WATER MIST SYSTEMS. Table of Contents

Transcription

1 FM Global Property Loss Prevention Data Sheets 4-2 January 2013 Page 1 of 16 WATER MIST SYSTEMS Table of Contents Page 1.0 SCOPE Changes LOSS PREVENTION RECOMMENDATIONS Equipment and Processes Plans and Specifications Acceptance Testing Detection and Operation Supply of Extinguishing Agent Containers of Extinguishing Agent Piping and Tubing Hangers Nozzles Valves Strainers and Filters Pumps Operation and Maintenance Calculations Nonstorage Occupancies [Light Hazard Occupancies (LHO)] Introduction Equipment and Processes Local Application Introduction Construction and Location Equipment and Processes Limitations SUPPORT FOR RECOMMENDATIONS General Design Obstructions Nonstorage Occupancies [Light Hazard Occupancies (LHO)] Enclosure Protection Local Application Systems Operating Experience Test Data Combustion Turbine Enclosures Cleanrooms Light Hazard Occupancies Continuous Wood Board Presses REFERENCES FM Global NFPA Standards Others APPENDIX A GLOSSARY OF TERMS APPENDIX B DOCUMENT REVISION HISTORY APPENDIX C ADDITIONAL INFORMATION C.1 Electrical Clearances C.2 Material of Construction C.2.1 Galvanized Steel APPENDIX D COMPARISON WITH NFPA STANDARD No part of this document may be reproduced, stored in a retrieval system, or transmitted, in whole or in part, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission of Factory Mutual Insurance Company.

2 4-2 Water Mist Systems Page 2 FM Global Property Loss Prevention Data Sheets 1.0 SCOPE This data sheet provides information on installation criteria for water mist systems. Water mist systems are special protection systems presently FM Approved for protection of enclosures with specific hazards containing limited amounts of ignitable liquids, and process equipment, such as: combustion turbine(s) industrial oil cookers continuous wood board presses machinery in enclosures computer room subfloors indoor transformers wet benches in cleanrooms light hazard occupancies. Additional information concerning water mist system installation criteria is contained in NFPA 750, Water Mist Fire Protection Systems. The effectiveness of water mist must be proven by fire testing on a hazard of the same configuration and general hazard type. Presently, there is no design procedure that would allow extrapolation of test results to different hazards or different enclosure configurations. 1.1 Changes January Minor editorial changed were made for this revision. 2.0 LOSS PREVENTION RECOMMENDATIONS In addition to the specific recommendations in this document, adhere to the applicable guidelines in the following data sheets: Data Sheet 2-81, Fire Protection System Inspection (for inspection, testing and maintenance guidelines) Data Sheet 3-0, Hydraulics of Fire Protection Systems Data Sheet 3-7, Fire Protection Pumps (for devices such as water pumps and water motor controllers) 2.1 Equipment and Processes A. For new installations, use FM Approved systems and components. B. Install water mist systems in accordance with this data sheet and the manufacturer s design and installation manual. For FM Approved systems, this manual is evaluated by FM Approvals. This manual may cover applications for which the system is not FM Approved Plans and Specifications Make contracts for new installations, or changes in existing systems, subject to FM Global acceptance of plans, materials, and the completed installation Submit final plans and calculations of new or modified systems to FM Global for review and acceptance before installation is started. Ensure final plans are to scale or fully dimensioned, with sufficient detail to define clearly both the hazard and proposed system. Clearly indicate the location and sizes of piping and nozzles together with the location of the extinguishing agent supply, fire-detecting units, and all auxiliary equipment. Show dampers, conveyor equipment, doors, and other features in any way related to the

3 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page 3 protection of the hazard. Submit a wiring diagram if fire detection or system operations are electric. Ensure all components are FM Approved for the applications and identified by part or model number Provide documentation showing hydraulic and pneumatic calculations. Ensure hydraulic calculations contain the following information: (a) location identification; (b) description of hazard; (c) design area of water application or volume of space protected; (d) total water requirements as calculated Provide Detail Sheets containing the following information: (a) nozzle description; (b) hydraulic reference point; (c) total flow and flow at each nozzle in gpm (l/min); (d) all pipe sizes; (e) pipe lengths; (f) equivalent pipe lengths for fittings and devices; (g) friction loss in psi/ft (bars/m) of pipe; (h) elevation head in psi (bars); (i) required pressure in psi (bars) at each reference point; (j) velocity pressure and normal pressure if included in calculations; (k) system flushing locations; (l) other calculations necessary for design of the water mist system Graph Sheet. Provide a graphic representation of the complete hydraulic calculation, including the water supply curve and the water mist system demand Pneumatic calculation documentation (for systems using gas). Provide pneumatic calculation summary sheets that include the following: (a) identification of location; (b) description of hazard; (c) total gas volume required Detail sheets for pneumatic calculations: (a) nozzle description; (b) pneumatic reference points; (c) gas flow rate and pressure at each nozzle; (d) the gas pressure to water pressure ratio at each nozzle; (e) pipe size; (f) pipe length; (g) total pressure loss between reference points; (h) required pressure in psi (bars) at each reference point Include a set of as-built installation drawings, drawn to scale, providing the configuration of the detection, actuation, and control system Include the Operation and Maintenance Manuals for each piece of equipment or device of the water mist system. Ensure the manuals include a complete step-by-step description of the functioning of abort and maintenance switches, delay timers, and all interlocked components Acceptance Testing Conduct a full flow test, where practical, to verify nozzle layout and discharge pattern. Flow tests also are intended to determine whether obstructions would interfere with the operation of the system and whether smaller piping and nozzles flow free and clear. Replace one of the nozzles with a pressure gauge and observe gauge readings to verify proper discharge pressure Operate the maximum number of nozzles or systems (when multiple systems are installed) that are expected to operate at the same time Test all operating parts of the system to verify they function properly Inspect, clean, and replace filters and strainers if necessary Detection and Operation Design the system to be automatically actuated. Provide a method for manual actuation Automatically shut off or close interlocked devices, such as exhaust fans or doors, before operation of the water mist system Install detection systems in accordance with Data Sheet 5-48, Automatic Fire Detectors Ensure abort switches, if used, are of the deadman type, requiring constant manual pressure Ensure design, operation and installation of automatic fire detection systems are compatible with the fire suppression goals of the system Supply of Extinguishing Agent Provide an adequate quantity of water and compressed gas (if applicable) to meet the demand specified by the applicable FM Global data sheet. Ensure the quantity is adequate for the largest single hazard or group of hazards protected by one system distributed through the appropriate manifolded selector valve.

