Retaining rings are engineered components used to hold many types of assemblies together. They are precision engineered to accurately position, locate and retain parts on shafts or in bores. The rings are installed into a groove, and all the other components of the assembly sit against and are retained by the ring.
Retaining ring designs include spiral, tapered and constant section. Spiral rings do not have ears or lugs to interfere within the assembly like standard stamp rings. Tapered section rings feature compressible lugs to give them a circular shape in the groove, allowing them to grip tightly along the edge. Constant section retaining rings are best suited for heavy-duty applications. They feature a uniform, constant section with no change in width throughout their entire circumference. Some specialty designs exist as well, including ones that feature a very shallow groove for use on thin-walled sections of components.
They help reduce costs by eliminating threading and other machining and offer reduced weights and sizes.
In hydraulic systems, spiral retaining rings are used most often on the cylinder, particularly to retain the seal packing in cylinders. Retaining rings replace machined “steps” to retain the packing. Additionally, retaining rings are also found in hydraulic couplers, hydraulic pumps and other hydraulic components that need secure fastening.
In pneumatic systems, they can be found in actuators, compressors, couplers, etc., to help fasten components as needed.
Standard materials for retaining rings include carbon steel, carbon spring steel, 302 stainless steel, and 316 stainless steel. Other available materials include phosphor bronze, beryllium copper, Inconel, Elgiloy, Hastelloy, and more.
A different type of ring design, called a “scraper ring,” is also used in hydraulic cylinders. These rings help keep debris out of the seal portion of the cylinder to extend the life. They are typically made out of a soft material, such as beryllium copper, so they can hone to the shaft.
Specifying rings for fluid power systems
The most important detail to know when selecting a retaining ring for your application is to know if the groove for the ring will be located on a shaft (external) or in a bore (internal) and then specify the diameter of that shaft or bore. Additionally, if the ring will be subjected to axial thrust loads, the ring specifications need to be checked to determine whether a light-duty, medium-duty or heavy-duty ring is required. Finally, the material needs to be selected based on what type of corrosive media the ring will be subjected to.
Filed Under: Fluid Power Basics
