Thermodynamic Steam Traps operate in a cyclic on/off process using the thermodynamic properties of flash steam as it flows through the trap. Thermodynamic traps use only one moving part, the valve disc, which allows condensate to escape when present and closes tightly upon the arrival of steam. These traps have an inherently rugged design and are commonly used as drip traps on steam mains and supply lines, at pressures over 30 PSIG, as well as tracer traps for critical steam tracing applications, where no back-up of condensate can be tolerated. Their solid construction and single moving part make them resistant to waterhammer and are freezeproof when installed vertically. Thermodynamic traps will only discharge small amounts of air and therefore are typically not used in process applications
The bellows type Thermostatic Trap uses a fluid-filled thermal element (bellows) that operates under the principle of thermal expansion and contraction. The fluid vaporizes and expands as the temperature increases, causing the bellows to close the valve. As the temperature decreases, the fluid condenses and contracts, causing the bellows to open the valve. These traps provide excellent air handling capability and are used for drip, non-critical tracing and process applications. The main advantage of the thermal element is that on start-up loads, the trap is in the open position, allowing air and condensate to be rapidly removed from the system. Watson McDaniel thermal element traps offer wide operating pressure ranges, rugged welded stainless steel bellows, and various orifice sizes, making them a great choice for a majority of applications.
The Float & Thermostatic (F&T) Trap uses a float connected by a linkage to the valve plug to discharge condensate from the system. In addition, F&T traps contain a thermostatic air vent to allow the discharge of air from the system. For this reason, these traps have excellent air removal capability, which is advantageous during system start-up when large amounts of air are present in the system. Float & thermostatic steam traps are generally the primary selection for steam system drip applications, up to 30 PSIG, and for drainage of process heat transfer equipment, up to 450 PSIG.