T-Ring Piston Seal
The piston is a key element relating to the performance of a pneumatic cylinder, as movements and dynamic load lead to friction and wear at the piston sealing element. Failure of the piston seal is not desired, as industrial requirements dictate reliable and durable sealing function even with increasing shaft speeds and cylinder load.
As a result, seal suppliers have developed new solutions to address piston seal failure for increasing speeds and loads. For example, the innovative design knowledge and essential material expertise used to qualify Simrit’s TR200 Low Friction piston seal provide a solution that far exceeds the required performance limits, while reducing friction by up to 50 percent, thus sustainably increasing process efficiency and safety.
If drives are to be highly efficient and reliable, it's necessary to minimize movement of mass and thereby minimize friction losses. If, however, the individual components are designed to be smaller, they become more compact and more susceptible to deviations of the operating and manufacturing parameters. Sealing stiffness directly influences friction behavior and thus wear and the effectiveness of the drive.
The smaller the seal cross-section, the larger the influence of reaction forces on sealing element friction. The dynamic sealing function of the TR200 is assumed by a sealing area with a large radius. With the new geometric design, the radial forces required for sealing can be achieved without any radial compression of the cross-section, as it is provided by the design interference alone. This reduces the effect of friction and stick-slip to a minimum.
The static sealing force of the TR200 is generated separately and optimized by the pressure from the system pushing concentric sealing edges against the front face of the installation groove alone. The static sealing function is built up simultaneously and separately from the dynamic seal edge, and is optimized according to function through the use of a much thinner area of the T-ring. Decoupling of the static and dynamic function resulted in a patented-pending uniquely shape seal.
Overflow tests were carried out under a range of conditions, for example, with varied housing tolerances in relation to a high-pressure area. Elaborate tests, involving extreme loads and operating conditions such as minimal traversing speeds and rapid pressure changes, confirmed the functional advantages compared to traditional seals. In service life tests, it achieved 15 million cycles without noticeable wear.
The new seal also requires minimal housing space, and its sealing function does not depend on piston clearance and radial piston movement. The most remarkable record, however, was achieved with regard to friction. When compared to traditional seals, both breakaway torque and stroke friction are up to 50 percent lower due to the innovative design. With the TR200, Simrit presents an innovative sealing geometry for the smooth operation of pneumatic cylinders with significantly increased efficiency.
The increasing popularity of pneumatic drives is partly due to continuous development of sealing materials and seal designs, which offer the prerequisites for excellent pneumatic cylinder efficiencies. New seal designs provide innovative solutions to lower friction, decrease system noise, extend performance, and give the end product the differentiating factors manufacturers are looking for.
— Joel Johnson is global vice president of technology for Simrit.