The expander, code 100100, is a precision-engineered mechanical element used in the MAN L21/31 engine to provide controlled elastic force within sealing, retaining, or positioning assemblies. Frequently installed together with piston rings, sealing systems, or retaining mechanisms, the expander maintains stable contact pressure and compensates for thermal expansion and operational movement throughout engine operation. Manufactured from high-grade spring steel or similarly resilient materials, it is designed to withstand continuous vibration, cyclic loading, and elevated operating temperatures without losing its elasticity or functional reliability. By ensuring efficient sealing and mechanical stability, the expander contributes to reduced leakage, minimized component wear, improved engine efficiency, and extended service life of critical engine assemblies.