Knoll Maschinenbau GmbG

Archiv for: Paints and Coatings

Agressive media and a robust pump

There are applications, e.g. in the chemicals industry or in the paints and lacquers industry, where elastomers cannot be used. Pumps would be susceptible to chemical attack, particularly when using mixtures of different solvents. Therefore, not only the medium itself but also the cleaning process must be taken into consideration when designing the pump.

In this case, a viable alternative would be to use PTFE (Teflon) both in the secondary seals and in the stator. KNOLL Maschinenbau recently assembled an MX20 for a south German paints manufacturer to meet its special requirements of suitability for use in paints production and frequent cleaning with a mixture of solvents. Given that these solvents are recycled, their composition and concentration may change, but this must not alter the properties of the eccentric screw pump.

To this end, the MX20 was fitted with a solid stator made of Teflon. The excentric movement of the rotor is compensated by a titanium torsion bar. No elastomer seals are used. As a result, the MX, first, has the required level of resistance to cleaning with solvents and, second, retains its KNOLL trademark properties:

  1. High ease of servicing even when using non-standard components;
  2. Good cleanability (CIP and SIP);
  3. Excellent pump characteristics (low pulsation, high pressures, suitability for high viscosity levels).

In the case of this special version, attention was also given to preserving the modularity of all key components so that the paints manufacturer can, when necessary, adapt the pump to changing conditions within the manufacturing process.

All in all, this MX20 is a great example of how KNOLL Maschinenbau responds flexibly to its customers’ needs to facilitate their manufacturing processes as best possible.

Pumping Abrasive Media Economically: The MX in a Special Design

When it is necessary to transport abrasive media the pump can easily become a problem child: Abrasive fluids can lead to high wear and short lifetimes. A Portuguese paint manufacturer experienced this when he had to promote calcium carbonate. So he gave the MX-Pump from KNOLL Maschinenbau a try.

His demand: To pump 70% calcium carbonate in aqueous solution with a particle size of 6 microns at a pressure of 5 bars and to convey a capacity of 60 m³ / h. KNOLL provided him with a MX50 progressive cavity pump in special design: The stator is lined with a wear resistant elastomer, the rotor coated in special stainless steel (“ductile coated”). The universal joint also receives a sleeve in a wear resistant elastomer. Overall this MX-Pump appears as highly abrasion- and corrosion-resistant and therefor meets the high requirements of the chemical industry, especially when it comes to paints and coatings.

The result: After one year of continuous use of the MX the Portuguese paint manufacturer was completely satisfied. In a three-shift manufacturing process the progressive cavity pump from KNOLL could fully convince: After more than 6.000 hours in use no loss of flow or pressure occured.

But not only the abrasion- and corrosion-resistant construction of the pump contributed to this result but also its design principle with a stator in Even-Wall-technology – a standard in every MX-Pump from KNOLL. This stator is responsible for the fact that practically no back flow of media occurs, which is very welcome especially when abrasive media such as calcium carbonate have to be pumped. As a consequence no blast wear appears.

Another advantage of EvenWall-technology is its significant improvement of the stators characteristic, compared to a pump with conventional stator. This has quite a considerable effect on the cost-effectiveness. The picture shows the characteristic of a conventional stator (left line) and of a stator in EvenWall-technology (right line).

Overall the MX-Pump with its special design convinces not only because of the very high resistance to abrasive media but also on the level of operation efficiency and cost-effectiveness.

Our Diversity of Pump Materials: It’s Your Choice!

A good pump can be adapted to many different transport media and it’s the pump materials that make a decisive contribution to this. Therefor KNOLL Maschinenbau offers a wide range of materials for its progressive cavity pump, even usable in different combinations, so that for nearly any type of transport medium the right pump can be selected.

For its standard design KNOLL applies stainless steel in food quality for all components in contact with product. In addition, however, designs in cast iron are available for applications where stainless steel is not required. In both cases, ie stainless steel or cast iron, of course, all other advantages of the pump stay the same: Ease of servicegood cleaning ability, and of course the benefits of EvenWall-technology.

Why is stainless steel so often used in pumps? It is its high corrosion resistance which distinguishes it from other materials. Depending on the composition of the steel this corrosion resistance can be increased even further.  Hence KNOLL’s MX-Pumps can be fully made of stainless steel or using stainless steel only for all components in contact with product. Progressing cavity pumps fully made of stainless steel are more and more requested from manufacturers with very high hygiene requirements.

Elastomers also play an important role in progressive cavity pumps. For the MX-Pumps more than 100 different types of elastomers (among them many with numerous certificates) are available. This allows an individual adaptation and thereby chemical resistance for each pump to its transport medium. If in your case experience on the resistance of your medium is not available yet, swelling experiments in the KNOLL laboratory are possible at any time.

