Failure Analysis
Analyse • Recognise • Solve • Prevent
From Damage to Analysis
Detect and prevent damage
Small components with a great effect – seals and other elastomer components are of great importance in technical applications. They are cheap to buy and challenging in their function. As long as they work, few think about the small, elastic components. However, if they fail, the consequences are usually not just inconvenient.
It is rather common for the entire machine or vehicle to come to a standstill, sometimes even resulting in a total breakdown. In such cases, it is not enough to simply replace the component and wait for the next failure. It is important to track down the causes of the failure, to recognise errors and learn from them in order to avoid future failures.
The Failure Analysis
Our Core Competence
Damage analysis of elastomer seals and technical moulded parts, for example diaphragms, elastomer or TPE hoses, is one of the core competences of the Elastomer Institut Richter.
Since 1996 we have been supporting our customers in the event of damage with our specialist knowledge and extensive experience. We assess and analyse faulty components, identify the cause of the damage and propose measures to eliminate the causes and prevent further damage.
Our expertise for your reputation
In well over 2000 cases, the expertise of the Elastomer Institut Richter has helped to identify and permanently solve problems. Regardless of where the cause lay – in the manufacturing process, the installation space, the quality of the formulation or the stress. In addition, our qualified and objective analyses contribute to an amicable settlement in cases of complaints and damage.
Often, only small changes and improvements in the manufacturing process or the application can save immense costs and repair the loss of image and reputation associated with the incident of damage. Moreover, we always pay attention to a pragmatic and practical approach so that you get the answers promptly and with manageable effort.
Typical Damages and Failure Modes
The first impression
Damage to a technical moulded part is usually only noticed when it no longer fulfils its function. Seals or hoses are suddenly leaking; leakage becomes obvious because liquid, oil or gas escapes from the device in conspicuous quantities. Dampers insufficiently absorb vibrations or shocks and diaphragms lose their switching or separating function.
Often, the observer can visually recognise a change or damage to the component at first sight. Where the component was smooth, elastic, black or coloured before installation, discoloured, cracked, brittle or smudgy components appear after a failure.
However, visual appearance alone does not usually provide a clue to the course of the damage. In addition to the component and material itself, the installation space and the application and environmental conditions should also be considered. Only in combination is it possible to find out reliably what really happened to the component.
Distinctive Features and Visible Traces
What can be seen
- The seal, hose or rubber part has cracks. The cracks are only visible when the part is stretched or are already clearly visible at rest.
- The rubber part is brittle and hard, the material partially or completely inelastic.
- The surface of the elastomer looks burnt or blackened.
- The elastomer component is damaged. The damage appears as pinching, or flat, abraded areas. However, the deformation, wear or abrasion should not occur at all or not yet in this manner.
- The rubber material is porous or rubber is peeling off. Many particles are visible.
- Das Bauteil ist weich oder schmierig. Die Erweichung ist untypisch für das Material.
- The component is soft or smudgy. The softening is untypical for the material.
- In the opposite case: The component is much larger than originally, it seems swollen.
Practical Failure Analysis
This is how we proceed
We only examine what is actually necessary and carry out all analyses following the motto “as much as necessary, as little as possible“. This saves time and significantly reduces the effort of an entire examination.
Thanks to our wealth of experience from numerous failure analyses, we are able to quickly overview the required inspection effort and effectively develop solutions. In some cases, you will receive initial reliable findings about the damage after just a few days. Of course, we will then explain the results of the analysis to you and recommend remedial measures to prevent future damage.
Our primary goal in a failure analysis is to identify the root cause in order to suggest suitable remedial measures.
In every case of damage, the first step is a microscopic examination of the defective seal, an examination of the installation space and the application conditions that led to the failure. Not until then the rather more cost-intensive use of complex analytics makes sense in order to confirm the assumed damage hypothesis and possibly exclude other causes.
We proceed systematically in five steps:
1. Identification of the sample or the defective component
Does the material of the damage sample really correspond to the specifications or supplier requirements? Pictures and user information alone are not sufficient for a reliable analysis. An identity check provides clarity.
Unfortunately, it happens repeatedly that simply the wrong material was used. In about 1-2% of cases of damage, this is already the solution to the problem.
2. Gather information on the application
In the next step, we ask for details about the application, the functional principle of the component, the damage and its history. The better we know the application and operating conditions of the component and the circumstances under which the damage occurred, the more accurately we can assess the cause of the damage.
3. Analysis of the damage pattern with evaluation
This third step is the most important of the entire failure analysis. It is about identifying and correctly assessing the damage and the traces of strain on the failed component, for example a gasket.
