Differential Pressure Bypass Valve

Differential Pressure Bypass Valve is a self-operated hydraulic control component specially developed for central heating, chilled water air conditioning and building circulating water systems. It maintains a constant pressure difference across water supply and return pipelines by automatically opening and closing the bypass channel, solving core system troubles such as pump overload, pipeline noise, overpressure and unbalanced flow when terminal fan coils or radiators are partially closed. This valve requires no external power supply, electric controller or manual adjustment during daily operation, relying purely on pressure signals from supply and return pipes to drive automatic bypass regulation, making it an essential balancing accessory for stable operation of HVAC circulation systems.

The whole assembly consists of a main valve body, double pressure sensing tubes, built-in diaphragm actuator and adjustable spring assembly. The valve body is cast from high-strength ductile iron with full internal and external epoxy coating for rust and corrosion resistance. The soft sealing disc lined with EPDM rubber achieves tight shutoff with zero leakage when the pressure difference stays within the preset range. Two pressure sampling ports connect separately to the supply pipe and return pipe, transmitting real-time pressure values to the upper and lower sides of the diaphragm. The internal precision spring determines the fixed differential pressure threshold; users can simply rotate the top adjusting bolt to set the target pressure difference according to system design requirements before commissioning.

Its automatic balancing working principle operates entirely through fluid pressure difference. When most terminal valves in the building are shut down, circulation flow reduces sharply, and the pressure gap between supply and return pipelines rises above the set value. The pressure difference pushes the diaphragm to overcome spring resistance and open the bypass passage. Excess circulating water flows directly from the supply side back to the return side through the valve, releasing redundant pipeline pressure and avoiding excessive pump head, violent water flow vibration and harsh pipeline knocking noise. When more terminal heating or cooling equipment is opened, system flow increases and differential pressure drops below the preset value. The spring resets the valve disc to gradually close the bypass channel, ensuring sufficient water flow to all terminals and preventing insufficient heating or cooling effect.

Compared with manual balance valves and motorized bypass valves, this self-operated differential pressure bypass valve has prominent practical advantages. Without electrical wiring and automatic control modules, it eliminates electrical fault risks in humid pump rooms and reduces construction wiring costs. The response speed is sensitive and continuous; it adjusts bypass opening in real time with flow changes to keep pipeline differential pressure stable all day long. The streamlined internal flow channel brings low flow resistance, which will not cause extra energy consumption to the circulating water pump. The compact vertical installation structure occupies minimal space in narrow equipment rooms, and all wearing parts including diaphragm, spring and sealing rubber can be replaced on-site without pipeline cutting, greatly shortening maintenance time.

Standard specifications cover DN40 to DN300 with nominal pressure PN10 and PN16, suitable for medium temperature from 5°C to 95°C of hot heating water and 5°C to 60°C air conditioning chilled water. It complies with HVAC system design standards and is widely applied in residential central heating stations, commercial shopping mall air conditioning pump rooms, office building circulating water systems, hotel heating and cooling pipe networks, and industrial workshop constant temperature circulation equipment. By stabilizing pipeline differential pressure, protecting circulating pumps and eliminating pipeline noise, the differential pressure bypass valve optimizes system operation efficiency, cuts pump energy consumption, and extends the service life of pumps, pipe fittings and terminal heat exchange equipment, realizing long-term stable and energy-saving operation of heating and air conditioning water systems.