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About flow regulators

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Operation of Vortex flow regulators



Mosbaek's range of flow regulators are designed such that they cover almost complete any perceivable control need. The head-discharge curves are considerably steeper than those of e.g. throttle pipes or gates.


This is how the cyclone flow regulator functions:


When the normal, small flow - the dry weather flow - passes in the sewage pipe, the water surface is  below the top of the controller inlet opening, and there is virtually no resistance to the flow (figure 1).


When it starts raining the feed flow increases - the water level in front of the regulator increases - and when the water surface is above the top of the regulators inlet opening, but is still below the top of the controller vortex chamber - air is trapped inside the vortex chamber, and the flow cross section is reduced.  This increased resistance limits the flow through the regulator (figure 2).


When the water surface in front of the flow regulator rises to above the top of the vortex chamber, the head will make the water in the regulator rotate.  The entrapped air forms a core in the cyclone flow regulator and the flow cross section is heavily reduced at the outlet.  The result is a considerable pressure loss, as intended (figure 3).


After the rain has stopped the feed flow decreases.  The water level in the structure eventually falls below the top of the  vortex chamber and due to the dropping pressure the vortex collapses.  Air is drawn into the vortex chamber - with some delay  - hence the hysteresis in the head-discharge curve, figure 4.


The collapse of the vortex produces a sudden increase in the flow through the regulator whereby any deposited sediment in the upstream pipe system will be flushed out.  See the characteristic 'bump' on the head-discharge curve, figure 5.

Other flow regulators


The description above dealt with the cyclone flow regulators.  There is however another design in Mosbaek's product range which functions in a similar way, but it is used for smaller flows than the cyclone flow regulator, namely the centrifugal flow regulator. 




Fig. 5: Application chart

At small flows the passageway of a cyclone flow regulator may become so small that there may be a risk of blockages.  Therefore, centrifugal flow regulators are recommended for smaller flows.

There are two  main types of Mosbaek's centrifugal flow regulators:


  • horizontal (CEH) which is used for combined sewage
  • vertical (CEV) which is used for storm water.


The double orifice plate (DB) is another

design in the Mosbaek product range. They are used for larger and large flows.  In those situations, the required vortex flow regulator, would simply be too large. The double orifice plate in general takes up only little space.


The plates of the double orifice plate yield resistance to the flow by blocking off part of the passageway.  At higher water levels the flow pattern changes and the water mainly enters the regulator from above.  This increases the resistance.


The diagram in figure 5 shows the application ranges for the various regulator types.


Example with a flow regulator at the outlet from a detention basin

As illustrated in fig. 7 the housing structure consists of two chambers.  A by-pass weir is mounted on top of the separating wall.  I.e. at large water levels in the inlet chamber, part of the water by-passes over the wall.

Those amounts of water which are initially discharged by the detention basin typically cause the most severe damages downstream.  The flow regulator creates the necessary delay.


Fig. 6: Mosbaek's flow regulators


Pricipitation  :

         Rain, sleet, snow and havel

Upstream      :

         Against the flow 

Downstream  :

         With the flow



Fig. 7: Outlet from detention basin

Mosbaek North America, Inc. 3525 Piedmont Road 7 Piedmont Center Atlanta GA 30305 E-mail info@mosbaek.com