Safety in the Plant
The flange protection challenge
The integrity of flanged connections is critical to the containment of fluids in a piping system. Juan Lopez and Alice Jucquois report.
Die Intaktheit von Flanschverbindungen ist entscheidend für die Eindämmung von Flüssigkeiten in einem Leitungssystem. Juan Lopez und Alice Jucquois berichten.
L’intégrité des rapports à bride est vitale pour contenir les fluides dans un système de tuyauterie. Juan Lopez et Alice Jucquois témoignent.
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Fig. 2. The Belzona flange encapsulation system.
langes present a unique corrosion protection challenge because solutions must not only prevent corrosion, but also allow
future access to fastenings in the event that maintenance or disassembly is required. Exposure to corrosive environments or polluted industrial atmospheres leads to high corrosion rates of unprotected flanges. In addition, due to the complex
geometry of a flanged connection, problems such as crevice corrosion found within the void between the two flange faces and galvanic corrosion found where dissimilar metals are used are common and can prove severely detrimental to the integrity of the piping system.
Inspection of flanges As flanged connections are a critical component within the piping system, effective monitoring and inspection techniques are required to minimise unscheduled shutdowns due to leakage in order to meet ever demanding production requirements. Usually, leakages occurring between the flange faces are the primary concern,
leaving fastenings and pipe external protection unaddressed, which can lead to serious problems especially when external environmental conditions are severe.
Fig. 1. An example of a corroded flange.
Insufficient external protection can lead to rapid and more extensive damage to the flanges and fastenings, which will in turn accelerate the deterioration of the sealing system as a whole. The consequences of such a situation are not easy to predict since they are dependent upon prevailing conditions. Depending upon the severity of the environmental conditions there may, at best, be a slow continuous degradation of the substrate, however, under extreme conditions, the external corrosion process may rapidly reach a point where the structural integrity of the system is adversely affected and could result in a catastrophic loss of containment. Since visual inspection of the sealing
faces of flanged connections can only be accomplished during a shutdown of the system, it is vital that this process is made as simple as possible and therefore elimination of external corrosion must be a high priority. If shut down is not an option, then an alternative method of inspection would be to use ultrasonic techniques but again this process can be made much more complex and inaccurate if external corrosion is not controlled.
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