This includes a microscopic examination of the damaged component:
We examine the condition of the surfaces, the type and extent of the damage and the dimensions of the component. We have various digital microscopes and a scanning electron microscope at our disposal for this purpose.
Further material analyses are used if necessary: In some cases of damage, additional material analyses are necessary to trace the damage mechanism. With the help of state-of-the-art testing methods and equipment, we are able to clearly analyse and narrow down a large number of cases of damage and identify the causes.
4. Validation of the Assumptions
Once a possible explanation for the cause of the damage has been found in steps one to three, it is important to secure this assumption as far as possible. This includes checking and questioning the peripheral and operational conditions. In unclear situations or in the case of several possible causes for a damage pattern, the use of further material analysis often helps to secure conclusions.
5. Report with recommendation of possible corrective actions
At the end of the failure analysis, a report is prepared. In it, the assumed cause of the damage is named and explained conclusively. The aim is to show the complete logic of the failure even to non-specialists and uninvolved parties and to clearly present and evaluate the objective results of all investigations.
Once the real cause of the damage has been identified with a high certainty, the report specifies suitable remedial measures to eliminate the failure and prevent future damage.
If, even after intensive investigation of all factors, uncertainties remain in the assessment of the damage pattern and thus in the naming of the main cause, it is important to also present this frankly and clearly to the client.
Download
In the report “Integral approach to failure analysis – the best way to the real cause of failure”.
Bernhard Richter describes in detail the five steps of a successful damage analysis
and uses examples to show how they are implemented in practice.
Assessment of Damages
Classification of damage mechanisms
As in most cases, a certain damage mechanism can be identified in the examined damage patterns. In practice, a subdivision of the occurring damage mechanisms, i.e. the main causes of the occurring damages, into four groups has proven successful:
1. Media
Damage caused by media includes chemical attack, that is chemical alteration of the material structure, as well as excessive swelling due to the absorption of media in the material. Extraction of material components, that is, inappropriate shrinkage of the components, is also possible due to the influence of media.
In an application, users should count all chemicals, liquids or gaseous substances the component comes into contact with as media.
2. Temperature and Ageing
If elastomers are thermally overloaded, which means they are heated far and permanently above their permissible service temperature, damage often occurs. Cracked and brittle surfaces or permanent deformation are the result. Similar damage patterns can sometimes also occur within the typical polymer temperature limits due to extended operating times. This group of causes also includes all related mechanisms, thus various forms of ageing, which ultimately lead to premature failure via an impairment of the network structure of the material.
3. Mechanical or physical impact
This group includes all mechanisms that damage the component without changing the network structure of the material. This includes typical causes that can be attributed to the installation space, for example sharp edges or incorrect groove dimensions and damage that can be attributed to improper assembly of the components. In addition, physical causes such as abrasion or explosive decompression fall into this group.
4. Manufacturing Defects
These include defects that are directly attributable to the manufacturing process and also clearly represent an impermissible deviation from the target state. Examples are cracks due to improper demoulding, flow lines, defects and other manufacturing defects.
For a more profound introduction to this topic, we offer our seminar “Failure analysis of elastomer seals”. Even if your focus is not on seals, you will find valuable information on the systematic analysis of a damage pattern and learn how to identify the logic of a failure.
In addition you can find out more about possible damage to elastomer components and the possible causes in our detailed reports:
Expertise in Damage Analysis
Downloads
Cause of damage
MECHANICAL / PHYSICALCause of damage
TEMPERATURE / AGEINGCause of damage
MEDIACause of damage
MANUFACTURING DEFEKTSCause of damage
MULTIPLE FACTORS
MECHANICAL / PHYSICALCause of damage
TEMPERATURE / AGEINGCause of damage
MEDIACause of damage
MANUFACTURING DEFEKTSCause of damage
MULTIPLE FACTORS
The mechanism of this damage can mainly be traced back to mechanical or physical causes.
The damaged components often show cracks, tears, wear or cut-outs.
Explosive decompression and explosive overheating
Gaseous or liquid media can become embedded in rubber materials through diffusion or swelling. In case of strong and sudden pressure or temperature changes, the embedded media abruptly escape from the material, causing serious damage to the components’ core. In the report, you will learn more about the failure modes and how to prevent explosive decompression or explosive overheating.
Excessive abrasion - The elastomer seal, a soft partner in a hard environment
The report describes the damage pattern of excessive abrasion of seals, identifies causes and gives practical advice on how to avoid the damage.
Extrusion - The sealing gap as the enemy of the seal
Under pressure, a rubber seal adapts to the installation space and is pressed into the sealing gap on the side facing away from the pressure. The seal can be damaged at these areas by different mechanical mechanisms. In the report you will learn more about how and under which conditions extrusion takes place and how you can prevent this damage.
