What basic principle controls all types of thermostatic traps?

The correct answer highlights the significance of temperature upstream of the trap in controlling thermostatic traps. Thermostatic traps are designed to discharge condensate and non-condensable gases while preventing the escape of live steam. Their operation is based on the temperature difference between the steam and the condensate.

When steam enters the trap, it is typically at a higher temperature compared to the condensate. The thermostatic element within the trap responds to this temperature difference; as steam enters the trap and condenses, the temperature drops, which activates the trap to open and allow the condensate to escape. This principle ensures that the trap operates effectively, allowing for the efficient removal of condensate while preserving the steam.

In essence, the performance of thermostatic traps relies fundamentally on the temperature upstream, making this principle paramount in their operation. It is this principle that drives the functioning of the entire device, allowing it to respond dynamically to changes in temperature and maintain optimal steam system efficiency.