Understanding Passive Fire Protection and the Potential Growth Opportunities to the Mechanical Insulation Industry

David Shong

February 1, 2017

The mechanical insulation industry has a long history of understanding and promoting the safety, process, and environmental benefits of properly designed and installed insulation systems on piping, vessels, and equipment. However, one area of relatively untapped demand is the use of non-combustible thermal insulations within industrial applications to provide what is referred to as passive fire protection (PFP). We’ve recently seen that stakeholders are currently demonstrating a lack of understanding regarding the proper application of PFP, revealing a major opportunity for the insulation industry to add value for our clients. PFP applications are currently increasing the overall market opportunity for the industry by creating new, organic growth into project scopes that wouldn’t have considered utilizing insulation previously. It offers an exciting new pathway to generate a significant increase in demand for insulation, cladding, and installation labor where the system is utilized specifically for fire protection in addition to or in lieu of thermal performance.

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The types of PFP discussed in this article are engineering concepts primarily associated with the industrial segment, but could provide benefit in many commercial projects as well. There are 2 main opportunities as they relate to PFP and mechanical insulation contractors: structural steel fire protection and pressure relieving and emergency containment systems.

Structural Steel Fire Protection

First, let’s look at structural fireproofing. In the event of a major fire in a chemical or power plant or in a petroleum refinery, PFP is designed to  protect the structural steel supporting the piping runs, equipment, and vessels. Non-heat treated steel will begin to lose much of its structural integrity  starting at 1000°F (538°C), so the installed PFP must be thick enough to slow the temperature rise of the protected steel for a specified amount of time during a fire (typically 1–4 hours). UL 1709 “Standard for Rapid Rise Fire Test of Protection Materials for Structural Steel” 1 is one of the laboratory  protocols that places a specimen assembly inside a 2000°F furnace and measures the number of minutes required for the internal steel under the fire protection to rise to a temperature of 1000°F.

Many industrial multicraft contractors offer scaffolding, heat-tracing,  insulation, and coatings. Some have made major capital investments in  equipment and real estate to specialize in shop-applying structural PFP coatings. Traditional PFP solutions involve either lightweight concrete (LWC) or intumescent epoxy coatings spray applied onto the structural steel. Carbon fiber mesh is embedded in between the layers of the epoxy coating or metal mesh, and standoff parts are mechanically fastened to the steel and embedded in the LWC. These reinforcement layers provide a matrix for the coatings to “grab” onto, which helps them remain in place longer during a fire. While these coating solutions are excellent choices for large scale, modularized capital projects, they can be difficult and expensive to install in an existing plant due to high mobilization costs and disruption to operations. In colder climates, the coatings will not adhere or cure properly at low temperatures and therefore the steel must be tented and heated for weeks at a time.

There are alternative solutions that any mechanical insulation contractor can install with no specialized pumping equipment or reinforcement layers. Some examples of generic materials approved for structural PFP are high-density calcium silicate boards, ceramic fiber boards, or flexible endothermic wraps. Endothermic wraps are a composite material made of an inorganic fiber blanket, impregnated with organic binder and inorganic filler. The filler chemically binds the water that is released during a fire (endothermic reaction) within the blanket, inherently providing a cooling effect. High density boards are typically 4’x 8’ sheets of calcium silicate that come in thicknesses up to 3”. These are cut and fabricated to “box” in the structural column or I-beam. The cut parts are fastened to each other using countersunk stainless steel screws. High-temperature adhesive is spread into the screw holes and in the board joints much like finishing drywall. In the case of certain high-density calcium silicate boards, the UL approved designs do not require metal jacketing. It can simply be coated with an approved industrial grade paint to provide a weather-resistant, attractive finish. All of these “non-traditional” PFP products can provide hourly fire ratings up to 4 hours and create very little disruption to operations inside an existing plant.

Pressure Relieving and Emergency Containment Systems

The second underutilized method that can help with fire prevention is the installation of a properly designed and approved assembly on piping and vessels to change the traditional paradigm of what happens during a fire. In order to help mitigate the spread of fire in a plant, engineers utilize the American Petroleum Institute (API) Standard 521 “Pressure-relieving and Depressuring Systems.” 2

This standard specifies requirements and gives guidelines for the following:

•     Examining the principal causes of overpressure;
•     Determining individual relieving rates; and
•     Selecting and designing disposal systems, including such component parts as piping, vessels, flares, and vent stacks.

In layman’s terms, industrial plants produce and store highly volatile fluids and gases. If a fire breaks out, these dangerous chemicals will get very hot, very fast. Traditional thinking assumes that if we don’t relieve the pressure buildup and move them somewhere else quickly, things will boil over and spread the fire or explode. The common practice is to install expensive pressure-relieving valves, build very large steel containment and flashback seal drums to dump the fluids quickly, and add flare units to burn off the gases in a hurry.

Of course, it is possible to look at this differently—prevention may offer a better option. What if engineers could design a system with a mechanical insulation assembly that will survive the fire and prevent the volatile fluids from boiling over in the first place? While that is an excellent concept, section 4.4.13.2.7 of the standard states, “Credit for thermal insulation is typically not taken because it usually does not meet the fire-protection insulation requirements….” Unfortunately, many commonly used thermal insulation and cladding types would not survive the fire. In order for a system to be considered effective for passive fire protection, it must meet the following design criteria:

1.     Must be able to withstand 1660°F (904°C) for 2 hours;
2.     Must not be dislodged by high-pressure water streams during firefighting operations;
3.     Must be able to withstand direct fire impingement; and
4.     Must consider corrosion under insulation (CUI) implications.

The API report lists 5 generic thermal insulations that meet the fire protection criteria when attached and clad with stainless steel banding and jacketing. Aluminum and all other types of jacketing will melt or burn during a fire and therefore are not approved for this type of assembly. Figure 1 shows a listing of the materials and the corresponding ASTM standard.

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Without getting too complicated, heat gain equations allow the engineering team to apply an “environmental credit” that helps justify lower-cost pressure relieving and emergency containment systems. Simply stated, adding a properly designed mechanical insulation system can reduce spending requirements on other big ticket items that will hopefully never be used.

Insulation as a passive fire protection function is experiencing tremendous growth through education of the design community on the ancillary financial benefits that can be realized by applying this proven engineering concept. Many recent projects have been installed with this assembly on vessels that would not previously have utilized any insulation whatsoever. This use expanded the overall market for mechanical insulation products, cladding, and installation labor, responsibly promoting the concept will continue to create new opportunities in the years to come.

References

1.     “Standard for Rapid Rise Fire Tests of Protection Materials for Structural Steel.” Standard 1709. UL, n.d. Web. 11 Oct. 2016.
2.     “Popular Publishers.” API Std 521. American Petroleum Institute, n.d. Web. 11 Oct. 2016.

 

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