resistance
• good resistance to many oil additives
• can be designed to meet gas approvals
• low temp -40°C to -20°C depending
on grade.
VMQ: SIL Silicone
• excellent low temperature properties,
capable to -60°C
• excellent high temperature performance
to 200°C
• good flexibility, tactile material
• can meet FDA, USP expectations
• poor mechanical properties
• poor resistance to fuels/oils
• high permeability.
FVMQ: FSIL Fluorosilicone
• excellent low temperature
dynamic performance
• increased resistance to fuels, particularly
useful for aerospace applications
• poor mechanical properties.
FKM: VF/VP Fluorocarbon
• excellent resistance to a wide spectrum
of chemicals: fuels, oils, biodiesel etc
• chemical resistance can be improved
by use of specific grades
• excellent resistance to heat
• can be designed to give high performance
in steam/water
• can be designed to offer excellent
compression set
• low permeability
• limited use at low temperarure, -20°C
(special grades are available to extend
this to -40°C)
• poor resistance to ketones,
amines and ethers.
Grades can be provided in a hardness range of 30 to 90 IRHD. Grades can be black or coloured (mineral filled). The choice of filler will however affect mechanical properties and approvals. Advice should be sought from the Technical Service department.
Material Nitrile Butyl Ethylene Propylene
Hydrogenated Nitrile
Fluorosilicone Silicone Fluorocarbon
Designation NBR IIR EPDM HNBR FVMQ VMQ FPM
Superior elastomer code MN, LN, HN, WN, FN
BB EP TH FSIL SIL VF, VP
Hardness range (IRHD) 40 – 90° 40 – 80° 40 – 90° 50 – 90° 40 – 80° 20 – 80° 55 – 85°
Colours Limited range Black Limited range Limited range Limited range Limited range Limited range
Heat resistance °C
Peak 120 130 160 170 230 230 250
Normal 100 110 130 150 200 200 200
Low temp °C -30 -50 low temp version
-50 -50 -40 -55 -60 -20 -35 low temp version
Resistances
Mineral oil (low aromatic) •• x x ••• ••• •• •••
Oxidisation •• ••• ••• ••• ••• ••• •••
Ozone x ••• / •• ••• •• ••• ••• •••
Weathering • ••• ••• •• ••• ••• •••
Radiation •• / • x ••• •• ••• ••• •••
Integrity
Tear strength •• •• •• ••• x x ••
Compression set •• • •• •• ••• ••• ••
Abrasion resistance •• •• / • •• ••• • • •• / •
Resilience •• / • • •• •• / • •• •• •
Gas permeability •• ••• •• •• x x •••
Electrical insulation • ••• ••• • ••• ••• Grade dependant
Inflammability x x x x ••• • •••
% Compression Set =original height – recovered height
original height – compressed height x 100
Superior technical guide
Hardness
The term hardness is the measure of a
material’s resistance to a set deforming force
exerted by a given standard indentation
implement over a defined length of time.
Hardness is measured in degree units of IRHD
(International Rubber Hardness Degrees).
It is generally the unit of measure on standard
dimensioned test pieces. It is also the unit
used for measuring the finished component
(e.g. o-ring cross section) by the Micro
Hardness Test.
Standard compounds are nominally 70 IRHD.
Superior can, however, provide compounds
from 20-90 IRHD range, depending upon
material type. Selection of hardness is
dependent upon specific application
requirements. For example:
Softer compounds
• deform more readily under load
(e.g. cover/housing assembly) conform
to surface irregularities
• lower stick/slip effect
• higher running friction.
Harder compounds
• higher extrusion resistance
• lower running friction
• higher stick/slip effect.
The hardness is usually expressed
and controlled as a nominal figure
with ± 5 points tolerance.
Compression set This is the measurement of a compound’s
loss of elastic memory. A standard cylindrical
test piece of rubber is subjected to a
defined pre-load at given temperature
and time parameters (e.g. 24hrs/100°C).
The test deformation is usually 25%
of the original height.
The measured recovery of the cross-section
is carried out at ambient temperature.
The end result is recorded as the height not
recovered, expressed as a percentage of the
amount by which the part was compressed.
Usually it can be stated that the better the
elastomeric memory, the lower the compression
set. This is regarded as an important feature
of any compound, as leakage will occur if high
set (and therefore loss of memory) occurs.
Tensile strength
This is the force necessary to rupture a
standard test piece at a given rate of
elongation and expressed as force per
unit area.
In practical terms, this property result does
not assist the end user to select a compound,
because a correctly assembled o-ring does
not rely on its tensile strength to achieve
effective sealing.
Elongation at break
Elongation at break is measured at the
moment of rupture of a test piece under
tensile load, expressed as a percentage.
This is a useful indication of a compound’s
suitability as a large percentage of stretch
may be necessary during assembly
(e.g. piston seal).
Tear strength
Resistance to tear propagation from
a point of initial damage, sustained
for example, during assembly.
Gas permeability Elastomers allow gas to enter into
the structure. They will diffuse or
permeate through and escape via
the low pressure side.
The rate of permeation is governed by
temperature, pressure, gas type and
elastomer type. This may be critical
for vacuum and gas containment.
To reduce permeability:
• use larger o-ring sections
• apply more compression
• optimise surface finish
• select high-density elastomers.
AbrasionAbrasion resistance is a general term
indicating wear resistance.
It can be noted, generally, that HNBR
compounds perform best.
NBR and EPDM have relatively good
abrasion resistance. FPM has a lower
abrasion resistance.
Abrasion resistance improves with hardness
(up to 80 IRHD). However, Silicone and
Fluorosilicone have poor properties
and should only be applied to static
environments.
Colour
Rubbers are usually formulated with the
addition of carbon black fillers. Hence, the
majority of compounds are black in colour.
Rubbers gain much of their strength and
heat resistance from the addition of carbon
black fillers.
However, at Superior we have the expertise
to formulate and produce colour pigmented
compounds for most of the elastomer
range. Colouring is mainly used as
a means of identification, allowing
differentiation of compound grades
in safety-critical applications.
In addition, colour can be used to separate
similar sizes on a customer’s production line.
Please consult our Technical Service
department on +44 (0)1202 854300 for
application and colour range availability.
Ageing
Heat ageing tests are widely used to record
changes in property of an elastomer.
Usually hardness, tensile strength and
elongation are measured and compared
to original properties.
Air and relevant fluid ageing over standard
time/temperature durations are meaningful
to compare life expectancies of rubbers.
Standard test conditions are:
NBR 24/70 hrs @ 100°C
EPDM 24/70 hrs @ 120°C
FPM 24/70 hrs @ 200°C
VMQ 24/70 hrs @ 200°C
If elastomers are pushed beyond their
ageing resistance parameters, they will suffer
from cracking, splitting and/or hardening.
Low temperature flexibility
The TR test (low temperature retraction)
provides a measure of the rate of recovery
of an elastomeric material after it has been
subjected to low temperature.
The test, which is described in ISO 2921,
consists of stretching a test piece with an
effective length of 50 or 100mm and placing
it in a bath at -70°C.
The test piece is allowed to retract freely
whilst the temperature is raised at the
rate of 1°C per minute.
The percentage retraction of the test
piece is plotted against temperature.
Retraction values are calculated automatically
with TR10, TR30, TR50 and TR70
values being most commonly recorded.
TR10 and TR70 values are of particular interest.
