What are expansion-type thermostatic traps operated by?

Expansion-type thermostatic traps operate based on the principle of thermal expansion and contraction of a liquid within a tube. When the temperature of the steam rises, the liquid inside the tube expands, which activates a mechanism that opens the trap to release condensate. Conversely, as the temperature decreases, the liquid contracts, causing the trap to close and prevent steam loss. This process is critical for maintaining efficient steam system operation, as it effectively separates the steam from the condensate while allowing for the removal of non-condensable gases and condensate.

Understanding this mechanism helps to appreciate why this particular method is widely used in steam systems; it provides a reliable and temperature-sensitive means of controlling the flow of condensate without relying on external energy sources or complicated mechanical systems. The other choices revolve around different operating principles unrelated to the thermal expansion of a liquid, emphasizing that the effective operation of expansion-type thermostatic traps specifically hinges on the thermal properties of the liquid used.