E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
E21D15/00—Props; Chocks, e.g. made of flexible containers filled with backfilling material
E21D15/50—Component parts or details of props
E21D15/51—Component parts or details of props specially adapted to hydraulic, pneumatic, or hydraulic-pneumatic props, e.g. arrangements of relief valves
Dispositif pilote distributeur pour la commande d'une vanne de securite, notamment vanne de securite pour stockage de gaz naturel en cavite souterraine