Elastomer properties To fully specify and select a compound, the most relevant physical characteristics should be known, these are:
Specifying compounds
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Recommended
Superior designation LN/MN HN EP TH FS SIL VF/VP compound
Maximum service temperature °C 100 100 150 150 200 200 230/2v00
Low service temperature °C -45/-30 -20 -50 -40 -55 -60 -20/-35
Water/steam resistance
Water/steam resistance <60°C ••• ••• ••• ••• ••• ••• ••• / ••• WN70/3
Water/steam resistance <80°C •• •• ••• ••• •• •• ••• / ••• EP1/1/5, WN12/7/1
Water/steam resistance <150°C x x •• •• x x *•• / • EP7/3/7, EP11/7/4
Water/steam resistance >150°C x x • x x x *•• / x VF12/99/3, EP11/7/4
Fluid resistance
Acids
Acetic 10% • • ••• •• x •• • / •••* EP10/00/2
Formic x x ••• x • •• • / •••* EP10/00/2
Hydrochloric 20% • • ••• • •• • •• / •••* EP10/00/2
Nitric 30% x x ••• x • • •• / ••• VF3/00/10
Phosphoric 20% • • ••• • •• •• ••• / ••• EP10/00/2
Sulphuric 30% x x •• x • x •• / ••• VF3/00/10, VP5/00/5
Alkalis
Baruim hydroxide •• •• ••• ••• •• •• ••• / ••• EP7/3/7, EP11/7/4
Calcium hydroxide •• •• ••• ••• •• •• ••• / ••• EP7/3/7, EP11/7/4
Sodium hydroxide •• •• ••• •• • • •• / ••• EP7/3/7, EP11/7/4
Alcohols
Butyl alcohol (Butanol) ••• ••• •• •• ••• •• ••• / ••• EP70, MN70
Ethyl alcohol (Ethanol) •• •• ••• ••• ••• ••• • / ••• EP70, MN70
Methyl alcohol (Methanol) •• ••• ••• •• •• •• x / ••• EP70, MN70
Amines
Ethylene diamine •• •• ••• •• x •• x / ••* EP7/3/7, EP11/7/4
Ammonia – cold gas ••• ••• ••• ••• x •• x / • EP7/3/7, EP11/7/4
Ammonia – hot gas x x •• • x •• x / x EP7/3/7, EP11/7/4
Chlorides
Ammonium chloride ••• ••• ••• ••• ••• ••• ••• / ••• EP7/3/7, EP11/7/4
Calcium chloride solution ••• ••• ••• ••• ••• ••• ••• / ••• EP7/3/7, MN70, EP11/7/4
Magnesium chloride ••• ••• ••• ••• ••• ••• ••• / ••• EP7/3/7, MN70, EP11/7/4
Zinc chloride ••• ••• ••• ••• ••• ••• ••• / ••• EP7/3/7, MN70, EP11/7/4
Recommended
Superior designation LN/MN HN EP TH FS SIL VF/VP compound
Fluids resistance (continued)
Gases
Butane •• ••• x ••• •• x ••• / ••• TH5/03/1, HN75
Carbon dioxide (dry) ••• ••• •• ••• •• •• ••• / ••• TH5/03/1
Chlorine (wet) x x • • •• x ••• / ••• VF75B
Freon 12 (R12) ••• ••• •• ••• • x •• / ••• HN75
Freon 22 (R22) x x ••• x x x x / x EP7/3/7, EP11/7/4
Freon 134a (R134a) o o ••• ••• x o x / x EP7/3/7, EP11/7/4
Natural gas •• ••• x ••• • •• ••• / ••• TH5/03/1, HN75
Methane •• ••• x ••• •• x ••• / ••• TH5/03/1, HN75
Propane •• ••• x ••• •• x ••• / ••• TH5/03/1, HN75
Oils and fuels
ASTM No 1 oil ••• ••• x ••• ••• •• ••• / ••• MN70
ASTM No 2 oil ••• ••• x •• ••• • ••• / ••• HN75
ASTM No 3 oil • ••• x • ••• x ••• / ••• HN75
ASTM fuel A •• ••• x ••• ••• x ••• / ••• HN75
ASTM fuel B • •• x x ••• x ••• / ••• VF75B
ASTM fuel C x • x x •• x ••• / ••• VF75B
Diesel oil •• ••• x ••• •• x ••• / ••• HN75
Diesel oil + RME (10%) x x x x • x ••• / ••• VF5/4/4, TH8/5/6
Mineral oil (low aromatic) ••• ••• x ••• ••• •• ••• / ••• MN70
Hydraulic oils (petroleum base) ••• ••• x ••• •• • ••• / ••• MN70
Lubricating oils ••• ••• x ••• ••• • ••• / ••• MN70
Paraffin ••• ••• x ••• ••• • ••• / ••• MN70
Petrol •• ••• x ••• ••• x ••• / ••• VF75B
Silicone oil / grease ••• ••• ••• ••• • • ••• / ••• EP7/3/7, EP11/7/4
Transformer oils ••• ••• x ••• ••• • ••• / ••• MN70
Vegetable oils ••• ••• • ••• ••• •• ••• / ••• FN70
Solvents
Acetone x x ••• x x • x / x EP7/3/7, EP11/7/4
Benzene x x x x •• x ••• / ••• VF75B
Carbon tetrachloride x • x • • x ••• / ••• VF75B
Dimethyl formamide • • •• • x •• x / •• EP7/3/7, EP11/7/4
Ethyl acetate x x •• • x • x / x EP7/3/7, EP11/7/4
Methyl ethyl ketone x x ••• x x x x / x EP7/3/7, EP11/7/4
Tetrachloroethylene x x x x •• x ••• / ••• VF75B
Toluene x x x x •• x ••• / ••• VF75B
Turpentine •• ••• x ••• • x ••• / ••• HN75
Xylene x x x x • x •• / ••• VF75B
Miscellaneous
Ethylene glycol ••• ••• ••• ••• ••• ••• ••• / ••• EP2/9/10
Detergents ••• ••• ••• ••• ••• ••• ••• / ••• EP7/3/7, EP11/7/4
Dioctyl phthalate x x •• x •• • x / •* EP7/3/7, EP11/7/4
Formaldehyde • • ••• • • •• x / x EP7/3/7, EP11/7/4
Hydrogen peroxide (90%) x x •• x •• •• •• / ••• VF3/00/10, VP5/00/5
Phosphate esters x x ••• • • • • / •• Consult
Potassium nitrate ••• ••• ••• ••• ••• ••• ••• / ••• MN70
Rating
••• Excellent – recommended (5-8% swell)
•• Good – minor to moderate effects (8-15% swell)
• Fair – moderate to severe effects (1-25% swell)
x Poor – not recommended (>25% swell)
o Insufficient data available
*Conditions apply Temperature or other limitation affecting polymer choice
The table above refers to room temperature tests.
For other conditions and additional media advice please refer to the Technical Service team for advice.
Please note that in some conditions a negative swell (shrinkage through extraction) may occur.
Superior technical guide
Media table
Specifying compounds
10 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 11
For dynamic applications it is recommended that a swell up to 8% maximum be adhered to (••• rated). For static seals a volume change up to 25% can be tolerated (••/• rated) as long as the groove volume accommodates any increase.
It is important to keep in mind that reliability,
standardisation and ease of manufacture
around mating parts is achieved through
consultation with our Engineering department
at the earliest possible stage of development.
Practicality demands that this is a concise
guide, as each application could present
infinite parameter variables compared with
previous examples. As a result, guidelines and
trends tend to focus in general areas, so we
always encourage additional direct contact
with our Engineering department to fine
tune and elaborate where conditions are
not covered specifically within this guide.
Precision o-rings
These are the most versatile and economical
form of sealing device available. O-rings
will conform most readily to general design
guideline recommendations, as they have the
most extensive record of service life in diverse
conditions. O-rings are mainly used in static
applications, sealing against liquids, gas and
general environments.
Our Engineering department is able to
assist in specifying for dynamic applications,
with special consideration given to individual
working conditions. O-rings are generally not
recommended for dynamic applications.
O-ring Size and Compound Selection Program
Superior has created a program to assist the
selection process for a specific o-ring. The
program allows the user to enter the criteria
required and media in which it will be used, as
well as the housing information if known, and
the program will select a number of options
available. There is also an option to contact
the sales department for a quotation based
on the information entered. Our O-ring Size
and Compound Selection Program can be
found on our website www.superiorltd.com.
