Large-Diameter Butterfly Valve Retrofit for a District Heating Network in North China
Project Overview
The project replaced large-diameter butterfly valves and ball valves on the primary network (main lines DN800–DN1400) of a city district heating system in northern China, solving internal leakage and excessive operating torque.
Challenge
The district heating network's "fix in summer for winter" window is only 2 months; the primary network has high flow and supply temperatures above 110 °C. Internal leakage in the original resilient-seated butterfly valves caused hydraulic imbalance and high makeup water, and operating torque was high with no space for extended stems on site, making manual operation difficult.
Our Solution
Triple-offset metal-seated butterfly valves (high-temperature resistant, metal-to-metal sealing, hardfacing on sealing faces) replaced the resilient-seated valves, with worm gearboxes to reduce operating torque. Valves were prefabricated to each section's pipe size and pressure-tested individually, and installed section by section during night heating shutdowns to minimize the heating interruption.
Results
All valves were replaced within the 2-month window. After the heating season started, primary network hydraulics improved noticeably, makeup water and pump power consumption fell, and heating complaints decreased. The heating company added triple-offset metal-seated butterfly valves to its recommended valve types for future retrofits.