4 4-2 Water Mist Systems Page 4 FM Global Property Loss Prevention Data Sheets If water discharge continues after the compressed gas supply has been exhausted, it is not effective for fire suppression. If the system has been FM Approved for intermittent discharge, the quantity required is for the actual time of discharge Provide agent supply dependent on whether the water mist system is used as a special protection or primary protection system. a) Water mist may be used as a special protection system when it is able to extinguish all of the fire scenarios for the hazard protected and where the installation has a limited agent supply. Double the agent quantity needed to extinguish the worse-case fire scenario or 10 min, whichever is greater. If the ignition source could remain (for example, hot surfaces on a combustion turbine), ensure the agent supply is adequate for the rundown time of the turbine or 10 min, whichever is greater. Specific exceptions to these guidelines may be made in the applicable occupancy data sheet. b) Water mist may be used as primary protection if the system has been tested for the hazard protected and duration of agent supply is that required for automatic sprinkler protection (see appropriate data sheet) Provide a reserve supply, at least equal to the minimum requirement for the in-service supply, under any of the following conditions: a) Provide a connected reserve when two or more hazards are protected by a single supply. A manually actuated main/reserve switch is normally provided at the control panel for this purpose. b) Provide a connected reserve when a special protection system is the sole protection for valuable and important occupancies, unless all of the following criteria are met: i) Protection can be fully restored within 24 hours, ii) occupancies are constantly attended, and iii) written impairment procedures have been established. c) Provide a reserve when the extinguishing agent cannot be replaced within 24 hours following system operation. Reserve supplies are necessary to permit prompt restoration of the system after a discharge, to minimize interruption of the process and the interval of impaired protection Provide water equivalent in quality to a potable water source. Supply systems that use nozzles with nozzle waterway dimensions less than 50 microns with demineralized water Provide gas supply from a dedicated source. Where facility dedicated air supply is available that meets the requirements in quantity, quality, pressure, and reliability, it may be used as a source of atomizing media. Monitor plant air or nitrogen used for this purpose at the fire control panel for high and low pressure. Set the low air or nitrogen alarm at least 50% above the availability of two full system discharge requirements Install a check valve or other means to prevent entrance of water into the atomizing medium Install a backflow preventer between the system and the connection to a potable water supply Containers of Extinguishing Agent General Clean containers prior to installation, so debris and other impurities do not enter the piping system and plug nozzles. Flush connections to municipal or private water supplies. Continue flushing for a sufficient time to ensure thorough cleaning. Ensure the minimum rate of flow is either the hydraulically calculated water demand or the maximum flow rate available to the system under fire conditions Design containers to meet the requirements of the U.S. Department of Transportation or Transport Canada, if used as shipping containers. Design, fabricate, inspect, certify, and stamp containers in accordance with Section VIII of the ASME Boiler and Pressure Vessel Code if not used as shipping containers. Note: Use equivalent codes within the country of origin Provide a pressure relief device on each pressurized container Ensure containers supplying the same manifold outlet are the same size and interchangeable.