In particular, we keep in mind the consistent quality of each elastomer used: For every single application the exact same elastomer recipe is used so that the repeatability of the pump parameters remains the same. Especially when the progressive cavity pump is used as a metering pump this is very important: A replacement of the stator must not lead to a re-parameterization of the pump in the manufacturing process. Therefor KNOLL Maschinenbau guarantees for its MX-Pumps and its original spare parts high repeatability.

Finally KNOLL also provides a stator in Teflon for cases in which an elastomer cannot be used. Such solid stators are suitable for aggressive fluids, as often used in the chemical industry, for example in form of paints with solvents.

Liquids, Metering Precision and Knoll’s MX Progressing Cavity Pumps

One of the main goals concerning the volumetric metering of aqueous to highly viscous liquids in containers (packages) is to achieve a high level of reproducibility. In Europe for example manufacturers of all industries have to comply with the (Council) Directive relating to the making-up by weight or by volume of certain prepackaged products.

Certain tolerances have to be respected, but of course not only for legal reasons: The metering accuracy is crucial to metering quantities and therefor for manufacturing costs. The smaller the tolerance, the smaller the fill quantity can be set.

The image (above) shows a “mono-pump” filling machine (named MFL) by Bünder & Schmitt, in which the MX-Pumps in CIP-capable version are employed. Such filling machines are used for example by Henkel or Bayer for filling of cleaning materials and pesticides.

The KNOLL MX progressing cavity pumps are highly competent in metering. In addition to the precise metering not only incompressible but also compressible fluids can get pumped without changing the structure of medium. A key feature is the standard set EVEN WALL (even elastomer wall thickness) which gives the MX-pump an absolutely precise and uniform sealing line. The precision of the sealing line helps to increase the quality of the reproducibility of the flow even under alternating pressure. Further it helps significantly to keep pulsation low.

So very shear sensitive media can be transported easily as they get prevented from damage by the EVEN WALL construction and the precise sealing line. In some cases heat input plays an important role. It is considerably lower in MX-pumps with their EVEN WALL stator compared to pumps with conventional cylindrical stators.

Another criterion which is important for metering, is the resistance of the materials not only for liquids to be pumped but also for the cleaning media and their temperatures. For this reason numerous materials are available from KNOLL, each corresponding to the fluids and carefully selected by our qualified laboratory.

Accessories used in the pump decide just as much on the level of metering accuracy as the metering pump itself. For each single request the necessary measurement and control technology gets individually designed and verified, so that a constant metering is demanded of a once calibrated pump or a simple on measured values dosage is, extensive accessories by KNOLL available.

Depending on the task, step motors, servo motors or induction motors can be used to support the MX-Pump in their exact metering.

The graph (above) shows the level of precision obtained in the measurement of a MX-Pump (for larger display click on the image). The idea was to code the amplitude and to measure its exact position with the help of a stepper motor and an encoder in order to be able to compensate it on the metering. Turned out that the metering was so extremly precise that it could get run without the encoder.
In practice MX-Pumps are already used in numerous cases where liquid amounts of a fraction of a drop have to be dosed under variances in viscosity, temperature and pressure.

MX-Pumps in the Paint and Coatings Industry

Manufacturing paints and coatings today is a high tech industry facing  high expectations from customers as well as from health-care and environmental regulations. Accordingly high are expectations in this industry on pumps which are used to transport and dose components and finished products.

The MX progressing cavity pump by KNOLL Maschinenbau has repeatedly shown proof of its power. For example with a paint manufacturer in Westphalia (Germany) who counts on the MX for carrying and filling emulsion paint because of its high efficiency: The MX easily builds up to 10 bar pressure at a very high degree of efficiency without any medium to be forced back into the pump.

The decisive factor here is the EvenWall-Design of the MX. Its stator is not a cylindrical one but turned (as visible on both fotos) so that together with the inside compressed elastomer it forms an “even wall”. The result of this principle is a significantly higher pressure resistance than with pumps formed of a (conventional) cylindrical stator.

Another important factor for chosing the MX for this paint manufacturer was the “hygiene” of the pump. For the processing of paints, the use of solvents is no longer allowed so that frequent and very specific cleanings of the pump are required. The MX convinces on this field with its low clearance volume design and its readiness for rapid disassembling (and reassenbling): clamping closures and screw unions in accordance with DIN allow to disassemble, to clean and reassemble the pump in minutes only. In the same way replace parts can be installed quickly and easily.

All in all the MX was so so convincing that meanwhile more than 50 units of this progressing cavity pump are in use today at this Westphalian manufacturer. So when it comes to pumping or dosing paints, varnishes and coatings the MX obviously is a good choice.