Detail Info Prerotation

			How Does Prerostal^® Work? The system involves arranging a Hidrostal screw centrifugal pump so that it draws its liquid from a specially designed prerotation basin via a custom designed bellmouth. It is the geometry of the sump formed by the basin and bellmouth working in conjunction with an open ended weir placed in front of the pump, which causes the flow entering the basin to rotate in a prescribed manner in the same direction as the pump. The rotational speed of the prerotating flow in the basin varies according to sump level and reaches a maximum at the lower levels. It is the variable rotational speed of the flow entering the pump which ensures the output varies to match sump inflow. As the level in the sump rises, due to increased flow, then the speed of prerotation decreases, and the pump progressively regains its maximum output. The sump geometry has smooth contours and large free passages which permits the pumping of liquids containing bulky solids and fibrous materials reliably and with minimum energy consumption.

			Simple and Reliable The self-regulating feature and simplicity of the PREROSTAL system keep both operation and maintenance costs low. The system uses standard pump starters and level controls. The whole system is based on familiar and easily maintainable technology which is a big bonus when compared to the alternative method of flow control using variable frequency drives which are very complicated and expensive to maintain, requiring the service of specialist engineers. Whereas any qualified mechanical / electrical engineer can attend to a PREROSTAL System.

			Hidrostal can offer a wide range of pumps from 80mm to 700mm branches with prerotation control. With multiple pump prerostal systems flow rates from 10 l/s to well in excess of 5,000 l/s can be achieved. The maximum pumping head depends to a certain extent on the size of pump selected. Generally Prerostal systems can be offered for heads as low as 2m. Typical schemes fall in the range of 4-10m, the maximum heads being in the region of 20m, which is well in excess of the upper limits of Archimedean screw pumps.

Applications

Prerostal-Systems can be used very flexible. The most installations are in:

Unscreened sewage
Activated sludge
Clarifier scum
Skimming of floatables
Oily water
Storm water
Impounding polluted water
Industrial effluents

The system can also be used, instead of expensive, conventional transportation quantity systems, like feed screws and pumps with speed control.

Clean Wet Wells

A primary benefit of the Prerostal system is its effectiveness as a skimming device.

Every time the PREROSTAL system goes into its prerotation mode, floables such as oil, hydrocarbons, floating sludges, grease, fats and bulky light solids are automatically drawn into the basin, where they are pumped to the downstream process and can be recovered if required to do so.

			Reduced Capital And Construction Cost The PREROSTAL system requires minimum sump size. Excavation depth and area requirements are less than the Archimedean screw and 'on-off' systems. Variable speed pumping systems have high initial capital and maintenance costs. Compared to pumps with variable speed drives or screw pump installations. PREROSTAL systems can offer savings of up to 40% on construction costs alone.


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Hidrostal AG - Gigering 27 CH-8213 Neunkirch - Tel +41(0)52 6870687 - Fax +41(0)52 6812084

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