ERD 43b: Hydrogen MEMbranes-test rig concept & membrane testing by Wentzel Dynamics

HYMEM –  Hydrogen MEMbranes – test rig concept & membrane testing

The aim of project Hymem2 is to demonstrate a test method for accelerated fatigue test of

membranes for diaphragm compressors. This is done by creating an experimental platform for the assessment of the kinematic behaviour of general and H2 compressor membranes. This utilises a specific generatrix shape to elevate stress levels under dynamic, repetitive motion. For accurate stress control, the stroke is variable allowing ramping up and down, avoiding overload such as might occur during compressor operation.

 

In the chosen design, the membrane deformation is realised by oil displacement, induced by a PID controlled piston assembly in an oil chamber. The gas side of the membrane can be compressed by air, driving the return stroke towards the oil plate.

Figure 1  Tensile test of a hollow specimen to characterize Hydrogen embrittlement

The instrumentation consists of:

• 5 LVDT sensors, spaced over the radial direction of the membrane.
• 1 air pressure sensor in the cavity above the membrane.
• 1 temperature sensor in the cavity above the membrane.
• 1 piston displacement LVDT sensor, serving as feedback signal.

The executed experiments indicated the importance of proper bleeding for the oil chamber, limiting the initial experiments. Nevertheless, the feasibility of representative stress cycling was demonstrated. A separate effort will have to follow allowing sufficiently high machine speed to be instrumental for high cycle accelerated fatigue testing. For the postprocessing, a dedicated routine has been created with significant accuracy.

 

A next development phase will aim at the demonstration and assessment of the test method for fatigue and membrane development purposes, supporting the development of more robust membranes.