Sealing types
The various configurations can be
defined according to the type of sealing,
as described below:
A correctly designed housing with the
appropriate sized seal is important. However,
this function is not solely responsible for an
effective seal: the compound used influences
the sealing performance.
In all applications, where possible the largest
o-ring cross section diameter d2 should
be specified for the application to overcome
tolerances and rolling.
The first part of this section considers
design criteria for o-rings.
Superior is able to select from an extensive
range of standard and non-standard
o-rings (see our Superior size list for
further details or download from our
website www.superiorltd.com).
We can also recommend and manufacture
bespoke sizes. We will then produce
precision moulds which exceed recognised
industrial standard tolerances – quickly and
efficiently, in-house.
d1 d2
Seal designSuperior technical guide
Producing an order specification
Seal design This section of the guide is intended to assist engineers when considering sealing criteria.
12 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Radial compression
Axial compression
To ease liaison with our Sales department
and ensure the correct compound and
size of seal is ordered, we advise that
you apply the following considerations
to your specification:
• Highest peak temperature/duration
• Highest operating temperature
• Lowest temperature at which components
are expected to still function
• Media contact on assembly and
during operation
• Approval for water, gas or other
legislative requirements
• Static or dynamic working condition
(cycle rates/duration)
• Weathering/ozone resistance required
• Likely material being considered: refer
to materials reference guide or provide
compound designation number (e.g. MN70)
• Specific physical property minimums
e.g. Tensile strength, elongation,
compression set
• System pressure
• Colour/hardness requirements
• Quality and documentation requirements
• Lead time plan
• Size of seal (in the case of o-rings,
inside diameter and cross section).
03
Letter symbolsb Seal housing width (b1 and b2 for anti-extrusion devices)
d1 O-ring inside diameter
d2 O-ring cross-section diameter
d3 Groove diameter
d4 Bore diameter
d5 Shaft diameter
d6 Groove diameter
d7 Outside diameter: axial application internal pressure
d8 Inside diameter: axial application external pressure
d9 Shaft diameter
d10 Bore diameter
g Radial clearance
h Seal housing depth: axial sealing
r1 Corner radius
r2 Edge radius (0.2mm)
t Seal housing depth: radial sealing
z Lead-in chamfer: piston and rod housing
Please note that Ød10H7 applies to dynamic application.
rounded, flash-free
(external pressure) (0.2mm max)
br1
g
t
r2z
d4
0° to 5°
d3d9
15° to 20°
B
AB
d7
d8b
B
0° to 5°
B A h
r2
r1
(internal pressure)
b
t
r10 - 5°
r2
Pressure direction
No back-up ringb
Pressure direction
One back-up ring
b1
Pressure direction
Two back-up rings
b2
Housing diametrical tolerances
Bore diameterShaft diameter
Axial – outside diameterAxial – inside diameter
d4/d10
d5/d9
d7
d8
H8
f7H11
H11
These tolerances are as specified in ISO/R286,ISO System for limits and fits – Part 1, generaltolerances and deviations.
d1 d2
0° to 5° r1z
g
A t
rounded, flash-free
r2
b
B
B
15° to 20°
d10 d6d5
rounded, flash-free
(external pressure) (0.2mm max)
br1
g
t
r2z
d4
0° to 5°
d3d9
15° to 20°
B
AB
d7
d8b
B
0° to 5°
B A h
r2
r1
(internal pressure)
b
t
r10 - 5°
r2
Pressure direction
No back-up ringb
Pressure direction
One back-up ring
b1
Pressure direction
Two back-up rings
b2
Housing diametrical tolerances
Bore diameterShaft diameter
Axial – outside diameterAxial – inside diameter
d4/d10
d5/d9
d7
d8
H8
f7H11
H11
These tolerances are as specified in ISO/R286,ISO System for limits and fits – Part 1, generaltolerances and deviations.
d1 d2
0° to 5° r1z
g
A t
rounded, flash-free
r2
b
B
B
15° to 20°
d10 d6d5
rounded, flash-free
(external pressure) (0.2mm max)
br1
g
t
r2z
d4
0° to 5°
d3d9
15° to 20°
B
AB
d7
d8b
B
0° to 5°
B A h
r2
r1
(internal pressure)
b
t
r10 - 5°
r2
Pressure direction
No back-up ringb
Pressure direction
One back-up ring
b1
Pressure direction
Two back-up rings
b2
Housing diametrical tolerances
Bore diameterShaft diameter
Axial – outside diameterAxial – inside diameter
d4/d10
d5/d9
d7
d8
H8
f7H11
H11
These tolerances are as specified in ISO/R286,ISO System for limits and fits – Part 1, generaltolerances and deviations.
d1 d2
0° to 5° r1z
g
A t
rounded, flash-free
r2
b
B
B
15° to 20°
d10 d6d5
Groove layouts
To identify each feature of the housing standard letter symbols can be applied in all cases.
Housing Dimensions – static axial (mm)
d2 h+0.10 b+0.20 r1 r2 Surface finish or texture
The above is for guidance only and covers the majority of the sealing applications. However, Superior should be consulted in areas of particular concern.
Letter
A
B
Surface
Housing sides
and static diameters
Mating surface in
contact with o-ring
e.g. cylinder bore for
piston seal
Application
Static
Dynamic
Static
Dynamic
Pressure
Non pulsating and
non alternating
Pulsating or alternating
All types
Non pulsating and
non alternating
Pulsating or alternating
All types
Surface roughness
Ra µm
1.6
0.8
0.8
0.8
0.4
0.4
Lead in chamfers Z (30° – 40° inclusive)
All edges to be rounded
d2
Z minimum
Up to 2mm
1.1mm
2.01 to 3mm
1.5mm
3.01 to 4.5mm
1.8mm
Above 6.01mm
3.6mm
4.51 to 6mm
2.7mm
Housing Dimensions – static axial (mm)
d2 h+0.10 b+0.20 r1 r2 Surface finish or texture
The above is for guidance only and covers the majority of the sealing applications. However, Superior should be consulted in areas of particular concern.
Letter
A
B
Surface
Housing sides
and static diameters
Mating surface in
contact with o-ring
e.g. cylinder bore for
piston seal
Application
Static
Dynamic
Static
Dynamic
Pressure
Non pulsating and
non alternating
Pulsating or alternating
All types
Non pulsating and
non alternating
Pulsating or alternating
All types
Surface roughness
Ra µm
1.6
0.8
0.8
0.8
0.4
0.4
Lead in chamfers Z (30° – 40° inclusive)
All edges to be rounded
d2
Z minimum
Up to 2mm
1.1mm
2.01 to 3mm
1.5mm
3.01 to 4.5mm
1.8mm
Above 6.01mm
3.6mm
4.51 to 6mm
2.7mm
rounded, flash-free
(external pressure) (0.2mm max)
br1
g
t
r2z
d4
0° to 5°
d3d9
15° to 20°
B
AB
d7
d8b
B
0° to 5°
B A h
r2
r1
(internal pressure)
b
t
r10 - 5°
r2
Pressure direction
No back-up ringb
Pressure direction
One back-up ring
b1
Pressure direction
Two back-up rings
b2
Housing diametrical tolerances
Bore diameterShaft diameter
Axial – outside diameterAxial – inside diameter
d4/d10
d5/d9
d7
d8
H8
f7H11
H11
These tolerances are as specified in ISO/R286,ISO System for limits and fits – Part 1, generaltolerances and deviations.
d1 d2
0° to 5° r1z
g
A t
rounded, flash-free
r2
b
B
B
15° to 20°
d10 d6d5
Piston sealing (radial) type A
The inside diameter (d1) of an o-ring
should always be smaller than the housing
diameter (d3). The maximum stretch must
be limited to keep the resultant loss in cross
sectional diameter to an acceptable level and
keep the tensile stress to a minimum.
Rod sealing (radial) type B The ideal condition is for the o-ring outside
diameter to be equal to, or slightly greater
than, the housing diameter (d6). Too higher an
interference of the seal outside diameter (d6)
will result in distortion of the seal profile. This
is due to its inability to cater for the difference
in circumferential length.
