[ sealings ]
was measured at different internal pressures ranging from 5 to 40 bar . In both diagrams , the hydrogen leakage at 40 bar internal pressure is slightly , but not significantly higher than the helium leakage .
Having an isolated view on the larger kinetic diameter of hydrogen compared to helium , one would expect a lower leakage of hydrogen , while with an isolated view on the higher effusion rate of hydrogen compared to helium , leakage of hydrogen would be higher . Our results show that the effusion rate is the governing factor .
Interestingly , under 30 MPa of surface stress , FA-NEW GENERATION displayed a 1,000 times superior sealing performance to FA-STANDARD with mass leakages of ca . 10 -5 and 10 -2 mg /( s · m ), respectively .
Leakage ( ml / min ) Leakage ( mg /( s · m ))
1.00E + 00 1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05
Mass leakage FA-NEW GENERATION at 15MPa
FA-NEW GENERATION at 30MPa
1.00E-06
0 10 20 30 40 50 Internal pressure ( bar )
Volume leakage
1.00E + 01 1.00E + 00
FA-NEW GENERATION at 15MPa
1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05
FA-NEW GENERATION at 30MPa
1.00E-06 1.00E-07 1.00E-08
0 10 20 30 40 50 Internal pressure ( bar )
Fig . 3 . Helium ( dashed line ) and hydrogen ( full line ) leakage curves for FA-NEW GENERATION at different installation surface stresses
In a trial simulating a sub-optimal installation of FA-NEW GENERATION ( i . e ., under 15 MPa of surface stress ), a significant increase in the leakage was observed ( see Fig . 3 ). However , this leakage still remained within the same level as that of FA-STANDARD , which was installed under the optimal conditions ( i . e ., 30 MPa ); this demonstrates the practical functionality and advantages of FA-NEW GENERATION .
Prospects
DONIT is committed to providing reliable and practical performance data concerning its gasket materials , especially for the ones which were purpose built for high-risk applications . For the sake of increased safety , reducing the hydrogen emissions in an installation using it is a top priority due to the hazardous nature of this fluid .
A safe and valuable hydrogen leakage testing method was developped and applied to
FA-STANDARD and FA-NEW GENERATION gasket materials as examples . This method , which is based on a further improvement of the VDI2440 / 2200 standard , offers concrete and reliable data for the evaluation of gasket materials destined for sealing hydrogen . This work demonstrates that the determination of mass or volume leakage according to the EN 1591-1 standard with helium as the test medium is valid also for the hydrogen medium .
FA-NEW GENERATION gasket material proved its superior sealing performance as it exhibited a 1,000-fold lower mass leakage vs FA-STANDARD – the latter exemplifies a common material within its category of applications . In addition , in a trial simulation , the former displayed higher tolerance to poor installation conditions . Therefore , we recommend the use of FA- NEW GENERATION in hydrogen sealing applications .
38 Hydrogen Tech World | Issue 8 | February 2023