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Approval of bottle washing machines

In order for bottle washers to do their job properly in a brewery's bottle cellar and to keep water consumption, energy costs and the use of cleaning agents within reasonable limits, new systems should be approved before they are put into operation and existing systems should be checked from time to time.

empty beer bottles

Faultless cleaning with low resource consumption

The purchase of a new bottle washer is a major investment for breweries. It should therefore also meet all the requirements of a modern machine, which are guaranteed by the manufacturer. On the one hand, the reusable empties must be cleaned without defects; on the other hand, economic factors such as water, energy or lye consumption also play a major role. Dr. Hubertus Schneiderbanger, Dario Cotterchio and Prof. Dr. Fritz Jacob from the Weihenstephan Research Centre for Brewing and Food Quality at the Technical University of Munich give an overview of the most important parameters that need to be checked [6].

The Weihenstephan Research Centre for Brewing and Food Quality has been inspecting and approving bottle washers for many years. The inspections are based on the guidelines of DIN 8784 and are usefully supplemented by microbiological tests, for example [1]. For breweries, however, it is not only advisable to check new bottle washers, but also existing machines from time to time. These examinations can partly be carried out by the breweries themselves, provided that the necessary equipment and laboratory facilities are available.
filling systemData acquisition is essential for a trouble-free filling process (Picture: BRAUWELT)

Safety requirements, manufacturer's warranty and data collection

The inspection of a bottle washer only makes sense if the system has been properly commissioned and fine-tuned by the manufacturer with regard to throughput times, caustic dosing, consumption figures, etc. The basic prerequisite is always that the manufacturer of the machine provides it with the CE mark and issues a declaration of conformity. The basic prerequisite is always that the manufacturer of the machine provides it with the CE mark and issues a declaration of conformity in accordance with Directive 2006/42/EC (the so-called EU Machinery Directive.)

Of course, the user of the machine should additionally check whether the elementary safety requirements are also fulfilled within the scope of the manufacturer's warranty. This is not the case if, for example, injuries and product damage cannot be ruled out due to sharp edges on equipment or a lack of intervention protection.

If unauthorised spare parts are installed or repairs are carried out independently, the manufacturer's warranty is likely to be voided. For the inspection of a bottle washer, a trouble-free filling process is essential for meaningful data acquisition. Long malfunction times during the filling process, which are associated with a long dwell time of the bottles in the bottle washer, falsify the overall picture.


Check the lye concentration

In order to enable a meaningful interpretation of the results during a check, the lye concentration is essential in addition to compliance with the target temperatures of the lye and the water baths. Here it is important not only to determine the total lye concentration, but rather the effective portion of the lye (sodium hydroxide).

This can be determined by ascertaining the soda content (sodium carbonate) in the lye and should reach a value of about two percent [2]. Depending on the type of washing machine or the requirements for cleaning the empties (for example, bottle-fermented wheat beers), this value can be lower or higher. This also depends on the soft liquor temperature set.
industrial bottle washerApproval and inspection of cylinder cleaning is advisable for both new and existing systems. (Picture: BRAUWELT)

Check temperatures of baths and waste water

The control of the various caustic and water baths serves on the one hand to ensure cleaning effectiveness, and on the other hand for economic verification. The guide values for the temperatures of the individual baths depend on the machine type or design and the manufacturer's philosophy.

The temperatures are usually shown on the outside of the machine or in the display of the control unit. Nevertheless, it is advisable to check these values. For example, during investigations by the research centre, all caustic and water baths as well as the waste water are wired with thermocouples and the values are recorded every second. On the one hand, this allows an average value to be determined over a representative period of time, which can be compared with the manufacturer's specifications; on the other hand, temperature fluctuations can also be made visible. Furthermore, the temperature sensors installed in the bottle washer are checked in this way. 

By measuring the steam and condensate temperatures, the efficiency of the heat exchanger for caustic heating can be determined. Another useful check is to measure the temperature (and conductivity) in the machine itself. In this case, a test bottle made of hard plastic and equipped with sensors detects on the one hand the cycle time of the bottles through the individual baths, and on the other hand any temperature differences in the machine can be detected. The latter can be detected by inserting the test bottle at different points (left, centre, right). 

Furthermore, it is also useful to measure the temperature of the cleaned bottles at the delivery. This is realised with the help of an infrared thermometer.
brown beer bottles on belt conveyor systemNot only the bottle filler itself plays a role in the microbiological situation, but also the bottles, air contamination and the empty bottle inspector (Picture: BRAUWELT)

Control of the microbiological situation

Microbiology is an essential aspect in the bottle cellar. The last production step, when the product reaches the bottle, is always delicate and deserves increased attention.

Here, however, the focus is not only on the bottle filler itself, but also on the cleaned bottle, as well as on air contamination or the empty bottle inspector. In the area of the bottle washer, the microbiological situation at the bottle discharge should therefore be checked before production begins and after approx. three to four hours of production. Sterile swab samples at various points (discharge conveyor, guide rail, head section, tooth plate, discharge/drip channel) are considered useful for this purpose; NBB-AM broth is suitable as a nutrient medium.

At the identical times, the air quality at the bottle delivery should be checked. For this purpose, it is advisable to use an air sampler that transports a defined volume onto an agar plate. It makes sense to check for beer spoilage bacteria on the one hand (for example with NBB agar), and on the other hand for general air contamination (more universal nutrient medium such as wort agar).