A maximum outside diameter interference
of 3% is considered optimum but on small
diameters this could be up to 8%.
Face sealing (axial) type C & D This is the simplest use of o-rings, provided the
basic rules are remembered. Seal compression is
controlled by the depth of the groove and should
be between 15% to 30%.
For internal pressure, the o-ring should be
supported by the housing diameter (d7) whilst for
external pressure the inner diameter (d8) is used.
It is possible to remove the internal spigot, where
there is internal pressure, provided there is no
risk of cavitation.
Housing diametrical tolerances For radial sealing it is important to use tight tolerances as specified for the shaft and bore.
This reduces possible eccentricity and possible loss of compression.
For face sealing it is important to use a tight tolerance to reduce the range of stretch
or o-ring outside diameter as applicable.
Coefficient of thermal expansion When an unloaded rubber is heated it will expand inline with the coefficient of thermal expansion
for that particular rubber grade. Rubber compounds have much higher coefficients of thermal
expansion than steel or Aluminium (approx. ten times of steel), thermal expansion may cause an
already tight seal to swell and overfill the groove as temperature rises. Housings have been known
to rupture under the force exerted by an expanding seal. A seal design that provides minimal
compression in a low temperature environment cannot rely on thermal effects for help in tightening
the seal. It is therefore imperative that the seal has the correct compression and groove width
to allow for these situations.
Coefficient of frictionThe coefficient of friction for a rubber seal is influenced by many factors. These include compound
hardness, surface finish of mating components, speed of movement and lubrication. Breakout
friction is generally higher than running friction. To lower breakout and running friction, coatings
or lubrication can be applied.
Superior offer a wide range of solutions to help alleviate frictional forces. Superior dry coatings can also
aid assembly and increase efficiency on automatic assembly lines while reducing assembly efforts,
reduce risk of rolling during installation, and eliminate sticking of components after long storage.
Lead in chamfers Z (30° – 40° inclusive) To enable the o-ring to be fully assembled without undue risk of damage, the appropriate
lead in chamfer needs to be applied to the housing.
Surface finish or texture Sealing efficiency can be directly related to surface finish. The application must be considered
from a number of aspects to establish the most effective and economic surface finish.
General housing guidelines
Seal designSuperior technical guide
14 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 15
Static axial face housingThe o-ring is compressed in the axial direction.
When the o-ring is subjected to a pressure
the o-ring will undergo a relative displacement.
Therefore it is important to correctly size the
o-ring to limit the movement when pressure
is applied. If the pressure is internal, then
the o-ring’s outside diameter should be in
contact with the housing outside diameter.
The circumferential interference should be
no more than 1%.
If the pressure is external then the o-ring’s
inside diameter should be in contact with
the housing. In this case the o-ring should
be stretched up to a maximum of 4%.
Housing Dimensions – static axial (mm)
d2
1.50
1.78
2.00
2.50
2.62
3.00
3.53
4.00
5.00
5.33
6.00
6.99
8.00
9.00
10.00
12.00
h+0.10
1.10
1.30
1.50
2.00
2.10
2.30
2.80
3.25
4.00
4.35
5.00
5.75
6.80
7.70
8.70
10.60
b+0.20
1.90
2.40
2.60
3.20
3.60
3.90
4.80
5.20
6.50
7.20
7.80
9.60
10.40
11.70
13.00
15.60
r1
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.8 - 1.2
0.8 - 1.2
0.8 - 1.2
0.8 - 1.2
0.8 - 1.2
r2
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
pressurefrom inside
pressurefrom outside
r1
r2
h
b
d7
B
B
A
0° to 5°
0° to 5° d8
b
B
A
h
Br1
r2
Housing Dimensions – static axial (mm)
d2
1.50
1.78
2.00
2.50
2.62
3.00
3.53
4.00
5.00
5.33
6.00
6.99
8.00
9.00
10.00
12.00
h+0.10
1.10
1.30
1.50
2.00
2.10
2.30
2.80
3.25
4.00
4.35
5.00
5.75
6.80
7.70
8.70
10.60
b+0.20
1.90
2.40
2.60
3.20
3.60
3.90
4.80
5.20
6.50
7.20
7.80
9.60
10.40
11.70
13.00
15.60
r1
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.4 - 0.8
0.8 - 1.2
0.8 - 1.2
0.8 - 1.2
0.8 - 1.2
0.8 - 1.2
r2
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
0.2 - 0.4
pressurefrom inside
pressurefrom outside
r1
r2
h
b
d7
B
B
A
0° to 5°
0° to 5° d8
b
B
A
h
Br1
r2
Housing Dimensions – static axial (mm)
d2 h+0.10 b+0.20 r1 r2
Lead in chamfers z1 and z2 (30˚ – 40˚ inclusive)
d2 Up to 2mm 2.01 to 3mm 3.01 to 4.5mm 4.51 to 6mm Above 6.01mm
Z minimum 1.1mm 1.5mm 1.8mm 2.7mm 3.6mm
All edges to be rounded.
Surface finish or texture
Letter Surface Application Pressure Surface roughness
Ra µm
A Housing Sides Static Non pulsating and 1.6
and static diameters non alternating
Pulsating or alternating 0.8
Dynamic All types 0.8
B Mating surface in Static Non pulsating and 0.8
contact with ‘O’ Ring non alternating
e.g. cylinder bore for Pulsating or alternating 0.4
piston seal Dynamic All types 0.4
The above is for guidance only and covers the majority of the sealing applications. However, Superior Seals should be consulted in areas of particular concern.
1.50
1.60
1.78
2.00
2.40
2.50
2.62
3.00
3.50
3.53
4.00
5.00
5.34
5.70
6.99
8.40
1.00/1.05
1.20/1.25
1.24/1.37
1.35/1.45
1.70/1.80
1.78/1.88
1.90/2.03
2.20/2.30
2.60/2.70
2.54/2.80
3.00/3.10
3.80/3.90
4.19/4.45
4.40/4.50
5.60/5.85
6.60/6.70
2.25/2.55
2.36/2.66
2.54/2.84
2.89/3.19
3.45/3.75
3.38/3.68
3.60/3.90
4.00/4.30
4.50/4.80
4.80/5.10
5.10/5.40
6.23/6.53
7.10/7.40
7.00/7.30
8.90/9.20
10.00/10.30
2.08/2.20
2.20/2.32
2.41/2.54
2.76/2.88
3.30/3.42
3.44/3.56
3.68/3.81
4.20/4.32
4.81/4.93
4.95/5.08
5.51/5.63
6.86/6.98
7.50/7.63
7.80/7.92
10.03/10.16
11.50/11.62
3.80
4.00
4.80
4.60
5.00
5.25
6.35
6.00
6.80
8.00
7.40
8.90
11.00
10.00
15.00
14.00
0.2
0.2
0.5
0.5
0.5
0.5
0.9
1.0
1.0
0.9
1.0
1.0
0.9
1.0
0.9
1.0
0.75
0.80
0.76
1.10
1.30
1.40
1.02
2.00
1.90
1.52
2.20
2.70
2.20
3.00
2.54
4.00
O-ring housing data for axial and triangular sealing applications
d2 h b t sminimum
Triangularr1
maximum
Axialr1
maximumd2
Static axial face housingThe ‘O’ ring is compressed in the axial
direction. When the ‘O’ ring is subjected
to a pressure the ‘O’ ring will be subject
to a relative displacement. Therefore it is
important to correctly size the ‘O’ ring to
limit the movement when pressure is applied.
If the pressure is internal, then the ‘O’ ring’s
outside diameter should be in contact with the
housing outside diameter. The circumferential
interference should be no more than 1%.
If the pressure is external then the ‘O’ ring’s
inside diameter should be in contact with
the housing. In this case the ‘O’ ring should
be stretched up to a maximum of 4%.