5 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page Securely install storage containers and accessories to prevent container movement during discharge Provide liquid level indicators for all liquid storage containers Install containers to facilitate inspection, testing, maintenance, and recharging Protect storage containers from weather and mechanical damage Low-Pressure Storage Containers Fabricate, test, approve, equip, and mark low-pressure containers in accordance with recognized international standards, such as the current specifications of the ASME Boiler and Pressure Vessel Code, Section VIII, or the requirements of U.S. Dept. of Transportation, Title 49, Code of Federal Regulations, Parts 171 to 190, Sections and , or equivalent national codes for the country of use. Ensure the design working pressure is in accordance with the manufacturer s listing Provide a high/low pressure supervisory alarm for each pressurized liquid container. Ensure the alarm is set at the values identified in the manufacturer s FM Approval High-Pressure Storage Containers Construct, test, and label high-pressure containers in accordance with recognized international standards, such as the U.S. Dept. of Transportation, Title 49, Code of Federal Regulations, Parts 171 to 190, Sections and , specifications for DOT-3A, 3AA-1800, or higher, seamless steel cylinders Provide an automatic means to prevent leakage from the manifold in the event the system operates while a cylinder is removed Heated Water Mist Systems Design pressure containers for heated water mist systems in accordance with the manufacturer s FM Approval Equip each pressurized liquid container with a pressure gauge, and a high/low-pressure supervisory alarm set at the values identified in the manufacturer s FM Approval. A container pressurized only during system activation does not require high/low-pressure supervisory alarms Piping and Tubing Install water and atomizing media piping in accordance with ANSI B31.1 Power Piping Code, unless the FM Approval criteria specifies differently, or unless it is for a low-pressure system. If the latter is the case, it may be installed in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems Ensure system piping and tubing is rated for the maximum working pressure to which it is exposed Install piping so the system can be drained Install supports (hangers) for low-pressure systems in accordance with the design manual or in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems Ensure the length of an unsupported arm over to a nozzle does not exceed 2 ft (0.6 m) for pipe, or 1 ft (0.3 m) for tubing Protect piping and containers subject to earthquakes in accordance with Data Sheet 2-8, Earthquake Protection for Water-Based Fire Protection Systems Provide corrosion-resistant piping from the system strainer to the nozzle. Ensure the material has corrosion resistance equivalent to drawn or seamless copper tube or stainless steel. This is to reduce the possibility of blockage of nozzles due to corrosion Provide fittings with a minimum-rated working pressure equal to or greater than the maximum operating pressure. For systems that use a pressure regulating device in the distribution piping, ensure the fittings downstream of the device have a minimum rated working pressure equal to or greater than the maximum anticipated pressure in the downstream piping Apply joint compound, tape, or thread lubricant to the male threads of the joint.

6 4-2 Water Mist Systems Page 6 FM Global Property Loss Prevention Data Sheets Clean each pipe or tube section internally before assembly in accordance with the manufacturer s installation manual. Ensure the piping network is free of particulate matter and oil residue before installing the nozzles Install fittings in accordance with the Manufacturer s Design and Installation Manual. Ensure fittings in low-pressure water mist systems conform to NFPA Label water and gas piping for twin fluid systems Hangers Support pipe 1 in. (2.5 cm) and larger in diameter with hangers as specified in Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers. Ensure smaller piping is as specified in the manufacturer s Design and Installation Manual Do not use power-driven fasteners to attach hangers to the building structure where systems are required to be protected against earthquake Nozzles Install nozzles within the minimum and maximum spacing criteria identified in the system FM Approval. This includes nozzle spacing, height limitations, distance from walls, distance below ceilings, spacing under pitched or curved surfaces, and distance from obstructions Ensure maximum and minimum operating pressurers at each nozzle are within the FM Approved range Locate nozzles in accordance with the FM Approvals listing and manufacturers design and installation manual for continuous or discontinuous obstructions, when present Use FM Approved guards, where needed, to prevent mechanical damage to nozzles so the effectiveness of the nozzle will not be reduced Use FM Approved escutcheon plates where specified by the manufacturer Use ordinary temperature ratings for automatic nozzles. If in unventilated areas such as attics, use intermediate-temperature rated nozzles. If located within 10 ft (3 m) of hot surfaces, such as exhaust pipes or steam pipes, use high-temperature rated nozzles Provide corrosion-resistant materials or coatings where there are corrosive atmospheres Provide FM Approved frangible disks, blow-off caps, or other suitable devices for discharge nozzles where clogging by external foreign materials is likely Keep a supply of spare, thermally activated nozzles in stock. The number of nozzles depends on the size of the system Valves Control/Activation Valves Use FM Approved valves Provide identification signs on control, drain, and test connection valves. Install valves so they are accessible for operation, inspection, and maintenance. Also install valves so they are not subject to damage that would prevent their operation Water Pressure Regulating Valves Install pressure regulating valves in accordance with manufacturer instructions where system pressure may exceed the maximum rated working pressure of the system or system components. Ensure the valves open when system pressure reaches 95% of the rated pressure Provide a water flow test valve sized to produce the designed flow on the downstream side of the pressure reducing valve.

