Holistic approach ensures performance of special protection systems

When it comes to industrial fire protection, loss prevention specialists need a wide range of tools to meet the daunting and varied challenges possible today. Ignitable liquids and chemicals, business-critical data and electronics, precision processes 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 when it comes to structure protection, many protection challenges call for alternative extinguishing systems such as foam, water mist or clean agent. But with sophistication comes complexity. How do these special protection technologies work, and are they reliable?

FM Approvals, an independent third-party certification agency, has approved sprinklers, foam, water mist and clean agent extinguishing systems for decades. These standards are often based on internal research activities and are in synch with best-in-class national and international standards. 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.

What makes special protection so special?

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.

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 (see figure 1 top right) are more complex than conventional sprinkler systems and are consequently subject to more electrical and mechanical failure modes as well as possible accidental discharges.

The detection 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 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 detector systems provide great flexibility and control 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.

It should be noted that throughout Europe and in many other regions, fire detection and alarm systems must be certified by an authorized (Notified) body in order to be CE-marked in accordance with the Construction Products Regulation, or demonstrate compliance with EN54 and its derivatives.

FM Approvals, a Notified Body (#1725) in the EU, is qualified to evaluate various detector types, as well as alarm control panels, power supplies, and other components of fire detection and special protection systems to EN 54.

Let’s take a closer look at some of the major special protection systems available today:

Fixed foam extinguishing systems

Approval Standard 5130, Foam Extinguishing Systems, covers only fixed systems and is used to accommodate a wide range of foam fire extinguishing systems and 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 Standard 5130 to ensure that accurate volumetric proportioning ratios over all conditions are compatible with the other system components.

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

Another critical performance factor that Approval Standard 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 only FM Approved 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 5560, Water Mist Systems, is a comprehensive standard for water mist fire protection testing. The standard provides test requirements for specific occupancies and applications, each covered in a separate appendix, including:

• 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 Approvals tests only complete water mist systems, rather than individual components such as nozzles. As with other special protection systems, water mist fire extinguishing systems can be complex, and therefore the functionality and effectiveness of the whole system is the only allowable basis for FM Approval.

FM 5560 was recently 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 to the standard that offers state-of-the-art computer modeling to identify potential system configuration, and enables scaled-down fire testing of water mist systems to simulate full-scale volumes.

The new scaled fire 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.

FM Approvals developed two new test protocols for the use of water mist systems to protect data centers in direct response to the needs of data center owners. The new data center test protocol for protection of above raised floors (see above) addresses the specific needs of these special occupancies, including the need to provide protection within hot/cold aisle containment areas, with active forced ventilation, significant amounts of power and telecom cabling, metal cable trays and an interlocked dry pipe/pre-action system.

The new test protocol for below raised floors is intended to evaluate water mist systems in the face of active forced ventilation, single- or double-tiered cable trays, and using an interlocked dry pipe/pre-action configuration.

Clean agent extinguishing systems

FM Approvals evaluates vaporizing liquid and inert gas clean-agent systems for total flooding protection under Approval Standard 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.

Standard 5600 requires testing of the clean agent itself, individual system components and the total system. Depending on the complexity of the system, 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. The system must successfully extinguish Class A fires within 600 seconds after the end of system discharge, with no signs of re-ignition. For Class B (i.e. ignitable liquid) fire tests, extinguishment must occur within 30 seconds after the end of system discharge.

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 enclosures 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.

Special protection technology will need to keep pace with the innovative industries it serves. From vast data centers supporting global enterprises, to petrochemical and pharmaceutical manufacturing, to semiconductor fabrication and aircraft hangars, many commercial and industrial protection scenarios present unique fire risks. Ensuring these systems perform – and protect – is critical.

For more information, go to fmapprovals.com