Tag Archives: sealing technology

Accurate Long-Term Predictions for Seals

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.

picture of wind turbinesThe 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. Continue reading Accurate Long-Term Predictions for Seals

What is the ZAVA® Seal-Ring

Here Comes the ZAVA® Seal-Ring

“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.

Four hours work in one minute

One of ZAVA® Seal-Ring’s prominent features is ease of installation. The rubber ring is locked in place using a quick-connect coupling, which is impossible to separate once it has been assembled. The designer is reluctant to say more. Patent protection is important.

As far as maintenance is concerned, vulcanizing is just a memory. The seal-ring is changed easily in less than a minute, without shutting down the filter. It’s an undertaking that would otherwise take three to four hours. The time saved is a strong argument for the ZAVA seal-ring, but not the strongest.

picture of zava seal-ring

The rubber composition withstands anything

No one would go out on a limb and claim that any material, exposed to all the chemicals present in a pulp plant, is maintenance-free. But the ZAVA® Seal-Ring is at least giving the maintenance people at Östrand cause to wonder.

For almost six months, the ZAVA® Seal-Ring has been tested on the plant’s filters without  sign of loosening or brittleness which are otherwise normal phenomena. The same thing is being experienced at MoDo in Husum.

“The rubber composition seems impervious to both acid and alkali environments of normal concentration,” says Sven-Erik Sundin, spare parts sales engineer at Sunds Defibrator, who has witnessed several less successful approaches to the problem.

Frans Sramek developed the rubber composition with the help of a good friend in the tire industry. If anything, the formula is an even bigger secret than the construction of the mounting device.

An end to mess and waste

An improved work environment is one of the main reasons why the ZAVA® Seal-Ring has won the approval of mill maintenance and operating personnel.

Previously, replacement of a leaking seal-ring was postponed until a normal production stop or periodic maintenance. As a result, it became increasingly difficult to keep machine areas clean as leakage increased.

So far, the ZAVA® Seal-Ring has proved to be completely tight. This also means that losses of black liquor and other chemicals have been minimized.

ZAVA® Seal-Ring creates new filter designs

Sunds Defibrator’s design people have become infatuated with the ZAVA® Seal-Ring. One idea being tested is to eliminate the inner seal-ring (V seal-ring) on VFA and CCA filters. This will result in a further reduction of maintenance since the seal cover would not have to be separated.

It can become a reality if the ZAVA® Seal-Ring proves that it can withstand the stresses. Åke Sundström, head of filter design at Sunds Defibrator says: ”We believe that, at last, we can avoid the troublesome V seal-rings on the covers. With a few minor design changes, an externally mounted ZAVA seal-ring should handle the entire job.”

Industry Application

ZAVA® Seal-Rings are available for many industries and in a number of materials and profiles. Industries like:

  • Chemical Processing
  • Energy, Oil & Gas
  • Heavy Equipment
  • Maritime Sealing
  • Pulp & Paper
  • Hydro Electric
  • …and more

Check out their video below:


For more information about the Zava Seal-Ring, contact Gallagher Fluid Seals or find more information on ZAVA’s website.