Session: 23-08 Annular Seals

Paper Number: 151971

Evaluation of Local Defects on Fractured-Ring Seal Leakage Rate 

In the mechanical sealing industry, circumferential seals operate radially between the shaft and the seal, minimizing leakage by sealing directly against the shaft and creating a tortuous path for fluid to escape during use. There are two primary types of circumferential seals: controlled-gap seals and fractured-ring seals. Controlled-gap seals maintain a consistent clearance during the thermal expansion and contraction of components as they heat and cool. In contrast, fractured-ring seals operate radially with a carbon ring that is fractured into equal segments. As the shaft temperature fluctuates, these carbon segments allow the fractured-ring seal to expand and contract, ensuring constant contact between the seal and the shaft.
 

Defects can be introduced during the production, assembly, handling, and installation of fractured-ring seals. Defects such as nicks, chips, scrapes, or scratches may impact the leakage performance of the seal. However, defects smaller than 0.13 inches in the largest dimension that occur on the inner diameter edge or fracture line of fractured-ring seals do not significantly affect leakage rates. The 0.13-inch maximum defect size tested is significantly larger than the maximum defect size that is acceptable by the workmanship quality standards. Therefore, this paper demonstrates that defects smaller than 0.13 inches in the specified locations do not impair the performance of fractured-ring seals. The findings are intended to serve as a precedent for future fractured-ring seal applications.

 

To test seal performance, leakage rates and differential pressure across the seal were measured. First, using several defect-free fractured-ring seals, a baseline leakage curve was established by measuring the correlation between leakage rate and differential pressure. Subsequently, fractured-ring seals with varying known locations and defect sizes smaller than 0.13 inches were tested to assess any relationship between defects and leakage. Additionally, two seals were intentionally damaged, with defect size and location noted, and leakage rates and differential pressure were measured both before and after the damage was applied. The results show that the size and location of known and inflicted defects do not affect the seal leakage rates. Testing of the intentionally damaged seals confirms that defects do not impact leakage performance within the limits of size evaluated.

 

Through experimentation, it was concluded that defects such as nicks, chips, scrapes, or scratches up to at least 0.13 inches on the inner diameter and fracture line of fractured-ring seals-do not affect the performance of the seal. This work also shows that the location of these defects had no measurable impact on seal performance.

Presenting Author: Justin Baldauff Technetics Group

Presenting Author Biography: As an intern at Technetics Group, I design seals for various industries such as aerospace or nuclear applications. Since transitioning to a full-time role as a test engineer, I perform a range of seal testing-including leak, vacuum, swell, and load tests-to confirm our seals meet the required design specifications.

Authors:

Justin Baldauff Technetics Group
Stefan Roeseler Technetics Group
Aaron Glafenhein Technetics Group
Todd Adams Technetics Group
Miguel Rodriguez Technetics Group
Luis Carrasco Technetics Group
Ryan Plessinger Technetics Group
Erin Volpe Technetics Group
Elaine Motyka Technetics Group
Tyler Noyes Technetics Group
Becca Jones Technetics Group
Shannon Depratter Technetics Group
Jonathan Kweder Technetics Group