Safety and Sustainability: A new standard of safety for onshore passive fire protection
The onshore energy and petrochemicals sector is defined by the strength of its safety culture, but it has only recently begun moving toward adoption of the highest fire protection standards. For many years, industry practice has been to protect onshore assets primarily against pool fires, but recently the industry has begun to recognize the need to adopt standards covering the more dangerous hazards of jet fires. This is particularly important in light of the huge increase in gas processing, transport and handling, whether from U.S. shale gas extraction, growth in LNG or other sources, such as hydrogen.
Gas processing facilities and shipping terminals are threatened by some of the biggest potential hazards in terms of leaks and spills, with the associated risks of cryogenic spills, explosions and jet fires (FIG. 1). The expansion of gas import and export capacity creates hazards different from those in refineries or petrochemical plants. To adequately protect these plants, designers and operators must consider protection from jet fires at a design level.
|FIG. 1. Multi-directional jet fire release from leaking flange joint. Photo courtesy of DNV GL.
This is an issue of concern for the U.S. natural gas industry, since the American Petroleum Institute (API) 2218 standard on fire safety is designed to cover fireproofing at petroleum refineries and petrochemical processing plants, rather than LNG terminals and gas processing facilities. The potential risks are far greater at gas export terminals because much more processing takes place before the natural gas can be turned into a liquid for shipment. The process to remove contaminants and process the gas to the required purity level involves a sequence of treatments at high pressure, bringing more complexity to the plant design and increasing the potential for leaks from multiple sources.
Emerging standards. The requirement for a standard against jet fires came to the public’s attention after the Piper Alpha disaster in the North Sea in 1988, in which 165 people on the platform and another two from the rescue boats lost their lives. One of the key findings of the subsequent enquiry was that the passive fire protection (commonly referred to as fireproofing) in place on the platform did not survive as long as predicted. In fact, the jet fire on Piper Alpha destroyed the fire protection materials within a matter of minutes, rather than the 1 hr–2 hr for which most systems are designed. For the offshore industry, it was a wakeup call.
Much subsequent research was carried out on the behavior of jet fires; however, such testing is expensive. In the early 1990s, work started on a more economical and repeatable test that could become a standard for testing of passive fire protection materials. The resulting standard—ISO 22899-1—became an internationally recognized benchmark that could be used to test the ability of fireproofing to withstand jet fire (FIG. 2). It is still the only recognized standard of its type.
FIG. 2. Medium-scale jet fire test to ISO 22899-1. Photo courtesy of PPG Industries.
For many years, the onshore industry paid much less attention to jet fires than to pool fires, despite the fact that these types of fires can happen anywhere onshore or offshore, and the result is a credible fire scenario that should be mitigated against. Fire protection in the onshore market has largely been driven by the API 2218 standard, which did not address jet fires until an incident at Valero’s McKee, Texas refinery in February 2007. A fire escalated significantly because jet fires were much more far-reaching than the pool fires for which the facility’s fire protection was designed. Again, fireproofing was installed, but in the wrong place and to the wrong performance standard.
The main body of API 2218 is applicable only to pool fires, but the revised standard now includes an annex stating that asset owners should consider jet fires in the design of their fireproofing. The guidance covers fireproofing of fittings and steel components, but direct guidance on non-pool fires at gas storage and processing facilities is outside of its main scope.
Industry trends. Even at a time when the industry was recognizing that hazards were becoming more severe, many passive fire protection (PFP) manufacturers were designing coatings for less severe fires because jet fire resistance standards did not exist in any meaningful way.
These pool fire-resistant materials are already in use on the U.S. LNG export facilities currently in operation, but when the potential risks are considered in detail, these coatings do not accurately address the hazards present at these facilities. A gas facility will have a low risk of pool fire but a very high risk of jet fire. However, some designers will still specify coatings designed only for pool fires because they are less costly than those designed to resist jet fires.
It is important to note that the intensity and high momentum of jet fires means that water deluge is not effective as a means of active fire protection. The jet will punch straight through water and will heat up the steel, vessel and piping very quickly, to the point where rupture and resulting boiling liquid expanding vapor explosion (BLEVE) is a real risk.
Another problem is that deluge may extinguish the fire without stopping the leak, which can result in clouds of gas that can then ignite and cause an explosion that is potentially more lethal than the jet fire, risking damage to active fireproofing or passive fire protection if it is not resistant to explosion.
No compulsion exists for fireproofing manufacturers to design against the most hazardous potential event; designing against jet fires is certainly more complicated (and potentially more costly) than designing for pool fires alone.
High-performance fireproofing coatings, including the newest coatinga on the market, have a minimum of 30 min of jet fire resistance. This ties into the API standard 520-1, which recommends that an operator should be able to depressurize the plant quickly enough to halve working pressure in 15 min.
Designing a good jet fire system requires a highly robust char, which is an open and lightweight structure for optimal insulation. New coatings feature effective insulating char at a lower thickness than pool fire-only products, but still provide good jet fire resistance. The use of very-high-temperature-resistant carbon fiber mesh extends the jet fire resistance to 4 hr while keeping the thickness and weight of the system very low.
Jet fire first. The latest stage in the jet fire testing process saw Underwriters Laboratories (UL), which underwrites safety standards at U.S. onshore chemical and energy plants, agree to adopt the ISO 22899 standard for jet fire testing. The process of testing for jet fires has undergone a significant evolution from simple observations providing a basic recognition to a minimum of three samples of each type of certification sought.
The test standard includes different configurations for structural steel, piping, walls, decks and bulkheads, each requiring a series of tests. When preparation of test specimens, witnessing of the test, assessment and certification are included, the per-test cost can reach $50,000. The process requires a large investment for proper completion, making certification a serious commitment (FIG. 3).
|FIG. 3. Large-scale jet fire test at the Spadaedam research facility in northern England. Photo courtesy of DNV GL.
A new way forward. The developments in safety that have taken place in the offshore industry over decades have demonstrated how standards can help effectively manage risk, but this must happen more and faster in the onshore market.
The energy industry sometimes moves slowly in adopting new or best practices, but development of new standards and recognition by U.S. agencies of international standards for resistance to jet fires is an encouraging step forward. The fact there have been, until recently, no published guidelines for jet fire resistance is not a justifiable defense when it comes to protecting people and assets to the highest degree possible.
LNG demand is expected to remain firm as it takes an increasing share of the energy mix in the future, and gas is also required as a feedstock for chemical and petrochemical plants—demand that will lead to growth in total market size.
As more facilities seek final investment decision and project greenlight, the natural gas industry must move faster to address the risks arising from complex fires. It would be unfortunate for a major incident to highlight this potential weakness in safety standards just as cleaner energy sources are needed.
Even in the post-COVID-19 environment, where project budgets are likely to be under pressure, there is a clear argument for using fire-resistant coatings that go beyond the minimum safety requirements. It is not a question of trading off price for safety, since such coatings can help make these critical facilities inherently safer. GP
a The PPG PITT-CHAR NX coating, which is certified to UL’s ISO 22899 standard
RICHARD HOLLIDAY is Global Director of Hydrocarbon PFP at PPG Protective and Marine Coatings, based in Aberdeen, Scotland. He is a recognized technical authority and subject matter expert in the fields of passive fire protection (PFP), thermal insulation, heat shielding and protective coatings. He has held senior technical and business development roles with manufacturers, engineering contractors and technical safety consultants for large corporations and small-to-medium enterprises. Mr. Holliday is a Mechanical Engineer by training with post-graduate qualifications in management and information systems and 35 yr of experience in the design, testing, specification, application and inspection of PFP systems, both onshore and offshore, on a global basis.