Hello !
We have just completed re installing a portion of H2 line in our Plant. The Piping material is carbon steel and the valves istalled are very high valve leak proof Tech. Becareful, when we tested the line using water, It was ok. However when we run Nitrogen test , it was leak every where. The valves need special maintenance to repair. If you need more information I can provide u with it. The line which we installed was 40 Kg/cm2 Presure and ambiant temperture.