Special Protection Systems

Some fire protection challenges call for more than plain water


In industrial fire protection, loss prevention specialists need a wide range of tools. Ignitable liquids and chemicals, business-critical data and electronics, precision processes, off-road equipment and irreplaceable archives are just some of the situations that call for special protection systems.

While traditional sprinkler systems are still the first line of defense, many protection challenges call for alternative extinguishing systems such as foam, water mist or clean agent. In this article, we’ll look at some of the leading categories of special protection systems.

What makes special protection so special?
The unique hazards found in many industrial and commercial facilities, including data centers, aircraft hangars, hospitals, petrochemical plants, and biotech laboratories require protection systems that will detect an incipient event and release an extinguishing agent in time to avoid catastrophic damage.

Special protection systems may use one or more fire suppression agents, including clean agents, inert gases, CO2, water mist, foam, hybrid systems and dry chemical. These systems are employed wherever the potential for property damage and business interruption from fire for a particular process or occupancy is considered unacceptably high. This protection rationale applies whether automatic sprinklers are provided as backup protection or not. (See figure 2)

Generally, special protection systems supplement automatic sprinklers and are not a substitute for them. Sprinklers can function much longer than most special protection systems and can be restored more quickly to service. Special protection systems are more complex and are sometimes subject to more electrical and mechanical failure modes as well as possible accidental discharges.

For all types of special protection extinguishing options, FM Approvals’ standards require examination of the complete system, including the structural and functional integrity of all components, fire performance tests for any agents or foam concentrates, review of system design and flow parameters, activation logic and full system discharge tests.

The detection and control system
While some special protection systems may be activated by the same type of fusible links used in automatic sprinkler systems, most require special detectors and control components to provide sufficiently early operation. These detectors may include spot-type heat-sensing fire detectors, smoke detectors, flame detectors, gas detectors and others.

These special detection and control systems provide great flexibility over what inputs are used to initiate the extinguishing system. For instance, well before a fire is fully developed, the system can be triggered from the first sign of smoke, from an unusual increase in heat, even from IR or UV light sources emanating from a fire. This early detection and activation can help to limit the loss of assets.

There are differing code requirements across the world, which fall broadly into two types. In North America and other regions that have adopted U.S. codes and standards, special protection Systems are covered by the requirement of NFPA 72, the National Fire Alarm and Signaling Code. Under NFPA 72, such equipment should be listed by a certifying body. FM Approvals is a certifier of all the detection and control components that comprise a special protection system and has developed a series of testing standards for all these products, designed to assure compliance with FM Global requirements and NFPA 72. Products that complete the test program successfully are listed in the online Approval Guide.

In Europe and other regions that have adopted European requirements, special protection systems must be certified by a Notified Body to be CE-marked in accordance with the Construction Products Regulation. The path to certification is to demonstrate compliance with EN 54 and its subsequent parts that apply to the individual detection and control components. FM Approvals, a Notified Body (#1725) in the EU, is qualified to evaluate various detector types, along with alarm control panels, power supplies, and other components of fire detection and special protection systems to EN 54 and to EN 12094-1. The latter standard applies specifically to gaseous agent releasing control panels. Here is a closer look at some of the major special protection systems available today:

Fixed foam extinguishing systems
Approval Standard FM 5130, Foam Extinguishing Systems, covers only fixed systems and is used to accommodate a wide range of foam systems and components. FM Approvals tests only complete fixed foam systems, not just nozzles or other individual components. The complexity of these systems is typically dependent on the type of foam proportioning device used to maintain the correct volume proportion of concentrate in water over the specified range of flows. Typical concentrations of 0.5%, 1%, 2%, 3% and 6% are tested in accordance with FM 5130 to ensure that accurate volumetric proportioning ratios over all conditions are compatible with the other system components.

FM 5130 is unique in its evaluation of both the minimum foam application rates and maximum water application rates for foam-water systems. FM Approvals tests the system at the actual installed application rate, and then applies water at the maximum foreseeable rate to test the integrity of the foam blanket.

Another critical performance factor that FM 5130 measures is the minimum and maximum distance from which a foam-water sprinkler, for instance, can extinguish a fire. This is important for occupancies where surfaces may vary greatly in elevation, such as warehouses, turbine halls and other industrial settings. The proximity of the foam discharge device to the fire surface can have a dramatic effect on the foam’s extinguishing effectiveness.

Foam concentrate is evaluated along with its corresponding system—including proportioning and discharge devices. FM Approvals tests only complete fixed foam systems, not just nozzles or other individual components. Therefore, this concentrate is FM Approved only when utilized in conjunction with the specific proportioning and discharge devices as shown in the Approval Guide (www.approvalguide.com).

All fixed foam extinguishing systems must be tested upon installation and retested annually. This and other instructions are contained in the manufacturer’s design, installation, operation and maintenance manual.