Static triangular housingLocation grooves with a triangular shape
are sometimes used for screwed flanges
and caps. However, manufacturing these to
accurate sizes is difficult. Since the sealing
function of the ‘O’ ring depends on the exact
shape of the locating groove, the dimensions
and tolerances given in the following table
are to be strictly observed. Installation in
rectangular grooves is preferable.
15° to 20°
Piston assembly
Use of a fitting aid
Rod assembly
15° to 20°
Axial compression or face seal
Sq
ueez
e %
d2 (mm)static-axial
O-ring cross section d2 in mm
1 2 3 4 5 6 7 80
5
10
15
20
25
30
35
max.
min.
Recommended axial compression
Static sealing – axial and triangular
rounded, flash-free
(external pressure) (0.2mm max)
br1
g
t
r2z
d4
0° to 5°
d3d9
15° to 20°
B
AB
d7
d8b
B
0° to 5°
B A h
r2
r1
(internal pressure)
b
t
r10 - 5°
r2
Pressure direction
No back-up ringb
Pressure direction
One back-up ring
b1
Pressure direction
Two back-up rings
b2
Housing diametrical tolerances
Bore diameterShaft diameter
Axial – outside diameterAxial – inside diameter
d4/d10
d5/d9
d7
d8
H8
f7H11
H11
These tolerances are as specified in ISO/R286,ISO System for limits and fits – Part 1, generaltolerances and deviations.
d1 d2
0° to 5° r1z
g
A t
rounded, flash-free
r2
b
B
B
15° to 20°
d10 d6d5
rounded, flash-free
(external pressure) (0.2mm max)
br1
g
t
r2z
d4
0° to 5°
d3d9
15° to 20°
B
AB
d7
d8b
B
0° to 5°
B A h
r2
r1
(internal pressure)
b
t
r10 - 5°
r2
Pressure direction
No back-up ringb
Pressure direction
One back-up ring
b1
Pressure direction
Two back-up rings
b2
Housing diametrical tolerances
Bore diameterShaft diameter
Axial – outside diameterAxial – inside diameter
d4/d10
d5/d9
d7
d8
H8
f7H11
H11
These tolerances are as specified in ISO/R286,ISO System for limits and fits – Part 1, generaltolerances and deviations.
d1 d2
0° to 5° r1z
g
A t
rounded, flash-free
r2
b
B
B
15° to 20°
d10 d6d5
Piston sealing (radial)
Rod sealing (radial)
Static/dynamic sealing – radial
O-ring stretch in piston sealing When an o-ring’s internal diameter is less than 50mm, the maximum stretch should be less than
8%. When an o-ring’s internal diameter is greater than 50mm, the maximum stretch should be less
than 6%. The maximum stretch is derived from the largest groove diameter and smallest o-ring
internal diameter.
Reduction of cross-section due to stretchWhen an o-ring is stretched, the cross-section distorts to assume an oval form. The o-ring cross-
section reduces when subject to stretch. As rule of thumb, approximately half of the stretch
e.g. 5% stretch equals 2.5% reduction in cross-section.
This reduction in cross-section lowers the compression and thus the sealing stress.
Guidelines• Static o-rings are squeezed to higher percentages than dynamic, as friction
concerns are reduced.
• Surface finish requirements can be relaxed in comparison to dynamic
applications (except where pulsating pressure is present).
• Dynamic o-rings are exposed to lower squeeze percentages compared to static
to reduce friction and wear.
• Surface finish requirements are critical to reduce friction, seal wear and damage.
• The groove width will need to be increased for one/two back up rings, if system
pressures are exceeded beyond normal o-ring capability.
• Oscillating and rotating conditions are regarded as dynamic.
• Although suitable for dynamic work, o-rings are best applied to short stroke/small
diameter applications.
• The preferred o-ring hardness is 60 to 80 IRHD.
• Media compatibility and temperature are critical, as swell or shrinkage should
be minimised for reliable function.
• Compounds with the highest wear resistance should be selected.
• Pneumatic and hydraulic applications can be accommodated.
Superior does not generally recommend the use of o-rings as rotary seals.
Gough-Joule effectWhen a freely suspended, loaded rubber is stretched and heated, the rubber will contract,
attempting to regain a less stressful state. This occurs because of the rubber’s stressed structure.
This phenomenon is of particular importance in rotary applications, where the combination of
installed stretch and system heat can cause the o-ring to retract and seize the rotating shaft.
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Unstretched O-ring
Stretched O-ring
Piston rod sealingType A
Type B
Type C & D
Piston sealing
Face sealing
% r
educ
tio
n o
f cr
oss
-sec
tio
n d
2
% stretch of inside diameter d1
2 4 6 8 10 12 14 16 18 20 22 24 260
1
2
3
4
5
6
7
8
9
10
11
12
13
Seal designSuperior technical guide
16 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 17
Static triangular housingLocation grooves with a triangular shape are
sometimes used for screwed flanges and caps.
However, manufacturing these to accurate sizes
is difficult. Since the sealing function of the o-ring
depends on the exact shape of the locating
groove, the dimensions and tolerances given
in the following table are to be strictly observed.
Installation in rectangular grooves is preferable. Housing Dimensions – static axial (mm)
d2 h+0.10 b+0.20 r1 r2
h
b
pressurefrom inside
Ø d70° to 5°
r2
r1
A
B
B
h
b pressurefrom outside
Ø d80° to 5°
r1
r2
A
B
B
b+0.2
rounded, flash-free
Ø d4Ø d3
t
Ø d9
r1
r2
0° to 5°
15° to 20°
z
B
B
Ag
Installation in atriangular groove
Ø h8
45°
t
s
O-Ring Rousing data for piston and piston rod sealing applications
Mode d2 t b t tb1 b2
Static
*Static
Static anddynamic
Pneumatic
Static anddynamic
Pneumatic
*Dynamic
*Static
Static anddynamic
Pneumatic
Static anddynamic
Pneumatic*Dynamic
Pneumatic
*Static
Static anddynamic
Static anddynamic
Static anddynamic
Pneumatic
Pneumatic
Static anddynamic
Static anddynamic
Pneumatic
*Dynamic
Pneumatic*Static
Static anddynamic
Pneumatic
*DynamicPneumatic
*Static
1.60
1.78
1.50
2.00
2.40
2.50
2.62
3.00
3.50
3.53
4.00
5.00
5.34
5.70
6.99
8.40
7.20/7.50
7.75/7.967.50/7.75
6.12/6.32
6.00/6.12
4.70/4.955.22/5.38
4.95/5.184.83/4.93
4.66/4.77
4.30/4.52
3.40/3.57
3.02/3.12
3.18/3.25
4.57/4.67
2.94/3.11
2.20/2.30
2.34/2.41
2.50/2.65
2.35/2.50
2.70/2.77
2.06/2.19
2.24/2.31
1.84/1.97
1.64/1.72
1.97/2.09
2.13/2.20
1.55/1.60
1.46/1.52
1.18/1.251.17/1.09
7.00/9.20
11.00/11.20
11.00/11.20
8.65/8.85
8.65/8.85
6.40/6.607.50/7.70
6.35/6.55
6.35/6.55
7.50/7.70
6.60/6.80
6.60/6.80
5.30/5.50
4.30/4.50
4.30/4.50
4.70/4.90
3.70/3.90
4.00/4.20
4.00/4.20
3.17/3.37
3.17/3.37
3.40/3.60
3.40/3.60
3.10/3.30
3.20/3.40
3.20/3.40
2.70/2.90
2.40/2.60
2.40/2.60
2.30/2.50
2.30/2.50
7.63/7.75
-
-
-
6.07/6.14
-
-
5.08/5.18
-
4.71/4.49
-
4.42/4.52
3.47/3.57
-
3.10/3.15
3.01/3.11
-
-
2.57/2.65-
2.26/2.31
-
2.12/2.19
-
-
2.01/2.09
1.68/1.72
-
1.47/1.52
-
-
13.20/13.40
--
10.05/10.18
-
--
9.30/9.50
-
7.60/7.73
-
8.40/8.60
-
6.70/6.90
5.50/5.63
-
6.10/6.30
-
5.40/5.60
-
4.60/4.73
-
4.80/5.00
-
-
4.60/4.80
-
4.10/4.30
-
4.10/4.23
-
7.63/7.75
--
-
6.07/6.14
--
5.08/5.18
-
4.71/4.79
-
4.42/4.52
3.47/3.57
-
3.10/3.15
3.01/3.11
-
-
2.57/2.65
-
2.26/2.30
-
2.12/2.19
-
-
2.01/2.09
-
1.68/1.72
1.47/1.52
-
-
15.40/15.60
-
-
-
13.50/13.63
-
-
11.10/11.30
-
10.20/10.33
-
10.20/10.40
-
8.10/8.30
7.40/7.53
-
7.50/7.70
-
6.80/7.00
-
6.50/6.63
-
-
-
6.20/6.40
6.00/6.20
5.50/5.70
-
6.10/6.23
-
-
1.00
0.90
1.00
0.90
1.00
1.00
1.00
0.90
1.00
0.80
0.80
0.50
0.50
0.50
0.500.50
0.40
0.40
0.40
0.40
0.40
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Withanti-extrusionrings
Withoutanti-extrusionrings
r. maximum
Corner radiid2
d2
b b1 b2b2
tt
b1
t
b
(100 bar maximum)pressure
(100 bar +) (100 bar +)
alternating pressure
*BS 4518 recommendations NOTE: All dimensions in mm
15° to 20°
Piston assembly
Use of a fitting aid
Rod assembly
15° to 20°
0
5
10
15
20
25
30Hydraulics, dynamic
Pneumatics, dynamic
Sq
ueez
e %
Sq
ueez
e %
Axial compression or face seal
Hydraulics, pneumatics, static
Sq
ueez
e %
Sq
ueez
e %
O-ring cross section d2 in mm
max.
