The nut marked with code number K 31038 is designed to securely fasten bolt K 31022, which anchors the counterweight (K 31020) to the crankshaft of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. This high-strength fastener ensures that the counterweight remains precisely in place during intense operational conditions, maintaining rotational balance and minimizing vibrations. Manufactured for durability and exact fit, the nut resists loosening under mechanical and thermal stress, playing a key role in preserving the structural integrity of the engine's core components.