[ sealings ]

For some time , hydrogen has been widely advocated as the future optimal alternative fuel . If hydrogen were to substitute methane even partially in this sector , hydrogen-running systems will become commonplace and their leak-proof certification a must . Therefore , DONIT engineers undertook the creation of a reliable and practical database purpose-made for the hydrogen barrier / permeability property of the company materials ’ portfolio , namely the TESNIT ^® brand . This would result from actual real corresponding leakage performance measurements using hydrogen as the test medium , which would then correlate with the ones obtained with the helium conventional test medium .

By Peter Uebelmesser , Barbara Mohar and Zvonko Majcen , DONIT

In the sealing sector , gasket materials should be , by definition , compatible with the transiting or contained fluid and should withstand the operating conditions . These requirements cannot be overstated in the case of corrosive , hazardous , or flammable fluids . In fact , hydrogen is one of the most difficult gases to contain and prevent from leaking . Besides , knowing that the explosive limit of hydrogen gas is approximately 20 % lower than that of methane , and combined with a lower ignition temperature ( Table 1 ), this translates into a significantly higher explosion risk for the former and a greater hazard for the installation and operating site . And naturally , one cannot tolerate a greater gasket leak of hydrogen than of methane . Therefore , it is crucial to determine the actual gasket material sealability for hydrogen itself .

To the best of our knowledge , not many practical studies have been conducted to date , and we were interested in obtaining such data for our TESNIT ^® gasket materials .

Conventional standards for gasket leakage measurements

Considering gasket functionality in applications , conventional fluid leakage tests are conducted according to established standards typified by the following ones :

• According to DIN 3535-6 , the specific leak rates are tested using nitrogen , the leaked gas volume is measured at room temperature ( 23 ° C ), 32 MPa gasket surface load under 40 bar internal pressure , e . g . with a gas burette , mass flow detector or differential pressure method . The ‘ DVGW criterion ’ applies here to a leakage of < 0.1 mg /( s · m ) for gasket materials measuring 2 mm in thickness .

• In DIN EN 13555 , the leak of helium gas ( as the test medium ) is measured at room

Table 1 . Explosion limits and ignition temperatures of some gases

Hydrogen Tech World | Issue 8 | February 2023 35