Silo cleaning and disinfection / verification and reporting

Silo cleaning and disinfection / verification and reporting

Silo cleaning and disinfection / detection and reporting management is located in our company with approx. 40% service application. This means that approx. 40% of our customers are food processing companies in Europe. NT Service GmbH is requested by companies that want to maintain or achieve a high quality standard.

Example of a “fictitious” system and operational inspection

Reason for inspection in accordance with the Industrial Safety Ordinance, Hygiene §18 Infection Protection Act


NT Service GmbH was commissioned to inspect the silo facility with protein meal content mentioned in letter XY at site XY in accordance with GMP standards. The reason for the inspection was, on the one hand, an assumption of contamination with Salmonella on the part of the operator and, on the other hand, the aim of supporting the plant operator in future decision-making criteria. On site, I, Matthias Natusch, met with the person responsible for the plant XY.

NT Service GmbH has very well-trained specialists, state-certified food technicians, internal REFA-certified GMP and IFS auditors with many years of experience in the QA area of various food companies. This know-how in professional core competence has never been achieved by any known competitor. We make our core competence available to our clients and always protect their interests in a binding and legally confidential manner.

Structure and points of view:

  1. structural analysis – was not recorded
  2. visual impression of the facilities
  3. value retention of the systems
  4. corrosion wear – was not recorded
  5. hazards – not recorded
  6. hygiene and analysis
  7. image systems and description
  8. conclusion

2. Visual impression of the systems

In the course of the inspection, a visual impression was created which inevitably shows that the system operator consciously promotes and pursues a very high level of cleaning and hygiene. The associated good cleaning status normally only allows for minor hygiene objections.

However, after viewing the image material, the silo system shows some worrying problem areas, which should definitely be remedied in the future. In terms of design, recurring and extensive cleaning of the silo systems, e.g. of the chain conveyor, is only possible with complex effort, but inevitably necessary.

The silo material conveyor unit, material removal device and filling devices are complex system components that require recurring and very thorough cleaning.

3. Maintaining the value of the systems

The plant operator had 2 new silo systems installed around 3-4 years ago. At the present time, however, both systems appear to be in a battered state. The reason for the external negative influence is apparently the “silo acidification” ordered by the operator, i.e. the wetting and fogging of the silo system with formic acid for the purpose of disinfection and germ reduction. However, this endeavor has strong negative consequences for the silo outer wall. Corrosive influences will have a negative impact on the silo outer wall in the foreseeable future.

A regular inspection shows you the current safety and functionality of your systems. Careful maintenance extends the service life and preserves the value of your systems. You save costs if defects are detected and rectified at an early stage.

The plant operator should be aware that extensive silo exterior maintenance is necessary to mitigate the negative consequences of “acidification”.

Fig. 1 – Acidic corrosion deposits on the outside of the silo – can be remedied by cleaning the outside.
The silo screw connection is relatively heavily corroded.

4. Corrosion wear


Hazards at the silo system are of a bacteriological, constructive and chemical nature. For the plant operator, hazards to humans must be prioritized. Hazards to plant safety are prioritized, but the plant operator makes this decision to the best of his knowledge and belief.

Due to the salmonella contamination found in the loading area, negative influences on production can be practically ruled out. According to the operator, no contamination of the company’s own or external personnel was detected at the time of the inspection.

The contamination only affects minimal segments and is localized. Negative pathogenic contamination in the production area is not present after extensive quantification.

I assume that the pathogenic findings are due to a lack of cleaning in the past. Since the plant operator has neither proof of disinfection from the cleaning company nor can they prove in any other way that a protein error can be ruled out, it can be assumed on the basis of this knowledge that germ colonies somewhere in the silo plant were not cleaned or disinfected.

In the case of technically sound disinfection, sanitation is always chosen before disinfection. If the sanitation cleaning is not rinsed properly, a soap error occurs and the success of the disinfection is also at risk.

Protein error:
Protein error is the reduced effectiveness of chemical disinfectants in the presence of proteins (proteins) or protein-containing material (e.g. blood, serum, pus).

Soap defects:
Reduced effectiveness of a disinfectant due to reaction with soap or anionic surfactants, such as those found in cleaning agents. A compatibility test should therefore always be carried out before adding detergents to disinfectants.

When disinfecting, the rule is: clean first, then disinfect. To avoid the soap error, cleaning agents and disinfectants should be coordinated. Check with the manufacturer.

If you use foam guns for cleaning and disinfecting, you should make sure that no cleaning agent remains in the storage container.

The practical user of a disinfectant must be aware of the basic conditions. The company offering disinfection for the purpose of silo cleaning must be aware that this company is liable for future damage if the disinfection was not carried out according to the state of the art. Not providing the plant operator with proof of disinfection without being asked is also unusual and speaks for the theoretical deficits of the company.

6. Conclusion / Recommendation

1. The plant operator makes every effort to maintain an extensively organized and implemented hygiene standard. Clean streets and outdoor work areas speak for themselves.

2. The system operator should consider carrying out regular staff training by competent persons. We are happy to provide appropriate personnel for this purpose. The system operator’s personnel should be trained in the following measures: Disinfection and sanitation (protein errors/soap errors), germ carry-over for outdoor and indoor areas.

3. The system operator should be advised to have the silo system in question cleaned and disinfected again. Cleaning the outside of the silo should also be included, as this is a matter of preserving the silo / maintaining its substance. In the course of internal silo cleaning and disinfection, the system operator must be provided with a comprehensive disinfection report, which breaks down and verifies the demonstrable steps of the disinfection. Disinfection must be carried out by a specialist company that is suitably qualified and can simultaneously evaluate cleaned and disinfected surfaces using negative ATP measurements.

4. Recurring assessments by the operator QA are important key elements in hygiene-compliant operational management. The QS can be provided with semi-quantitative rapid test equipment in order to be able to react even more quickly to any hazards in the event of contamination.

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