Going Without The Piston

Volumetrically dosing and filling applications with high viscosity, pasty or filled liquids in the food and beverage industry could be handled much easier and cheaper with pumps and fillings systems based on the endless piston principle. By Wolfgang Merklein, MD, ViscoTech Asia

Pumps and filling systems using the endless piston principle are able to pump and fill temperature sensitive, pasty, abrasive or shear-sensitive fluids in an excellent way. Even fluids with particles, like fruit-pieces, could be filled in a highly precise way. This technology guarantees an accurate dosing and filling result and helps to save costs by exactly filling the required amount. The yield can be significantly improved.

It is possible to use this design and technology for different application fields, like the food and beverages, cosmetics and pharmaceutical industries. Difficult liquids like spices-marinades, vaseline, fruit extracts and fruit sauces, cheese, honey, mascara, chocolate, peanut butter or dental fluids are filled with this pump and dosing principle all over the world.

Main Principle

The main principle is the volumetric dosing principle invented by René Moineau. The combination of an eccentric moving stainless steel rotor in an adapted rubber stator results in a dosing and pumping process, which is similar to an endless moving piston. Therefore, the principle is also called endless-piston-principle.

According to the geometry of rotor/stator, for every revolution of the pump, a defined volume is forwarded. The pumping direction is reversible, which means the pump could be run at both directions (forwards and backwards). The volume is exactly defined by the angular degree of the pump/motor.

This principle also offers a pressure-resistant, linear characteristic pump curve. This allows a defined relation between revolutions, time and volume.

In a specific application, the pump can dose either by time or by number of revolutions for a fixed volume. This leads finally to a dosing and pumping accuracy of +/- one percent (depending on the fluid). In practice, the accuracy is even better than +/- one percent.

Another advantage is the constant cavity which is created during the pumping process. This offers the possibility to pump also filled fluids with particles. This pump type does not use any additional valves in most cases and applications, because by using the ‘suck-back’ at the end of the dosing or filling dripping could be prevented.

New Design, More Advantages

As the principle of René Moineau is quite old, it is possible to improve on it and create an optimised design. By using a joint-less and flexible shaft instead of the classic shaft with joints, a better process and dosing characteristic could be achieved. At the same time, a flexible shaft can also allow better cleaning, as well as less wear.

The stator is a high-tech component that is manufactured with several different raw materials. The inner portion of the stator can be made of different types of rubber. Depending on the characteristics of the fluid, the most suitable rubber should be chosen, for example with consideration given to the chemical resistance of the rubber towards acids or bases, grease and chemicals.

Even abrasive fluids could be dosed and pumped without any problems. All wetted parts within the pump are of course FDA-certified as they have to fulfil all hygienic requirements for Food and Pharmaceutical applications.

Advantages Of Endless Piston Principle

One of the main advantages of the endless piston principle compared to piston filling systems is the smooth and low-pressure handling and filling of liquids and pastes.

The liquids, for example fruit pastes with particles, are not pressurised and are filled without stressing the liquids. Compared to piston fillers, there is no pulsation or downtime for refilling the piston. With the endless piston principle, a continuous filling process is possible without any stops. This saves valuable process time and improves the output of the filling machine.

If pastes like toothpaste should be filled, this is normally a problem for piston fillers as there will be high wear and tear costs incurred by the abrasive particles of the tooth-paste. The endless piston pump, however, is very suitable for abrasive particles and mainly used for this type of liquids or pastes.

The precise dosing process (tolerance +/- one percent) also helps to save liquid and rejected parts and costs. Finally, a good reason to switch from piston to endless piston systems is that for automated processes which require cleaning-in-place (CIP) and sterilisation-in-place (SIP), it is difficult to connect piston fillers to this cleaning system. Whereas endless piston pumps are suitable for these cleaning methods, offering a highly automated and faster cleaning process.

Application Example

The pumping principle is suitable for numerous of food applications. An example of that is the filling of tomato and chili sauce.

A big manufacturer of tomato and chili sauce was looking for a solution for the filling of different kinds of tomato and chili sauces in a hygienic way. The initial systems and technologies the company has tried were not able to fulfil the requirements (for example, piston fillers).

Besides the difficulty in achieving consistency of the sauces, the main problem for the dosing and filling was the content of tomato and chili particles in the sauces.

The company also required an accuracy of +/- one percent and the system must be capable of CIP and SIP cleaning. CIP means that the system can be cleaned without disassembling. Normally, this cleaning procedure consists of several single cleaning processes, depending on the application, for example, flushing with water, base or acid. SIP is quite similar to CIP, but instead of fluids (acids, water), hot steam is used to clean and sterilise the pump.

