Product group: RS cord rings
The primary application for cords is as the basic material for joined O-rings. They are similar to the O-ring in the way they are handled and applied. They are used as static seals, e.g. for sealing larger pipe unions and as cover seals in container construction. Cords are frequently used for on-site repairs, being joined together to provide the "customized" dimensions.
The process of end-joining cords to form a joined O-ring can be undertaken using cyano-acrylate or 2-component adhesives. However, for applications in seawater or other more demanding applications, bonding by means of an end-vulcanisation process is required.
Production of joined RSR O-rings
The normal procedure is to first cut the cords to length and then bond them using a cyano-acrylate adhesive (e.g. Loctite 406 ®). The operational temperature limit is approx. 80 °C.
With EPDM, VMQ and FKM cords, in certain circumstances the use of a special primer (e.g. Loctite 770 ®) may also be required. Ensure that the manufacturer's product information and safety instructions are observed.
Before bonding, both ends to be joined should be roughened with a fine sandpaper and cleared of any grease using a suitable cleaning agent (e.g. Aceton ®). The two ends should not be under any pressure during the bonding process. Then check that the joint has cured completely through. The end-joined cord must not be stretched at its joint. The joint created displays a distinctly lesser degree of bending elasticity than the cord itself.
Avoid damaging the O-ring during installation, as this will cause leakage. Observe the following:
- The end-joined O-ring must not be stretched over the joint and the rest of the O-ring must not be expanded to its elongation limit.
- Edges must be burr-free, radii and angles applied smoothly.
- Dust, dirt, metal chips and other particles must be removed.
- Tips of screws and installation housings for other sealing and guiding elements should be covered by an assembly sleeve.
- A suitable grease to be applied to the assembly surfaces and O-rings.
- Elastomer materials are made smoother if they are heated in oil or hot water to approx. 80 °C. This makes it easier to stretch the O-ring for assembly.
- Any assembly tools used, such as expansion mandrels or sleeves, should be made of a soft material (e.g. POM) and not have any sharp edges.
- The cord or joined O-ring should not be rolled over assembly surfaces. Ensure it is not twisted as it slots into the groove.
For further information please look at cord.