The joint ring K 43574 is an important sealing component designed for the screw plug K 43573 within the automatic starting-air stop valve of the Adriadiesel/Jugoturbina/Zgoda/Sulzer ZV40/48 engine. Its primary function is to provide an effective seal between the screw plug and its corresponding seating surface, preventing unwanted compressed-air leakage through the threaded closure and helping maintain the pressure integrity required for reliable operation of the starting-air system. Although relatively small, the joint ring plays an essential role in preserving the tightness of the valve assembly and supporting consistent pneumatic control during engine starting. Its sealing effectiveness depends on accurate dimensions, appropriate material properties, correct seating geometry, surface condition, and proper compression during installation. During service, the K 43574 joint ring may be exposed to repeated compressed-air pressure cycles, vibration, temperature variations, and extended periods of standby readiness, requiring resistance to deformation, deterioration, and loss of sealing capability. During maintenance or overhaul, the joint ring should be inspected for flattening, cracking, corrosion, surface damage, and other signs of wear, while the corresponding sealing surfaces of the K 43573 screw plug and valve casing should also be examined for irregularities or damage. Replacement and installation should follow the manufacturer's specifications to ensure correct sealing performance. By maintaining a secure and pressure-tight connection around the K 43573 screw plug, the K 43574 joint ring contributes to reduced compressed-air losses, dependable operation of the automatic starting-air stop valve, stable starting-air control, and long-term operational reliability of the ZV40/48 engine.