Mechanical testing in high-pressure hydrogen is the most versatile HE testing method. Various kinds of specimens (tensile, fatigue, pre-cracked) are connected to specimen holders inside the testing cell. Regular loading patterns are applied. The loading devices are essentially similar to the ones that are used in conventional HT HP applications in an aqueous environment.
The challenge is related to the gas management and safety features. The loading device is typically installed in a draft cabinet. Based on the explosive area classification, the draft cabinet interior area is classified as ATEX Zone 2, if adequate and continuous ventilation is available. The area around the draft cabinet is no zone, a normal area.
The gas dosing procedure is somewhat complicated including the testing cell nitrogen flushing and vacuum pump cleaning to decrease the oxygen level in the testing cell. The draft cabinet and the ventilation system will be instrumented with various sensors measuring the possible hydrogen leakages, operation of the ventilation and potential flames.
The hydrogen operation is controlled using a special PLC that operates the gas management in normal and alarm situations. As the hydrogen operation is somewhat complicated, special attention must be paid to the cooperation with the customer's safety officer. The instrument design must be accepted before starting the manufacturing and delivering the goods.