Thermostatic steam traps operate on the temperature difference between steam and condensate. They open when condensate cools below steam temperature and close when steam arrives. Two main types are available: balanced pressure (bellows) traps that respond quickly to temperature changes, and bimetallic traps that provide adjustable subcooling for specific applications.
AQ Process Systems sources and exports thermostatic traps in carbon steel, stainless steel, and bronze for pressures up to 42 bar. Available in sizes from 1/4" to 1", compact and lightweight for tracing lines, HVAC systems, and small process equipment. Many models are freeze-proof when installed with a slight downward pitch.
Thermostatic traps are the most compact trap type and are particularly valued for steam tracing applications where space is limited and subcooled condensate discharge actually benefits the tracing system by extracting additional heat from the condensate.
| Product | Specification | Description |
|---|---|---|
| Balanced Pressure Traps | ||
| Balanced Pressure Bellows Traps | 1/4", 1" | PN up to 17 bar | CS, SS, or bronze | Balanced pressure thermostatic traps with liquid-filled bellows, compact, lightweight, excellent air venting. For tracing and HVAC. |
| Capsule-Type Thermostatic Traps | 1/2", 1" | PN up to 42 bar | CS or SS | Higher-pressure thermostatic traps with sealed capsule element, suitable for process applications with moderate pressures. |
| Bimetallic Traps | ||
| Bimetallic Steam Traps | 1/2", 2" | PN up to 100 bar | CS or SS | Bimetallic thermostatic traps with adjustable subcooling, the bimetallic element provides robust, high-pressure capability. |
| High-Pressure Bimetallic Traps | 1/2", 1" | PN up to 170 bar | Forged steel | High-pressure bimetallic traps for power plant and refinery applications, adjustable discharge temperature below saturation. |
| Specialty Thermostatic | ||
| Compact Tracing Traps | 1/4", 3/8" | Miniature body | For tracing lines | Miniature thermostatic traps specifically designed for steam tracing systems, extremely compact for manifold installations. |
Balanced pressure traps use a liquid-filled bellows that expands when heated (steam) and contracts when cooled (condensate), they respond quickly and discharge condensate just below steam temperature. Bimetallic traps use stacked bimetallic strips that deflect with temperature, they respond more slowly and discharge condensate well below steam temperature (adjustable subcooling). Balanced pressure is preferred for quick response; bimetallic for high pressure and adjustable subcooling.
Steam tracing lines (compact size, subcooled discharge benefits tracing), HVAC heating coils (excellent air venting, compact), instrument tracing, small process drains, and applications where waterlogging from subcooled condensate is acceptable. They are not ideal for large process heat exchangers where immediate condensate removal is critical.
Balanced pressure traps are inherently freeze-proof, when the trap cools in a shutdown, the bellows contracts and the valve opens fully, draining all condensate. This self-draining feature prevents freeze damage in outdoor installations. Bimetallic traps also open on cooling but may retain some condensate depending on piping arrangement.
Subcooled condensate is condensate that has cooled below the saturation (steam) temperature at that pressure. Thermostatic traps deliberately hold back condensate until it cools, bimetallic traps can hold back 15-50°C below saturation. This subcooling extracts additional heat from the condensate before discharge, but can cause waterlogging if the equipment requires immediate drainage. For tracing, subcooling is beneficial; for process heat exchangers, it is usually unacceptable.
Balanced pressure bellows elements typically last 3-5 years and are easily replaced without removing the trap body. Bimetallic elements are more robust and can last 5-10+ years but response degrades over time as the bimetallic strips lose calibration. We supply replacement elements for all major equipment types.
Share your application, steam pressure, condensate load, equipment type, we respond within 24 hours.