Container cleaning with high hygiene requirements

Care is required in the production of pharmaceuticals; after all, health and life depend on the correct composition of active ingredients and the avoidance of contamination with undesirable substances. Production plants and containers must therefore be meticulously cleaned at prescribed intervals after each product change, in sometimes quite elaborate processes, according to precisely specified recipes. For many years, L.B. Bohle Maschinen + Verfahren GmbH (cf. company box 1) has been considered a specialist in this field. The company has established itself worldwide with its machines and systems for the pharmaceutical industry, ranging from weighing, granulating, sieving and mixing to the film coating of tablets and the corresponding cleaning systems. This includes, for example, the Pharma Universal Cleaning System PUR (Fig. 1). This system, which is specially designed for cleaning containers and vessels of very different sizes, is particularly impressive due to its compact design.

Everything fits into a compact stainless steel control cabinet
All components for conveying and processing the cleaning water are housed inside a stainless steel cabinet. This means that the compact unit can be easily accommodated in the washroom; washing processes are then recipe-controlled and automatically documented. A touch panel directly on the system ensures convenient on-site operation.

In the recipes for the different cleaning processes and steps, the quantity ratio of water and the alkaline or acid-based cleaning agents is stored. The mixing ratio is usually between 1 and 3%, with cleaning solutions of all pH levels being used. At the same time, for many cleaning steps the recipes also specify certain temperature values so that the process can run optimally. This means, on the one hand, that the amount of water in the PUR systems must be continuously measured in order to control the cleaning agent pumps according to the recipe specifications. On the other hand, the temperature must also be measured and, if necessary, readjusted accordingly in order to maintain the minimum or maximum values specified in the recipe.

One sensor measures flow and temperature
Here it was possible to kill two birds with one stone, because the FLOWave flow meters Type 8098 (Fig. 2) from Bürkert can perform both tasks. They operate according to the patented SAW (Surface Acoustic Waves) method, i.e. they use surface waves for measurement (see box). They also have an integrated temperature sensor. This saves one sensor in the PU systems. This saving not only benefits the compact dimensions of the system, but also reduces the number of parts. This in turn leads to the hygiene requirements being met more quickly, because one less device has to be included in the cleaning cycles.

In the meantime, the machine manufacturer L.B. Bohle has been able to convince itself of numerous advantages of these flow meters in practical use: The SAW method is ideally suited for hygienic use because there are no installations or constrictions and thus no dead spaces in the measuring tube. In addition, the measurement takes place without any contact between sensor elements and medium. There are no fluid effects on the sensor elements, nor is it possible for the medium to be contaminated by them. This is hygienic and facilitates cleaning (Hygienic Design). Since the measuring tube does not differ fluidically from any other straight pipe section in the system, there is also no pressure drop. The measurement works with stagnant liquids as well as with fast flow or flow changes.

The compact size and low weight also allow uncomplicated installation in the control cabinet (Fig. 3). With a nominal width of 50 mm, for example, FLOWave weighs only around 3.5 kilograms and can be easily installed or replaced by one person. The installation position is arbitrary, so that the display can be easily adjusted and the flow meter is easily accessible for configuration during commissioning. During operation, the flowmeter consumes significantly less energy than, for example, Coriolis flowmeters, which are also usually much larger. In addition, no maintenance work is required, which significantly reduces the operating costs for users of the PUR systems.

Accurate and future-proof
The all stainless steel flow meter measures the volumetric flow with an accuracy of 0.4 % of the measured value. The temperature is measured simultaneously with an accuracy of ≤ 1 °C. Depending on the nominal size, the nominal pressure is up to 40 bar. The temperature range is designed so that both CIP and SIP cleaning procedures can be carried out. The measuring device is offered in the nominal pipe sizes DN15, DN25, DN40 as well as DN50 with pipes and clamp connections according to ASME, ISO and SMS and can in principle also be used without display.

In addition to the measurement of volume flow and temperature, FLOWave can also determine other measured values such as density factor (for liquid detection) and acoustic transmission factor (for gas bubble detection). L.B. Bohle is also interested in the latter in order to further optimize the cleaning process in the future.