Factors influencing the useful life of a O-ring can be classified as part-specific (housing design and material selection) and external to the part, such as installation, handling and working conditions, among others.
Even if the housing design is correct and the right material is chosen, the service life of the housing will be reduced. O-ring may be shorter than expected and deteriorate. As a result, if fragments of the O-ring If they are in process and are also easily recognizable by a machine vision system, then the chances of detecting foreign bodies will increase significantly.
In this context, it is useful to “customize” the O-ring with a specific color. Nowadays there is a technology that allows the piece to be colored with the color of your choice.
There are also surface treatments that significantly improve their performance, such as anti-wear coatings.
Other times, due to the assembly of the O-ring, If the part does not slide effectively into its housing. This can be remedied with a surface finish that is sufficiently slippery and increases lubrication.
The treatments mentioned above have in common that they do not alter the elasticity or impoverish the chemical resistance of the material. O-ring. In addition, all of them, to a greater or lesser degree, reduce the effect of “Stick-slip” or irregular movement in the displacement of a rod, jerking.
However, before applying any coating or treatment, the part must be properly cleaned.
CLEANING TREATMENTS
The current cleaning processes guarantee that the part is free of any contaminant and do not affect the properties of the material (hardness, working temperatures, color, etc...). There are 4 levels of cleaning:
- Surface impurities are removed with water and specific detergents.
- Level 2 cleaning is done in a ISO Class 7 clean room. The piece is delivered with double packaging.
- Level 3 is a cleaning with an ultrasonic bath according to “CleanSafe 787C” in ISO Class 7 clean room and delivery with double packaging. This procedure is recommended for parts that will work in contact with oxygen.
- The most demanding cleaning is applied to those parts, to which a protective paint has been previously applied, and must be cleaned with plasma scanning to be certified “PWIS free”according to standards VW PV 3.10.7, FN 942010-2 y QZ 24, among others.
Once the O-ring has been cleaned, the high performance surface finish is applied.
PIGMENTATION
The part is colored with a determined color (RAL and PANTONE scales) that facilitates its identification in the field, without altering the properties of the O-ring.
Permanent treatment suitable for static and dynamic service conditions.
LUBRICATION TREATMENTS
There are various lubricating agents such as silicone oils, molybdenum disulfide, PTFE or talc.
- The silicone oil is transparent and is certified for USP Class VI.
- Molybdenum disulfide (MoS2) performs well in a humid or high temperature environment.
- PTFE is applied as a transparent film that facilitates part assembly due to its self-lubricating properties.
- Talc fills the cavities on the surface of the part, making it slippery. Pharmaceutical quality talc.
Lubrication agents are absorbed into the surface of the O-ring and gradually disappear with use. Suitable for static service conditions only. For dynamic conditions, a coating is recommended.
COATINGS
Coatings are used to improve some property of the elastomer and are mostly based on PTFE resins with additives.
They increase abrasion resistance, improve chemical resistance and may even increase hardness slightly. They are usually a few microns thick and most are permanent.
The parts treated in this way can be used for both static and dynamic applications.
The results obtained are for specific working conditions that do not necessarily coincide with those in the field.
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