Rubber O Rings Engineering Design
O rings are acceptable for static sealing but inappropriate for dynamic sealing applications such as pumps and compressors, and high and low pressure applications.
In cases where dynamic sealing applications are required such as pumps and compressors, and high and low pressure applications, a single elastomer may be used with an X-ring profile to prevent twisting in rotary applications. However a composite seal design is often preferred.
A composite seal is a combination of two or more materials to produce a seal that offers the best attributes of both materials. For example, a T-shaped seal comprises an elastomer T-shaped component and two plastic back up rings. The seals are used in reciprocating piston, rod and rotary applications. The T-shaped design prevents the elastomer rolling and the plastic back-up rings, energised by the rubber elastomer, provide improved high pressure performance. Importantly the T-seals can be installed into standard O-ring grooves. Other standard composite seal designs include spring reinforced seals, encapsulated seals, lip seals, energised lip seals and cap seals.
Where greater customisation is needed seal design engineering techniques based on popular CAD packages such as Solidworks, Catia, Pro Engineer and AutoCAD are employed. 3D modelling and analytical behaviour predictive tools such as finite element analysis (FEA) can then be used to explore ‘what if’ simulation scenarios to produce a ‘right first time’ design.
Seal selection tools to assist the engineer are also available sonline. Temperature and chemical compatibility, groove dimensions for the most common o-ring sizes, and physical performance datasheets enable selection of the most appropriate o-ring seal.
Seal customisation is possible for the physical properties of an elastomer. By making changes to the filler system it is possible to optimise the physical properties of a particular grade of material when compared to others within the same grade. The reinforcement effect of a filler is complex and dependent upon its structure, particle size and chemical make-up of the particles themselves.
In conclusion, the combination of online material selection tools, and application of seal engineering techniques, make it easier than ever for design engineers to optimise the specifications (and performance) of equipment rubber o rings and rubber seals.