The O-ring K 43597 is an important elastomeric sealing component designed for the screw plug K 43594 within the automatic starting-air stop valve assembly of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. Its primary function is to provide an effective pressure-tight seal between the screw plug and its corresponding mating surface, helping prevent unwanted compressed-air leakage and maintain the pressure integrity required for dependable operation of the starting-air system. Working together with the K 43594 screw plug, the O-ring supports secure sealing of the threaded closure and contributes to stable pneumatic pressure conditions within the automatic starting-air stop valve. Its sealing performance depends on accurate cross-sectional dimensions, appropriate elastomer hardness, elasticity, chemical compatibility, surface condition, and correct compression within the designated sealing groove. During engine operation, the K 43597 O-ring may be exposed to repeated compressed-air pressure cycles, vibration, temperature variations, and prolonged periods of standby readiness, potentially resulting in hardening, compression set, cracking, swelling, or loss of elasticity over time. During maintenance or overhaul, the O-ring should be inspected for cuts, flattening, deformation, surface deterioration, and other signs of aging, while the corresponding sealing groove, screw plug K 43594, and mating surfaces should also be examined for scratches, contamination, corrosion, or mechanical damage. Replacement and installation should follow the manufacturer's specifications, ensuring correct positioning, cleanliness, and compatibility with the operating conditions. By maintaining effective sealing around screw plug K 43594, the K 43597 O-ring contributes to reduced compressed-air losses, reliable automatic starting-air stop valve operation, consistent pneumatic control, and long-term operational readiness of the ZV40/48 engine.