Knoll Maschinenbau GmbG

RONDO FOOD relies on KNOLL – the MX delivers the goods in the pet food industry


Rondo Food_LogoThe RONDO FOOD company, which specialises in snack products for cats and dogs, has been using MX progressing cavity pumps by KNOLL for a number of years now with highly satisfactory results. RONDO FOOD has made an international name for itself as a supplier of private label products to commercial and industrial enterprises in the European, US and Asian markets.

When it comes to the production of pet snacks, RONDO FOOD places great emphasis on fast and hygienic processing of fresh meat. The meat is made into a slurry with a viscosity of between 1,000 and 3,000 mPas. This slurry contains chunks of meat 1.5 x 0.5 mm in size. Gentle product delivery is very important because these chunks must not be destroyed. This unique feature of the MX progressing cavity pump by KNOLL is a key criterion for RONDO FOOD. Today, nearly 50 MX progressing cavity pumps are used by RONDO FOOD at various production sites so as to ensure maximum customer satisfaction.

The MX also has other advantages in addition to gentle product delivery: the proven EvenWall® technology of the high-compression stator allows pressures of up to 10 bar per pressure cycle, which saves space and, most importantly, cost. That means KNOLL can also supply small and cost-effective MX progressing cavity pumps for high-pressure applications. Due to the stringent hygiene requirements which apply in the pet food industry, cleaning and maintenance are important to RONDO FOOD. In this department, the MX scores highly with its service-friendly design. Thanks to its modular principle, it can be disassembled easily and quickly. The MX progressing cavity pump by KNOLL is at home in the hygiene sector and can be easily cleaned and sterilised using CIP and SIP methods by virtue of its virtually pocket-free design. Another plus-point is the low part diversity – which greatly simplifies both maintenance and stocking of parts by the customer. Because the pumps in the MX series differ from one another only in terms of their pump unit, which comes in nine different sizes, the wear parts of, say, the shaft seal and universal joint are identical and can be used flexibly.



KNOLL’s MX does not heat up even at 140 °C


The MX progressing cavity pump from KNOLL is used in many different areas, from the food and beverage industry to pharmaceuticals to the chemical industry. This pump also stands the test in extreme cases. This has been proven at Europe’s leading manufacturer of building shells, interior fittings, and insulation technology. Here, the MX is incorporated into the process of reclaiming fibrous plasterboard. It withstands temperatures of 140 ° C and an extremely abrasive fluid.

Progressing cavity pump MXWaste and remains of the plasterboard panels are relegated to a viscous suspension of approx. 500 mPas. Using the MX, this fluid is pumped back into a reactor before it is processed into new fibrous plasterboard. A challenge of this use is the high temperature of the fluid, 140 °C. Thanks to its special design, the MX performs well: the EvenWall® technology of the KNOLL stator guarantees even pressing even at high temperatures. This improves the durability of the stator considerably. Another challenge of the fluid is its abrasive character. The plaster suspension contains 10 – 15 µm particles with a concentration of 32 – 50 %. The MX also has the solution for this: a stator of wear-proof special elastomer for high temperatures as well as a specially-coated rotor, which also demonstrates wear-proof qualities despite the extremely abrasive fluid.

An additional benefit of the KNOLL MX progressing cavity pump is the even flow speed in the suction housing, which prevents sedimentation and thus the settling of the fluid. This is the result of the even diameter of the cardan joint and the pump’s design, which keeps the clearance volume low. Therefore, no fluid accumulations form on the joint or on the housing wall.

Rotary piston pumps were used for this process in the past, however without any success. After just a few weeks, the pumps had to be replaced due to wear. The MX progressing cavity pump from KNOLL has been used for six months already and shows no traces of wear.

The function of the progressing cavity pump MX


Application of the KNOLL progressing cavity pump in the wastewater industry


A new application for the MX is the loading of chamber filter presses in the wastewater treatment sector.