7 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page Provide a sign indicating the correct static and residual discharge pressure for the pressure reducing valve Compressed Pressure Regulating Valves (PRVs) Install PRVs in accordance with the manufacturer s recommendations Install PRVs when the supply pressure is higher than the design operating pressure of the water mist system. Ensure PRVs are capable of providing a stable, regulated output at the rated flow capacity and design set point over the full range of input pressures that will be experienced during discharge Ensure pressure set point adjustments on PRVs are tamper resistant, and the adjustment indicated by a permanent marking Check Valves and Backflow Preventers Install FM Approved check valves in accordance with the manufacturers instructions Install a check valve between the system and the connection to a potable water supply Strainers and Filters Provide FM Approved strainers and filters at all water supply connections Provide flush-out connection(s) for strainers and filters Keep a stock of spare strainers and filters to service nozzles for the largest single hazard or group of hazards protected simultaneously Pumps Provide FM Approved pumps sized to 120% of the required system water flow rate, at minimum system operating pressure Start pumps automatically on system activation Provide pressure relief valves from discharge to supply side of piping for pumps capable of over-pressurizing the system. Ensure the pressure rating does not exceed the working pressure of the piping system Do not arrange pumps to take suction under lift Install the power supply for pump drivers in accordance with NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection; NFPA 70, National Electrical Code, and the manufacturer s instructions Arrange power supplies so that disconnecting power to the facility during a fire will not disconnect power to the circuit feeding the pump Operation and Maintenance Hydrostatic Tests Filter or strain water used for testing to remove solids that would obstruct water mist nozzles Low-Pressure Systems. Hydrostatically test piping and attached appurtenances subjected to system working pressure at 200 psi (13.8 bars) for 2 hours. If parts of the system are subjected to pressures in excess of 150 psi (10.4 bars). Test them to 50 psi (3.5 bars) above normal working pressure Intermediate- and High-Pressure Systems. Hydrostatically test all piping and attached appurtenances to 150% of the normal working pressure for 2 hours Hydrostatically test high-pressure cylinders before recharge if more than 5 years has elapsed from the date of the last test. Discharge and hydrostatically test cylinders that have been in continuous service at 12 year intervals or in accordance with the manufacturer s instructions.

8 4-2 Water Mist Systems Page 8 FM Global Property Loss Prevention Data Sheets Inspection and Testing Inspect and test all components and systems to verify they function as intended. Ensure inspection and testing frequency is in accordance with Table 10(a) and 10(b) of NFPA 750; Standard on Water Mist Fire Protection Systems, or the manufacturer s instructions, whichever is more frequent Conduct an air pressure leakage test for dry and preaction systems. Conduct the test at 40 psi (2.8 bars) for 24 hours. Repair leakages resulting in a loss of 1.5 psi (0.1 bars) during the 24 hour period Inspect a representative sample of water mist nozzles after each system activation. Include 10% of the water mist nozzles in the activated zone. If contamination of filters or strainers is found on inspection, inspect all nozzles in the activated zone Clean or replace filters and strainers after each system operation due to fire Calculations Use the Hazen-Williams calculation method for hydraulic calculations for low-pressure systems with no additives. The Hazen-Williams method also can be used for intermediate- and high-pressure systems having a minimum pipe size of 3 4 in. (20 mm) if the maximum flow velocity does not exceed 25 ft/s (7.6 m/s). For copper and stainless steel piping or tubing, Hazen-Williams C values of 150 may be used Use the Darcy-Weisbach calculation method for hydraulic calculations for intermediate- and highpressure, single fluid, single-phase systems that cannot be calculated using the Hazen-Williams method (see Chapter 6, NFPA 750, Standard on Water Mist Fire Protection) Hydraulic calculations for twin fluid systems can be conducted as follows: 1. Determine water pressure required at the most remote nozzle using nozzle specifications supplied by the manufacturer. Determine flow rates and pressure at each nozzle location. 2. Determine water pressure and flow rates at each nozzle from information provided by the nozzle manufacturer. 3. Calculate the pneumatic piping system independently to verify the pipe sizes are adequate to provide the required pressure and flow at each nozzle, and that the system is sized to provide the flow rate and pressure needed. 2.2 Nonstorage Occupancies [Light Hazard Occupancies (LHO)] Introduction Use water mist systems FM Approved for LHO to protect non-storage and non-manufacturing occupancies designated as Hazard Category 1 (HC-1) in Data Sheet 3-26, Fire Protection Water Demand for Nonstorage Sprinklered Properties Equipment and Processes Limitations Where systems are FM Approved for Light Hazard Occupancies (HC-1), the following limitations apply from their FM Approvals listing: Maximum enclosure area Maximum ceiling height Maximum nozzle spacing Minimum water pressure Maximum water pressure Clearance from obstructions Minimum fire-resistance rating of room walls: 30 minutes The maximum room size limitation does not apply to corridors that can be protected by one row of nozzles.

9 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page Limit the maximum ceiling height to that specified by the FM Approvals Listing and listed manufacturer s design and installation manual Use water mist systems FM Approved for a Light Hazard Occupancy with an unrestricted maximum enlosure area to protect large compartments Limit application of FM Approved systems to wet pipe systems and to pre-action systems designed per Data Sheet 2-0. Do not use dry systems Plans and Specifications Use Data Sheet 2-0 and the manufacturer s recommendations to develop plans and specifications Hydraulically calculate water mist systems used in light hazard occupancies in accordance with Data Sheet Supply of Extinguishing Agent Use clean and clear fresh water, free from debris and algae, for system water supply. Do not use open bodies of water Base water supply and system demand for light hazard occupancies on the recommendations in Data Sheet 3-26, Fire Protection Water Demand for Nonstorage Sprinklered Properties Base hydraulic design and system demand on the minimum nozzle operating pressure specified in the FM Approvals listing for each system. Add 250 gpm (946 lpm) minimum hose demand to the system demand. Provide a 60 minutes duration for water supply. 2.3 Local Application Introduction Local application water mist systems are typically used for ignitable liquid hazards. Water mist is considered a special protection system. An automatic sprinkler system is normally required for building protection Construction and Location Provide curbing or diking where a pool fire could occur to contain liquid release. Provide water mist protection over the equipment and the curbed or diked area Equipment and Processes Use water mist systems that are FM Approved for local application system protection. Install systems in accordance with the manufacturer s design and installation manual Activate the system automatically by FM Approved heat detection, and with manual pull stations near the hazard area Limitations Limit the system to protection of the fluid tested. If the system has been tested using a specific ignitable liquid, limit the system to protection of ignitable liquid fire hazards with equivalent or higher flash points Install using nozzle type, nozzle height, spacing, and angle of discharge as specified in the manufacturer s design and installation manual identified in the FM Approvals listing. 3.0 SUPPORT FOR RECOMMENDATIONS 3.1 General Design No general design method is recognized for water mist protection systems. Performance objectives need to be proven by fire test in the configuration and for the hazard and types of fire scenarios expected.

