The O-rings (or more synthetically OR) are toroidal shaped sealing elements with a circular cross-section; generally their dimensional definition is given by the inner diameter and the diameter of the cross-section. The O-rings can be used as static or dynamic seals and are normally installed inside hollow seats with a rectangular section.
O-rings are undoubtedly the most widespread and used type of seal : simple and symmetrical shape, ease of manufacture, cost-effectiveness, low design costs, warranty single sealing or double-acting, small size and ease of installation have promoted their use in all industrial and non-industrial applications.
The O-ring choice, both in terms of size and in terms of material, is related to factors like the working temperature of the sealing area, the working pressure (fluid hammer), the chemical aggressiveness of the fluid and the abrasion degree of the containment surfaces.
Any minimum damage compromises the sealing function of the O-ring. Thus, it is critically important to adopt every precaution to ensure the integrity of the seal, which may get damaged by sharp edges, threads or machining burrs. Also dust, machining waste, dirt and other impurities must never come into contact with the O-ring.
Both the seal and the housing shall be manufactured observing scrupulously the indicated tolerances: the backlash is decisive for the effectiveness of the seal and for the duration of the life of the O-ring. To assure functionality of the O-rings it is recommended to store them in a place away from UV radiation, air and atmospheric agents, with humidity at 70% and at a temperature of 10-20 ° C. The O-rings shall not be unnecessarily pulled, loaded, hung or folded.
Many elastomeric materials and certain thermoplastics are used for the production of O-rings. The choice of the suitable material depends on parameters like the materia resistance to the fluid to be contained, the permanent deformation, the hardness in relation to the backlashes, the resistance to high and low temperatures.
Here are the most commonly used materials and their characteristics.
There are also special materials ideal for critical applications such as cryogenics, medical instrumentation, aeronautics, painting, the food processing and beverages, electrical equipment, and petrochemical plants.
In addition, the elastomeric O-rings can be encapsulated with a FEP or PFA coating to ensure maximum performance. The FEP / PFA coating guarantees a high degree of resistance to breakage, a low coefficient of friction, chemical inertness and therefore the possibility of application in the food, chemical, medical and pharmaceutical industry.