Water Distribution Valves
The Parabolic disk has been used in Balancing and flow regulating valves since the very first designs of Lock Shield Valves in the one pipe systems. The first parabolic disk in the UK was installed in a Globe valve installed in the return. A second Globe valve with a flat disk was installed in the flow with test points either side of the Disk. The two test points were used to measure the pressure drop across a known seat diameter. This was known in the UK as two valve commissioning, as one valve was used to measure the flow and the other valve in the return was used to regulate the flow.
In Europe, particularly Sweden, a Globe valve with a parabolic disk and test points was used to regulate and also measure the flow. The moving parabolic disk meant that area through the valve was continually changing, so a scale to determine the valve position was required to allow the flow to be calculated. This method was not as accurate and more difficult to use than the fixed orifice method.
The design of a Double regulating valve can take many different styles depending on what and where it is trying to regulate. Typically most DRV valves are Y pattern globe valve arranged in this way to present the smallest pressure loss to the system when fully open. However characterised Ball valves can be used. The DRV feature is included in manifolds and Radiator valves.
Adjustment of this valve will add resistance to the system and hence reduce the flow. The description DOUBLE regulating means that it has a feature whereby you can set the position that the valve is to operate at in such a way that you can still close the valve for maintenance purposes
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