A Review of the Robustness of Epoxy Passive Fire Protection in Offshore Environments
a report by Robin Wade
International Paint Ltd., Protective Coatings, United Kingdom
Millions of kilograms of epoxy passive fire protection (PFP) have been applied and are in service, preserving oil and gas steel structures worldwide in the harshest of conditions and in varying climates (Antarctic to tropical). This special coating intumesces (swells up) in a fire scenario to provide insulation, due to the formation of a charred foam layer, to protect the steel. This thick insulation layer delays the steel reaching its critical failure temperature.
Properly formulated epoxy PFP coatings have been used for more than 30 years and are the tried and tested solution for the protection of steel in the event of potentially catastrophic fires. For most of the life of an epoxy PFP, the primary function is that of a barrier coat to prevent the corrosion of the steel substrate for the lifetime of the facility (see Figures 1 and 2). The expectation is that environmental weathering of the epoxy PFP will not impede its fire protection ability.
Improper selection of epoxy PFP can, however, result in cracking, blistering, delamination, disbondment, reduction in mechanical properties (i.e. hardness) and most importantly a reduction in fire performance that may result in inadequate steel protection when required.
Many of the product issues that are present in the field can be related to the use of binder systems, which have a positive influence on the efficiency of the product in fire testing. Paradoxically, these binders can easily compromise the integrity of the system when exposed to environmental stresses (varying atmospheric conditions or periodic immersion).
The following information is focused towards product considerations that need to be taken into account from a time soon after the product is applied to the steel and then throughout its service life. This ensures that performance can be assured for the lifetime of the asset. Although not the primary focus of this article, product consideration alone is not the only factor in attaining the expected performance. Application and
Robin Wade joined International as part of the future technologies group in 1987 prior to attending university. Having been sponsored through Cambridge University by International Paint, Robin achieving a Masters degree in Natural Sciences (specialising in Chemistry). He then took up a permanent post with International Paint as part of the World Wide Marine and Protective Coatings Technology Centre in 1991. After a brief period in the Rheology and Colloid science group, Robin joined
the World Wide Protective Coatings Division in 1993. Between 1993 and 2006, Robin then lead the development of water-borne and high solids anti-corrosion solutions contributing to the World Wide Product Range. In 2007–2009 he took a post as the Technical Manager for the World-wide Protective Coatings Laboratory leading the Fire Protection Support and Development activity which included leading the development of a New multi-million pound Fire Protection Facility. He became Technical Marketing Manager for Chartek Fire Protection in 2009, leading support and development strategy for the World Wide Protective Coatings business.
installation issues are many and are a significant contributor to product performance both early in its design life and when in service.
What are the Challenges?
Two challenges critical to lifetime performance have been evaluated. These can be summarised as:
• what happens when different epoxy PFPs are exposed to trapped (or ‘ponded’) water when in service; and
• what happens when different epoxy PFPs are exposed to prolonged atmospheric weathering?
It is difficult, if not impossible, to avoid scenarios where periods of water immersion or standing water occur during the period between epoxy PFP application and construction, especially when it is considered that transport to stations offshore may take many weeks on open decks of marine vessels.
Top-coating the epoxy PFP could be thought of as a means to protect against the effects of water exposure. In practice, however, to anyone who has visited a construction yard it is evident that damage can easily occur during fabrication of the final steelwork. Upon construction, preparation required for attachments and incomplete work in the coating yards often leads to top coats being damaged and missed. If top-coating the epoxy PFP is critical to its long-term performance then in-service maintenance of the top-coat is critical; yet it is known that in reality such maintenance cannot be relied upon once out in the field (see Figure 3).
Given that epoxy PFP is a safety-critical element of design, it is important to demonstrate that the integrity of the epoxy PFP is not reliant upon the top-coat. The inherent resistance to water and atmospheric weathering of the epoxy PFP should not be underestimated.
The selection of a particular epoxy PFP material at the time of construction can be driven purely by product and installation costs. However, should the wrong selection be made, the value saved from application is extremely small compared with the exceptionally high cost of replacing/maintaining materials offshore. This is ultimately a complicated and hazardous operating environment in which to carry out maintenance. It should also be noted that the savings due to PFP application are small in comparison with the overall cost of the installation.
How Do We Answer These Challenges?
This article presents the results from a series of tests on four commercially available epoxy PFP products (hereon referred to as products A–D). The tests were selected to address the challenges just discussed. They are representative of generating the type of failure observed in the field.
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HSE
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