Revising the City of Houston’s Standard Butterfly Valve Detail for Large Diameter Butterfly Valves

Approximately 16 mi of 108-in. diameter water transmission main is being constructed across northeast Houston to supply various regional water authorities to meet their projected 2060 water supply demands. Historically, the city of Houston has installed butterfly valves for isolation in large diameter water transmission mains. Typically, the City of Houston requires the butterfly valve to be connected to the pipe via flange and bolts and the assembly supported with bank run sand embedment. Butterfly valves have been a constant maintenance concern for the City’s operations department for a variety of reasons. Recent studies have indicated butterfly valves cannot be fully closed if the adjoining pipe is deflected over 1% of the diameter. The city allows a maximum deflection of 3% which can be problematic for a butterfly valve. Therefore, special design considerations were implemented for the proposed 108-in. pipeline project. The adjoining pipe was designed to ensure the pipe and soil loading would not negatively affect the integrity of the valve. Pipe wrappers and saddle supports were designed to keep the pipe from deflecting. The steel wrappers not only provided stiffness to the pipe, but also assisted with supporting the pipe over the concrete saddles. The load is then transmitted to the concrete foundation. Many factors were considered in the design of the support including soil loads, valve weight, water weight, and associated pipe loads. A flowable fill material is proposed as the embedment material to proper support for the pipe and valve. Future maintenance was also considered in the design of the valve. The seat was designed to be mechanically retained to allow for the seat to be field repaired in place rather than remove the valve entirely. A vault was designed to allow for future access of the worm gear actuator and packing. The concrete foundation extended under the pipe saddles and the actuator vault to avoid differential settlement issues. Six butterfly valves have been installed according to the revised detail and are operating as designed.