A so-called feed pump feeds the sludge or suspensions into the cavities of the filter chamber, initially at zero pressure and at a high delivery rate. The pressure inside the filter chambers begins to rise when the solids form a layer upstream of the filter cloth. The speed of the feed pump, i.e. the delivery rate, decreases with rising pressure. The process medium is fed into the chambers at pressures of up to the set maximum of approx. 16 to 20 bar. The adjustment range of the feed pump should, because of the time factor, be as large as possible, i.e. the initially pressureless filling process requires a very high delivery rate compared to the low delivery rate during the pressure holding cycle at maximum pressure.

This is why two pumps are normally used for the filtration process. A larger single-stage pump fills the filter press until a medium pressure of 4 – 6 bar is achieved. A small 4-stage pump is used for the high-pressure process until dewatering has been completed and a sufficiently dry filter cake has formed. A further reason for using two pumps is the poor efficiency of conventional progressing cavity pumps at very low speeds. A strong backflow, which also decreases the lifetime of the equipment, occurs in conventional stators at low speeds and high pressures.   

KNOLL Maschinenbau requires only one progressing cavity pump for the entire filtration process. This pump operates both as a filling pump and as a high-pressure pump. The MX handles the process in a two-stage configuration and can cover the full control range with a high level of efficiency. Thanks to the stator with EvenWall® geometry, the MX pump has a very linear characteristic and reliably provides the required pressure at a very low frequency. The KNOLL technology saves the investment in a second pump and minimises the cost of process control. It also cuts energy costs by approx. 50 %.

The two-stage MX pump can deliver pressures of up to 24 bar and is ideally suited to this application as a filling and high-pressure pump.

Efficient antipasti production using KNOLL progressing cavity pumps


Progressing cavity pumps from KNOLL Maschinenbauare used world-wide in various sectors. In addition to being used for processing paints and lacquers, chemical or pharmaceutical products, they are the pumps of choice in the foodstuffs industry in particular. The versatile MX can be used in many processes, for example as a dosing pump or transfer pump or for the plastification of media. KNOLL has developed the MX plastifier version specially for plastifying highly viscous to compacted media – an application in which it offers a number of advantages.

A german manufacturer of antipasti products has greatly simplified its production process by using the MX P version. The filling of olives, peppers and chilies with fresh cheese was a very complex and time-consuming process before the introduction of the MX. Each individual husk had to be filled manually using a pressure system.
Used in combination with the dosing system from a south German plant manufacturer, the MX50P-80/10 allows olives, peppers and chilies to be filled fully automatically – all in a single operation. 100 fillings are possible per dosing cycle.

The hard fresh cheese, which is stored in 10 kg buckets and cooled to 6°C, is collected by the pump from the large top-mounted hopper and plasticized to a viscid product with the aid of the feed screw and a special hopper geometry. Stuffing of the fresh cheese products is achieved by co-ordinated operation of the feed screw and pump assembly. This allows air to escape upstream of the pump assembly, preventing air from being trapped in the fresh cheese.

This efficient system has been in operation for several years now and has simplified and improved the working process for the producer.

KNOLL is developing innovative solutions for the chocolate industry


Did you know that on average every German eats more than 10 kg chocolate per year!?!?

In most cases, a chocolate filler is required in order to produce chocolate. This filler can, for example, consist of chocolate, vegetable fats, nut paste and flavouring.

Before the chocolate filler can be processed, it has to be heated to the correct temperature. In this process, the filler is cooled under shear and then heated slightly. This ensures that it has a smooth texture and is stable in storage after it sets. The heated filler is poured into a block mould and then stored for a week at 12°C.

For further processing, the solid chocolate filler must be heated in a warming room at 28°C for approximately one week. After that, the soft block is homogenised and plasticised in a mixer with additives such as nuts or raisins. This mixture is now fed into the extruder, a task often performed manually by mobile transport containers. Finally, the chocolates are injection-moulded on a conveyor belt by the extruder, coated with chocolate and decorated, then cooled and finally packaged.

