Thermodynamic Steam Traps Thermodynamic traps, also called disc traps, operate as a function of velocity. GENERAL INFORMATIONThermodynamic traps contain only one moving part, a flat disc. The disc moves between a cap and seat, regulating the flow of condensate out of the trap. Movement of the disc depends upon pressure changes within the trap. Disc traps may also have a screen that filters out particles from the system. ..