FLUID POWER HANDBOOK
WWW.FLUIDPOWERWORLD.COM
RETAINING
RINGS
Retaining rings fit into a machined groove either on the inside of a bore or on the outside of a shaft and are used to reduce vibration and withstand axial loading while holding 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. They help reduce costs by eliminating threading and other machining and offer reduced weights and sizes. 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 shallow groove for use on thin-walled sections of components. 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 and so on, 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 and Hastelloy. 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 be honed to the shaft. SPECIFYING RINGS FOR FLUID POWER SYSTEMS The most important detail to know when selecting a retaining ring 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. Also, if the ring will be subjected to axial thrust loads, the ring specifications need to be checked to determine whether a light-, medium- 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.
IMAGES COURTESY OF SMALLEY
58
FLUID POWER WORLD
Retaining Rings 7-19_FPW.indd 58
7 • 2019
www.fluidpowerworld.com
7/15/19 10:00 AM
