Friday, August 18, 2017

Thermodynamic Steam Traps

cutaway view thermodynamic steam trap
Cutaway view of disc type thermodynamic steam trap
Image courtesy of Spirax Sarco
Condensate return is an essential operation in any closed loop steam system. Steam that has lost its latent heat will collect in the piping system as hot liquid water (condensate). This liquid needs to be separated from the steam and returned to the boiler feedwater equipment without letting steam escape in the process.

Various items of steam utilization equipment and processes will result in condensate formation at different rates. The device that collects and discharges condensate to the return portion of the system is called a steam trap. There are numerous physical principals and technologies employed throughout the range of available steam trap types. Each has application limitations and strengths making them more or less suitable for a particular installation.

A thermodynamic steam trap relies on the energy provided by the condensate to move a disc which controls the flow of the condensate into the return system. The disc is the only moving part in the device. Condensate flows through a port to a chamber on the underside of the disc, lifting the disc and directing the flow to the return system or drain. Eventually, the fluid flowing into the chamber will reach a point where some of the condensate flashes to steam. A portion of this steam flows through a channel into the space above the disc, called the control chamber. The increase in pressure in the control chamber due to the steam influx pushes downward on the disc, seating it in a closed position. The trap, with the disc seated, remains in the closed position until the flash steam in the control chamber cools and condenses. Then the disc can be opened again by the inflow of condensate.

The thermodynamic disc trap is:

  • Easy to install
  • Compact
  • Resistant to damage from freezing
The single trap can cover a wide range of system pressure, and the simple construction translates into low initial cost. Properly matching any steam trap to its application is important. Share your condensate return and steam system challenges with specialists, combining your knowledge and experience with their product application expertise to develop effective solutions.