Proceedings

Hydraulic drop structures are used to manage the risks involved in flow elevation changes in sewers and flood relief schemes. If not controlled correctly, erosion, cavitation, vibration, pressurisation and hydraulic shocks can occur. The paper presents a unique drop shaft design (Hydro-Brake® Drop) which utilises a quasi-syphonic behaviour that is self-activating, non-powered and non-mechanical operation. The syphonic operation offers many hydraulic and pneumatic, as well as footprint, cost and safety advantages over traditional designs.

Although this quasi-syphonic design is less well known than traditional drop-shafts, there are now around 100 installations globally, some of which have been operating for nearly 60 years.

The paper presents a summary of the design and operation of the Hydro-Brake® Drop system to illustrate the advantages and limitations of the system. The design and operation are validated against recent full-scale testing that was performed at the Scottish Water Horizons Bo’ness test facility. Case studies are also presented to illustrate the range of flow, drops and scenarios for which these systems have been used.