Kaco U-rings with adhesive component PNA are predominantly used in hydraulics up to 100 bar as well as in pneumatics as piston seals. In the radial direction, they require only a small installation space.

For the purpose of longitudinal support, the internal, static sealing lip is longer than the dynamic lip. Therefore, it is possible to use it without a support ring or any other additional support.

The diameters of PNA type U-rings are somewhat smaller than the rated dimension and these are expanded somewhat during installation. Thus, it is possible to ignore the relatively large tolerances referred to the diameter, especially in the case of cylinder diameters over 100 mm, and to base production on the essentially smaller tolerances referred to the sealing ring cross-section. The advantage achieved by this tolerating measure especially has an effect on the dynamic sealing lip and results in a lower frictional force range.

For sealing of fluids, the dynamic sealing lip has sharp edges and its cross-section is designed for a lower frictional force and a long service life. For some time now, we have been applying our optimum sealing lip design experience (refer to page 5) to this version for use in the field of pneumatics. Due to the high demands placed on the frictional force behavior and service life in the case of oil-free or untreated compressed air, the sealing edges are increasingly being designed in accordance with the rounded version.

Refer to the designation for the design of the sealing lips:

PNA…N  sharp sealing edge (trimmed)
PNA…A   rounded sealing edge (completely molded).

Technical data:
Pressure range

hydraulics                                 ≤ 100 bar

pneumatics                               ≤  16 bar
Permissible sliding speed

hydraulics                                 ≤  0.3 m/s

pneumatics                               ≤  1 m/s
Tolerances

dynamic (cylinder)             H11

static (piston)                      H11

Because of their small cross-section, PNA U-rings can be easily expanded to enable easy manual installation on the piston (figure 29). Installation spaces can be easily obtained with low manufacturing effort. Ensure that the groove width is always 0.5 to 0.8 mm larger than the installation width of the sealing ring.