KNOWLEDGE ABOUT ELASTOMERS AND SEALINGS MADE CLEAR

Scientific Papers by Bernhard Richter and Ulrich Blobner

Expertise testing procedures

EXPERTISE TESTING METHODS - SPECIAL ISSUE OF THE JOURNAL "DICHT"!

Starting with issue 04/2014, a series on limits and possibilities of important test methods for elastomers was published for three consecutive years in the journal DICHT! by O-Ring Prüflabor Richter.

EXPERTISE TESTING METHODS - PHYSICAL ANALYTICS

Thermogravimetric analysis (TGA), Dynamic Differential Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) have become indispensable test methods, both for rubber materials and for finished parts made from elastomers.

EXPERTISE TESTING METHODS - 100 YEARS HEAT AGING ACCORDING TO W.C. GEER

In 1916, the American W.C. Geer presented his method for accelerated ageing of rubber, which is still practiced in large parts unchanged.

EXPERTISE TESTING METHODS - INDISPENSABLE RUBBER TESTS YESTERDAY AND TODAY FROM THE VIEWPOINT OF ISO 3601 - 5

The historical development of the most important basic test methods (tensile test, hardness,heataging, DVR) is briefly introduced while the current O-ring standard ISO 3601-5 demonstrates why these test methods are still indispensable.

EXPERTISE TESTING METHODS - 100 YEARS OF SHORE A

Modern technical literature on elastomer testing contains little on the origin and background of the important basic test types, such as hardness tests.

EXPERTISE TESTING METHODS - IDENTITY TESTS - HARDNESS AND DENSITY

Identity tests allow the conformity of an inspection lot with reference values from sampling or previous deliveries within a defined framework.

EXPERTISE TEST METHODS - HARDNESS

Hardness is defined as the resistance that a body sets against a harder penetrating body. The force of the indenter is usually determined in advance.

EXPERTISE TEST METHODS - COMPRESSION SET

Elastomers are not ideal elastic materials. If, for example, a seal is deformed over a longer period of time, it will not return to its original shape once the deformation has been removed.

EXPERTISE TEST METHODS - TENSILE SET

In the tensile set, the specimen is stretched. It is either a constant strain or a strain under constant load.

EXPERTISE TEST METHODS - TENSILE TEST

During the tensile test, standardized test specimens (in most cases, so- called "dumbbell bars") are clamped in a tensile testing machine and stretched at a constant feed rate until they tear.

EXPERTISE TEST METHODS - TENSILE TEST ON RINGS

The basic standards for the tensile test of elastomers (DIN 53504, ISO 37, ASTM D412 06a) describe also the testing of a few standardized rectangular rings.

EXPERTISE TEST METHODS - HEAT AGING ON ELASTOMERS

In the case of elastomers, the term "aging" describes a large number of processes which lead to the chemical and physical conversion and degradation of vulcanized test specimens or finished parts.

Expertise o-rings - quality assurance on o-rings: how can this be done?

Causes for quality fluctuations of O-rings are described and how the hardness and compression set of O-rings can be measured reproducibly.

Expertise testing methods – chemical-analytical test methods

FTIR analysis is a frequently used analysis method in elastomer technology for fast and simple polymer determination, while GC-MS can be used for deeper insights due to very high sensitivity.

Expertise Failure Analysis

failure analysis - HIGH PERMANENT DEFORMATION

If a seal fails significantly before its age-related service life limit due to a lack of elastic re-deformation, a high permanent deformation is the cause of failure.

EXPERTISE FAILURE ANALYSIS: EXTRUSION

Sealing gaps that are too large along with many other causes can trigger extrusion, which is sometimes also referred to as gap intrusion.

EXPERTISE FAILURE ANALYSIS: EXCESSIVE ABRASION

This type of damage mainly occurs with dynamic seals and can have many different causes.

EXPERTISE FAILURE ANALYSIS: AUTOXIDATION

Rubber poisons such as copper or manganese can rapidly accelerate elastomer aging. EPDM is often affected by the dezincification of brass in hot water applications.

EXPERTISE FAILURE ANALYSIS: INCORRECT INSTALLATION SPACE

A properly designed installation space is essential for obtaining a functioning seal. Even small details can make the crucial difference

EXPERTISE FAILURE ANALYSIS: EXPLOSIVE DECOMPRESSION AND OVERHEATING

This type of damage is caused by sudden and severe fluctuations in pressure or temperature and can cause serious damage to the seal.

EXPERTISE FAILURE ANALYSIS: ASSEMBLY DAMAGE

This is an often-underestimated cause of damage, although it could be largely avoided by using lubricants and assembly aids. After all, approx. 10% of all seal failures are caused by assembly damage.

EXPERTISE FAILURE ANALYSIS: CRACKS DUE TO MANUFACTURING DEFECTS

This is a serious error. It can be caused by inadequate vulcanization, superimposed compounds, impurities, the demolding process, post-processing steps or shrinkage of the material.

EXPERTISE FAILURE ANALYSIS: OZONE CRACKS

Although the damaging effect of ozone on many elastomers has been known for over 150 years, it still causes seal failure. Ozone cracking always occurs perpendicular to the direction of stress.

EXPERTISE FAILURE ANALYSIS: THERMAL OVERLOADING

Overheating of sealing materials in most cases leads to embrittlement and premature seal failure.

Expertise of damage analysis: chemical degradation and swelling

The use of sealing materials in incompatible media can cause chemical degradation or excessive swelling, which should be avoided in any case.

INTEGRAL APPROACH TO DAMAGE ANALYSIS

The performance of a damage analysis is not only a matter of material and microscopic examination but also needs to be dealt with systematically.

Expertise O-Rings

LONG - TERM PROPERTIES OF O - RINGS

Although the long-term behavior of O-rings is of great practical importance, the technical literature provides hardly any guidance on how to realistically estimate the load limits of O-rings.

EXPERTISE O - RINGS - THE MOST DIVERSE SEALING ELEMENT OF ALL TIME

Although O-rings have been used as seals for over 170 years, they are still unbeatable in many technical applications due to their numerous advantages, simple design and reliability

BETTER AND CHEAPER - WHY THIS CAN CONTINUE TO WORK WITH O - RINGS

Billions of O-rings work with decreasing procurement prices

EXPERTISE TEST METHODS - TENSILE TEST ON RINGS

The basic standards for the tensile test of elastomers (DIN 53504, ISO 37, ASTM D412 06a) describe also the testing of a few standardized rectangular rings.

EVALUATION OF ENDURANCE AND AGING TEST RESULTS

O-Ring users are constantly faced with the question of sufficient durability.

The o-ring as standard part

With the new ISO 3601 Part 5, the O-ring finally becomes a standard part. This article explains the various parts of this O-ring standard.

State of the arts for o-rings

O-ring failures still occur far too often in practice, partly due to insufficient specification. The new edition of ISO 3601-5 (2015) provides guidance with regard to material standardization.