With what is the bellows of a thermostatic steam trap usually filled to enhance its sensitivity?

The bellows of a thermostatic steam trap is typically filled with a substance that can change its volume with temperature changes, enhancing the trap's responsiveness to temperature variations. In this case, the combination of alcohol and water serves a specific purpose. Alcohol has a lower boiling point than water and expands more significantly with temperature fluctuations. This property enables the bellows to respond quicker to the temperature of the steam and condensate, allowing the trap to open and close efficiently based on changes in temperature.

When the temperature rises, the alcohol expands more than water would, making it a more effective choice for quick adjustments in the trap's operation. This heightened sensitivity ensures that the steam trap can effectively manage the flow of condensate while preventing steam loss, which is important for overall system efficiency and performance.

Other substances, like air or steam, do not provide the same level of responsiveness or thermal expansion characteristics needed for optimal operation. While water alone could work, it wouldn't offer the same sensitivity as the combination of alcohol and water does, particularly under varying temperature conditions.