Static seals are universal sealing elements that impress with easy installation, small footprint and versatile application is the reason why they are used very frequently. ttv ensures that these seemingly simple parts are still produced with the utmost care.
ttv seals are distinguished by the highest technical quality standards and the best materials, as a specialist in sealing technology, we know, the seemingly simple parts need to be.
If machine elements to be sealed do not move relative to each other, we speak of static or stationary sealing.
The O-ring is ideally suited for sealing such stationary machine elements.
Provided the installation space is properly designed, the right material is selected and the application is structurally correct, O-rings can be used to seal pressures of up to 900 bar.
In the case of a static seal, problematic constellations can also occur, for which additional back-up rings must then be used.
The rectangular groove is mainly used for cover and flange seals where axial deformation of the O-ring occurs.
Here, care should be taken during installation to ensure that the O-ring is positioned exactly on the side of the groove facing away from the pressure.
This is the only way to prevent the O-ring from moving in the groove when it is pressurised or the pressure
pressure in the groove.
This is because such movement causes compression and superimposed elongation of the O-ring, which results in fatigue or premature wear of the material.
If the direction of pressure is observed, twisting and thus destruction of the surface of the O-ring can be avoided.
The outer diameter of the O-ring should be adjacent to the outer diameter of the groove or up to a maximum of 4% larger (compression of the O-ring).
The inner diameter of the O-ring should be close to the inner diameter of the groove or a maximum of 5% smaller (expansion of the O-ring).
To prevent the gap between the sealing surfaces from exceeding the permissible size at high pressures and thus squeezing out the O-ring, care should be taken to ensure strong cover screw connections during axial installation.
If the system pressure to be sealed is lower than the atmospheric pressure (patm = 1.01325 bar), this is called vacuum sealing.
For this special form of static O-ring sealing - contrary to the general installation guidelines for static O-ring seals - the following recommendations must be taken into account:
The cross-section of the O-ring should be compressed by approx. 30%.
The compressed O-ring should fill the groove almost 100%. This results in larger contact areas and a higher penetration time through the elastomer material.
Vacuum grease should be used to reduce the leakage rate.
The surface quality of the sealing surfaces and groove should be significantly better here than with standard static seals. The contact ratio (tp) should be more than 50%.
For standard applications, ttv recommends fluoro rubber or a similar elastomer material with low permeability, good gas compatibility and a low compression set.
The opposite of the static seals, which also include the X-rings, sealing caps and Usit rings. are the so-called dynamic seals.