Assembly damage - The often underestimated cause of failure
In addition to an assembly-friendly design of the housing, lubricants, coatings or assembly tools help to install seals or other elastomer components safely and without damage. Despite these possibilities, damage to components occurs time and again during installation. How this damage happens and what you should pay attention to when assembling rubber parts you will learn from Bernhard Richter and Ulrich Blobner in the detailed technical report.
Incorrect housing - Details can make all the difference
If the installation space of a rubber part is not properly designed, this can lead to mechanical malfunction or overload of the components. The report describes possible damages to seals that can be caused by a installation space and shows the appropriate design of a seal housing.
The mechanism of these damages mainly can be traced back to temperature influence or ageing processes.
The components often show changes in properties, cracks and hardening.
Thermal overload - When components overheat
In contrast to metals, polymers generally have lower operating temperatures. While thermoplastics melt at high temperatures, elastomers are irreversibly damaged by prolonged exposure above their service temperature. Rarely, however, temperature alone is the problem, but the wrong combination of temperature and time. In the report, you will learn more about how the temperature limits of elastomers are defined as a function of time, how thermal overload of materials can be identified and what should be taken into account when selecting materials.
Autoxidation - Rubber toxins
During the ageing of a rubber material, oxygen is absorbed from the ambient air and partially bonded in the vulcanisate. There, even small quantities of oxygen can have a damaging effect on the elastomer. In the report you will learn more about the process of autoxidation and the influence of rubber toxins. It describes the different appearances of the resulting damage and gives practical tips about prevention and testing possibilities.
Special edition Industriearmaturen & Dichtungstechnik 01/2020 - Rubber toxins (German)
A special edition of the trade journal Industriearmaturen & Dichtungstechnik by the authors Bernhard Richter and Ulrich Blobner on the effects of rubber toxins and the damage caused by autoxidation.
Ozone cracks on elastomer seals and components - Common but easily avoidable
Highly unsaturated polymers in particular, especially NBR, NR and SBR, can be attacked by ozone. In this article, you will find background information on the damage pattern of ozone cracks and learn how you can distinguish this damage from others. We provide information about testing possibilities and give tips on how ozone cracks can be prevented in practice.
High permanent deformation - When the seal is stuck
If a seal shows very high permanent deformation well before its age-related service life limit, this can lead to seal failure. In this report, you will learn more about permanent deformation as a cause of failure, the mechanisms that can lead to premature and greatly increased permanent deformation, prevention and testing options.
This damages to elastomer components are predominantly caused by the influence of the media.
The components often show property changes, discolouration and deformation or volume change.
Chemical attack and swelling - Destruction of the crosslinking by a contact medium
In the technical report, Bernhard Richter and Ulrich Blobner explain the causes and effects of chemical attacks and swelling, show the typical damages and advise on how to avoid media-related damages.
Industriearmaturen & Dichtungstechnik 04/2017 - Chemical attack (German)
An offprint of the trade journal Industriearmaturen & Dichtungstechnik by the authors Bernhard Richter and Ulrich Blobner on chemical attack and swelling of seals.
Manufacturing defects can also lead to damage and thus to the failure of elastomer components.
They often show up visually in the form of cracks, defects, inclusions in the material or other similar damage patterns.
Cracks due to manufacturing problems - A serious fault that often leads to seal failure
The report shows how cracks evolve during the manufacturing process and explain their impacts on the practical application. The authors describe the different characteristics of production-related cracks, distinguish them from similar defects and give an insight into the necessary requirements for crack-free production.
Some damages cannot be attributed exclusively to a single main type of damage mechanism.
They are caused by the influence of several factors at the same time.
Failure due to hydrolysis (German)
Water and steam are often underestimated by seal users. The detailed report provides important, technical background knowledge on the damage process, the chemical principles and causes of hydrolysis. In addition, it describes different elastomer types with regard to their vulnerability to hydrolysis and provides helpful practical tips.
Fatigue cracks (German)
Fatigue cracks are cracks that occur primarily as a result of cyclic loading, this corresponds to ageing inside the material, and the additional effect of oxygen, ozone and light, that is ageing due to external influences. The report explains the many factors of material fatigue and distinguishes fatigue cracks from other types of cracks. You will learn more about the effects and how fatigue cracks can be prevented.
Material mix-up and formulation change (German)
For its use in technical applications, an elastomer is adjusted to the thermal and mechanical requirements as well as to the media used. If the elastomer formulation changes or the material is even mixed up, this usually results in an overload of the material in one or more of these areas. Therefore, the damages can be quite different. The detailed report provides insights into the background and mechanisms, describes failure modes and provides assistance on how to prevent the problem.