For the certain applications, the SIP was connected for 30 minutes with hot steam of 130 deg C in order to sterilise the system completely. For CIP cleaning, it is necessary to have a flow-speed of the cleaning solvent of at least two m/s in order to achieve turbulent flow behaviour for maximum cleaning effect.

Therefore, the pump housing was built with an additional CIP connection. This CIP connector is designed for the purging of the pump housing. The filling nozzles are removed during the cleaning process and can be cleaned manually.

As the rotor-stator system has a completely sealed geometry, the pump is running at a fixed 30 rpm during CIP-cleaning. The cleaning result is the same as for the pump housing, as the natural friction in the rotor/stator leads to good cleaning without having turbulent flow. It is the same for SIP with the hot steam pumped through the system and the bypass used for creating turbulent flow in the pump housing.

Hygiene & Functionality

The requirements for human food are very high, so the best choice for this application was a hygienic pump with the endless piston principle (FDA certified).

This version of the pump allows high level of cleaning and the hygienic design of the mechanical seal (encapsulated mechanical seal) is able to fulfil the stringent requirements. It is also very important to have a pump housing design without any dead spots and a polish level of the stainless steel (surface condition of 0.4 micrometre).

Direct Filling

Leslie Seaton, Washington, US
Leslie Seaton, Washington, US
The filling unit consists of one line with six filling nozzles that can dose all different dosing volumes, so it is possible to fill containers of different sizes. As every filling nozzle has its own dosing pump, the filling quantity could be set individually.

For example, two different sizes of 100 ml and 200 ml could be filled without any problem in the same dosing time. The partially hot (90 deg C) tomato and chili sauce is supplied out of the mixing tank into a buffering tank.

Then the buffering tank is sealed and set under vacuum. After that, the sauce is pumped out of the buffering tank through a hose and manifold to the six different dosing pumps and filling nozzles. This direct dosing saves a lot of energy, as well as additional buffering tanks. After the filling of the sauces into sales packaging/containers, they are being cooled and processed to labelling and final packaging in carton boxes.

As mentioned earlier, the system and pumps are used for a wide range of applications. It is also used to supply fluids to the filling process, for example, from barrels (in this case, it is the raw tomato paste). The endless piston pump is used to empty containers and barrels completely (less than one percent residue is left in the barrel) and supply the fluid smoothly to the filling station.

Other applications examples include honey, different sauces, cheese, fruit jams and marmalades, various fluids of the dairy industry (for example, yoghurt and cheese), vegetables, crèmes, mascara, food grease and other raw materials.

Costs Vs Quality

The investment for this technology and pumping/filling system is a little bit higher compared to other cheaper technology and systems available in the market. However, the system can help minimise the costs for maintenance, downtimes and spare parts. As a result, the return on investment can be reached in a short time compared to other technologies.

The filling and pumping process saves a lot of trouble, money, efforts and time. For example, costs and time could be saved which are normally spent on maintenance, cleaning and troubleshooting. There are fewer interruptions in the production process and therefore, a higher output and yield for the line. Avoiding downtimes and improving and shortening the process time can help achieve return on investment quickly.

Feeding & Emptying Systems

Feeding and emptying systems are strongly related to filling applications. This means that the liquid or paste has to be transferred out from the barrel or pail to the filling system itself.

It is necessary to have a reliable and proper emptying process, where not too much liquid is lost as leftover in the pail in order to save costs. A fast pail change also saves time and money. The endless piston principle can offer a good solution here. The technology can be used to suck the liquid out of the pail instead of dosing or dispensing.

With the help of a follower plate, the liquid is smoothly pumped out of the pail by just the suction capability of the pump. There is no additional pressure applied to the liquid to press or force it into the hose. This is the main advantage of the system compared to the common piston pump emptying system: no stress or pressure that may damage the structure and properties of the liquid.

The liquid is fed into the filling system. The emptying result ensures that less than one percent of the liquid is left in the pail. This help save money, which would otherwise be wasted and thrown away.

The whole emptying system is monitored by pressure and level sensors and offers a very good automated pail emptying and feeding system. Finally, the whole process (from the pail up to the nozzles) could be realised by endless piston pumps, which are ideal for liquid dosing.

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  • Last modified on Friday, 29 November 2013 12:04
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Asia Pacific Food Industry (APFI) is Asia’s leading trade magazine for the food and beverage industry. Established in 1985, APFI is the first BPA-audited magazine and the publication of choice for professionals throughout the industry with its editorial coverage on the latest research, innovative technologies, health and nutrition trends, and market reports.

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