Fire Protection and Safety for Offshore Topside Structures

[Editor's note: A version of this story appears in the September 2020 edition of E&P Plus. Subscribe to the magazine here.]  

As the offshore industry continues to push the limits when it comes to extending the life of assets and supporting operation in increasingly harsh conditions, the need for reliable and durable solutions that deliver proven performance has never been greater.

The focus on technical safety in oil and gas production is continuously increasing, with an expectation that all products and solutions are tested, qualified and certified to relevant regulations and standards. Companies need to be committed to designing high-performance, robust and reliable solutions that will improve safety and protect people, equipment, critical components and structures in the most demanding environments.

Fires in offshore or onshore installations can lead to immense destruction, making the uses and understanding of the properties of passive fire protection (PFP) materials crucial. PFP is typically used in defined areas highlighted in project-specific design accidental load specifications and is required to meet blast and fire requirements.

A wide range of PFP materials is available in the market, including syntactic phenolic resin-based coating, elastomer-based coatings, epoxy systems, cementitious protection, mineral wool wraps and insulation, and fireproof cladding, as well as concrete products.

As the properties of each material vary, finding the most effective material and technical solution for a project is crucial. Factors to consider when choosing the right material include the potential source of a fire, its possible duration, temperature and blast, along with qualifications, certificates and material properties.

The objective of PFP is to prevent or mitigate the serious consequences of fire:

• Prevent escalation of fire to adjacent areas;

• Ensure a temporary refuge is intact for a specified amount of time;

• Protect people from the fire (heat and smoke) and make escape or evacuation possible;

• Protect essential systems and equipment; and

• Maintain structural integrity for a set period.

Elastomer materials

Elastomer-based PFP products and systems are well suited for protection against corrosion and fire scenarios. The most extreme fire scenarios are cellulose, hydrocarbon, jet fire and high heat flux—all distinctive to topsides offshore. Elastomer materials can be used alone or in various combinations to meet specific requirements.

Corrosion under insulation is a serious form of localized external corrosion that occurs in insulated carbon and low-alloy steel equipment. This form of corrosion happens when water is absorbed by or collected during the insulation process. The advantage of using elastomer-based materials for PFP is the excellent steel substrate bonding properties offered, providing additional corrosion protection.

Testing of PFP materials

Offshore projects require elastomer materials that show excellent fire protection properties in accordance with relevant authorities, regulations and standards.

Hydrocarbon testing fire, or pool fire, is a fire fueled by hydrocarbon compounds (oil and gas), having a high flame temperature up to 1,000 C within 5 minutes, achieved almost instantaneously after ignition. The heat rises to 1,100 C shortly thereafter, following a given temperature curve in accordance with a standard. Fire resistance tests designed to determine the resistance to jet fires of PFP materials and systems. The material’s performance in tests gives an indication of its behavior in a jet fire.

Specialized extended jet fire testing, also referred to as high heat flux, is performed in a much larger chamber allowing increased temperatures of 1,300 C to 1,400 C, with higher heat flux (350 kW/sq m) and allows testing of larger specimens.

Qualification tests are typically performed at accredited fire test laboratories in accordance with set standards and certified by a third-party approval institute. The most common type of testing is the performance of project-specific sequential testing, combining the different fire scenarios, including blowout, jet fire, pool or hydrocarbon fire.

Using elastomer-based PFP materials

PFP elastomeric materials used as deck protection ensure water repellence, flexibility and noise reduction, minimizing corrosion effects by protecting anti-corrosion systems. The prevention of fire escalation between partitions is essential. Due to its flexibility, elastomer-based PFP materials can be applied to any surface, flooring, walls or roofing, and it is mounted with a chemical or mechanical bond. The systems ensure water repellence, flexibility, noise reduction and minimize corrosion effects by protecting anti-corrosion systems.

Protection between partitions, escape tunnels and routes are also an important part of any total protection solution. Elastomer-based PFP seals offer a flexible connection between rigid metal sections. Capable of handling large displacements, they connect modules, maintaining a fireproof partition, absorbing misalignments, angular deviations and eliminating concentrations of stress. Elastomer-based seals used in escape tunnels and door seals offer protection of door frames and connecting fire-safe escape areas.

The benefits of elastomeric seals include the

• Elimination of the propagation of vibrations, dynamic loads and deviations caused by a fabrication process;

• Customization to fit any shape and size to suit individual project requirements; and

• Installation on a variety of structures with bolting.

In areas where drainage is required, elastomer-based seals can be made as a drain gully that supports the design of a closed deck, eliminating the need for fireproofing of process deck structures. Drain gullies allow spillage from process modules to drain, eliminating the requirement for multiple drainage boxes and integrated overflow.

Risers

Oil and gas export risers, flexible risers and pipes have the potential risk of being exposed to blast and fire, together with corrosion under insulation. Using elastomer-based PFP for risers can combine corrosion protection with blast, jet and pool fire properties as well as mechanical protection. Elastomer coatings on risers as corrosion protection is an extremely robust solution, widely recognized as the most effective method for riser corrosion protection, particularly in the highly corrosive splash zone area where the elastomer coating is chemically bonded to the substrate.

Pipe penetrating through partitions increases risk in the event of a fire, allowing a fire to spread between areas.

An elastomeric pipe penetration seal acts as a water- and gas-tight shield against both blast and fire. Suitable for a wide variety of different size and shape applications, penetration seals close the pipe penetration and allow movement of the pipe during operation.

Nuts and bolts

Installations can be exposed to leakages of flammable and/or explosive substances, and severe operating conditions increase the likelihood of leakages, with the majority originating from flanges or fittings. Bolts can easily lose their load-bearing capacity when exposed to heat and are subject to pretension, with the load carried by the threads. When threads (bolt and nut) are heated sufficiently, the nut will disconnect and leakage will occur. PFP of bolts and flanges is an important part of any installation, and they can be protected in several ways. The most common is to build a PFP box around the flanged connection, focusing the protection on covering the most critical area, explicitly covering the bolts and nuts to extend service life in the event of a fire.

Developments in elastomeric materials allow nuts and bolts to be directly covered with molded material, providing a lightweight, space-saving solution that is easy to apply, offering improved levels of protection.

Conclusion

Elastomer-based PFP products are maintenance-free, watertight, resistant to ozone, seawater and UV-light as well as suited for use in harsh and cold environments, absorbing and preventing stress and strain transfer within structures.

While the oil and gas industry continues to push limits when it comes to extending the life of assets and operation in even harsher environments, PFP will be a key to mitigating the risk effects of fire, saving lives and assets.