10 4-2 Water Mist Systems Page 10 FM Global Property Loss Prevention Data Sheets FM Approval testing for water mist systems involves the completion of a series of fire tests identified in a fire test protocol, as well as reliability testing of the components that make up the water mist system. The test protocol describes the fire tests needed to prove the water mist system is effective. The fire test specifies the type of fuel in configuration(s) that would be most realistic for the hazard protected. Reliability testing consists of testing all components of the system to verify they will function properly Obstructions Obstructions will affect the performance of water mist protection and vary according to the type of spray technology and the type of application. Water mist nozzles have a wide range of projection distances, spray velocity and spray patterns. Spray from nozzles that impinge too close on obstructions will not fully atomize, and a portion of the water mass will be removed from suspension. Such losses diminish the extinguishing effectiveness of total flooding or local application systems. For combustibles where prewtting is an important factor in preventing fire growth, obstructions to spray development prevent wetting of unburned materials and diminish the performance of the water mist system. Additional nozzles can be required to ensure complete water mist fire protection when obstructions and maximum coverage distances to obstructions are not evaluated as part of the FM Approval Nonstorage Occupancies [Light Hazard Occupancies (LHO)] Recommendations are included for water mist system protection of light hazard occupancies (LHO). Light Hazard is an occupancy classification that has been traditionally used by the National Fire Protection Association (NFPA) and others in the fire protection and loss prevention industry. Light hazard occupancies are defined in Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers, and typically involve Miscellaneous, Non-Manufacturing occupancies, identified in Data Sheet 3-26, Fire Protection Water Demand for Nonstorage Sprinklered Properties. Water mist systems FM Approved for LHO are intended to control fires in these occupancies with less water than standard automatic sprinkler systems Enclosure Protection Initial testing by FM Approvals was for water mist protection of gas turbine compartments. A test series had been completed by a European laboratory. The results indicated water mist would be most effective on high heat release rate fires. In designing the FM Global Research Test Protocol for combustion turbine protection, the water mist system tests were arranged to be conducted on low heat release rate fires. For enclosures, if low heat release rate fires can be extinguished, then high heat release rate fires could easily be extinguished. The extinguishing mechanism is a combination of inerting and flame cooling. When water mist is vaporized, air is displaced, resulting in lower oxygen concentrations. For this reason, much of the enclosure fire testing involving ignitable liquids conducted by FM Global is carried out at heat release rates of 1 and 2 MW. These heat release rates are considered high enough to result in damage to equipment and enclosures but low enough to provide worse-case test conditions for a water mist system. If the system extinguishes a 1 to 2 MW fire it will more quickly extinguish a fire with an order of magnitude higher (10 to 20 MW) heat release rate. It was also determined that there was a minimum size fire that would not be extinguished. The larger the volume the larger the minimum fire size. For example, fires with heat release rates on the order of 500 kw may not be extinguished in test enclosures larger than 9,170 ft 3 (260 m 3 ). The water mist system controls the heat release rate and the fire could be extinguished by portable extinguishers. It was found that the larger the fire, the less critical the tightness of the enclosure. For example, with a 2 MW fire a door could be open and the fire would be extinguished. However, with the same size fire, if the door and a roof panel were open the fire would not be extinguished. If a gaseous agent was used it is unlikely that an extinguishing concentration could be achieved with a door open. The following are general rules for water mist systems used for enclosure protection: 1. FM Approved water mist systems are pre-engineered systems for enclosure protection. The enclosure volume, ceiling height, and ventilation are considered critical parameters.