min.
1.8 2.65 3.55 5.3 7
O-ring cross section d2 in mm
1.8 2.65 3.55 5.3 7
O-ring cross section d2 in mm
1.8 2.65 3.55 5.3 7
d2 (mm)static-axial
0
5
10
15
20
25
30
0
5
10
15
20
25
30
max.
min.
max.
min.
max.
min.
0
5
10
15
20
25
30
35
1 2 3 654 7 8
15° to 20°
Piston assembly
Use of a fitting aid
Rod assembly
15° to 20°
0
5
10
15
20
25
30Hydraulics, dynamic
Pneumatics, dynamic
Sq
ueez
e %
Sq
ueez
e %
Axial compression or face seal
Hydraulics, pneumatics, static
Sq
ueez
e %
Sq
ueez
e %
O-ring cross section d2 in mm
max.
min.
1.8 2.65 3.55 5.3 7
O-ring cross section d2 in mm
1.8 2.65 3.55 5.3 7
O-ring cross section d2 in mm
1.8 2.65 3.55 5.3 7
d2 (mm)static-axial
0
5
10
15
20
25
30
0
5
10
15
20
25
30
max.
min.
max.
min.
max.
min.
0
5
10
15
20
25
30
35
1 2 3 654 7 8
15° to 20°
Piston assembly
Use of a fitting aid
Rod assembly
15° to 20°
0
5
10
15
20
25
30Hydraulics, dynamic
Pneumatics, dynamic
Sq
ueez
e %
Sq
ueez
e %
Axial compression or face seal
Hydraulics, pneumatics, static
Sq
ueez
e %
Sq
ueez
e %
O-ring cross section d2 in mm
max.
min.
1.8 2.65 3.55 5.3 7
O-ring cross section d2 in mm
1.8 2.65 3.55 5.3 7
O-ring cross section d2 in mm
1.8 2.65 3.55 5.3 7
d2 (mm)static-axial
0
5
10
15
20
25
30
0
5
10
15
20
25
30
max.
min.
max.
min.
max.
min.
0
5
10
15
20
25
30
35
1 2 3 654 7 8
Typical compression range
Typical o-ring housing data for piston and rod sealing applicationsWhilst the adjacent table is a guideline for o-ring compression, the following graphs display a more accurate representation.
Pressure
600
500
400
300
200
150
1009080706050403020100
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
70degrees of hardness 80 90 IRHD
diametrical play (mm)
wor
king
pre
ssur
e: b
ar
extrusio
n
no extrusio
n
mm
Pressure
Cle
aran
ce (r
adia
l)
70 80 90 rubber hardness (IRHD)
0 70 140 210 280 350 410 bar0
0,05
0,10
0,15
0,20
0,25
0,30
• Anti extrusion rings are required when
considering conditions to the right of
the hardness curve.
• For temperatures above 100°C use
the curve for the next hardness rubber.
A good quality 70 IRHD compound will resist
extrusion at room temperature up to 100 Bar.
However, extrusion resistance is influenced by:
• temperature
• pulsating pressure spikes
• seal cross section
• housing design (radii, draft angles).
Please consult our Engineering department
for detailed information regarding particular
working conditions.
Elastomers tend to act as a viscous fluid when under pressure, resulting in migration into the
‘extrusion gap’.
Therefore, under certain conditions, a supporting back-up ring is used in conjunction with
an o-ring to reduce the risk of extrusion. The back-up ring effectively bridges any gap due
to the clearance between the shaft and bore.
For axial face-sealing applications, extrusion gaps should be eliminated, ensuring that pulsating
pressures do not create ‘panting’ between mating faces.
When exceeding the recommended gap size (in accordance with the graph below)
an anti-extrusion device is required.
• Recommended extrusion gap is based upon radial clearance if eccentricity is zero,
or diametral clearance if concentricity of mating diameters cannot be assured.
• It should be noted that Silicone and Fluorosilicone (due to low tensile strength) should
only be applied in grooves with extrusion gaps at half the recommended radial clearance
for other compounds.
• If a selected radial clearance will not achieve a given pressure, then the next
hardness range should be considered.
• If a 90 IRHD rubber compound does not satisfy the given parameters, then a PTFE
or Thermoplastic back-up ring should be selected.
Zero pressure
Pressure
Extrusion
Zero pressure
Pressure
Extrusion
Zero pressure
Pressure
Extrusion
Seal designSuperior technical guide
18 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 19
Our state of the art toolroom designs and manufactures precision prototype and production moulds to meet the engineering challenges of our customers.
Precision mouldings / custom seals
Where a specific moulding profile is required,
we apply our extensive experience to guide
the design evolution to achieve the most
reliable and cost effective solution.
Our broad design capabilities at Superior
enable us to supply unique profiles for
applications where traditional o-rings
are not suitable.
Our portfolio includes generic profiles
such as:
• diaphragms
• precision flat washers
• spherical balls.
Although there is an infinite number of different
seal profiles which can be used to suit
individual applications, there are a number
of more commonly used custom seal profiles.
Listed below are just a small number and their
advantages.
Lip seals / U-seals / V-seals
• Self energising when pressure acts
against the lips
• Lower assembly force than the
equivalent o-ring
• Lower dynamic running force than
the equivalent o-ring
• Require less space than the
equivalent o-ring
• Less creep in housing
• Able to cope with larger tolerances
• Able to cope with eccentric conditions
• Able to cope without flatness
(axial sealing).
Symmetrical seals • Lower assembly force than the
equivalent o-ring
• Greatly reduces the chance of spiralling
• Symmetrical design enables seal to be
assembled both ways
• Less volume than the equivalent o-ring
• Can cope with pressure from both sides.
Quad rings
• Two sealing beads in contact with both
the groove and bore
• Greatly reduces the chance of spiralling
• Symmetrical design enables seal to be
assembled both ways
• Lower friction for dynamic applications.
Moulded gaskets
• Low assembly force
• Tailored profile
• Able to cope with larger tolerances
• Able to cope without flatness
• Plastic housings
• Retention
• Axial (face) sealing
• Multiple sealing ports
• Customer information
• Location tags
• Stabilising features.
