Inflatable rubber dam

A simple and inexpensive way for construction of a weir at smaller watercourses is the inflatable weir. By using a water-filled or air hose to impede water flow and the setting of the storage level, accounting for an elaborate design of the foundation as well as numerous, expensive mechanical parts as they are required by other military types. Rubber dams are particularly suitable for use in small and medium-sized rivers and are increasingly used for the replacement of old equipment for water level regulation.

Technology

In a concrete foundation on the river bottom and the side walls, a flexible tube is attached, which is filled with water, air or a heterogeneous mixture of both media. By filling the tube and the resulting increase in volume will lift the tube top and impedes the flow of water. Thus, the level of the upper water increases. The tube material mainly consists of an elastomeric membrane with inserted fabric (such as polyester or polyamide) for stabilization. The attachment of the elastomeric membrane at the weir box is made by clamping rails which can be located both inside and outside the tube depending on the manufacturer. In the unfilled state, the hose collapses and lies almost flat on the weir body from. This can be largely avoided damage to the military in the event of a flood. Venting valves, vent lines and possibly the use of pumps, ensures that can be completely emptied and folded at each environmental condition of the hose.

Rubber dams are used to water widths ( jam widths ) of several hundred and storage heights up to ten meters (eg in Ramspol ) become successful. In addition, the technology is used for the storage of dams to increase as well as an emergency device for flood protection.

The advantage of inflatable dams compared with conventional height-adjustable weirs is the relatively simple manner of construction and the low maintenance. This is due to the fact that a rubber dam without complex drive technology (eg hydraulic cylinder or chain drives ) and storage manages. A complex foundation for the sinking of the weir is not necessary.

Regulation of the water level

The water level above the weir can be adjusted by filling or emptying of the tube. In this case, the pressure inside the hose with water- filled weirs by approximately 20 to 60 percent higher than the pressure altitude of the upper water level. For water- filled weirs setting the desired pressure is usually done by a control shaft that is filled by a pump with water. The control shaft is hydraulically connected with the tube interior. As an effect of the water column of the control shaft thus results of the internal pressure in the inflatable weir. With air-filled dams, the internal pressure is built up via a compressor and regulated.

Filling medium

In addition to the application, a distinction Rubber dams with respect to their filling medium. The following are some specific characteristics of each medium are listed.

Water

  • Elliptical tube shape due to heavy weight of the filling. This results in a increased material consumption for achieving a certain storage level, as compared with the filling medium air.
  • High inertia of the filled tube, thus less tendency to vibrate
  • Low compressibility of the filling medium, thereby increased dimensional stability of the hose and uniform flow over
  • Possible damage by freezing at temperatures below the freezing point. This risk can be counteracted by a continuous flowing over the weir as well as a circulation and possibly heating of the filling medium.
  • More complex construction of the foundation, caused by control shaft
  • Risk of contamination of the filling line

Air

  • Similar circular tube shape due to the low weight of the filling. This results in less material required to achieve a given storage level, compared with the filling medium of water. This leads to a reduction of material costs.
  • Increased susceptibility to vibration
  • From the compressibility of the filling medium resulting deformation of the hose with changes in the input and overflow, to the buckling of the weir.
  • Maintenance of the weir through the commission of the hose possible.
  • Less filling and emptying times

Air-water

  • With the use of air and water within a tube weir results in the advantages and disadvantages of both media.

History

A first water-filled rubber dam was built in the mid -fifties in the USA. As the inventor of the technology is working with the Los Angeles Department of Water and Power engineer Norman Imbertson.

Examples

Bellows weir at Ramspol

Swell

  • DIN 4048-2, Publication date: 1994-07, Hydraulic Engineering; terms; Part 2: Water turbines.
  • Photo gallery and models - Water and Shipping Administration of the Federal
  • Michael Gebhardt; State of the hose Defense Technology Applications and operating experience; Newsletter of the Federal Waterways No. 91 (2007 ) (PDF, 2.3 MB)
  • Floecksmühle Energy Technology
  • Michael Gebhardt; Hydraulic and structural design of inflatable dams; University Press of Karlsruhe ( 2006)
  • Weir Type ( Hydraulic )
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