April 2005
Modular centrifugal immersion pumps –
for the transfer and circulation of liquids

When pumping from sumps and tanks centrifugal immersion pumps are available in various lengths with delivery rates suitable for transferring or circulating, abrasive and aggressive liquids with viscosities up to about 2500 mPas. The main areas of application are to be found in the chemical, process technology, surface treatment and electro-plating industries as well as in water and waste water treatment. The decisive factor in the selection of a particular pump is usually the medium to be delivered, the delivery rate and the delivery head. FLUX-GERÄTE GMBH, based in Maulbronn, offers four different pump series to cover a wide range of solutions customised to suit an extensive selection of transfer and circulation applications. As the centrifugal immersion pumps are constructed using a modular principle, the components of the individual model sizes can be interchanged and so used to adapt the pump to each particular requirement.

Chemical and thermal resistance achieved by different pump materials

In order to achieve the chemical and thermal resistance demanded in the areas of application mentioned, the pumps are manufactured using a range of materials and designs. Stainless steel is suitable for use with neutral, thin liquids such as non-flammable solvents, dilute inorganic acids and alkalis. Polypropylene (PP) is used for aggressive liquids such as acids and alkalis. Polyvinylidene fluoride (PVDF) is also suitable for aggressive liquids such as concentrated acids and alkalis. Pumps made from PP can be used in temperatures up to + 60° C, and pumps made from PVDF or stainless steel can be used in temperatures up to +100 °C.

Many models for many areas of application

Centrifugal immersion pumps are made in different models to suit the application. Pumps of the F 620 to F 640 series are vertical centrifugal immersion pumps and consist of an internal and external tube. A special model in this series the F620S TR and F640PP TR are available for mounting horizontally or vertically and in this version the pump outer tube is not immersed in the liquid but by connection direct to the pump inlet from a tank or IBC. This model can be mounted either horizontally on a pedestal, on a moveable trolley (as an emergency pump) or vertically on the container. The drive shaft of these pumps is inside the inner tube and the seal is provided by a mechanical seal. The liquid is pumped between the inner and outer tube to the pump outlet by an open rotor or a closed impeller. In this case stainless steel to German standard 1.4571 (type 316 Ti), PP or PVDF is used for the pump. When PP or PVDF is used, the inner tube has a plastic cover and a steel core; this method of construction ensures that there is virtually no thermal expansion even at high temperatures. The mechanical seal therefore continues to operate safely. The outer layer of plastic provides protection against aggressive media and the steel core provides excellent stability in the pump as it absorbs both the internal and external hydraulic and mechanical forces. The pumps are always fully immersed in the liquid ( except F620S TR and F640PP TR ) thus excluding hazards from leaks.
Immersion lengths vary from 400 to 4000 mm and delivery rates of up to 44 m3/hour mean that these pumps are often used in waste water treatment plants where acidic liquids have to be conveyed and passed through filter systems.

The seal-less centrifugal immersion pumps of the F 706, F 716 and F 726 series are made from PP or PVDF and are designed for continuous operation in a fixed position and wet running. The pump motor is in the dry area above the installation flange; only the pump itself is immersed in the liquid. The robust pump case is welded to the support tube and so ensures that the pump is vibration-free when operating. This type of construction means that the pumps are particularly suitable for continuous operation in unpressurised containers, open tanks or sumps. The maximum delivery rate possible is 74 m3/hour. Mechanical bearings, which are lubricated by the medium and used in the F 706 series, make immersion lengths of up to 1000 mm possible; this length can be extended to 2000 mm if an inter-mediate bearing is used. In the case of the F 716 series, the motor shaft is also the pump shaft, an arrangement which creates a very compact design. These pumps are available in immersion lengths of 300, 400 and 500 mm. The F 726 series has a very robust pump shaft, the bearings of which are located in a bearing carrier with two roller bearings separated from each other. These bearings absorb the radial and axial forces and ensure vibration-free running even under heavy loads, as neither the bearing nor the seal are in the area in contact with the liquid, the pumps suffer from little wear, are maintenance-free and suitable for dry running. The design of the welds between all the components ensures that the medium has no sudden changes of direction which prevents wear spots and deposits from forming in the pump. A base screen welded to the pump case cover or located at the end of the extension pipe protects the pump from serious contamination. The pumps operate without creating metallic ions i.e. no fine particles are abraded from the components or seals; this is particularly important in the manufacture of silicon or semi-conductors. The long-lasting pumps of the F 706 series are particularly suitable for moving or circulating acids and alkalis or chemically contaminated liquids in the small particle field and are used, for example, in pickling tanks, electro-plating baths and liquid storage or other large containers. The F 716 and F 726 models are ideal for moving thin, aggressive and abrasive liquids such as occur for example in enamel production, in liquids containing sediment suspensions as well as in gas and air scrubbers. They are also suitable for circulation pumps in high-performance electro-plating plants, not to mention chrome and copper-plating baths.

Flexible performances provided by a range of impellers, rotors and motors

The use of a range of impellers and motors enable pumps made from PP and PVDF to be customised to suit various operational conditions and performance requirements. Impellers with diameters from 50 mm to 250 mm produce different pressures and delivery rates.

The pump duties can be varied to suit the required operating conditions by altering impeller geometries. All pumps are tested by FLUX-GERÄTE GMBH before delivery to the customer and the required performance data is verified. There are three different types of standard impellers which can be further optimised by adjustments to their geometry - the normal closed impeller for higher pressures, open impellers for highly contaminated or abrasive media and self-cleaning tapered rotors (with a 45° angle). The impellers can be used for liquids up to 150 mPas and the tapered rotors for liquids up to 2500 mPas. The use of two-pole three-phase current motors with 3000 rpm or four-pole motors with up to 1500 rpm and outputs of 0.37 up to 5.5 kW of protection type IP 55 which are also explosion-proof if required enables the pumps to be optimally adjusted to suit the application. More powerful motors can also be retro-fitted if the specific gravity of the medium is higher than was assumed during the planning stage. A different impeller can be fitted to an existing pump which is to be used in a varied application, thus easily making the pump suitable for its new task.

Excellent quality and long service life

Centrifugal immersion pumps are used in all type of plants across the world; a long service life is an important criterion for the pumps. FLUX ensures a long service life by using high-quality materials as well as by the in-house development and manufacture of all major components including the drives. FLUX backs this design and manufacturing quality with its guarantee periods which can normally extend well beyond 12 months. In addition, the design of the pumps focuses on a high efficiency level (up to 60% in the case of pumps with support bars) and the lowest possible energy consumption.

FLUX centrifugal immersion pumps, like all other FLUX pumps, are constructed on the modular principle so that a number of components can be inter-changed. The company, which has been DIN EN ISO 9001 certified since 1994, guarantees the highest quality with the result that the pumps can be used in the most extreme operational conditions.

Information on the author:
FLUX-GERÄTE GMBH in Maulbronn
Email: marketing@flux-pumpen.de