Flowserve ZK 313 - Manual (Page 6)

6
Explanatory Notes
(continued)
Function
Every control valve is equipped with a ZK radial stage nozzle.
This is a system comprising several sleeves nesting within one another and containing radial
orifices drilled in them. By rotation of the sleeves, the orifices are shifted relative to one
another, thus forming a large number of throttling points in parallel, with turbulence chambers
(expansion chambers) in between.
The throughput through the ZK radial stage nozzle is set by means of the valve plug.
Depending on its position, this valve plug opens up the individual orifices partially or
completely, thus producing different flow rates.
As a result of this design, the pressure drop is reduced in steps and the medium flowing
through is split up into many partial flows. This ensures high resistance to wear and reduces
the noise level.
The control valve ZK 313 is also equipped with a dual (tandem) shut-off. At the moment of
closing and at the beginning of opening the flow velocity at the valve seat is zero, which
means that wire drawing and wear on the seating surfaces is prevented. The lift difference
between the control piston and the leading valve plug is balanced out by disc springs.
The closing process of the control valve ZK 313 with radial stage nozzle:
Valve plug in control position Valve plug interrupts flowrate Main valve plug in closed
position