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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.