TetraSeal: An Alternate Sealing Solution When an O-Ring Isn’t Working
Our applications engineering team takes more than a few calls each month where the O-ring is leaking, either immediately or after just a short time in service. Once we drill down to the details, we learn the failure mode is an improperly sized groove and O-ring. It isn’t all that uncommon for a groove to be cut in a flange and a novice designer learns the hard way that standard O-rings cannot fit in just any groove geometry. For hardware that has already been machined, frustration ensues as the caller learns the O-ring solution requires tooling. Tooling can have a lead time of at least a month to cut and can cost thousands of dollars. Parker offers a TetraSeal® solution, which often does not require tooling and can be made of many of the same materials used for O-rings.
Benefits of TetraSeals
The TetraSeal is a circular precision-cut seal with a square cross-section. Unlike O-rings which require a unique mold for each material family and size, TetraSeals are extruded, cured and machine cut to the target thickness. Our manufacturing facilities in both Spartanburg, South Carolina and Goshen, Indiana are tooled in a variety of interchangeable extrusion dies, making this type of seal an easily sourced seal solution without the lead time and cost of a custom molded O-ring.
The manufacturing process for TetraSeals includes two dimensions on the cross section: a cut and a width. However, this methodology is used to achieve other seal profiles as well. The flexibility on the sizing of precision cut seals allows us to change the square to a rectangle, or other configuration, as an alternate seal solution if it better suits the preexisting groove. This customization can be a great alternative for unconventional groove profiles where an O-ring simply will not work. One common example of an unsuitable groove geometry is having the width too narrow for the depth. Using a seal with a round or square cross-section means choosing proper seal compression at the risk of overfilling the groove or, selecting a smaller cross-section for proper volume fill but sacrificing with too low compression. Both of these options can result in leaking or shortened seal life.
Additional benefits to TetraSeals, and other precision cut geometries are the absence of typical molding surface anomalies (such as parting line flash, non-fills, and dirty mold.) TetraSeals have a smooth, homogenous, radial sealing surface resulting from the extrusion process. Parting line disruptions can be problematic in sensitive radial sealing applications, making the TetraSeal an appealing solution.
TetraSeals can be made with an inner diameter ranging from 0.188 up to 18.000” (4.78 to 457.20 mm) and a thickness of 0.066” up to 0.265” (1.68 to 6.73 mm). In addition, the seals can be made as a direct replacement for many AS568 sized O-rings. Common materials include:
*TetraSeal is a registered trademark of Parker Hannifin Corporation.
This article was contributed by Dorothy Kern, Applications Engineering, Parker O-Ring & Engineered Seals Division.