Using KNOLL technology, it is possible to process solid chocolate filler even at 12°C and to eliminate the warming room and the holding time from the process. This makes the production process more flexible, timesaving and efficient.  There is no longer any need for long transport routes between the cooling and warming rooms – and for the warming room as such. One of the important factors here is that the system is a fully integrated, closed-loop system which meets the highest hygiene standards. It is also worth highlighting the possibility for continuous production where previously only batch mode production was possible. Given that KNOLL pumps deliver high pressures, even large distances can be bridged. On the pressure side, solids such as nuts and raisins are admixed homogeneously on the conveyor line by static mixers.

Depending on the how chocolate products are produced, KNOLL can provide the manufacturer with an optimal solution which will streamline – or even bypass – time-consuming stages of production.

Pumping pumpkin mix with the MX


A US company in existence since the 1950’s has specialised in processing fruit and vegetables.
In addition to a wide variety of tinned fruits, they also make the cake filling for pumpkin pie, a favourite dessert among Americans.
“Pumpkin Pie” is a traditional US dessert, traditionally served from late autumn to early winter, and especially on public holidays such as on Halloween and Thanksgiving.

The pumpkin harvest takes place in the autumn.Processing of the pumpkin harvest takes from October until December, a phase described by the producers as the “pumpkin drive”. 
The customer previously used a rotary piston pump manufactured by a well-known US manufacturer for the further processing of pumpkins.
Even though the pumpkins were shredded, boiled and thoroughly cleaned prior to processing, tiny particles of sand still cling to their skins. The abrasive properties of the sand grains make pumping very difficult for the radial piston pump.
Since both the housing and the piston in these pumps are metallic, the sand particles act like sandpaper on the metallic components of the pump and wear out the inner workings of the radial piston pump within just 72 hours.
During the so-called drive, manufacturers of pumpkin cream incur enormous costs due to the high rate of wear and tear on the radial piston pumps. To reduce these costs, a KNOLL progressing cavity pump is now being used in place of the radial piston pump.

KNOLL uses a standard type MX30S-60/10 pump for this application.
Thanks to MX EvenWall® Technology, which provides exact and even pressure between the ductile coated stainless steel rotor and the soft elastomer of the stator, the MX offers many advantages in this field of application.
The closed pressure chambers of the KNOLL pump prevent medium from flowing back into the lower-pressure chamber (eliminating jet abrasion). This has two advantages: firstly, it allows very high operating pressures to be used and, secondly, the abrasive particles effectively have no chance of damaging the pump surfaces. It also allows the pump to be better primed with up to 100 mbar of absolute vacuum.
A further advantage of a KNOLL progressing cavity pump is that it is easy to clean.
A MX can also be operated filled with water, thus enabling the pump to clean itself. This also allows the remaining pumpkin mix to be pushed out of the pipes in order to clean the pump system and piping. This means that the MX is capable of achieving the same high pressures with water as with high-viscosity media. During cleaning, it is important that RPM can be regulated. Using the MX, pump speed can be regulated in stages from 1 to 20 as standard.

A radial piston pump, on the other hand, can only build up a low pressure when running at low RPM and using low-viscosity media. Backflow into the preceding pressure chamber cannot be prevented because the pressure chambers are not closed. A “buster pump” is needed for cleaning because a radial piston pump cannot clean itself or the piping.

The KNOLL progressing cavity pump was used for the first time midway through a pumpkin drive. At the close of the pumpkin season, the pump was examined at our factory. It had been in use for approx. 1-2 months and exhibited minimal sign of wear and tear.
The KNOLL pump has now been in use for 2.5 pumpkin drives. For the producers of the pumpkin cream, the extended life of the pump is a major boon as it cuts costs significantly and allows many processes to be simplified.

Reducing, pumping and plasticizing blocks of cheese with the KNOLL MX


A cheese dairy from the Netherlands has been making a variety of finest-quality cheese products since the early 19th century, and has meanwhile made a name for itself as the leading Dutch brand world-wide.

