Getting PFP right

Picking the right passive fire protection (PFP) product can be a minefield. Richard Holliday assesses the issues.

Passive fire protection (PFP) is often considered a nuisance. It seems to cover every bit

of metal on oil and gas platforms, terminals, refineries and petrochemical plants. It frequently gets damaged, and when it becomes loose at height, it can be a dropped object hazard. Poorly specified and applied materials can also increase corrosion risk through corrosion under Insulation/fireproofing CUI/CUF.

In the event of a fire, people need time to escape or tackle it, and PFP buys that time by protecting safety critical elements (SCE’s) from hydrocarbon fires. It isn’t applied randomly—fire risks are assessed and areas that need protection have the correct type and thickness specified to keep the facility safe. Unfortunately, few asset managers fully understand how this substance came to be there, what it is or how to look after it.

A hierarchy of needs – inherently safer design

When designing or assessing PFP, it is essential to consider more than just the fire rating; virtually all PFP materials sold will have fire certification; but many systems are not fit for purpose or the fire certification is not applicable to the end use. The following aspects should be considered as an order of precedence for a PFP system:

1. Shall not generate hazards, e.g. cause corrosion, leading to leaks or integrity loss.
2. Shall not degrade with time in the environment it is exposed to, including design life and process operating conditions.
3. Shall survive an initial explosion, with resultant overpressure, drag force, deformation of substrates, and impact from flying debris.
4. Shall survive an initial high heat flux, high momentum jet or spray fire that may occur.
5. Shall provide fire protection for the required time and maintain the temperature of the item below being protected under its critical temperature.

There are many types of PFP and each has its place and use; however all have strengths and weaknesses.

In some circumstances, combinations of these systems are used – for example combining epoxy intumescent materials applied over cellular glass, either to protect the epoxy PFP from hot or cold substrate conditions or to provide combined fire and thermal insulation. Today, using asbestos containing materials (ACM) is prohibited; however, its use was common in PFP, even up until the mid-1980s, and care should be taken when inspecting old PFP. For prevention of CUI/CUF, these systems can be simply characterized into two categories:

1. Fully bonded, joint-less and impermeable systems. These can generally be considered as low risk CUI/CUF systems (assuming compatibility with substrate materials is checked), and there is substantial track record and evidence to show that these per- form better than anti-corrosion paint systems.

2. Non-bonded, demountable, permeable or porous systems. In all instances it will be necessary to pre-treat steel substrates with a robust full anti-corrosion coating system. No matter how well you seal it there will be the potential for water vapor to reach the substrate and be trapped there. Coating systems should be suitable for immersion use at the operating temperatures expected.

PFP integrity management

Industry regulations and guidance typically require operators to verify and maintain PFP throughout the life of the facility, which is only possible if good records are maintained. To facilitate this, it is essential to establish a database detailing where and why PFP is used. This would generally include the following steps:

1. Establish an asset register of items requiring PFP. This could include primary and secondary structure, process equipment, pipelines and ESD valves, temporary refuge (TR) and command and control centers, blow-down and flare/vent system, fire zone divisions (walls, decks), and fire pumps.
2. Define the criticality of each item. This would consider facts such as TR impairment, escalation control, loss of production, asset protection, and environmental impact.
3. Establish functional requirements for item being protected. This would include aspects such as structural resistance, hydrocarbon containment, smoke and toxic fume integrity, separation for fire zoning, and fire water demand.
4. Establish hazards and conditions in the area. Blast/explosion hazards, impact, fire hazards (jet fire, diffuse fires, pool fires) and environment hazards (UV, salt spray, heat, vibration).
5. Determine required fire resistance time. How long do you require it to perform the function(s) identified in No. 3 above?
6. Establish fire resistance rating. Consider the structural resistance oedigital.com
7. requirements (including self-weight), integrity requirements and insulation requirements (now commonly known as REI – resistance, integrity and insulation).
8. Establish the maximum critical temperature the item can reach and from this the allowable temperature rise under fire conditions.

Inspection of the PFP is undertaken based on the condition of the PFP, the severity of anomalies and the extent of anomalies.

Armed with the information in the table “Example of anomaly ranking,” it is possible to establish a matrix to assess the integrity of the PFP and plan repairs and maintenance.

Against each ‘score’ will be a series of outcomes, ranging from removal and replacement with upgrade, to future re-inspection.

Fire seal penetration insulation failed. Photos from MMI Engineering.

PFP Inspection

It is essential to understand the modes of failure for each different PFP system and this requires detailed knowledge of both the materials used, their system design/specification and the application principals, which often involves a degree of detective work.

Typical anomalies include: cracking; disbondment; water logging; mechanical damage; loss/removal of material; exposed reinforcement; Corroded or damaged reinforcement; reinforcement not located in correct position or missing; thermal degradations; UV damage; incorrect jointing and sealing details; missing components; exposed top flanges; or missing coat-backs.

For some systems, under certain fire conditions, these may have little effect on fire performance in other cases even a visually small (or hidden) anomaly could lead to rapid failure. It is often the combination of anomalies that determine the severity. There are no simple rules of thumb and the author has person- ally witnessed a 180 minute fire barrier be destroyed in less than five minutes by a jet fire.

The key to a successful PFP integrity management process is to ensure it is carried out independently; maintenance contractors and PFP manufacturers often offer a “free” service, but do they really understand the hazards and risk? Competence comes from experience and a fire-proofers ticket for attending a two-day training course on one material is no substitute for years of practical experience.

Richard Holliday is principal consultant at MMI Engineering. Holliday is a technical authority in passive fire protection (PFP), thermal insulation, heat shielding, and protective coatings. He has an MSc in Information Systems from Robert Gordon University, Aberdeen.