Thermodynamic Steam Traps

Thermodynamic traps, also called disc traps, operate as a function of velocity.

 

GENERAL INFORMATION

Thermodynamic 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. The filtration prevents particles from getting caught in the pressure chamber and jamming the disc.

 

 

EQUIPMENT DESIGN

On startup, cold condensate and air flow raise the disc and open the discharge port. When steam (pink) arrives there is a decrease in the pressure below the disc, lowering the disc and closing the discharge port. The discharge port remains closed as long as pressure is maintained above the disc. When hot condensate (blue) enters the steam trap, heat radiates out through the cap, diminishing the pressure over the disk and opening the trap to discharge the condensate.

 

 

USAGE EXAMPLES

Thermodynamic disc traps are most commonly used for applications similar to that of inverted bucket traps but with lighter condensate loads. These traps are usually chosen for heat trace lines and smaller steam distribution lines. Their poor ability to remove gases can limit their use in many applications. The typical disc trap safety factor used for trace line applications is 2:1. The steam trap on the left has a maximum working pressure of 1,010 psi and capacities up to 1,800 lb/hr. The steam trap on the right has a maximum working pressure of 450 psi and capacities up to 800 lb/hr.

 

 

ADVANTAGES

• Excellent corrosion resistance.
• Relatively small and compact for the amount of condensate they are capable of discharging.
• Can handle a wide range of pressures.

 

 

DISADVANTAGES

• Poor energy conservation.
• Poor resistance to wear.
• Cannot handle very light loads.
• Cannot handle dirt.
• If pressure is not maintained above the disc, the trap cycles frequently, wastes steam and fails prematurely.
• Difficulty in discharging air and other non-condensable gases.