Flowserve ZK 313 ASME User Manual
Page 7
7
Explanatory Notes
– continued –
Function
All pressure parts of the ZK 313 are forged. Internals (incl. seat) are easily exchangeable, even after a
long period of use. The radial stage nozzle
®
ZK combines the function of a control valve with a
conventional shut-off valve and guarantees maximum wear protection and absolutely tight shut-off.
The radial stage nozzle
®
ZK consists of several sleeves nesting within one another, containing radial
orifices drilled in them. 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, where poten-
tial energy in the form of pressure is converted into kinetic energy in the form of flow. Due to the
successive expansion in the flash chambers the pressure drop at the seat of the valve plug is
considerably reduced.
The flowrate through the radial stage nozzle is determined by the valve plug. According to its position
the individual stage nozzles are either partially or completely set free, thus producing different
flowrates. The valve plug and the seat form the shut-off unit of the radial stage nozzle.
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.
Depending on the pressure drop to be coped with different stage nozzles and valve plugs are available.
Due to the special design of the radial stage nozzle
®
ZK the noise level is reduced to a minimum. As a
result of the expansion through a multitude of individual nozzles, the noise emitted by the control valve
is below 85 dB (A) within the control range of the valve.
The valve body is available as straight-through or angle version, sizes 1" to 3". The valve can be easily
fitted with a pneumatic actuator. Leak rates in accordance with EN 12266-1. Tightness better than
ANSI Class V.
Design
ZK 313 ASME-D/20:
Straight-through valve with butt-weld ends. Fig. 6
ZK 313 ASME-E/20:
Angle valve with butt-weld ends. Fig. 7