The drain trap, code P51208-03, is a vital part of the MAN L21/31 engine's turbocharging and air intake system, designed to collect and expel condensed water or oil mist before it can enter the combustion chambers. Its function ensures cleaner intake air and protects critical engine components from corrosion or damage caused by accumulated moisture. Essential in humid or marine environments, the drain trap contributes to improved operational reliability and longevity.