Endurance Test Of Hydraulic Piston And Rod Seals
Grönlund, Jaakko (2016)
2016
Konetekniikan koulutusohjelma
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
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Hyväksymispäivämäärä
2016-12-07
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201611244757
https://urn.fi/URN:NBN:fi:tty-201611244757
Tiivistelmä
There is observed deviation of endurance in dynamic and static sealings in the hydrau-lic system of an airplane which is suspected to be caused by differences in material and quality between different manufacturers. In order to find out and verify these dif-ferences series of comparing tests were conducted on specifically made test equip-ment. The main goal of this Master’s Thesis was to perform the needed tests on the seals and to evaluate the test results.
The test system consisted of a hydraulically driven test cylinder which was able to test both the dynamic and static seal. The test cylinder was designed in such a way that it could be used to test two sealing systems at the same time. The test was conducted in conditions that resembled real life usage. The main points were that pressure, tempera-ture and movement speed were the same as in the original application. Control logic was used to run the test cylinder continuously from one end to the other.
During the test the force needed to move the cylinder was monitored. From this force the friction and the deviation of friction behavior in dynamic seal during the test were computed. Leakage was monitored both on the dynamic seal and on the static seal. Pressures, position and temperature were also used as survey measures. Speed of the test cylinder was calculated from position. The system allowed testing of two piston seals, two rod seals and two O-rings simultaneously. Both piston seal and rod seal were T-seals. T-seals consist of a T-shaped elastomer sealing element supported by back-up rings on both sides. The wearing of seals was determined by change of weight before and after the experiment. The possible effect of absorption of fluid on the mass and properties of the sealing was examined with separate tests.
The properties of the seals between the two manufacturers differed in the present study and the seals of manufacturer 2 lasted wearing better than the seals of manufacturer 1. This result is based on the leakage during the test, weighting after the test and friction behavior during the test. Also visual observation of the seals supports this finding.
The test system consisted of a hydraulically driven test cylinder which was able to test both the dynamic and static seal. The test cylinder was designed in such a way that it could be used to test two sealing systems at the same time. The test was conducted in conditions that resembled real life usage. The main points were that pressure, tempera-ture and movement speed were the same as in the original application. Control logic was used to run the test cylinder continuously from one end to the other.
During the test the force needed to move the cylinder was monitored. From this force the friction and the deviation of friction behavior in dynamic seal during the test were computed. Leakage was monitored both on the dynamic seal and on the static seal. Pressures, position and temperature were also used as survey measures. Speed of the test cylinder was calculated from position. The system allowed testing of two piston seals, two rod seals and two O-rings simultaneously. Both piston seal and rod seal were T-seals. T-seals consist of a T-shaped elastomer sealing element supported by back-up rings on both sides. The wearing of seals was determined by change of weight before and after the experiment. The possible effect of absorption of fluid on the mass and properties of the sealing was examined with separate tests.
The properties of the seals between the two manufacturers differed in the present study and the seals of manufacturer 2 lasted wearing better than the seals of manufacturer 1. This result is based on the leakage during the test, weighting after the test and friction behavior during the test. Also visual observation of the seals supports this finding.