[ cylinders ]
Containarised test bays at one of Kiwa ’ s testing facilities
The cylinder testing process is relatively simple yet critical for manufacturers to obtain initial data . The dynamic hydraulic load cycle test , which involves the ingress of a liquid into the cylinder , is essential and required by many standards . The test starts at a predetermined low pressure and gradually increases to an upper limit , which depends on the maximum allowable working pressure ( MAWP ), the standard used , and manufacturer requirements .
The number of load cycles can vary , but 30,000 cycles are common . To simulate the cylinder ’ s lifetime , several external influences are added . Chemical exposure ( automotive fluids ), dropping from a height , impact tests , and even creating a flaw in the outer materials of the product are just some examples of what a cylinder endures during the test phase of certification . Additionally , lowand high-temperature testing is performed at -40 ° C and + 85 ° C during the load cycle test .
Gas testing
Some standards require a hydrogen gas leak rate test to be conducted at working pressure . This test is static , meaning that the pressure remains constant and does not create any stresses on the material . The permeation is measured over a longer period of time , which can take up to 3 – 4 weeks .
During the simulation of the fuelling of a highpressure hydrogen system the cylinder is pressurised with pre-cooled hydrogen for 500 pressure cycles at different temperatures , and intermediate permeation is measured . However , very few test laboratories can comply with these demanding parameters , especially as cylinders are increasing in size (> 400 liters / 700 WP ).
When testing the cylinder for external influences , such as fire and high velocity impact , it is pushed to its limits .
20 Hydrogen Tech World | Issue 9 | April 2023