Custom radial seals
• Low dynamic force
• Eccentric conditions
• Tolerances
• Special conditions
• Profile.
Moulded Seals are homogenous rubber parts
which are components that operate within
static and dynamic applications.
Superior engineering Superior’s core strength is providing our
customers with optimal design and robust
sealing solutions. Superior has the ability to
assist in the design of sealing solutions which
exceed customer expectations. Support
and Technical Service are always on hand
to provide advice on component design,
compound selection and analysis.
When an o-ring is desired we can calculate
the ideal housing geometry and o-ring size
for given parameters. Where an o-ring cannot
be used, Superior can offer help and advice
to find a solution for you.
Seal integrity
We are focused on the fact that our precision
o-rings and special mouldings are a crucial
part ‘of the bigger picture’. The integrity and
quality of Superior products are fundamental
to the integrity of each end product, helping
to achieve outstanding product performance
and enhance our customers’ hard-won
reputations. The unique integrity of our
products is achieved through a combination
of 3 Key Elements; Compound, Design and
Manufacturing process.
Seal Integrity
Design Compound
Manufacturing Process
Custom seal designSuperior technical guide
22 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 23
04 Custom seal design and manufacture Using Superior custom designed seals can mean fast service and quality assurance to you.
Seal performanceThe performance of the seal is dependant
on 5 factors:
• system media
• hardware
• service conditions
• seal design
• seal compound.
Seal design assistanceGetting involved at the earliest possible stage of
development, our engineering department aims
to become an integral part of our customer’s
team, providing services such as:
• seal design
• housing recommendations
• design for manufacture and assembly
(DFMA)
• CAD
• problem solving
• advice.
All these services combined assist in reducing
project lead times.
Custom seal designSuperior technical guide
24 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 25
Tolerances for moulded partsMoulded seals are subject to changes
in their geometry during vulcanization.
These changes should be allowed for when
designing. The greater the degree of accuracy
demanded, the closer the control which must
be exercised during manufacture. When
particular physical properties are required
in the product, we advise consultation with
Superior’s Engineering department.
All rubber shows some shrinkage when
cooled after moulding, and allowance for this
is made in the mould design. The amount of
shrinkage is dependent on rubber type.
Moulds are made in various ways depending on
the type of product and accuracy demanded.
Superior recommend the use of ISO 3302-1
Class M2 tolerance for high-quality precision
mouldings (see table below).
In compression moulding more rubber is
used than is required to fill the cavity, and
the excess is flashed. This flash can prevent
the mould sections from fully closing and
thus affects the finished part dimensions.
However, for injection and transfer moulding
all dimensions can be considered as fixed.
A heritage of excellence
Since 1972 Superior has built a reputation
for engineering excellence. Our tool-making
expertise and capabilities ensure we
consistently meet the tightest tolerances,
not to mention budgets and deadlines,
every single time.
Our tool roomAs a full service facility we are able to manage
projects from prototyping right through to
production. We focus on providing engineers
and product designers with physical samples
in the shortest possible lead time.
The marketplace and our customers’ needs
are constantly changing. We are flexible
enough to react to changing demands
quickly, and can use off-line programming
to take new designs to machine as quickly
as possible.
We have complete control of the tool making
process, and are committed to expanding
our facility in line with client needs. In fact we
constantly invest in the latest, state-of-the-art
technology to ensure all tooling and products
are manufactured with 100% accuracy and
meet our customers’ tightest deadlines.
The service we offer to our customersOur success is based on our clients’ success.
That’s why we do everything we can to make
working with Superior benefit their business.
Our clients can expect to have samples
perfectly bagged, delivered on their desk
ready for practical trials. We are here to help
our customers win business and launch new
products in the most compressed time scales
and above all with confidence.
Above Up to and including
F ±
C ±
Nominal dimension Class M2
0 4.0 0.10 0.15
4.0 6.3 0.15 0.20
6.3 10 0.20 0.20
10 16 0.20 0.25
16 25 0.25 0.35
25 40 0.35 0.40
40 63 0.40 0.50
63 100 0.50 0.70
100 160 0.70 0.80
160 - 0.50% 0.70%
Dimensions in mm
F
F
F
C
C
C
lower half of mould
flash
upper half of mould
moulded part
Two types of tolerances, F and C are used.
Fixed dimension (F): Dimensions which are
not affected by influences like flash or lateral
movement of different mould parts.
Closure dimension (C): Dimensions which
can be altered by flash thickness or lateral
movement of different mould parts.
O-ring size range standardsAt Superior, we pride ourselves on our
precision o-ring range which exceeds the
cross-sectional tolerances for the following
dimensional standards;
ISO 3601-1
DIN 3771 Part 1
BS 4518
The benefit of close tolerances on an o-ring
cross section (d2), is the ability to reduce our
customer’s tolerance chain and improve the
overall performance of the customer’s product.
In the Superior o-ring size list, the internal
diameters conform to ISO 3601-1 tolerances
and the cross section diameter has a reduced
tolerance. These precision o-ring tolerances
apply to NBR 70 compounds. O-rings
manufactured in other compounds and
hardness’ are produced to conform
ISO 3601-1 tolerances, however
dimensions for the internal diameter
may be towards the lower end.
High shrinkage compounds may
require dedicated tooling to comply with
ISO 3601-1 dimensions and tolerances,
but will still allow for the principle of a more
accurate cross-section. Superior can also
supply o-rings to customer’s specifications.
A continually updated version of the Superior
o-ring size list can be downloaded from our
website www.superiorltd.com
d1 d2
Quality acceptance criteria ISO 3601-3
b+0.2
rounded, flash-free
Ø d4Ø d3
t
Ø d9
r1
r2
0° to 5°
15° to 20°
z
B
B
Ag Off-register
mismatch(offset)
Combinedflash
Backrind
Excessivetrimming
Flow marks
Foreignmaterial,non-fills andindentations(includingparting-lineindentations)
e
f
g
h 0.08
0.18
0.10
0.08 0.10
0.12
0.27
0.08 0.10
0.36
0.14
0.13 0.15
0.16
0.53
0.10 0.13
0.70
0.18
0.15
Grade N
O-ring section diameter d2
Size limitLimitingdimension
Surfaceimperfection
<2.25 >2.25<3.15
>3.15<4.50
>4.50<6.30
>6.30<8.00
e e e
f
f
g
h
n
j
k
m
l
l
Not less than o-ring section diameter on lower tolerance
n
j
k
l
m 0.08
0.60
0.08
1.50 * 1.50 *
0.08
0.80
0.08 0.10 0.10
1.00
0.08
6.50 * 6.50 * 6.50 *
0.08 0.08
1.30 1.70
0.13
* or 0.05 x o-ring internal diameter, whichever is greater but not exceeding 50 mm
Limits of size for surface imperfections for Grade N o-rings
QualitySuperior technical guide
Quality Standards compliance05
26 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 27
Quality is an integral part of the Superior customer service philosophy
Total control of all aspects of seal
manufacture ensures that we always
comply with recognised standards
applied by the industry.
With our expertise we can closely define
and control seal tolerances and surface
characteristics. Our continual investment
programs enable us to apply the latest
control and inspection techniques.
This section is designed to give guidance
to quality and design engineers.
We thoroughly recommend that all quality
and specification issues are addressed at
the earliest point in the development stage
of any new project. This ensures that all
customer-critical features and commercial
issues are identified from the outset.
Quality control: documentation
All documentation for despatch to the
customer conforms to the ISO 9001 standard.
The documentation issues and details are
continually being revised and updated
according to demands from individual
customers and the industry in general.
Please consult our Quality department
for specific requirements.
Seal surface inspection levels
All our o-rings are inspected to ISO 3601-3
DIN 3771 part 4. The standard level is Grade N.
For more information on inspection levels
please consult our Quality department.
Special moulding tolerances
Dimensional tolerances on special
mouldings will relate to ISO 3302-1
or customer specification.
