Gravity Circulation Non-Return Check Valves | Gestra

GESTRA SBO – Check Valve for Gravity Circulation Control

The GESTRA SBO 11, SBO 21, and SBO 31 are spring-loaded check valves designed for installation in heating and domestic hot water circulation systems. Their primary function is to prevent unwanted gravity circulation when the pump is off, thereby avoiding undesired thermal flows within the piping network.

Types and Connections

• SBO 11: Inlet with union end for pump connection, outlet with female thread.
• SBO 21: Inlet with union end for pump connection, outlet with male thread.
• SBO 31: Female-threaded inlet for direct pump connection, male-threaded outlet.

Technical Data

• Nominal pressure: PN 6
• Sizes: DN ¾", 1", 1¼" (varies by type)
• Operating pressure: 6 bar
• Max. operating temperature: 130°C (cone must not be under pressure at this temperature)
• Body material: forged brass CW614N
• Cone: plastic PPO
• Spring: stainless steel 1.4310
• Seat seal: EPDM (SBO 11 / SBO 21)

Media Limitations

Suitable for heating water, domestic hot water, and Group 2 fluids per PED. Not suitable for glycol-based circuits, as PPO cone is not resistant to glycol.

Installation and Operation

Valve opens via pump differential pressure and closes when the closing force exceeds the opening force. With spring, installation is possible in any orientation; without spring, vertical installation with upward flow is required.

FAQ

Actuator available? No. Operation is mechanical, via differential pressure and spring force.
Steam application? Not intended for steam. Designed for heating and hot water circuits.
Why select SBO over standard check valves? To prevent gravity circulation in pump circuits and to allow pump replacement without full system drainage, when installed in suitable configurations.