How Thermostatic Steam Traps Can Save You Energy

Thermostatic steam traps refer to a newer trap design with one of three main types of actuating mechanisms:

•	Alcohol-filled bellows or diaphragms
•	Bimetallic strips or plates
•	Wax-filled elements

All three of these mechanisms operate by reacting to temperature changes inside the trap body and exerting force to open or close the trap, allowing condensate to discharge at the desired degree of subcooled temperature. Thermostatic traps allow the user to select the proper type of trap as well as the desired discharge temperature for the specific steam trap application. Older technologies, such as thermodynamic disc traps, bucket traps, or F&T traps, could only discharge condensate at the saturating temperature of the inlet pressure; This often results in live steam being discharged along with the condensate. A disc or bucket trap typically loses about 2 lbs/hr of live steam even when brand new.

Hot condensate, just like steam, is a valuable commodity in any industrial plant due to its latent heat content. A pound of hot condensate at 300F has about 300 BTU heat content, about a quarter of the heat content of a pound of steam. An efficient plant will utilize as much of this latent heat as possible, before it's dumped to the sewer or returned to the flash tank of the boiler feed system. Winterization or instrumentation tracing are ideal applications for this, and effectively using condensate heat can save significant amounts of energy. It's like converting an noisy old steam heating system in your house to an updated, quiet, and efficient hot water heating system.

Let's assume that a 100 psig instrumentation tracing system with a thermodynamic disc trap (discharging 50 lbs/hr of condensate at 338F) was replaced with a PT Series 41 TEMPTROL Valve (discharging condensate at 180F). Let's further assume this tracing system operates six months a year at a steam cost of $10.00 per 1,000 lbs of steam:

(338-180) btu/lb x 50 lbs/hr divided by 1200 btu/lb of steam =
6.56 lbs of steam saved in an hour

6.56 lbs/hr x 24 hr/day x 180 days x $10.00 and divided by 1000 lbs of steam =
$283.40 saved annually

From this simple calculation, one can see that change to a more energy efficient steam trap can recover the cost of the trap within the first six months of operation, and provide consistent energy savings down the road.