Sommaire
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- Implantation d’une méthode microbiologique alternative et polyvalente au laboratoire. Exemple du BACTALERT 3D®
- From Variable Operator Numeration To The Standardized 3P® Station Automated Colony Counting On Environmental Monitoring Culture Media Plate
- Analyse de la charge microbienne en temps réel pour prévenir les risques de contamination et mieux contrôler les procédés.
- ISO 22519 PW/WFI production systems standard: Quality aspects.
- Eau pour préparations injectables en vrac (productions, coûts). Étude de cas axée sur la qualité microbiologique.
- Coming to basics on rouging.
- Winning combination: Reducing particles in RTU packaging by aligning lid material, adhesive and sealing parameters in a holistic approach.
Coming to basics on rouging.
The presence of rouging in high purity water distribution system is stated as a troubleshooting well known but definitely diffcult to explain. owever the last few years the default is highly increasing. This paper statement is intended to bring to debate a further point of view on learning experience and to share with the other colleagues their point of view. Basically, its purpose is to offer some practical guidance on what to do when rouge appears in the system and what to consider in terms of its impact on the operation
1. What is rouge ?
Rouge is discolouring typically found on the internal surface of water system based on SS and operated at elevated temperature over 65°C. The name rouge comes from the likeness in appearance to the extremely fine powder used by jewellers for polishing purpose. In pharmaceutical water system, rouge is interpreted simply oxidation-corrosion. The appearance of red/brown discolouration on the internal water surface of stainless steel is always alarming!
The rouge is considered as a product of corrosion phenomenon of iron which leads to ‘ferrite’. Rouge is consists of a mixture of iron oxides and hydroxides. The metallurgical specialists describe many kinds of rouge from grey through pink to black colour depending on the environment. We can distinguish 3 classes of rouge:
Class 1 rouge: the rouge is migratory type coming from external source (rouge coming from an external pipe to the system such as the carbon steel of feeding water).
Class 2 rouge: initiated by presence of chlorides or halides which are, the residue from process installation or from water soluble halide ions. These aggressive chemical products destroy the passive layer.
Class 3 rouge: black in colour associated with high temperature e.g. steam. This form of rouge leads to pitting corrosion.
2. Where is rouge found ?
Many observations have been found rouge in the following equipment: • Pump impellers
• PTFE surface such as tri clamp gaskets
• Connections hoses nylon/Silicon / PTFE
• Storage vessel surfaces
• In line filters and housings
• Vessel spray balls.
3. When is rouge found ?
The Rouge formation request basically three ingredients:
• High purity of water system constructed from SS,
• Polished surface to give suitable internal environment on welded • Construction Operation at high elevated temperature.
When new water system has been installed, commissioned and validated, it starts free of rouge. Most installation contractors these days employ commissioning procedures such as:
• Degreasing
• Chemical passivation using nitric acid at 2% -3% volume
The purpose of passivation process is to remove grease, ferrite particles and to create a passivation layer which will protect the internal surface SS from the aggressive environment.
For Rouging one can assume that the chromium oxyde layer has been broken or has not been regularly formed on the metallic surface.
How important is the polishing surface for the SS?
Generally, electro polishing process seems to offer protection from surface vessels because polishing occurs after the manufacturing is complete. How ever rouge seems to appear in pipe work systems whether mechanically polished or elecropolished material has been employed.
4. Where does rouge come from ?
In pharmaceutical water system rouge emanates from aggressive pure water on the ferrite content of the SS. So, one obvious way to avoid it is simply not employ SS in the first place. But we couldn’t since the SS material is accepted as the most and best hydro-hygienic material.
But what about the grade of SS?
We remind that SS contains chromium (16,18%), nickel (10-15%) and molybdenum (2 to 3%) in the necessary proportion. The applicable norms as ASTM 270, DIN 17457 or BS 316S12 defines the composition of SS in quite variation.
5. External indicators of rouging
We have mentioned before that rouging is found on elastomeric surfaces, nylon and silicon rubbers. We have seen rouge discolouration appears in translucent silicone hoses used in tubing connecting TOC instruments.
This area could be used as a reference to check whether rouging is in the circuit.
6. What is the impact of rouge on quality of a water system ?
We should carry out a risk assessment before to decide to continue using pharmaceutical water. The presence of high amount of rouge will affect definitely the conductivity. It has been found that the presence of rouge will not affect the conductivity limits specified in USP 28.
7. How to avoid rouge ?
System design, specification and construction are the main subjects to be carefully followed according to cGMP and cGEP:
• Employ 316 L
• Consider electro-polishing processes vessels and piping Ra 0,4 to 0,6 μm
• Material certificate 3.1.B
• Follow correct welding specification
• In process control of installation and welding consistency
• Correct degreasing
• Correct passivation procedure
• Use test ferroxyl test piece or similar to demonstrate passivation.
• Consider lowering the operating temperature a little if rouging appears
• Select observation points in the system and check regularly the rouge.
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Mongy SAKLY – SANOFI PASTEUR
Mongi.Sakly@sanofi.com