11 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page There are no scaling rules for water mist systems. Do not extrapolate a protection system design from a smaller tested compartment to a larger, untested compartment. For example, if fire testing was done on a compartment 10,000 ft 3 (283 m 3 ) in volume, do not assume that a 20,000 ft 3 (568 m 3 ) volume compartment could be successfully protected using twice the number of nozzles and twice the amount of agent. Also, do not extrapolate from a 10,000 ft 3 (283 m 3 ) compartment to a 5,000 ft 3 (142 m 3 ) compartment using 1 2 the number of nozzles and 1 2 the agent. Use the same number of nozzles and same amount of agent as for the tested system unless the system has been tested for smaller compartments. 3. Do not make a judgement that the system will extinguish a fire based on a discharge test. A discharge test is important to verify a system will operate properly. However, a successful discharge test does not guarantee the system will extinguish a fire. For example, nozzles were installed at 20 ft (6.1 m) elevation above a simulated diesel generator in the 60 ft (18.3 m) high section of the FM Global Research Campus. The area was not enclosed. When the system was activated, the diesel generator was completely enclosed by the water mist. When a 6 MW fire was started on the diesel generator and the system was activated it had no apparent effect on the fire. A ceiling was constructed over the nozzles. Again there was no apparent affect on fire intensity. When the sides were enclosed some test fires could be extinguished. 4. Do not assume that one successful fire test is proof that a water mist system will adequately protect the hazard. Typically, several tests have to be conducted to characterize the hazard. The combustion turbine testing includes shielded spray and pool fires and spray fires in the open. 5. Conduct tests in as realistic a manner as possible. Effects that adversely affect water mist systems are simulated during the test. For example, if ventilation will not be shut off in a fire, the tests are conducted with ventilation in operation Local Application Systems Local application system test protocols have been developed for water mist system testing. The test protocols involve extinguishment of ignitable liquid pool and spray fires. Local application systems work largely by flame cooling. Larger fires are harder to extinguish. Inerting is not as big a contribution as for enclosure fires. 3.2 Operating Experience Several fires have been reported in combustion turbine enclosures and machinery spaces on North Sea oil platforms. There were two operations reported on a fiberboard press and one operation reported in a diesel engine test cell. These operations were successful. A failure was reported at a wood-working facility in an enclosure that contained logs and sawdust. This enclosure had been protected with a CO 2 system. The CO 2 system was replaced with a water mist system. A fire was detected and the system operated automatically. Reportedly, an operator opened the enclosure too soon and the fire reignited. The following deficiencies were noted in acceptance tests: (1) failure of the system to discharge. Improper gaskets were used on the air cylinder, resulting in loss of air pressure. (2) Plugged nozzles. This was believed to be due to the use of pipe dope rather than oil on threaded fittings. (3) In addition, a potential problem was identified when residue was found inside piping following an acceptance test. The powder residue was analyzed and determined to be zinc oxide. There is a concern that this residue could plug nozzle openings. The residue was from the tank or the piping, both of which were galvanized steel. The conclusions were as follows: 1. Acceptance tests, including discharge of the system or equivalent, are critical to system reliability. 2. Systems are being installed in applications for which they have not been tested. 3. A method is needed to obtain information on acceptance testing and operating experience. The NFPA 750 Committee (Standard on Water Mist Fire Protection Systems) is attempting to obtain information using a Water Mist System Questionnaire. The questionnaire is part of the NFPA standard. The information requested includes acceptance test and operating experience as well as background information on the system.

12 4-2 Water Mist Systems Page 12 FM Global Property Loss Prevention Data Sheets 3.3 Test Data FM Approval testing is directed at specific hazards, such as combustion turbine enclosures, machinery in an enclosure, wet benches, light hazard occupancies, and continuous board presses. Systems that have been FM Approved for protection of a specific hazard may be used for protection of other hazards provided the hazards are similar. For example, a system that has been FM Approved for machinery in an enclosure can be used to protect indoor transformers, provided the volume and height of the room is equal to or less than that tested Combustion Turbine Enclosures Fire testing is conducted within 2,280 ft 3 (80 m 3 ), 9,170 ft 3 (260 m 3 ), and larger enclosures. The shielding effect of the combustion turbine casing is simulated using a mockup of the turbine. There is no ventilation in operation. The fire testing involves shielded and unshielded No. 2 fuel oil spray and shielded pool fires. The spray fires are located above and below the turbine casing. The pool fire is located below the turbine casing. Fire intensities are 1 to 2 MW (equivalent to a heptane pool fire 8.3 to 16.1 ft 2 [0.77 to 1.5 m 2 ]) in area. Testing also is done to verify that the cooling effect of water mist would not result in unacceptable stresses to the turbine casing. A 2 in. (5.1 cm) thick steel slab with thermocouples embedded in the steel at distances of 0.5, 1.0, and 1.5 in. (1.3, 2.5, and 3.8 cm) from the surface is used. The metal slab is heated to 570 F (300 C) and the water mist system is discharged. For a direct impingement system, water mist is directed onto the steel plate from the minimum distance specified in the manufacturer s literature. An FM Globaldeveloped computer program is then used to predict whether the casing would distort sufficiently to come into contact with the turbine blades (blade rubbing). Time to extinguish is determined, and distortion of the casing cannot result in blade rubbing Cleanrooms Fire testing is conducted on a wet bench in a simulated cleanroom. One test series simulates a fire within the sub-surface area of the wet bench. Another test series simulates a fire on the surface of the wet bench. Fire testing conducted below the surface is conducted in an enclosure ft ( m) high. Fire tests involve burning pools of polypropylene beads and ignitable liquid in pans ranging in diameter from 4 to 12 in. (10.1 to 30.5 cm). The pan is shielded from direct impingement from the water mist nozzles to simulate obstructions in the plenum. Tests also are conducted on the surface of the wet bench. The surface is 2.5 ft (0.8 m) 7.5 ft (2.3 m) long. Tests are conducted with ventilation rates of up to 140 ft 3 /min/linear ft (13 m 3 /min/linear m) of bench. The tests require fire extinguishment within 1 minute Light Hazard Occupancies Fire testing can be conducted in three compartment sizes as follows: (a) a small compartment ft ( m) high, (b) a large compartment of equal length sides, no greater than 400 ft 2 (37 m 2 ) in area and 8 ft (2.4 m) high. With two doors at opposite ends of the compartment remaining open during the test, (c) an open space. The open space test is conducted inside a building large enough so the results of the test will not be influenced by the size of the building. A ceiling is arranged at least 860 ft 2 (80 m 2 ) in area and 16.4 ft (5 m) above the floor. The small compartment is designed to simulate a room. The room contains two bunk beds on each side. The bunk beds have polyurethane foam mattresses ft (2 0.8 m). The mattresses are 4 in. (100 m) thick. The large compartment contains a wooden crib in a steel pan and two pieces of simulated furniture. The wooden crib is ft ( m) and weighs approximately 13 lbs (6 kg). The furniture consists of two wooden frames with 3 in. (76 mm) thick polyurethane foam stapled to the frames. The open compartment has two sofas as the fire exposure. The sofas are ft (2 0.8 m) with 4 in. (100 mm) thick polyurethane foam over the frames. Three tests are conducted with: (a) sofa location under one nozzle; (b) sofa location between two nozzles and (c) sofa location between four nozzles. Ceiling temperature must not exceed 500 F (260 C). Damage to the cushions must not exceed 40% by volume in the small compartment test and 50% by volume in the large and open tests. For the large test, a

