ZK Control Valves with Radial Stage Nozzle9 For power-station and plant engineering

ZK Control Valves for Power-Station and Plant Engineering Overview For many years now, GESTRA control valves of the type ZK have given proof of their reliability under extreme operating conditions. Long experience and know-how form the sound basis for a generation of efficient and tight-closing control valves for applications in power stations. Thanks to the easy maintenance and repair of the valves as well as the extremely high wear resistance afforded by the design, reliable operation is achieved together with a long service life. 1 Heating steam valve b Main feedwater pump 2 Feedwater leak-off...

Control Valves with ZK Radial Stage Nozzle® High pressure Intermediate pressure Low pressure GESTRA products

Applications of the ZK Control Valves ZK control valves are suited for various fundamental applications in industry and power stations: w Leak-off control (recirculation) w Drainage and warm-up w Level control w Injection cooling w Steam control GESTRA offers: w Complete solutions w Subsystems with definite interfaces The ZK control valve consists of a valve body and the ZK RADIAL STAGE NOZZLE® with valve plug integrated into the body to act as the control unit. The ZK RADIAL STAGE NOZZLE® ensures a rapid and reliable adaptation to the prevailing operating conditions. If the operating conditions...

Control Valves with ZK Radial Stage Nozzle® With the aid of the ZK control valve, level control systems can be realized under difficult technical conditions. The GESTRA level control system consists of a control valve with ZK RADIAL STAGE NOZZLE®, an actuator, a level electrode and a control unit. GESTRA injection cooling systems are offered as complete systems consisting of an injection-cooling valve with radial stage nozzle, an actuator, a temperature acquisition system, and the control unit. Injection cooling valves have to cope with high differential pressures, whilst ensuring extreme wear...

Application Examples of the ZK Control Valves Leak-off valve ZK 213 with compact electro-hydraulic actuator Drain control station using ZK 29 valves with electri33 actuator Leak-off control consisting of: w ZK 213-E4/40 DN 200 with 6-stage nozzle and tandem seat w Hydraulic actuator with opening spring w Control cabinet with SIEMENS S7 PLC w GESTRA software with stored characteristic for leak-off valves H.P. preheater in a nuclear power station equipped with a condensate drain control valve type ZK 29 ZK 213 as spray injection valve in a high-pressure bypass station

Control Valves with ZK Radial Stage Nozzle® The ZK RADIAL STAGE NOZZLE® Automatic Control The flow through the radial stage nozzle is determined by the valve plug. Depending on its position, the individual stage nozzles are either partially or completely set free. The valve plug and the seat together form the shut-off unit of the radial stage nozzle. Due to the successive expansion in the flash chambers, the pressure differential across the cross-sectional flow area of the valve is reduced to a minimum. Various stage nozzles and valve plugs are available to account for the pressure drop in a...

The ZK RADIAL STAGE NOZZLE® Technical Properties ZK control valves are designed to meet the highest operational requirements. They offer a number of special features in comparison with conventional control valves. w Extreme wear resistance The successive expansion of the fluid in the throttling sleeves of the radial stage nozzle produces a considerable reduction in pressure drop across the cross-sectional flow area. Special design details at the seating surfaces ensure safe and reliable valve operation. In addition, the mass flow is split up into many partial flows. w Leakage rates FCI 70-2-2006,...

Control Valves with ZK Radial Stage Nozzle® Changing the valve characteristics using the ZK 29 as an example Position of the sleeves for linear characteristic Crosssectional flow area Valve lift [%] Position of the sleeves for equal-percentage characteristic Linear characteristic Equal-percentage characteristic

Control Valve ZK 29, Valve Plug in Open Position Option for special applications: Adjustable lift limitation in closing direction ZK 29: Valve plug in closed position Valve plug ZK 29: Valve plug no longer in closed position; control edge does not yet set free any orifices Control edge Sealing surface Seat ZK 29: Valve plug in control position ZK radial stage nozzle®

Control Valves with ZK Radial Stage Nozzle® Control Valve ZK 29 PN 160 and class 900 pmax 100 bar (1450 psi) k vs 0.7 – 130 m3 /h hence a large annular channel has been opened between the seat of the valve and the sealing surface of the plug, are the annular rings of the radial stage nozzle set free one after the other by the control edge. With its permissible differential pressure of 100 bar, the ZK 29 control valve covers a large range of k vs values. The valve plug and seat of a control valve are as a rule subjected to very high flow velocities during the opening and closing processes. To...

Control Valve ZK 313 with Tandem Shut-Off ZK 313: Valve plug in closed position Valve plug Disc springs Valve cone ZK radial stage nozzle® Secondary seat Main seat ZK 313: Valve plug no longer in closed position; valve cone still in closed position, control edge does not yet set free any orifices ZK 313: Valve plug in control position

Control Valves with ZK Radial Stage Nozzle® Control Valve ZK 313 PN 630 & Class 2500 pmax 40 bar k vs 20 – 46 m3 /h pmax 300 bar k vs 1 – 17 m3 /h pmax 370 bar k vs 4.5 – 9.5 m3 /h The control valve ZK 313 is also available as an ASME version as per ASME B 16.34. Due to the tandem shut-off, it combines the function of a conventional isolating valve and control valve, and offers long service lifetimes. The leakage rates are in accordance with the highest EN and FCI classifications. cone follows only after a certain lift. At the moment of closing and at the beginning of opening, the flow velocity...