FIRE PROTECTION FOR DESALINATION AND WATER REUSE FACILITIES
PART 1: ADMINISTRATIVE CONTROLS AND GENERAL PLANT DESIGN
BY CASEY C. GRANT, P.E.
Fresh water is vital to the life and function of every community across the nation. Where a constant supply of fresh water is not readily available, communities depend directly on manufactured fresh water supplies that are continual and reliable. Methods such as desalination have been developed and water reuse facilities have been constructed to ensure such a supply remains constant. But what happens when that fresh water supply is interrupted by fire? Such an interruption is a realistic threat for almost all industrial processes and facilities. Desalination plants are no exception.
The fire hazards associated with water-treatment processes are generally related to the handling of fuels needed to energize the processes but are also related to lubricants, hydraulic fluids, normal combustibles, and other materials involved in the treatment process or process structure. Also of concern are water reuse facilities and, most notably, wastewater treatment plants. Additional hazards for these facilities include the possible intake of flammable or combustible liquids and the generation of flammable gases.1
Fire in a desalination plant or water reuse facility can affect all portions of the facility; therefore, measures must be taken to protect that facility. In fact, these measures should be factored in during all stages of any new facility`s design.
ADMINISTRATIVE CONTROLS
Fire Prevention Activities
A written fire prevention program, similar to what is needed for all industrial facilities, should be established for the plant. This program should include but not be limited to the following:
a fire risk evaluation, initiated early in the design process, to ensure that fire prevention and protection recommendations have been evaluated in view of the plant-specific considerations regarding design, layout, and anticipated operating requirements;
fire safety information for all employees and contractors concerning fire prevention procedures, plant emergency alarms and procedures, and methods of reporting a fire;
documented plant inspections and provisions for handling remedial actions to correct conditions that increase fire hazards;
a description of the general housekeeping practices and the plan for control of transient combustibles; and
the control of flammable and combustible liquids and gases in accordance with appropriate codes and standards, such as NFPA 30, Flammable and Combustible Liquids Code.
Testing, inspection, and maintenance should be documented with written procedures, and the results and follow-up actions should be recorded. A written procedure that addresses impairments to fire protection and other plant systems that impact the level of fire hazard (e.g., dust collection systems, HVAC systems, and so on) should be established.
Plant Emergency Operation
A written fire emergency plan should be developed and include the following as a minimum:
response to fire alarms and fire systems supervisory alarms;
notification of personnel identified in the plan;
evacuation of employees not directly involved in firefighting activities from the fire area;
coordination with security forces or other designated personnel to admit public fire departments and control traffic and personnel;
fire extinguishment activities;
periodic drills to verify viability of the plan; and
specification of control room operator(s) activities during fire emergencies.
Requirements of Plant Fire Brigade
The size of the plant and its staff, the complexity of firefighting problems, and the availability of staff to serve on the brigade should determine the requirements for a plant fire brigade. If a brigade is provided, its organization and training should be identified in written procedures.2
A plant fire brigade should be available for shift personnel who have plant duties that do not prevent immediate response to a fire or other emergencies. Each brigade member should be physically qualified to perform emergency response duties and receive an annual physical examination to determine ability to use respiratory protection equipment. Furthermore, the brigade leader and at least two brigade members should have sufficient knowledge of plant systems to understand the effects of fire and fire suppressants on the plant`s processes.
Quarterly drills to test the response capability of the fire brigade should be conducted, and records detailing the drill scenario, fire brigade member responses, and the ability of the fire brigade to perform the assigned duties should be maintained. In addition, specific prefire plans should be developed for all site areas and should detail the fire area configurations and possible fire hazards in each fire area. These plans should be reviewed and, if necessary, updated at least every two years. They should be available in the control room and to the plant fire brigade.
GENERAL PLANT DESIGN
Plant Arrangement
The plant should be subdivided into separate fire areas as determined by the fire risk evaluation for the purposes of limiting the spread of fire, protecting personnel, and limiting fire damage to the plant. Those areas should be separated from each other by approved fire barriers having at least a two-hour fire resistance rating. Determination of fire area boundaries should be based on consideration of the following: types, quantity, density, and locations of combustible material; location and configuration of plant equipment; consequence of losing plant equipment; and location of fire detection and suppression systems.
If a fire area is defined as a detached structure, it should be separated from the structures by an appropriate distance [e.g., 9.1 m (30 feet) minimum for a structure with moderate combustible loading and a nonfire rated enclosure]. Unless consideration of the above factors indicates otherwise, it is recommended that fire area boundaries be provided to separate the control room; computer room; major concentrations of electrical equipment, such as a switchgear room or a relay room; telecommunication rooms, cable spreading room(s) and cable tunnel(s); battery rooms; maintenance shop(s); office buildings; warehouses; beneath the underside of the operating floor for turbine generators (where provided); fuel oil pumping or heating facilities used for continuous firing of boilers; storage areas for flammable and combustible liquid tanks and containers; emergency diesel generators; and fire pumps.
