The Gestra BW31 return temperature control valve is an automatic temperature control valve designed for hot-water service. It features a steel valve body (EN 1.0460) and a stainless-steel regulator. The Thermovit temperature regulator and spring pressure control the flow. The valve supports EN/ASME flanged or threaded connections, with nominal sizes up to DN15–DN40. An optional external adjustment device enables the shut-off temperature to be adjusted during operation without removing the valve cover. Installed in hot-water return lines, it is suitable for hot-water return temperature control, flow regulation, and hot-water process temperature control applications requiring temperature setpoint adjustment during operation.
Gestra BW31 return temperature control valve product image
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BW31 Return Temperature Control Valve | Gestra
Hot water return temperature control valve combining a Thermovit regulator with spring force for flow control, with an optional external actuator for setpoint adjustment during operation.
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Specifications
- Medium
- Hot water
- Nominal size
- DN15, DN20, DN25, DN40
- Pressure rating
- DN15–DN25: PN40; DN40: PN25; ASME Class 150
- Maximum permissible differential pressure
- 6 bar (DN15, DN20, DN25)
- Shut-off temperature range
- Without external adjustment device: DN15 20–130 °C, DN20/DN25 20–115 °C, DN40 20–110 °C; with external adjustment device: DN15 60–130 °C, DN20/DN25 40–115 °C, DN40 50–110 °C; with special external adjustment device: DN15 20–110 °C, DN20/DN25 20–90 °C, DN40 20–75 °C
- Shut-off temperature setting
- Without an external adjustment device, fixed shut-off temperature settings are available in 5 °C increments
- Control method
- Thermovit temperature regulator with spring pressure control; flow increases as temperature decreases and decreases as temperature increases
- Minimum flow characteristic
- The flow opening remains slightly open at all times to maintain a bleed flow
- Connection types
- EN 1092-1 B1 flanges, ASME B16.5 Class 150 RF flanges, G-threaded female connections (ISO 228-1), NPT-threaded female connections (ASME B16.11)
- Valve body material
- Steel, EN 1.0460 (ASTM SA 105)
- Regulator material
- Stainless steel
- External adjustment device
- Optional; enables shut-off temperature adjustment during operation without removing the valve cover
- Installation position
- Installed in the return line; horizontal installation is recommended, with the valve cover facing upward or downward
Application scenarios
Hot-water return temperature control and flow regulation
Installed in a hot-water return line, the valve uses the Thermovit temperature regulator and spring pressure control to automatically regulate flow according to the return temperature. Flow increases as the temperature decreases and decreases as the temperature increases, maintaining the specified shut-off temperature.
Hot-water process temperature control with an adjustable shut-off temperature during operation
An external adjustment device can be selected for return control in hot-water process piping. It enables the shut-off temperature to be adjusted during operation without removing the valve cover, making it suitable for applications requiring on-site temperature setpoint adjustment.
Installation & maintenance notes
External adjustment device configuration
When equipped with an external adjustment device, the shut-off temperature can be adjusted during operation without removing the valve cover.
FAQ
How does the Gestra BW31 return temperature control valve automatically regulate flow according to the return temperature?
The BW31 uses a Thermovit temperature regulator in conjunction with spring pressure to control the opening of the flow passage. When the return temperature decreases, the flow passage opens further and the return flow increases. When the return temperature increases, the regulator closes the flow passage further and reduces the flow rate. When the return temperature reaches the shut-off temperature, the valve retains a slightly open flow passage to maintain a bleed flow, keeping the Thermovit regulator immersed in the medium and allowing it to respond directly to temperature changes.
What media and piping locations are suitable for the BW31?
The BW31 is suitable for hot-water service and is installed in hot-water return lines to control return temperature and regulate flow. During installation, follow the flow-direction arrow on the valve nameplate. The valve can be installed in various orientations; however, horizontal piping installation is recommended, with the valve cover facing upward or downward.
How should the Gestra BW31 be selected according to pipe size and temperature setting range?
The BW31 is available in DN15, DN20, DN25, and DN40 sizes. Without an external adjustment device, the shut-off temperature range is 20–130 °C for DN15, 20–115 °C for DN20 and DN25, and 20–110 °C for DN40. Fixed shut-off temperatures can be set in 5 °C increments. If shut-off temperature adjustment is required during operation, an external adjustment device or special external adjustment device can be selected; however, the available adjustable temperature range varies by pipe size.
What connection types and pressure ratings are available for the BW31?
The BW31 is available with EN 1092-1 B1 flanges, ASME B16.5 Class 150 RF flanges, G-threaded female connections, and NPT-threaded female connections. The EN flange pressure rating is PN40 for DN15, DN20, and DN25, and PN25 for DN40. ASME Class 150 flange connections are available for all sizes. The maximum permissible differential pressure for DN15, DN20, and DN25 is 6 bar.
What is the function of the BW31 external adjustment device, and is additional installation space required?
The BW31 can be equipped with an optional external adjustment device to adjust the shut-off temperature during valve operation without removing the valve cover. With the external adjustment device installed, the valve height increases from 128 mm to 170 mm for DN15 to DN25, and from 188 mm to 230 mm for DN40. Devices adjusted with the corresponding socket wrench also require an additional 100 mm of operating clearance.