The lock washer, code 06.16169-0003.0, is an essential fastening security element used in the MAN L21/31 engine to prevent loosening of bolted connections under vibration and dynamic mechanical loads. Medium-speed diesel engines operate under demanding conditions where continuous vibration, thermal expansion, and cyclic stress can gradually reduce clamping force. The lock washer’s specialized geometry creates additional friction and mechanical resistance, helping maintain stable preload in threaded joints. Manufactured from durable, fatigue-resistant materials and designed to strict dimensional standards, this component plays a vital role in protecting engine assemblies, ensuring structural stability, and supporting safe long-term operation in marine and power-generation environments.