Probably the most important microbiological check is carried out on the cleaned bottles themselves. Neither beer-spoiling bacteria nor cultured yeasts should be found in them. For this check, it is recommended to interrupt the production process and remove a complete row of cleaned bottles from the dispenser. The removed bottles should be immediately sealed with a sterile foil or cap to avoid subsequent contamination. In addition, the bottles should be numbered for better interpretation of the results. Depending on the desired extent of the examination, several bottles can be combined into one sample in the laboratory.

Furthermore, it is also essential to microbiologically test the fresh water quality at the facility, as otherwise an interpretation of the results is not meaningful. If the rinse water is treated according to § 11 TrinkwV, testing this water before and after the administration of the disinfectant, as in the case of dosing with chlorine dioxide, can also lead to decisive findings.
contaminated beer bottleExample of an insufficiently cleaned bottle with standardised contamination (Picture: Hubertus Schneiderbanger)

Checking the cleaning performance

Another important control is the cleaning check using standardised contaminated bottles. Such standardised contaminated bottles can either be produced in-house for brewery-internal tests or obtained directly from various suppliers (for example from the Weihenstephan Research Centre for Brewing and Food Quality or from VLB Berlin). The production of these bottles for brewery-internal examinations can be found in the BRAUWELT article "Empty bottle control: cleaning proof of bottle washing machines" [3].

To carry out this test, the production process must be stopped and a complete row filled with the test bottles. After the cleaning process, all bottles are visually inspected. In this case, too, it is advisable to label the bottles with a number in order to retrospectively relate the weak points to the transport carrier row (often also called basket row). 


Surface tension of the residual liquid

Another important aspect to check is the surface tension of the residual liquid from the cleaned bottles. For this purpose, a complete series of cleaned bottles should also be removed after a process time of around two hours and immediately sealed. There are various methods for measuring the surface tension, which must be taken into account in the run-up to the guarantee fixation.

In any case, the average value determined for cleaned bottles should not be below 60 mN/m, as otherwise the foam stability of the beer may deteriorate [4]. The quality of the glass must also be taken into account in this investigation, as older returnable containers lead to poorer surface tension values due to their higher surface roughness.
beer bottle belt conveyor systemIn new plants, the lye carry-over through transport carriers or chains is not yet too high - but this can change (Picture: BRAUWELT)

Lye carry-over through transport carriers

Caustic carry-over is the amount of caustic that is carried over from the individual baths to the subsequent baths on bottles, transport carriers and chains [5]. In new plants, the leach carry-over through the transport carriers is usually not yet too high, but this can change with age in the case of increased stone formation. From this point of view, it makes sense to check this value occasionally, even in older plants.

Otherwise, the determination of the caustic carry-over can indicate that the system is running too fast (too little dripping time), that labels are not being discharged sufficiently (labels on the chain increase caustic carry-over, for example) or that the seals on the sprays are defective (caustic can get into the neighbouring zones).

The lye carry-over should therefore not exceed a technical guideline value of 12-18 ml/bottle. The easiest way to determine the lye carry-over is to use an indirect measuring method, in which the lye concentrations of the two baths following the soft lye bath are determined several times and calculated using the volume flow of fresh water and lye.


Evaluate consumption data

The determination and evaluation of consumption data is also of great importance. An essential factor for breweries to purchase a new bottle washer is the saving of energy, water and additives. Modern bottle washers should have a water consumption of 160-240 ml/bottle. In addition, the consumption of additives is usually recorded and documented.

As a rule, the consumption data can only be recorded via the installed measuring devices. From these, the heat losses per bottle can normally be calculated via the steam consumption and the temperatures of the steam as well as the condensate, which should not exceed a value of 6-12 kcal/bottle. The pH value in the waste water should also be checked and usually not exceed pH 11.5.
In addition to the investigations shown, further measurements are possible. In addition, the number of bottles with labels and the amount of water in the cleaned bottles are usually detected. The number of bottles with labels should be determined by counting over a representative period of time and should not exceed a value of 0.02-0.05 per cent. The detection of the residual water content in cleaned bottles verifies that the bottles have sufficient dripping time and should be between 0.5-0.7 ml/bottle.
1. DIN 8784, Getränkeabfüllanlagen – Mindestangaben und auftragsbezogene Angaben, 2013.
2. MEBAK, Band IV,, Alkalische, carbonathaltige Reinigungsmittel, 1998, S. 61 ff.
3. Schneiderbanger, H. et al: „Leerflaschenkontrolle: Reinigungsnachweis von Flaschenwaschmaschinen“, BRAUWELT Nr. 28-29, 2020, S. 756 ff. External source
4. Glas, K.: „Oberflächenspannung – ein zunehmend aktuelles Thema in der Brauerei“, Der Weihenstephaner, 2, 1999, S. 98 ff.
5. Kompetenzforum Getränkebehälter: Praxishandbuch für die Reinigung von Mehrwegflaschen aus Glas oder PET, 2. Auflage, 2005.
6. Schneiderbanger, H.; Cotterchio, D.; Jacob, F.: „Überprüfung und Abnahme von Flaschenreinigungsmaschinen“, BRAUWELT Nr. 46-47, 2020, S. 1239–1242. External source