Leak Rates of a Candidate Main Interface Seal at Selected Temperatures

Wasowski, Janice L.; Penney, Nicholas; Garafolo, Nicholas G.; Daniels, Christopher C.

doi:10.2514/6.2009-5320

Cited by 17 publications

(5 citation statements)

References 5 publications

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“…This allowed comparison between the tests conducted with helium, which measured the leak rate of the redundant seal bulbs, and previously reported tests conducted with air (Ref. 7), which measured the leak rate of the primary seal bulbs. The experimental error for the results shown in Table 1 was 33% of the reading.…”

Section: Resultsmentioning

confidence: 99%

“…7), differences in the type of measurement (volume versus mass) and the type of gas (helium versus air) needed to be addressed. The conversion from a volumetric leak rate to a mass leak rate was accomplished using the density of the gas.…”

Section: Comparison Of Helium Leak Rates To Air Leak Ratesmentioning

confidence: 99%

“…7). While useful in understanding the behavior in application, dry air is rarely utilized during qualification, acceptance, and verification testing processes.…”

Section: Introductionmentioning

confidence: 99%

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Temperature and Atomic Oxygen Effects on Helium Leak Rates of a Candidate Main Interface Seal

Penney

Wasowski

Daniels

2010

46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Section: Resultsmentioning

confidence: 99%

Section: Comparison Of Helium Leak Rates To Air Leak Ratesmentioning

confidence: 99%

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Temperature and Atomic Oxygen Effects on Helium Leak Rates of a Candidate Main Interface Seal

Penney

Wasowski

Daniels

2010

46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

Self Cite

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“…1 Elastomeric seals have been used in part for their performance at temperatures, 2-9 reusability, 10 ability to distort with their substructure, 11 and low leak rate. [2][3][4][7][8] As the United States plans to embark on missions with longer durations, 12 the challenges of utilizing elastomer compound seals become more evident. Destinations such as low-Earth orbit, asteroids, and the lunar and Martian surfaces are harsh environments for materials to survive and require materials to withstand atomic oxygen, 13-17 ultraviolet and particle radiation, [13][14][15]18 micrometeoroids and orbital debris, 14,[18][19][20][21] and dust, 18,[22][23] amongst others.…”

Section: Introductionmentioning

confidence: 99%

Elastomer Seal Performance after Terrestrial Ultraviolet Radiation Exposure

Daniels

Oravec

Mather

et al. 2015

7th AIAA Atmospheric and Space Environments Conference

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Ultraviolet radiation was evaluated to determine its negative effects on the performance of elastomeric gas pressure seals. The leak rates of the silicone elastomer S0383-70 O-ring test articles were used to quantify the degradation of the seals after exposure to vacuumultraviolet and/or middle-to-near-ultraviolet wavelength radiation. Three groups of seals were exposed in terrestrial facilities to 115-165 nm wavelength radiation, 230-500 nm wavelength radiation, or both spectrums, for an orbital spaceflight equivalent of 125 hours. The leak rates of the silicone elastomer S0383-70 seals were quantified and compared to samples that received no radiation. Each lot contained six samples and statistical t-tests were used to determine the separate and combined influences of exposure to the two wavelength ranges. A comparison of the mean leak rates of samples exposed to 115-165 nm wavelength radiation to the control specimens showed no difference, suggesting that spectrum was not damaging. The 230-500 nm wavelength appeared to be damaging, as the mean leak rates of the specimens exposed to that range of wavelengths, and those exposed to the combined 115-165 nm and 230-500 nm spectrums, were significantly different from the leak rates of the control specimens. Most importantly, the test articles exposed to both wavelength spectrums exhibited mean leak rates two orders of magnitude larger than any other exposed specimens, which suggested that both wavelength spectrums are important when simulating the orbital environment. Nomenclaturea 0 = zero-order regression coefficient a 1 = first-order regression coefficient β = bias error i, k = indices m = mass ̇ = mass leak rate N = number of samples p = absolute pressure φ = precision error R = specific gas constant T = temperature t = time

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“…Two common methods to evaluate the leak rate of gas pressure seals are the tracer gas leak detector method and the pressure change or pressure decay technique. These methods have long been used to quantify the leak rates of silicone elastomer seals used in habitat type space applications, e.g., docking system seals [4][5][6][7][8][9][10]. The tracer gas leak detector method is often a preferred test method due to its sensitivity to small leaks and relatively short test time.…”

Section: Introductionmentioning

confidence: 99%

Validation of Test Methods for Air Leak Rate Verification of Spaceflight Hardware

Oravec

Daniels

Mather

2017

Volume 1B, Symposia: Fluid Measurement and Instrumentation; Fluid Dynamics of Wind Energy; Renewable and Sustainable Energy Con

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As deep space exploration continues to be the goal of NASA’s human spaceflight program, verification of the performance of spaceflight hardware becomes increasingly critical. Suitable test methods for verifying the leak rate of sealing systems are identified in program qualification testing requirements. One acceptable method for verifying the air leak rate of gas pressure seals is the tracer gas leak detector method. In this method, a tracer gas (commonly helium) leaks past the test seal and is transported to the leak detector where the leak rate is quantified. To predict the air leak rate, a conversion factor of helium-to-air is applied depending on the magnitude of the helium flow rate. The conversion factor is based on either the molecular mass ratio or the ratio of the dynamic viscosities. The current work was aimed at validating this approach for permeation-level leak rates using a series of tests with a silicone elastomer O-ring. An established pressure decay method with constant differential pressure was used to evaluate both the air and helium leak rates of the O-ring under similar temperature and pressure conditions. The results from the pressure decay tests showed, for the elastomer O-ring, that neither the molecular flow nor the viscous flow helium-to-air conversion factors were applicable. Leak rate tests were also performed using nitrogen and argon as the test gas. Molecular mass and viscosity based helium-to-test gas conversion factors were applied, but did not correctly predict the measured leak rates of either gas. To further this study, the effect of pressure boundary conditions was investigated. Often, pressure decay leak rate tests are performed at a differential pressure of 101.3 kPa with atmospheric pressure on the downstream side of the test seal. In space applications, the differential pressure is similar, but with vacuum as the downstream pressure. The same O-ring was tested at four unique differential pressures ranging from 34.5 to 137.9 kPa. Up to six combinations of upstream and downstream pressures for each differential pressure were compared. For a given differential pressure, the various combinations of upstream and downstream dry air pressures did not significantly affect the leak rate. As expected, the leak rate of the O-ring increased with increasing differential pressure. The results suggested that the current leak test pressure conditions, used to verify spacecraft sealing systems with elastomer seals, produce accurate values even though the boundary conditions do not model the space application.

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Leak Rates of a Candidate Main Interface Seal at Selected Temperatures

Cited by 17 publications

References 5 publications

Temperature and Atomic Oxygen Effects on Helium Leak Rates of a Candidate Main Interface Seal

Temperature and Atomic Oxygen Effects on Helium Leak Rates of a Candidate Main Interface Seal

Elastomer Seal Performance after Terrestrial Ultraviolet Radiation Exposure

Validation of Test Methods for Air Leak Rate Verification of Spaceflight Hardware

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