Can a composition disc globe valve be interchanged from one type of service to another simply by changing the disc?

A composition disc globe valve can indeed be interchanged from one type of service to another simply by changing the disc. This is because the disc is designed to be the primary sealing component that interacts with the flow of fluid, and different disc materials can be used to accommodate various types of fluids or pressures.

The ability to change the disc allows for flexibility in the valve's application, making it suitable for different services, such as varying temperatures, pressures, or chemical compatibilities. For instance, if a globe valve initially used for water service is needed for a more corrosive application, replacing the disc with one made from a more resistant material can effectively allow the valve to meet the new service requirements.

Other factors involving the overall construction of the valve and its material compatibility must also be considered, but specifically regarding the interchangeability of the disc itself, it is correct to state that it can be done without needing to replace the entire valve.