Knoll Maschinenbau GmbG

Archive for: 2012

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.