The Parker Prädifa rod sealing set profile M2 consists of 5 chevron rings (3 fabric-reinforced and 2 rubber seals, 1 header ring, and 1 back-up ring). The header ring may be
manufactured of hard fabric material or of plastic. The back-up ring is only manufactured in hard fabric. In case of dimensions different from those mentioned in this leaflet please choose a packing set combination from our MO-programme. Our sales department will inform you of the respective order code.

The main advantages of these Parker Praedifa rod sealing sets are:

• Adjustability to different fluids and temperature ranges by proper choice of suitable compounds.
• Adaptability to exceptional working conditions by changing or adjusting the axial preload (shims or screw rings).
• Not sensitive to high-pressure peaks on account of
  form stability.
• Not sensitive in case of contamination of the medium
  or slight damages of the sliding surfaces in comparison with one-part seals.
• Excellent sealing performance due to long contact
  area and several sealing lips.
• It is possible to split the seals to facilitate the
  installation. Thus it is not necessary to fully dismantle the cylinder in the case of maintenance or repair.

For special requirements (pressure, temperature, speed, etc.) please contact our Consultancy Service, so that suitable materials and/or designs can be recommended.

Field of application:

Working pressure:                  ≤ 350 bar

Working temperature:         – 40 to + 100 °C

Surface speed:                         ≤ 0,5 m/s

Chevron sealing sets are well suited for the sealing of plungers, piston rods of presses, cylinders, valve shafts, and spools, even in difficult working conditions. Thus they can be recommended for use where the actual conditions are difficult to predict.

Compounds:

Back-up ring: Hard fabric, NBR-based (0502 Q5022).

Chevrons: Fabric reinforced rubber material, NBF-based (Q5018/05019)  resp.  NBR  elastomer (N3578).

Header ring: Polyacetal (POM-W5001) or hard fabric, NBR-based (Q5021/05022).

Installation:

Due to the relatively low elasticity of the fabric chevrons and the required axial preload of these sealing sets, an installation groove, which is open on one side has to the provided. The actual height of the set is normally in accordance with the length “L” of the housing. Manufacturing tolerances of the seals and the metal parts (especially in case of large dimensions) may be compensated for by screwrings or shims in order to achieve an optimum function. (Adjustability at least 5 % of the length “L”).

When strongly squeezed the flexibility of the sealing set may be substantially reduced. Thus it could be transformed to act as rod guidance with excessive friction and high wear. Due to the adjustability, it is possible to use these sets for special applications: For example in case of high speed, exceptionally large temperature range, strongly varying pressure, or a combination of these parameters. The various components of the set must be installed individually according to their sequence within the set. Oiling or slightly greasing will facilitate the assembly. Fabric chevrons with relatively large cross-sections can be made more flexible by slightly kneading them in warm oil.  This will facilitate the installation considerably. For easier maintenance, the sealing sets may also be slit. The chevrons and the back-up ring are cut at 45° angle, the header ring with a 90° angle. The cuts of the components must be staggered by 120° at installation, which will not alter the length of the housing.