The flange protection challenge

The integrity of flanged connections is critical to the containment of fluids in a piping system. Loss of containment, whether in chemical lines such as hydrocarbons and gas systems or water distribution lines, will have significant environmental, operational and commercial impact, and could pose a serious safety risk. Flanges 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.

Figure 1. flange corroded

Figure 1. Flange corroded

Corrosion issues and 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.

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. 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.

Therefore, external corrosion protection of flanges and fastenings is critical in order to be able to both monitor the system and provide more effective and realistic quality control and inspection procedures.

Existing solutions to answer the corrosion protection dilemma of flanges

Due to the complexity of the flange geometry, it has become a challenge to design efficient solutions to protect flanges against corrosion. The ideal solution would be a system that combines excellent corrosion protection along with a simple installation procedure and is suitable for all flange sizes and shapes, in conjunction with easy bolt access for inspection purposes.

Common solutions available on the market like conventional paints, clamps and covers, solid or semi-solids tapes and polymer bags are widely used but none have proved to be an infallible solution. New solutions like hot-melt thermoplastics offer an interesting and cost-effective alternative, as the material can be re-melted and recycled after removing it to access the flange; however, it requires hot work as well as specialist equipment.

Peelable coating for flange corrosion protection

To offer an alternative answer to flange corrosion issues, Belzona has formulated a new peelable coating concept, Belzona 3411 (Encapsulating Membrane), specifically designed for the protection of flanges, fastenings and associated pipework. Belzona’s R&D Chemist, Ruckseeta Patel, has stated that “with the use of clever polymer chemistry, we have created a flange protection system strong and flexible enough to be peeled back without tearing. This solution features the flexibility of elastomers but is based on a completely new technology excluding the use of isocyanates and toxic metal catalysts. The system bonds to manually prepared surfaces and does not involve hot work, making it safe and easy to use.”


Figure 2. Belzona flange encapsulation system

This system can be used to protect any flange shape, size or configuration from corrosion and completely encapsulates the flange to exclude any moisture and can be hand applied at temperatures between 15°C-60°C. When maintenance is required, the system can be cut open around the circumference between the flange faces using a sharp knife. Once the required maintenance has been completed, the system will fold back to its original position where it can be simply re-sealed by application of a further layer of Belzona 3411 over the cut area thereby maintaining corrosion protection of the flange and fastenings.

Belzona 3411 exhibits excellent corrosion protection, UV and heat resistance up to 60°C, demonstrates a good fire resistance and has a low hazards class. Excellent adhesion properties onto manually prepared surfaces such as ISO 8501-1 St2 or SSPC SP-2 have also been reported.


Figure 3. Salt spray test showing no corrosion under the encapsulating system


Figure 4. Salt spray test showing no corrosion under the encapsulating system – close up

This encapsulating system can be used not just to provide an excellent corrosion protection for the flanges, fastenings and pipes associated but also as a preventive system which helps improving and easing further monitoring and inspection of flange faces.

Ensuring asset reliability has become one of the major challenges faced within many industries today. As a result of this, a growing demand for new and more effective corrosion protective systems can be identified. The corrosion protection challenge presented by flanges has led to the development of a number of solutions. However, most of them fail to meet all the requirements of providing excellent corrosion protection, a simple installation, are suitable for all flange sizes and shapes, and allow easy access for inspection purposes. Made available in 2014, Belzona’s innovative encapsulating membrane system has been specifically developed to meet all of these requirements. Its unique design ensures that further monitoring and inspection of flanged connections can be easily carried out.

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