Water mist extinguishing systems
Approval Standard FM 5560, Water Mist Systems, is a comprehensive standard for water mist fire protection testing. FM Approvals tests only complete water mist systems, rather than individual components such as nozzles. As with other special protection, water mist systems can be complex; hence, the functionality and effectiveness of the whole system is the only allowable basis for FM Approval (see figure 1). The standard provides test requirements for specific occupancies and applications, each covered in a separate appendix, including but not limited to:

  • machinery spaces and special hazard machinery spaces
  • combustion turbine enclosures
  • industrial oil cookers
  • non-storage and non-manufacturing areas (e.g. residential, offices, meeting rooms, hotels, museums, restaurant seating areas, institutions and schools)
  • wet benches and similar processing equipment
  • local application occupancies
  • computer room subfloors
  • continuous wood board presses

FM 5560 was updated to introduce two new test protocols for water mist systems intended for the protection of above and below raised floors in data centers. In addition, a new test methodology will be added that offers state-of-the-art computer modeling to identify potential system configuration and enables scaled-down fire testing.

The new scaled testing methodology is for total flooding applications only—such as turbine and machinery enclosures—and is intended to help reduce the time and cost associated with test programs. Scaled testing can help determine, for instance, which full-scale tests are worth the investment, or to eliminate the need for full-scale tests in some circumstances.

Clean agent extinguishing systems
FM Approvals evaluates vaporizing liquid and inert gas clean-agent systems for total flooding protection under Approval Standard FM 5600, Clean Agent Extinguishing Systems. As with all other special protection systems, this standard requires the examination of the complete system, as well as design, installation, operation and maintenance instructions.

Clean agent fire extinguishing systems are widely used to protect ignitable liquids and materials, electrical equipment and ordinary combustibles in areas where surface burning is anticipated. These systems are not effective or appropriate for hazards that may produce deep-seated burning or those that involve chemicals containing their own oxygen, metal hydrides, or reactive metals such as sodium, magnesium or uranium.

FM5600 requires testing of the clean agent itself, individual system components and the total system. Depending on system complexity, component testing may include high-pressure discharge integrity, cycle operation, 30-day minimum and maximum temperature leakage, hydrostatic integrity, resistance tests, corrosion, strength, vibration and compatibility testing.

Clean agent systems must undergo Class A and Class B extinguishment tests. For engineered clean agent systems, FM Approvals also evaluates the flow calculation software provided by the manufacturer to ensure that it can accurately predict discharge time, nozzle pressure and distribution of the clean extinguishing agent within established limiting parameters.

All clean agent systems must also undergo a series of nozzle distribution verification tests to ensure they can adequately distribute the agent throughout a hazard to reach the minimum extinguishing concentration within 30 seconds after the end of system discharge. These tests are run in various enclosure sizes at worst-case system conditions, including minimum and maximum ceiling height, maximum area of coverage, maximum discharge time, minimum nozzle pressure and minimum storage temperature.

Heavy-duty mobile equipment fire suppression
Machines of mammoth proportions and capacity are required in many industries in order to meet production demands and keep operational costs as low as possible. Some of the biggest heavy duty mobile equipment (HDME) can be found in mining, petroleum and gas production, road and industrial construction, the lumber industry, and bulk material handling.

Huge HDMEs can carry thousands of gallons of diesel fuel, hydraulic fluid and other ignitable liquids. These liquids flow through pressurized lines close to extremely hot engine components, creating a risk for pool, spill and three-dimensional spray fires. HDME fires can not only result in damaged or destroyed equipment, but significant business interruption as well. Large equipment can take months, even years, to replace.

FM Approvals evaluates fire protection systems for HDMEs under Approval Standard FM 5970—Heavy Duty Mobile Equipment Protection Systems. Introduced in 2015, FM 5970 represents four years of cooperative development efforts between FM Approvals, FM Global, and industry. “There was no previous standard that provided a comprehensive systems-based approach to evaluating fire protection systems for the HDME market,” notes Armand Brandao, FM Approvals senior engineering specialist.

HDME fire protection systems are classified into one of two general categories, according to protection type: total flooding or local application. Total flooding systems are designed to uniformly discharge suppressant throughout the entire protected volume, and are intended to be used for the protection of Class A hazards, Class B hazards or both. Local application systems are designed to discharge suppressant directly onto a specific area of protection, and are intended to be used for the protection of Class B hazards only.

FM 5970 requires the examination of complete systems, which can include:

  • A complete HDME fire protection system, including detection, control, agent storage and delivery;
  • Suppressant storage and delivery system for HDME protection; or
  • Detection and control systems for HDME protection.

One manufacturer of an FM Approved compressed air foam (CAF) fire protection system for HDME applications is ACAF Systems, Inc., based in Coventry, Rhode Island, USA.

“I would say that FM 5970 has raised the bar in terms of real-world testing of fire suppression systems for the HDME market,” notes ACAF president David Munroe. “This is how fire performance testing needs to be done. Anything less is not a true test of overall system performance.”

Special protection fire suppression systems are as innovative and unique as the industries they are designed to protect. FM Approvals continue to provide the most advanced standards and certification services to meet the needs of protection system manufacturers and their customers.