A thermostatic trap opens when which component contracts?

The correct answer is that the thermostatic trap opens when the bellows contracts. In a thermostatic steam trap, the bellows is a primary component that responds to changes in temperature. When steam enters the trap and heats the bellows, the bellows expands. Conversely, when the steam condenses and the temperature drops, the bellows contracts.

This contraction of the bellows is crucial as it triggers the opening mechanism of the trap, allowing condensate to escape. The functioning of a thermostatic trap relies on this thermal response to effectively manage condensate while preventing steam loss, ensuring energy efficiency in the system.

Understanding the operation of the bellows is essential for recognizing how the trap maintains the proper flow of steam and condensate in a steam heating system. The other components mentioned, such as the valve seat, diaphragm, and expansion chamber, play different roles in other types of traps or systems and do not directly control the opening mechanism of a thermostatic trap in the same way the bellows does.