13 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page 13 nozzle located in the doorway must not open. For the open tests, no more than 5 nozzles can open. Fires are suppressed by the water mist system and manually extinguished after 20 minutes Continuous Wood Board Presses Fire testing was conducted in a mock-up of areas of a continuous wood board press. These areas included the press pockets and heat tunnel. Press pockets are formed by frames that are the width of the press. The frames are varying distances apart. The mockup of the press pocket simulated a pocket of the largest area determined in a field review. The pocket is 3.3 ft (1 m) 12 ft (3.6 m) long. The pockets are open at both ends. The frame walls are partial height walls. It is anticipated that a pool oil fire and/or a spray oil fire could occur in this area. The fire would expose the frame walls (steel) of the press and the platens used to heat the stainless steel belt. Pool and/or spray fires could occur in this area involving either hydraulic fluid or thermal oil. The objective is to determine whether the water mist system will extinguish or control temperature from pool and spray fires. Temperature control is considered to be providing adequate cooling to prevent damage to the press frame. 1. Heat tunnel tests. The heat tunnel runs the length of the press. It contains the stainless steel belt used to form the board. The fire exposure is oil that has dripped off the belt and collected on one side of the bottom of the tunnel (tunnel floor is sloped). There also is a concern that rapid cooling will damage the belt. Testing is done using a 16.4 ft (5 m) long mock-up of the tunnel with a stainless steel belt in the tunnel. a) One test is conducted in which the belt and the enclosure are heated to normal operating temperature and the water mist system is activated to simulate accidental activation. Belt samples are taken for metallurgical analysis. b) A second test is conducted with fuel oil in the trough. Fuel oil is ignited and allowed to burn until the channel is fully involved. The water mist system is actuated. The time to extinguish the fire is determined. Belt samples are taken for metallurgical analysis. Tests such as tensile strength, measurements of the width and length of the belt section tested, and bendability testing are done before and after fire testing to identify changes in belt properties. 4.0 REFERENCES 4.1 FM Global Data Sheet 2-8, Earthquake Protection for Water-Based Fire Protection Systems Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers Data Sheet 3-26, Fire Protection Water Demand for Nonstorage Sprinklered Properties Data Sheet 4-0, Special Protection Systems Data Sheet 5-48, Automatic Fire Detection 4.2 NFPA Standards NFPA 13, Standard for the Installation of Sprinkler Systems. NFPA 15, Standard for Water Spray Fixed Systems for Fire Protection. NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection. NFPA 70, National Electrical Code. NFPA 750, Water Mist Fire Protection Systems. 4.3 Others ASME, Boiler and Pressure Vessel Code, Section VIII, Rules for Construction of Pressure Vessels. ANSI B31.1 Power Piping Code. ANSI, National Electrical Safety Code. U.S. Dept of Transportation, Title 49, Code of Federal Regulations, Parts 171 to 190, Sections and APPENDIX A GLOSSARY OF TERMS FM Approved: References to FM Approved in this data sheet mean the product and services have satisfied the criteria for FM Approval. Refer to the Approval Guide, a publication of FM Approvals, for a complete listing of the products and services that are FM Approved.

