Bimetallic steam trap - BK | Gestra

GESTRA BK – Bimetallic Thermostatic Steam Trap

The GESTRA BK series is a thermostatic/thermodynamic steam trap featuring a Thermovit regulator made from bimetallic strips and a staged nozzle. It remains open during startup to discharge air and cold condensate. As temperature increases, the strips move the nozzle towards the seat, closing just below saturation temperature.

Versions and Operating Limits

• BK 45 / BK 45-U / BK 45-LT / BK 46: PN40, DN15–DN25. BK45 with Δp up to 22 bar, BK46 with Δp up to 32 bar. Body temperature limit up to 420 °C for BK45 and up to 450 °C for BK46, depending on connection and material.
• BK 15: PN40 / Class 300, DN40–DN50, externally adjustable Thermovit, Δp up to 22 bar.
• BK 27N: PN40/PN63, DN40–DN50, 16Mo3 body, Δp up to 40 or 45 bar.
• BK 37 / BK 28 / BK 29: PN63 / PN100 / PN160, DN15–DN25, with Δp 45 / 85 / 110 bar respectively.
• BK 212: High-pressure version DN15–DN25, Δp up to 275 bar, with special alloys for temperatures up to 650 °C per type.

Connections and Materials

Available with flanges EN 1092-1 and ASME B16.5, threads G or NPT, socket weld per EN 12760 / ASME B16.11, and butt weld per EN 12627 / ASME B16.25. Internal parts are stainless steel, with graphite/CrNi gaskets in standard versions.

Typical Applications

• Draining saturated and superheated steam lines,
• steam tracing,
• thermal venting of steam networks,
• points with water hammer,
• high-pressure and temperature units.

Selection

The BK is selected when a metallic thermostatic controller is required, withstanding superheated steam and integrated non-return function. For exchangers where condensate accumulation is not allowed, a float steam trap is considered.

FAQ

Is subcooling adjustable?
In several versions, adjustment is factory-set or external, depending on type.

Is a filter needed?
Many versions have an integrated filter. In new networks or after welding, line cleaning is required.