The Gestra UNA25 is a float-type steam trap and condensate lifting unit designed for steam systems. It features an EN 5.3103/ASTM A 395 body and stainless steel internal components, with a nominal size of DN 40 and flange or threaded end connections. UNA25-PS is used as a cyclic lifting unit, while UNA25-PK provides continuous condensate discharge when sufficient differential pressure is available and uses motive steam for cyclic pumping when the differential pressure is insufficient. It is suitable for condensate discharge and recovery in steam systems with high back pressure, vacuum, or insufficient differential pressure.
Gestra UNA25 ball float steam trap product photo, three-quarter view
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UNA25 Float-Type Steam Trap and Lifter | Gestra
Float-type steam trap and condensate lifter, DN40, with continuous draining or cyclic pumping options.
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Specifications
- Operating mode
- UNA25-PS is a cyclic condensate lifting unit; UNA25-PK provides continuous condensate discharge when sufficient differential pressure is available and cyclic pumping when the differential pressure is insufficient
- Maximum allowable pressure/temperature (PN 40, G thread, or NPT)
- 40.5 bar at 20°C; 38.3 bar at 120°C; 31.6 bar at 250°C; 25.0 bar at 350°C
- Maximum allowable pressure/temperature (Class 150 flange)
- 17.2 bar at 20°C; 13.9 bar at 200°C; 12.1 bar at 250°C; 6.6 bar at 350°C
- End connections
- PN 40 flange (EN 1092-2); G thread (EN ISO 228-1); 1½ NPT threaded socket (ASME B1.20.1); Class 150 flange (ASME B16.5)
- Nominal size
- DN 40; G/NPT connection size 1½
- Maximum motive-steam pressure and differential pressure
- 6 bar or 13 bar, depending on the design
- Minimum motive-steam pressure
- 3 barg; motive-steam pressure must exceed the back pressure by 1 bar
- Maximum operating back pressure
- 3 bar (6 bar design); 5 bar (13 bar design)
- Orifice specification (PK version)
- Orifice 6: Kvs 3.5 m³/h, orifice diameter 11.0 mm; Orifice 13: Kvs 2.1 m³/h, orifice diameter 8.5 mm
- Motive-steam connection
- G1/2 female thread
- Vent connection
- G1/2 female thread
- Minimum filling head
- 0.5 m
- Inlet piping requirements
- Minimum length 2.5 m, DN 40; alternatively, use a 3 l buffer tank
- Body material
- EN 5.3103 / ASTM A 395
- Internal component material
- Stainless steel
- Overall length
- 230 mm (DIN/EN flange); 227 mm (G thread, NPT threaded socket, or Class 150 flange)
- Required maintenance clearance
- 200 mm
Application scenarios
Condensate discharge in steam systems with high back pressure or insufficient differential pressure
UNA25-PK provides continuous condensate discharge when sufficient differential pressure is available and uses motive steam for cyclic pumping when the differential pressure is insufficient. It is suitable for condensate discharge in steam systems with high return-line back pressure or insufficient differential pressure across the equipment. The motive-steam pressure must be at least 3 barg and must exceed the back pressure by 1 bar.
Condensate lifting and recovery in low-pressure or vacuum steam systems
UNA25-PS operates as a cyclic condensate lifting unit to lift or discharge condensate from a steam system to the condensate recovery system. It is suitable for applications where the equipment pressure is insufficient to overcome the return-line back pressure.
Installation & maintenance notes
Motive-steam and back-pressure conditions
The motive-steam pressure must be at least 3 barg and must exceed the operating back pressure by 1 bar. The design motive-steam pressure is 6 bar or 13 bar.
Motive-steam and vent connection
Both the motive-steam connection and the vent connection have G1/2 female threads. During installation, each connection must be connected to the corresponding line and securely sealed.
FAQ
How does the float-type steam trap in the UNA25 work?
In the UNA25, the rising float actuates a linkage that opens the steam inlet and closes the vent valve. The motive steam then forces the condensate out. Once the liquid level falls, the float drops and reseals the chamber, completing a cyclic drainage sequence that removes condensate from the steam system.
What is the main difference between the UNA25-PS and the UNA25-PK?
The UNA25-PS is a cyclic condensate lifter without a valve shutoff function, suitable for applications where the upstream pressure is lower than the back pressure. The UNA25-PK has a rolling-ball valve shutoff in pumping mode and provides continuous drainage when the differential pressure is sufficient, or operates as a modulating steam trap.
Can the UNA25 still discharge condensate at low steam pressure?
Yes. The UNA25 is designed to discharge condensate even when the steam pressure is too low for a conventional steam trap to drain effectively, ensuring continuous drainage of the system.
What are the key installation and piping requirements for the UNA25?
The unit must be connected as shown in the installation diagram, with a motive steam line and a vent line installed and connected. In addition, a minimum flooding head of 0.5 m is required between the heat exchanger condensate outlet and the bottom of the unit, together with an inlet line or buffer tank to ensure proper pumping.
What are the operating pressure and temperature limits of the UNA25?
The unit is available with EN 1092-2 PN 40 flanges and EN ISO 228-1 threaded end connections, each with the corresponding pressure/temperature limits. The exact values depend on the model (e.g., UNA25-PK/UNA25-PS) and the end connection, so the specifications of the actual model apply.