sealing technology
- November 10, 2022
The ZAVA® Seal-Ring - Quick and Easy Installation
"At last" - that's the reaction of those who have been plagued by the constant need to change rubber seals on VFA and CCA filters at pulp plants all over the world. As an electrician at SCA Pulp in Sundsvall, Frans Sramek is the man that has solved this well-known, and seemingly hopeless problem. The ZAVA seal can be mounted in minute and cuts maintenance costs substantially.
"It’s always a pleasure to be able to offer our customers products on which they make money,” says Lars Bylund, Customer Service Division at Sunds Defibrator.
- February 12, 2021
The manufacturing and installation of specialty seals must be handled in a certain way to ensure their quality and longevity.
The following guidelines and/or rules are the basics for regulating the engineering of seals to ensure top performance.
Performance vs Knowing Your Seals
The performance of your machine(s) depend on the quality of your seal and the conditions they succeed in. They can directly affect how well or how poorly your machines function. By extending the life and care of your seals, you can, in turn, extend the life of your equipment.
- January 28, 2020
The static seals used in large energy and industrial facilities can be challenging to install and difficult to replace. They must, therefore, function flawlessly for periods longer than 20 years. Up until now, the existing tools used to calculate the long-term performance of sealing materials for these kinds of applications have often led to the components being larger than actually necessary.
Freudenberg Sealing Technologies has now developed a method that takes into account the material changes at the molecular level when predicting the long-term durability of seals. The new methodology is more reliable than previous models and ensure fewer materials to be used.
The seals used in plant engineering must have a very long service life. Once they are installed – to protect offshore wind turbine towers from salt corrosion, for example – customers typically require that they perfectly fit for more than 20 years. The service life of a seal is limited based on two things: First, by setting or stretching (physical relaxation). And second, chemical changes cause the material loses its elasticity over time.
Under the influence of atmospheric oxygen or ozone, two basic effects that influence the aging of seals can be observed: First, the polymer chains and networks can fracture under mechanical stress, and second, additional oxygen bridges can develop in the network as a result of oxidation processes. Both effects influence important properties of relevance for seals such as stiffness, contact pressures or the ability to regain their original shape after deformation, also referred to as resistance to deformation.
Extrapolation with the Arrhenius Equation
To determine whether a material actually meets the requirements for a specific application, engineers usually conduct so-called “storage tests” in which the test specimen is exposed to temperatures well over 100° C for a longer period of time – usually 1,000 hours – to predict temperature-dependent aging. Engineers typically extrapolate the measured values using the Arrhenius Equation, a method named after the Swedish chemist and Nobel Prize winner Svante August Arrhenius.