Ball float steam trap with pump function - UNA | Gestra

GESTRA UNA 25-PK / UNA 25-PS with Pump Functionality

The GESTRA UNA 25-PK / UNA 25-PS is a PN40, DN40 unit designed for condensate removal from steam systems using motive steam. It is utilized when the pressure at the outlet of a heat exchanger or heating element falls below the backpressure of the return line, and a simple steam trap cannot evacuate.

Operational Difference PK / PS

• UNA 25-PK: operates as a continuous float steam trap when sufficient differential pressure is present. When differential pressure is inadequate, it switches to cyclic condensate pumping with closure via rolling ball valve.
• UNA 25-PS: functions as a cyclic condensate lifter without a shut-off valve; applied when inlet pressure is less than backpressure.

Technical Data

• Nominal Pressure: PN40.
• Diameter: DN40.
• Connections: flanges EN 1092-2, threads G per EN ISO 228-1, NPT per ASME B1.20.1 or ASME Class 150.
• PN40 Limits: 40.5 bar at 20 °C to 25 bar at 350 °C.
• Max Motive Steam Pressure / Δp: 6 or 13 bar, depending on version.
• Max Backpressure: 3 or 5 bar.
• Body and Cover: EN 5.3103, internal parts made of stainless steel.

Installation Requirements

Motive steam line and vent line with G½ connection are required. Minimum filling height from the exchanger outlet to the device bottom is 0.5 m. The inlet line must be at least 2.5 m DN40 or a 3 l buffer tank should be provided. Motive steam pressure must be at least 3 barg and 1 bar higher than backpressure.

Typical Applications

• heat exchangers with variable load,
• steam coils in HVAC and processes,
• low steam pressure under partial load,
• condensate return lines with lift,
• stall conditions due to high backpressure.

FAQ

Does it replace a condensate pump?
In specific drainage points, yes, when motive steam is available and the flow is covered by sizing.

What is checked in sizing?
Condensate flow, backpressure, lift height, motive steam pressure, available filling height, and operating cycle.