Dosing of abrasive fluids into tubular bags

Phase change materials (PCM) are used in thermal energy storage and in cold storage. They are filled into different sized tubular bags at Climator. Not only has the wide range of fill weights (from 30 mL to 1.000 mL) imposed high demands on the filling, but also the high abrasiveness of the salt crystals in the media. To meet those requirements, the filling pump 2RD40 Pharma from ViscoTec, which uses the progressive cavity pump principle, was chosen.

The progressive cavity pump is particularly suitable for conveying and filling abrasive and solid-containing media. The abrasive solids are transferred in a product- and pump-gently way in the carrier medium through the chambers between the rotor (stainless steel) and stator (elastomer). The friction coefficient between rotor/stator combinations is reduced trough the tribological film of a few µm. Therefore premature wear is avoided.

As progressive cavity pumps are dosing pulsation-free and under low pressures, in this case approx. 3-4 bar, also concentrations of the filler are avoided. Furthermore the progressive cavity technology operates without metal-to-metal contact between the rotating parts.

The dosing geometry allows for a constant volume per turn (proportional to the angle of rotation) resulting in a uniform product flow. This prevents premature sedimentation of fillers. The volume is clearly defined by the angular degree; no backflow or undercuts (uniform distribution of the solids) are existing. This technique results in a pressure-constant, linear pump performance curve. A clear statement can be made about the relationship between revolution, time and delivery. Therefore, a wide range of different volumes can be filled using only one pump - with safe processing and repeat accuracy.

All these advantages are adopted by manufacturers of tubular bag filling machines, for example the company Hastamat located near Frankfurt, who relies on the reliable and precise technology of ViscoTec. A typical configuration is the assembly of a progressive cavity pump mounted on top of the machine, which is filled via a container. The filling nozzle at the end of the pump is directly mounted in the forming tube of the tubular bag filling machine. After filling, the filling nozzle is closed with a plunger to prevent dripping of the product. In this way, a clean seam for the sealing of the bag is ensured.