Certification
Certification can be provided with the product,
but must be stated at point of order.
Environmental compliance
Superior is able to provide materials compliant
to current European and Worldwide legislative
requirements e.g. ROHS, REACH and IMDS.
AssemblySuperior technical guide
Assembly This section of the guide is intended to assist engineers when considering sealing criteria.06
28 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 29
Use of a Fitting Aid
An o-ring is a precision component requiring
care during installation and handling. Many
failures of o-rings can be directly related to
improper installation. Long-term, leak-free
o-rings can only be achieved when the
correct size for the housing is chosen.
O-ring stretch during assembly
During assembly an o-ring inside diameter
can be stretched up to 50% for most
compounds, however it is advisable to keep
below this value where possible to prevent
damage to the o-ring. Sometimes this value
may be unachievable, this is particularly
true with o-rings of small inside diameter
and large section.
It is essential to give the o-ring time to
recover, this is especially important during
automatic assembly.
Fitting aids and sharp edges
O-rings should not be drawn over sharp
edges, threads, slits, bores and splines
during fitting. The use of fitting aids during
assembly ensures the avoidance of sharp
edges and features.
Suitable assembly tools, as detailed,
aid location and avoid contact with sharp
edges. The aid should be manufactured
from materials which will not damage sealing
locations and surfaces (e.g. plastic or brass).
For manual assembly or removal of an
o-ring from a groove, a spatula-type tool
can be manufactured from a soft material.
All edges should be smooth, rounded
and free from burrs.
Rod sealing assembly aids
Piston sealing assembly aid
StorageSuperior technical guide
30 | www.superiorltd.com Material Science Department +44 (0)1202 854300 | 31
Housing chamfers To prevent damaging the o-ring section
during assembly, chamfers are necessary
on all leading edges, all other edges must be
free from burrs. Dimension X should always
be greater than dimension Y to ensure
trouble free assembly.
Traversing cross drilled ports An o-ring can be sheared when a
spool or a rod moves in a bore broken
by cross-drilled ports. The deformed
o-ring returns to its original round cross
section as it enters the port and is sheared
as it leaves the drilled area. To avoid this,
connection holes should be repositioned.
If repositioning is not feasible, an internal
chamfer is recommended.
Rolling O-rings are at risk from rolling when fitted
over a diameter. This risk can be accentuated
on large inside-diameter/ small section
o-rings. This can result in spiral failure and
leakage. To reduce the risk of rolling we
recommend that suitable lubrication be
applied to the o-ring prior to assembly.
Cleanliness / cleaning materials At Superior we rigorously control cleanliness
at all process stages, particularly during the
final post-deflashing cleaning cycle.
All seals are supplied to the customer free
from surface silicone film and surface particle
contamination (e.g. flash particles).
Foreign particle contamination on seals
can cause leakage after assembly.
If applying lubricants, the seal should be
assembled immediately into the housing,
or protected if placed in storage or transition.
All cleaning media must be compatible
with the elastomer.
Leading edge chamferX>Y
Y
X
15°to 20°
Leading edgechamfer and an ‘O’ ring beforedeformation.Dimension xshould always be greater thandimension y toensure trouble-free assembly
leading edge chamfer x > y
y
15° to 20°x
15° to 20°
15° to 20°
Piston assembly
Rod assembly
Use of a fitting aid
Fitted ‘O’ ring,rolled
Optimal solution is chamfering the full bore circumference, allowing the o-ring to return to a round cross-section before re-compression
Leading edgechamfer and an ‘O’ ring beforedeformation.Dimension xshould always be greater thandimension y toensure trouble-free assembly
leading edge chamfer x > y
y
15° to 20°x
15° to 20°
15° to 20°
Piston assembly
Rod assembly
Use of a fitting aid
Fitted ‘O’ ring,rolled
Optimal solution is chamfering the full bore circumference, allowing the o-ring to return to a round cross-section before re-compression
Recommended storage conditions for products based on Superior rubber compounds.
Optimum service is the primary objective
in the development of any compound
at Superior.
We give careful consideration to minimising
the compound factors that may adversely
affect seal performance. It is in the nature
of rubbers that changes can occur during
extended component storage and become
exacerbated by inappropriate conditions
and practices. Recommended conditions
should always be followed.
Light Sunlight and intense artificial light can cause
surface deterioration of rubber components.
In extreme cases, this is manifested as
shallow crazing.
We recommend that storage of such parts
should take place in dark or very low-intensity
artificial light conditions.
Humidity
You should avoid conditions where
condensation may occur prior to
assembly/installation.
Contaminants
Airborne contaminants deposited on the
surface of o-rings prior to installation can
promote surface attack. Examples include
cutting oil mists, powders and active
chemicals used in production processes.
In the case of particulates, such
contamination can create a leakage
path when in service.
As far as is possible, o-rings should be
kept in their sealed delivery bags until
required for installation.
Stress
Always store o-rings in their unstressed,
free state, avoiding distortion and the risk
of ozone attack. Large rings should never
be hung on pegs.
Temperature
Finished components should be stored
below 30°C and preferably below 25°C.
Extended exposure to higher temperatures in
air can accelerate ageing effects and cause
distortion, hardening, elongation loss and
impairment of low temperature flexibility.
If inadvertent freezing has occurred, the
apparent hardening effect can be reversed by
warming to normal ambient temperatures.
Oxygen and ozone Superior o-rings are supplied in sealed
polythene bags which prevent exposure to
circulating air and atmospheric impurities.
We recommend that o-rings are kept in these
bags until required – it is the combined effect
of atmospheric oxygen and temperature that
promotes the problems encountered above.
Ozone is present in low concentrations
in the atmosphere and at much higher levels
near some electrical equipment. It will attack
rubber components based upon particular
elastomers when they are stretched or
distorted. This appears as cracks at right
angles to the direction of distortion.
Of all common o-ring elastomers,
only nitrile (NBR) is significantly prone
to ozone attack.
Once again, storage in the original
sealed polythene bags in dark or very
low-intensity artificial light conditions
offers full protection.
Shelf life It is practically impossible to define a specific
maximum shelf life for finished elastomeric
products. To achieve the best results, always
rotate stock and store as recommended.
The following table of suggested
shelf life is for guidance only.
These storage times are more
conservative than those proposed in
BS ISO 2230:2002, ‘Controlled storage
and packaging of vulcanised rubber
and rubber products’.
Storage
3 years
Superior FN
Superior WN
5 years
Superior LN
Superior MN
Superior HN
7 years
Superior EP
Superior SIL
Superior PA
Superior TH
Superior VF/VP
We are fiercely proud of our place in the world of engineering.
Superior technical guide
We are also constantly aware of the continuous challenges that face us in order to maintain our position and ensure we continue to fulfil obligations to our customers.
By continually monitoring our performance, sharpening our technical expertise and tightening
response times, we are able to reinforce our added value. If you would like to learn more about
how Superior can contribute to your business’ success we would be pleased to answer your
questions and welcome you to meet our people, see our facility and discuss your requirements.
A warm welcome awaits you at Superior.
Superior Seals Limited
Nimrod Way
Ferndown Industrial Estate
Wimborne, Dorset BH21 7SH, UK
Tel: +44 (0)1202 854300
Fax: +44 (0)1202 854313
Email: [email protected]
Superior Specials Limited
Nimrod Way
Ferndown Industrial Estate
Wimborne, Dorset BH21 7SH, UK
Tel: +44 (0)1202 891180
Fax: +44 (0)1202 894468
Email: [email protected]
01.1
3.02
All technical information included in this document is provided free of charge for guideline purposes only and is based on
technical data which Superior believes to be reliable. This information is intended for use by suitably skilled and qualified
persons entirely at their own discretion and risk. As the end use of our product is beyond our control, we make no warranties
express or implied and no liability can be accepted in connection with the use of this information, which is subject to revision
without prior notice as additional knowledge and experience are gained. COPYRIGHT © 2013 Superior GROUP LIMITED
www.superiorltd.com