Life Safety Considerations
The potential for loss of life due to the fire in an industrial occupancy is directly related to the processes performed in the occupancy. Fire records typically indicate that a majority of industrial fires causing multiple deaths are the result of flash fires with highly combustible contents or explosions involving combustible dusts, flammable liquids, or gases. Although industrial fires can constitute a high percentage of a country`s total annual national fire loss from a property standpoint, such fires have not typically resulted in extensive loss of life. For example, in the United States in 1995, 16,270, or 2.8 percent, of the 573,500 structure fires reported to fire departments occurred in manufacturing and industrial occupancies. These fires caused 32, or 0.8 percent, of the 3,985 civilian structure fire deaths; 587, or 2.7 percent, of the 21,725 civilian structure fire injuries; and $1.25 billion in direct property damage. This represents 16.5 percent of the $7.62 billion of direct property damage in structure fires. Between 1980 and 1995, 3.3 percent of the structure fires occurred in the manufacturing and industrial occupancies. These fires caused 0.8 percent of the civilian structure fire deaths and 10.9 percent of total direct property loss.3
To a great extent, NFPA 101, Life Safety Code®, was developed from a review of past catastrophic events–including disasters at industrial facilities–as well as from considerable research and applied engineering judgment. The result is an approach to building design and operation that, if properly applied, reduces the potential for loss of life from fire. It should be noted that portions of the Life Safety Code® specifically address industrial facilities.
Building Construction Materials
Construction materials for the facility should be classified by recognized test methods appropriate to the end-use configuration of the material.4 All walls, floors, and structural components, except interior finish materials, should be of noncombustible construction. Roof coverings should be Class A, as determined by tests described in NFPA 256, Standard Methods of Fire Tests of Roof Coverings. Carpeting should not be installed on walls in any plant area. Floor carpeting should have critical radiant flux greater than 0.45 watts/cm2 when tested in accordance with documents such as NFPA 253, Standard Method of Test for Critical Radiant Flux of Floor Covering Systems Using a Radiant Heat Energy Source, and should have a smoke development rating of less than 450 when testing in accordance with documents such as NFPA 255, Standard Method of Test of Surface Burning Characteristics of Building Materials.
Ventilation Systems
Heating, ventilating, and air-conditioning systems should be included in the plant`s fire protection design. For example, air-conditioning for the control room should provide a pressurized environment to preclude the entry of smoke should a fire occur outside the control room.5 Heat vents should be provided for areas identified by the fire risk evaluation. Where heat vents are provided, heat generated under fire conditions should be vented from its place of origin directly to the outdoors. Smoke venting should also be provided for areas identified by the fire risk evaluation. Where smoke venting is provided, smoke should be vented from its place of origin in a manner that does not interfere with the operation of the plant. Separate smoke ventilation systems are preferred; however, smoke venting can be integrated into normal ventilation systems using automatic or manually positioned dampers and motor speed control. Smoke venting may also be accomplished with portable smoke ejectors.6
Drainage
Provisions should be made in all the plant`s fire areas for directly removing all liquids to safe areas or containing them in the fire area. Drainage and prevention of the flooding of equipment may be accomplished through floor drains; floor trenches; open doorways or other wall openings; curbs for containing or directing drainage; equipment pedestals; and pits, sumps, and sump pumps.
The provisions for drainage and any associated drainage facilities should be sized to accommodate all of the following: the spill of the largest single container of any flammable or combustible liquids in the area; the maximum expected number of fire hoselines [31.5 L/sec (500 gpm) minimum] operating for a minimum of 10 minutes; and the maximum design discharge of fixed fire suppression systems operating for a minimum time period.
Electrical Considerations
The electrical design and installation of electrical generating, control, transmission, distribution, and metering of electrical energy should be provided in accordance with NFPA 70, National Electrical Code, or ANSI C2, National Electrical Safety Code, as applicable. Group cabling should be routed away from exposure hazards and never be routed near sources of ignition or flammable and combustible liquid hazards. Cable raceways should be used only for cables.
Furthermore, emergency lighting should be provided for means of egress, as indicated in the Life Safety Code®. Emergency lighting should be provided for critical plant operations areas. Lightning protection should be provided for those structures having a risk index (R) of four or greater when evaluated in accordance with NFPA 780, Standard for the Installation of Lightning Protection Systems. The plant-approved voice/alarm communication system should be established in accordance with NFPA 72, National Fire Alarm Code, and be available on a priority basis for fire announcements, for directing the plant fire brigade, and for fire evacuation announcements. The fire brigade and any other operation personnel involved with the plant`s safe shutdown should use a portable radio communication system. n
Endnotes
1. NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities, specifically addresses fire protection concerns in these facilities.
2. Detailed information on the subject can be found in NFPA 600, Standard on Industrial Fire Brigades.
3. National Fire Incident Reporting System (NFIRS) 1980-1995, NFPA Survey of Fire Departments for U.S. Fire Experience.
4. Examples of documents that can be referenced are the following: NFPA 220, Standard on Types of Building Construction; ASTM E136, Standard Methods of Fire Tests of Building Construction in a Vertical Tube Furnace at 750ºC; NFPA 251, Standard Methods of Tests of Fire Endurance of Building Construction and Materials (ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials); NFPA 253, Standard Method of Test for Critical Radiant Flux of Floor Covering Systems Using a Radiant Heat Energy Source; NFPA 255, Standard Method of Test of Surface Burning Characteristics of Building Materials (ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials); NFPA 256, Standard Methods of Fire Tests of Roof Coverings; and NFPA 259, Standard Test Method for Potential Heat of Building Materials.
5. Further consideration of this topic is addressed by NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems, and NFPA 90B, Standard for the Installation of Warm Air Heating and Air Conditioning Systems.
6. Addressing ventilation are NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems; NFPA 92A, Recommended Practice for Smoke-Control Systems; and NFPA 204M, Guide for Smoke and Heat Venting.
CASEY C. GRANT, P.E., serves as assistant vice president of Code & Standards Administration and as secretary to the Standards Council. He has been with the National Fire Protection Association (NFPA) since May 1988. His responsibilities include the oversight of the approximate 300 documents in the NFPA codes- and standards-making system.
