Application ranges

Installation

The type RI (internal) and type RA (external) rotary seals can be fitted without problem in continuous grooves. To facilitate mounting, it may be advisable to warm the seal in oil at a temperature of approx. 80°C prior to fitting. After fitting the preload and sealing elements, PTFE rotary seals have to be sized. In the case of the externally sealing type RA, this can be done by using the insertion bevel on the cylinder barrel which should have an angle of between 15° and 20° and a length of between 2 mm and 8 mm depending on the as-designed sealing height. The internally sealing type RI has to be deformed into a kidney shape – ensuring that there is no kinking – prior to fitting and then inserted in this form. Once inserted, the seal can be reformed back into its ring shape in the groove. Once the preload and sealing elements have been fitted, the PTFE rotary seal must be sized with a mandrel featuring a bevel of approx. 10°-15° and a length of approx. 30 mm. The piston rod can likewise be used for this sizing operation provided that it has a sufficient insertion bevel. Likewise, a separate sizing sleeve or a sizing pin can be used. It must always be ensured that sharp edges are removed by rounding or bevelling. Thread tips should be covered. Before fitting, ensure that all machining residues such as swarf, chips, dirt and other foreign particles have been removed.

The surface quality of the mating faces being sealed is of decisive importance for the functional reliability and service life of the seal. Where rotary sealing applications are concerned, we recommend that the mating surface exhibit a hardness of approx. 55 HRC with a depth of hardness of at least 0.3 mm. In the case of coated/plated surfaces, it must be ensured that no ablation has taken place. Adequate heat conduction/dissipation must also be ensured by the coating. Unhardened mating surfaces should have a Brinell hardness of at least 1800 N/mm2.

It is important to ensure that there are no ridges, scratches or recesses, nor any concentric or spiral machining marks on the surface. The parameters usually applied for surface description such as Ra, Rz, Rt and Rmax are defined in DIN 4762 and DIN 4768.

In order to properly assess surface quality for sealing applications, the material ratio (bearing curve tp) should also be taken into account. This profile shape parameter is influenced by the machining process applied. The material ratio (Mr) should lie between 50 and 70% as determined at a slice depth of approx. 0.25 x Rz based on a reference percentage of approx. 5%.

Directives

All information and values stated concerning our product portfolio are based on the knowledge optained through a long experience of manufacturing and application.
These figures are for indicative purposes only and may vary (exceed or deceed) according to the particular circumstances. Unknown factors in the applications and practice can considerably change the conditions and reduce and change statements, which may cause the above information to be invalid.
No liability can be accepted for any mistakes or omissions, error and subject to change without prior notice.