A sluice (// SLOOS) is a water channel controlled at its head by a gate. A mill race, leet, flume, penstock or lade is a sluice channelling water toward a water mill. The terms sluice, sluice gate, knife gate, and slide gate are used interchangeably in the water and wastewater control industry.
A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway. Sluice gates commonly control water levels and flow rates in rivers and canals. They are also used in wastewater treatment plants and to recover minerals in mining operations, and in watermills.
"Sluice gate" refers to a movable gate allowing water to flow under it. When a sluice is lowered, water may spill over the top, in which case the gate operates as a weir. Usually, a mechanism drives the sluice up or down. This may be a simple, hand-operated, chain pulled/lowered, worm drive or rack-and-pinion drive, or it may be electrically or hydraulically powered.
Types of sluice gates
- Flap sluice gate
- A fully automatic type, controlled by the pressure head across it; operation is similar to that of a check valve. It is a gate hinged at the top. When pressure is from one side, the gate is kept closed; a pressure from the other side opens the sluice when a threshold pressure is surpassed.
- Vertical rising sluice gate
- A plate sliding in the vertical direction, which may be controlled by machinery.
- Radial sluice gate
- A structure, where a small part of a cylindrical surface serves as the gate, supported by radial constructions going through the cylinder's radius. On occasion, a counterweight is provided.
- Rising sector sluice gate
- Also a part of a cylindrical surface, which rests at the bottom of the channel and rises by rotating around its centre.
- Needle sluice
- A sluice formed by a number of thin needles held against a solid frame through water pressure as in a needle dam.
- Fan gate
- (Dutch: waaier sluis) This type of gate was invented by the Dutch hydraulic engineer Jan Blanken in 1808. He was Inspector-General for Waterstaat (Water resource management) of the Kingdom of Holland at the time. The Fan door has the special property that it can open in the direction of high water solely using water pressure. This gate type was primarily used to purposely inundate certain regions, for instance in the case of the Hollandic Water Line. Nowadays this type of gate can still be found in a few places, for example in Gouda. A fan gate has a separate chamber that can be filled with water and is separated on the high-water-level side of the sluice by a large door. When a tube connecting the separate chamber with the high-water-level side of the sluice is opened, the water level, and with that the water pressure in this chamber, will rise to the same level as that on the high-water-level side. As there is no height difference across the larger gate, it exerts no force. However the smaller gate has a higher level on the upstream side, which exerts a force to close the gate. When the tube to the low water side is opened the water level in the chamber will fall. Due to the difference in the surface areas of the doors there will be a net force closing the gate.
In the mountains of the United States, sluices transported logs from steep hillsides to downslope sawmill ponds or yarding areas. Nineteenth-century logging was traditionally a winter activity for men who spent summers working on farms. Where there were freezing nights, water might be applied to logging sluices every night so a fresh coating of slippery ice would reduce friction of logs placed in the sluice the following morning.
Placer mining applications
Sluice boxes are often used in the recovery of black sands, gold, and other minerals from placer deposits during placer mining operations. They may be small-scale, as used in prospecting, or much larger, as in commercial operations, where the material is first screened using a trommel or screening plant. Typical sluices have transverse riffles over a carpet, which trap the heavy minerals, gemstones, and other valuable minerals. The result is a concentrate.
Types of material used for sluice gates
- Traditionally wood was the material of choice for sluice gates.
- Cast iron
- Cast iron has been popular when constructing sluice gates for years. This material is great at keeping the strength needed when dealing with powerful water levels.
- Stainless steel
- In most cases, stainless steel is lighter than the older cast iron material.
- Fibre-reinforced plastic (FRP)
- In modern times, newer materials such as fibre-reinforced plastic are being used to build sluices. These modern technologies have many of the attributes of the older materials, while introducing advantages such as corrosion resistance and much lighter weights.
Regional names for sluice gates
Sinhala people in Sri Lanka who had an ancient civilization based on harvested rain water, refer to sluices as Horovuwa.
- Gatehouse (waterworks) – An (elaborate) structure to house a sluice gate
- Zijlstra – A Dutch name referring to one who lives near a sluice
- Control lock
- Blanken J. Jz. (1808). Nieuw ontwerp tot het bouwen van minkostbare sluizen, welke alle de vereischten der bekende sluizen bezitten, en daarenboven de steeds ontbrekende, meer uitgebreide nuttigheden van dezelve vervullen kunnen (in Dutch).; Goudriaan, Adrianus Franciscus (1809). Verhandeling over het ontwerp van sluizen, volgens de uitgave van den heer inspecteur generaal bij den waterstaat van het Koningrijk Holland , J. Blanken Jansz., het eerste aan de Benschopper Sluis beproefd: opgesteld ter aanleiding tot eene naauwkeurige overweginge van hetzelve, in vergelijking met zijnen over dit onderwerp gedrukten brief, en het antwoord door eerstgenoemden daar op uitgegeven (in Dutch). Amsterdam: Van Esveldt-Holtrop.
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