A solution for reducing, pumping and plasticizing young to medium-aged cheeses has been found by using the KNOLL type MX50R-60/30 progressing cavity pump in combination with a frozen block cutter.

The firm to very hard blocks of cheese, which weigh as much as 30 kg, are reduced to a pumpable size of 25 x 35 x 20 mm by the reducer and conveyed through a feed hopper adapted to match the frozen block cutter outlet, and directly into the MX pump system.

The feed screw on the feed hopper pump has a special non-stick coating which prevents cheese from sticking to the feed screw and so provides for a smoother conveying process.

This coating has other advantages too, as it allows the feed screw to be cleaned more quickly and easily.

Plasticizer plates built into the discharge nozzle or at the end of the pressure line shape the cheese into narrow strips, thus speeding up and simplifying subsequent processing. The Even Wall® geometry is a key factor here because it allows pressures of up to 80 bar to be used.

Preventing bridging with the MX50 feed hopper version


KNOLL develops, designs and produces solutions customised to the specifications of its customers. These include one of the world’s leading oil companies, which has successfully been using KNOLL progressing cavity pumps for several years now.

An existing progressing cavity pump was replaced with an MX pump by KNOLL by optimising a production process. With this application, grease is pumped at temperatures in the 100 – 200 °C range and at a viscosity of approx. 10,000 mPas. The process is such that it is possible for clumps of grease to arrive at the pump despite the high temperature and the liquid properties of the medium.

In this case, an MX50R-60/10 with bridge breaker and separate drive was used in order to prevent bridging. Taking account of the medium’s complex properties, the bridge breaker ensures controlled and troublefree delivery of the low-viscosity grease.

The universal joint runs in needle bearings lubricated with heat-resistant lubricants and, thus, is suitable for applications involving temperatures up to 250 °C.

Given the customer’s pre-existing machine set-up, the current pump’s connecting dimensions were adapted to match those of the MX pump, both at the feed hopper flange and at the pressure connection. This enabled Knoll to provide the customer with a more simple and, above all, more efficient refit.

Processing adhesives with the MX vacuum pump


A well-known Swiss adhesives manufacturer is an important supplier to the international automobile industry of glues for bonding car bodies, windscreens and dashboard kits. Air trapped in the adhesive would allow gaps in the sealing contours, which in turn would result in leakage inside the vehicle due for example to the ingress of rainwater through the windscreen. The adhesive must therefore be absolutely free of trapped air in order to ensure a continuously tight adhesive bead. For this reason, the adhesive is manufactured under vacuum and delivered to automobile manufacturers in vacuum-sealed drums.

For this application, an MX50R-80/20 with an electric heating jacket and dry run protection was placed below a vacuum mixer. The MX is used as a mixer discharge pump and fills the drums with adhesive under vacuum. A vacuum of 20 mbar absolute is maintained in the mixer. In this process, the filling time of the moisture-reactive adhesive including 800 µ filtration is about 4 minutes per drum.

The feed housing and the conveyor worm of the progressing cavity pump MX from KNOLL have a special nanotechnology-based non-stick coating to avoid unwanted bonding effects and bridging. Due to the highly abrasive properties of the medium and high viscosity values ranging from 700,000 – 1,500,000 m Pas, a solid stator made of a specially hardened material is used for this pump. The KNOLL solid stator uses the tried and tested “half-shell system” employed in the production process for the KNOLL screw spindle pumps type KTS.progressing cavity pump with solid stator

The pump was tested for vacuum tightness for a week prior to delivery, and it was found that the high vacuum level remained absolutely constant. 

In this specific application, our competitors’ pumps achieved a maximum life of only approx. 3 months and showed the first signs of wear after only a few weeks. The MX by KNOLL Maschinenbau GmbH has already been in use for more than 16 months and so far has not shown any signs of wear.