8.3 Gates，Trash Rack and Hoisting Device for Power...
8.3.1 Quick shutoff gates shall be installed if the units or pressure water pipeline require protection by gates in case of emergency.If the quick shutoff gate is not provided with maintenance condition，a bulkhead gate shall be installed in front of the quick shutoff gate.
For the diversion type hydropower station with a long headrace，the emergency gate should be installed at the headrace intake.
For siphon-type intakes，air suction valves shall be installed at the top of the siphon pipe.
8.3.2 The closing time of quick shutoff gates shall meet the requirements for protecting units or penstocks，and the closing velocity should not be greater than 5m/min if the gate is closing to sill.
The hoist for quick shutoff gates shall be operable both on site and remotely，and be equipped with an opening indicating device.The quick shutoff circuit of the hoist shall be provided with reliable control power source.
8.3.3 For bulkhead gates at the intake of at-dam-toe hydropower station or hydropower station in river channel，one gate may be installed for hydropower stations with no more than four units，more gates may be installed if there are more than four units.The hoisting equipment should be mobile.If the layout of project permits，hoist may be used for both the above-mentioned gates and for the bulkhead gates of the water release system.(https://www.daowen.com)
8.3.4 Measures of preventing surges shall be taken for surge chamber gates.
8.3.5 The tailrace bulkhead gates should be plain sliding or stop log type gates，and the number of the gates shall be defined after techno-economic comparison of orifice number，installation，debugging and construction conditions of units，etc.If there are no more than four units，one or two tailrace bulkhead gates may be installed.The hoisting equipment should be mobile.
8.3.6 Trash racks shall be installed at the intake.The layout and type selection of trash racks and trash cleaning facility shall be defined according to the characteristics and volume of trash in the river and the requirements for trash cleaning.Trash cleaning platform and trash removing facility should be set up for the trash racks.In the design of the trash racks，measures shall be taken to minimize the loss of water head passing through the racks.
8.3.7 The design of trash racks shall meet the requirements for structural strength and stability，and its load shall be defined based on the types and quantity of debris and trash cleaning measures to be taken，while a 2m-4m water level difference should be adopted in the design.
8.3.8 Differential pressure measuring instruments and alarm devices should be installed at the intake of the hydropower station to monitor the difference of water levels in front of and at the rear of trash racks.
8.3.9 The trash racks should be of mobile type，and mechanical equipment shall be installed to hoist the trash racks.If the trash rack is of inclined type，the inclination angle shall be consistent with the layout of hydraulic structures.
