WIKA selects its materials based on the mechanical and technical characteristics for later loading, also using simulations. This is inevitably a balancing act, as each material has specific strengths and weaknesses. In addition to constructional stiffness and strength settings, chemical resistance is a decisive criterion, i.e. resistance to corrosion, aggressive media and influences from weather, among other things. WIKA's own materials laboratory subjects materials to a series of resistance tests to ensure the required quality. These include exposure, salt mist, UV and media compatibility tests.
Depending on the application, additional factors influence the choice of material. This includes thermal, electrical, magnetic or wear-promoting properties, the behaviour when combined with other materials and the effect of process variables. A property profile for the possible materials must therefore be created for each requirement.
Gases can penetrate metal structures. Therefore, material selection to minimise permeation is crucial. Additional coatings made of materials with a significantly lower diffusion coefficient than, for example, stainless steel are extremely effective. For this reason, for pressure gauges, WIKA has stainless steel diaphragms with a protective layer of gold or tantalum coating in its portfolio. There are also abrasive-resistant ceramic coatings under the Wikaramic® label.
Special materials for higher resistance
A high level of material resistance is equally the basis for emission protection and the service life of the measuring instrument used. For processes with particularly critical influences, WIKA manufactures customer-specific solutions with special materials, including tantalum, zirconium and copper-nickel alloys such as Hastelloy®, Monel® or Elgiloy®. In the case of high-temperature applications, for example, customers can use protection tubes made of monocrystalline sapphire (in combination with the TC83 Calitum® or TC84 thermocouples). This gives you a more durable alternative to protection tubes made from conventional ceramic materials.
Avoidance of damage
A material selection that is oriented towards the process medium and depends on the properties, not only reduces the probability of environmental emissions, but also reduces the possibility of emission-related measured errors or even failure due to leaks. Furthermore, in order to counteract possible damage, a constructional solution with double seals is recommended.