Bearing housing. Bearing housing. Large bearing housing with adequate cooling capacity, even without external cooling system. Both bearing sides are lubricated with oil. In the event of high pump loads, the lubricating oil can be cooled using an additional heat exchanger.
External bearings. External bearings. The external, application-optimized bearing concept ensures a long lifetime.
Bearing spacing. Bearing spacing. Bearings are spaced much closer together and screws are reinforced, thereby increasing the differential pressure capacity.
Integrated housing heater. Integrated housing heater. Innovative heating jacket designed for optimal heat transfer for high viscosity media.
Optional integrated circulation valve. Optional integrated circulation valve. A spring-loaded overflow valve integrated in the housing protects the pump’s differential pressure and prevents pumped liquid from entering the housing.
Pump housing. Pump housing. The unique delta design reduces internal flow losses and facilitates optimal suction performance. High viscosity media and brief phases with high gas content are no problem.
Variable screws. Variable screws. Optimized for fatigue strength. Application-specific protection against wear is also possible. Screws can be inserted as one-piece or multi-piece components.
Mechanical seals. Mechanical seals. Single- and double-acting mechanical seals depending on design and application. Can also be used with leakage monitoring and supply systems (API plans).
Optional leckage monitoring of mechanical seals. Optional leckage monitoring of mechanical seals. Leakage is conducted via a drain to a monitored reservoir.
Oil level check. Oil level check. Long intervals between oil changes and low service costs, thanks to external monitoring and replenishment of hermetically sealed oil chamber.
Precision gears. Precision gears. Hardened and tempered precision gears can be positioned exactly for reduced backlash and increased efficiency.

KRAL Z Series Screw Pumps.

The screw pump for demanding liquids.

Proven KRAL pump quality suitable even for aggressive and contaminated media.
In the new Z series, KRAL applies its expertise in pump design and technology to two screw pumps. As a result, the KRAL Z series is capable of delivering aggressive, low- or non-lubricating, and contaminated media with the reliability and quality that KRAL products are valued for by customers worldwide.


Operation, materials, components.

  • Delivery rate: 330 to 17,660 l/min or 20 to 1.060 m³/h.
  • Max. differential pressure: 25 bar.
  • Temperature range in the pumped media: -40 °C to +300 °C.
  • Housing: Ductile iron or welded steel.
  • Screws: Solid or engineered.
  • Approvals: ABS, BV, DNV-GL, LRS, RINA, others on request.
  • ATEX: Device Group II, Device Category 2.
  • Heating: Electrical, media or steam.
  • API: Manufacturing according to API 676 possible.

How it works.

The KRAL Z series pumps are positive displacement pumps that draw the liquid through the suction connection and continually feed it in two partial streams to the two screws. As a result, the pump is pressure-equalized axially. The pressure builds up linearly along the length of the screw. The housing design ensures that the gap between the screws and the housing remains sealed. This ensures that the pump can be primed very effectively, even when the suction line is empty.


Customized solution.

The KRAL Z series can be implemented as a customized solution for any required application. For example, depending on the application, the screws can be designed solid or engineered. This results in substantial benefits for important aspects such as fatigue strength, media resistance, maintenance costs, and costs over the life-cycle of the pump. 


Maximum flexibility by unlimited options for connection arrangements.

Pumps are often built into existing systems, where predetermined installation conditions can easily become a problem. The KRAL Z series offers the solution with a unique innovation for screw pumps. The connections can be flexibly arranged both horizontally and vertically. The installation options are therefore unlimited.

Both installation variations are designed with external bearings so that the bearings don’t come into contact with the liquid. This significantly increases their lifetime. The mechanical seals are located on the suction side of the pump flow and are cooled and lubricated by the pumped liquid. Both single- and double-acting mechanical seals can be used in combination with an extremely broad range of seal supply systems. Different materials can be used in the design, depending on the pumped liquid.


Your advantages.

  • Very broad range of applications.
  • Flexible connection arrangement.
  • Excellent suction characteristics.
  • Low-pulsation delivery.
  • Adjustable screw design.
  • Little space required.
  • Dry running protection.
  • Support for different delivery heights without booster pump.
  • Optional delivery direction can be changed easily for a short time.
  • No need for a separate stripping system with control unit.
  • Technical data.
    Technical data 3000 5000 11000
    Q l/min 4,500 8,160 17,660
    Max. discharge pressure at 50°C bar 16 25 25
    Temperature max. pumped liquid °C      
    Horizontal installation ZBH   120    
    Vertical installation ZBV   80    
    Horizontal installation ZEH     120 120
    Horizontal installation ZTH     300 300
    Vertical installation ZEV     80 80
    Viscosity mm²/s      
    min.   0.7 0.7 0.7
    max.   100,000 100,000 100,000
  • Models.
    Horizontal installation.

    Horizontal installation makes the pump very easy to service without separating the pump from the pipe system. This installation has a positive effect on thermal performance.

    All the connections can be arranged horizontally (inline) and at several angles.

    Examples of connection arrangements for horizontal installation.

    The diagrams only show a few examples of connection arrangements. The design possibilities are extremely variable. All the connections can be arranged horizontally (inline) and at several angles.

    Vertical installation.

    The benefit of this design is its very compact layout, which makes it ideal for systems with limited space. It is installed via a pedestal, and the motor is mounted over the pump with a motor support.

    All the connections can be arranged vertically (inline) and at several angles.

    Examples of connection arrangements for vertical installation.

    The diagrams only show a few examples of connection arrangements. The design possibilities are extremely variable. All the connections can be arranged vertically (inline) and at several angles.

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