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KSB Thermodynamic Steam Trap STH-S — High Pressure & Superheat

ECOLINE STH-S compact disc-type steam trap for high-pressure and superheated steam. Stainless steel up to 42 bar / 427°C, WC6 alloy steel up to 62 bar / 540°C, F22 alloy steel up to 170 bar / 540°C. Sizes ½″ to 1″. The most compact KSB steam trap with the widest pressure range.

Thermodynamic Steam TrapSS 42 bar / WC6 62 bar / F22 170 barSizes ½″ to 1″

Specifications

ParameterSpecification
SeriesECOLINE STH-S
Body MaterialStainless Steel (ASTM A743 CA40), WC6 Alloy Steel (ASTM A217 WC6), or F22 Alloy Steel (ASTM A182 F22 Cl.3)
Size Range½″ to 1″ (DN 15 to DN 25)
Max Pressure (SS)42 bar @ 427°C
Max Pressure (WC6)62 bar @ 540°C
Max Pressure (F22)170 bar @ 540°C
Max Temperature (SS)427°C
Max Temperature (WC6)540°C
Max Temperature (F22)540°C
Design StandardKSB Manufacturer Standard
End ConnectionsScrewed (NPT/BSP); Socket Weld
ConstructionThermodynamic disc mechanism — single moving part. Integral strainer.
Trim / InternalsSS AISI 420 control disc (SS body); chromium steel disc and seat (WC6); AISI D2 disc and seat (F22)
✓ KSB proprietary

Material & Applications

Why CS / Alloy / SS Thermodynamic: The thermodynamic mechanism uses the velocity difference between steam and condensate to operate a simple disc — the only moving part. When condensate enters, it lifts the disc. When flash steam forms, the high velocity creates a low-pressure zone above the disc that holds it closed. This simple mechanism provides the widest pressure range of any trap type (up to 170 bar), handles superheated steam reliably, and offers the most compact installation envelope. With only one moving part, maintenance is minimal.

Typical applications: HP steam main drip legs, superheated steam lines, boiler blowdown recovery, turbine drain, steam header drainage, and any high-pressure application up to 170 bar. The most compact steam trap option for space-constrained installations and high-pressure systems.

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Other Variants

Inverted Bucket SIB-S Ball Float SBF-S All Steam Traps →

Service Area

Pune, Ahmednagar & Beed.

CS / Alloy / SS Thermodynamic Steam Trap FAQs

What is the advantage of thermodynamic over inverted bucket at high pressure?
Thermodynamic traps are much more compact at high pressures — a thermodynamic trap rated for 170 bar is roughly the same size as one rated for 16 bar. An inverted bucket trap for the same pressure would be significantly larger and heavier. Thermodynamic traps also have only one moving part (the disc), making them simpler, cheaper, and easier to maintain. However, they discharge intermittently with an audible click and are not suitable for continuous discharge applications.
Can thermodynamic traps handle superheated steam?
Yes. The STH-S is specifically designed for superheated steam up to 540°C. Thermodynamic traps are one of the few steam trap types that operate reliably with superheated steam, because the mechanism depends on the flash steam principle which works regardless of the degree of superheat. Inverted bucket and ball float traps can struggle with superheated steam.
Are thermodynamic traps noisy?
Thermodynamic traps produce an audible click each time the disc opens and closes (cycling). The cycling frequency depends on the condensate load and pressure. In quiet environments, this can be noticeable. If noise is a concern, inverted bucket traps are quieter as they discharge more gradually.

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