14 4-2 Water Mist Systems Page 14 FM Global Property Loss Prevention Data Sheets Atomizing Media: Compressed air or other gases that produce water mist by mechanical mixing with water. Dv f : A drop diameter such that the cumulative volume, from zero diameter to this respective diameter, is the fraction, f, of the corresponding sum of the total distribution. Dv 50 : The volume median diameter; that is 50% of the total volume of liquid is in drops of smaller diameter and 50% in drops of larger diameter. High Pressure System: A water mist system where the distribution system piping is exposed to pressures of 500 psi (34.5 bar) or greater. Intermediate Pressure System: A water mist system where the distribution system piping is exposed to pressures greater than 175 psi (12.1 bar) but less than 500 psi (34.5 bar). Local application systems: A water mist system arranged to discharge on the protected hazard and within the containment or confinement area around the hazard. Low Pressure System: A water mist system where the distribution system piping is exposed to pressures of 175 psi (12.1 bar) or less. LPCD: Loss Prevention Certification Board, UK. Machinery Space: These areas include internal combustion engines, generators, transformers, oil pumps, oil reservoirs, fuel filters, gear boxes, drive shafts, lubrication skids, and other similar equipment using liquid hydrocarbon fuel and/or hydraulic, heat transfer, and lubrication fluids, and enclosures with incidental luse of ignitable liquids of not more than two 55 gal (208 L) drums arranged for dispensing with safety bungs. Primary protection: Water mist may be considered primary protection if the system has been tested for the hazard protected, and the duration of the agent supply is equivalent to that required for the same hazard protected by an automatic sprinkler system. Single Fluid System: A water mist system utilizing a single piping system to supply each nozzle. Nozzles may be supplied with water or a mixture of gas and water. Special protection systems: Water mist is considered a special protection system when it is able to extinguish all of the fire scenarios for the hazard protected, and where it has a limited agent supply. The agent supply is usually specified as the greater of (a) twice the time to extinguish the worse-case fire scenario in an accepted fire test scenario, (b) the total time to shutdown process equipment including the time it takes surfaces to decrease to a safe temperature, or (c) 10 minutes. Safe surface temperature may be specified in the data sheet pertaining to protection of the occupancy. Discharge times other than 10 min may also be allowed in the data sheet pertaining to protection of the occupancy. Special protection systems such as CO 2, dry chemical, or clean agent may also be suitable for protection of the hazard. Occupancies suitable for protection by special protection systems are described in FM Global data sheets. SSL: Scientific Services Laboratory, Melbourne, Australia. Total Flooding System: A system designed to protect all the hazards in an enclosure. Twin Fluid System: A water mist system in which water and atomizing media are supplied to the water mist nozzle using separate piping systems. VdS: Verband der Sachversicher, Cologne, Germany. Water Mist: A water spray for which the Dv 0.99, for the flow weighted cumulative volumetric distribution of water droplets, is less than 1,000 microns at the minimum design operating pressure of the water mist nozzle. Water Mist Nozzle: A special purpose device containing one or more orifices designed to produce and deliver an atomized water spray meeting the definition of water mist or meeting the specific requirements of an FM Approved water mist fire test protocol. Nozzles can be designed to operate independently of other nozzles, as a group of nozzles, or a combination of the two. Zoned Application System: A system designed to protect hazards in a predetermined portion of an enclosure.

15 Water Mist Systems 4-2 FM Global Property Loss Prevention Data Sheets Page 15 APPENDIX B DOCUMENT REVISION HISTORY January Minor editorial changed were made for this revision. July Minor editorial changed were made for this revision. April Moved occupancy related recommendations to occupancy-specific data sheet. September Replaced all references to Data Sheet 2-8N, Installation of Sprinkler Systems (NFPA), with references to Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers. September Minor editorial changes were made for this revision.january Clarified recommendations for when a reserve supply of agent is needed, and added three new definitions to Appendix A. Also, the water demand for light hazard occupancies is now based on area rather than number of sprinklers. January Minor editorial changes were made for this revision. September Section was modified to allow the use of light hazard water mist systems FM Approved for open area protection. January Minor editorial changes were made for this revision. September Minor editorial changes were made for this revision. January Minor editorial changes were made for this revision. September Minor editorial changes were made for this revision. September The following changes were made for this revision: 1. Loss experience was added. 2. Fire test descriptions were included for FM Approved water mist systems. 3. General criteria for water mist system installation was provided. APPENDIX C ADDITIONAL INFORMATION C.1 Electrical Clearances Locate system components minimum distances from energized electrical components as shown in Table A in NFPA 750, Standard on Water Mist Fire Protection, 2010 Edition. C.2 Material of Construction Ensure piping and nozzle construction are of corrosion-resistant material, such as stainless steel, brass, or copper. Where these materials are not suitable, such as for wet bench protection in cleanrooms, plastics have been FM Approved for this application. Materials that will corrode under the environmental conditions are not suitable because nozzle diameters are small and, even if filters are provided, cannot be expected to remain operational. C.2.1 Galvanized Steel C General Galvanized steel was examined as a material of construction for piping used in water mist systems. Some of the earlier systems were FM Approved with galvanized piping. In hot dip galvanizing, a zinc coating is applied to iron or steel by immersing the material in a bath consisting primarily of molten zinc. A layer of zinc is formed on the pipe. As long as the coating is continuous and unbroken it will corrode like solid zinc. The fresh zinc surface initially corrodes rapidly until it is covered with a protective film of corrosion products. The corrosion then continues at a reduced rate. When there is a break in the coating, the corrosion rate of galvanized steel pipe is similar to carbon steel pipe. C Metallurgical Analysis Fourteen metallurgical reports of failed galvanized piping were analyzed. The piping was largely from dry pipe sprinkler systems. The analysis indicated the following: (a) deteriorated pipes are mostly thin wall