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 mechanism:
- Alcohol-filled bellows or diaphragms
- Bimetallic strips or plates
- Wax-filled elements
All three 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 subcooling. Thermostatic traps let the user 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, can only discharge condensate at the saturation 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 lb/hr of live steam even when brand new.
Condensate is valuable heat
Hot condensate, just like steam, is a valuable commodity in any industrial plant because of its heat content. A pound of hot condensate at 300 °F holds about 300 BTU, about a quarter of the heat content of a pound of steam. An efficient plant will use as much of this heat as possible before the condensate is dumped to the sewer or returned to the flash tank of the boiler feed system.
Winterization and instrumentation tracing are ideal applications for this, and using condensate heat effectively can save significant amounts of energy. It's like converting a noisy old steam heating system in your house to a quiet, efficient hot water heating system.
A worked example
Assume a 100 psig instrumentation tracing system with a thermodynamic disc trap (discharging 50 lb/hr of condensate at 338 °F) is replaced with a PT Series 41 TEMPTROL Valve discharging condensate at 180 °F. Assume the tracing system operates six months a year at a steam cost of $10.00 per 1,000 lb of steam:
(338 − 180) BTU/lb × 50 lb/hr ÷ 1,200 BTU/lb of steam =
6.56 lb of steam saved per hour
6.56 lb/hr × 24 hr/day × 180 days × $10.00 ÷ 1,000 lb of steam =
$283.40 saved annually
From this simple calculation, changing 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 after that.
Choosing a thermostatic trap
Process Technology offers a full range of thermostatic steam traps for different application requirements:
| Application | Recommended trap |
|---|---|
| Drip leg and light process applications with 5 to 10 °F subcooling | Series 40 Bellows Steam Traps |
| General tracing with 20 to 50 °F subcooling | Series 46 Bimetal Steam Traps |
| Instrumentation and low temperature tracing with 60 °F or more subcooling | Series 41 TEMPTROL Valves |