The connecting plug K 43557 is an important connecting and securing component of the automatic starting-air stop valve used in the starting-air system of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. Its primary function is to provide a secure mechanical connection within the valve assembly, helping maintain the correct positioning and integrity of the associated components under the operating conditions of the compressed-air starting system. Depending on the specific valve arrangement, the connecting plug may also form part of a threaded connection or closure interface, where accurate dimensions, suitable material strength, and proper engagement are essential for dependable operation. During engine starting, the K 43557 may be exposed to repeated pressure fluctuations, mechanical loading, vibration, and temperature variations, requiring resistance to loosening, deformation, corrosion, and fatigue. Correct installation is particularly important because damaged threads, insufficient engagement, incorrect positioning, or deterioration of contact surfaces can compromise the stability of the connected components and potentially affect valve performance. During maintenance or overhaul, the connecting plug should be inspected for thread damage, cracks, corrosion, deformation, wear, and signs of loosening, while its mating surfaces and associated connections should also be checked. By ensuring a secure and stable connection within the automatic starting-air stop valve, the K 43557 connecting plug contributes to reliable component positioning, mechanical integrity, dependable valve operation, and long-term reliability of the ZV40/48 starting-air system.