Water spray systems

Water spray systems for hydrocarbon facilities are routinely specified because of the rapid application means the system can provide and the excellent heat absorption a water based system represents. Water sprays are also used when passive fire protection measures (i.e., fireproofing, spacing, etc.) cannot practically be utilized. The key to providing an effective system is to ensure the surfaces to be protected receive adequate water densities and that the arrangements to activate the system are equally fast acting. By far the highest 

Deluge protection can be applied over the entire hazard area with open sprinkler heads located at various floor levels or fixed water spray systems can be applied specifically on the equipment to be protected. Specific water spray application is preferred because it provides better equipment cooling and reduces the water wasted due to wind and fire draft. 

It can be difficult to install fixed water spray protection for equipment located in multilevel process structures, in congested areas, or in areas containing numerous pieces of small equipment. In such situations, the use of deluge protection of an area is an acceptable and cost-effective alternative to the specific protection afforded by fixed water spray. 

Water spray systems are used for protection against hazards involving gaseous and liquid flammable materials and combustible solid materials. These systems are used to  

The water demand for enclosed process structures may depend on the degree of compaitmentalization by solid floors and the number of separate systems used to protect the structure. At a minimum, ground floor systems should be assumed to operate in a spill fire scenario. But, if water spray systems are used, it should be assumed that all systems will operate in order to estimate maximum water demand. 

For open structures protected by water spray systems, it should be assumed that all systems within the structure will operate. The water demand for each system is summed to get the total demand for the unit plus manual firefighting. 

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Steel stmctures should be protected by approved fireproofing treatment, eg, concrete or insulating, ie, intumescent or ablative materials untreated steel should be protected by some method of cooling, eg, a water-spray system. 

Fine water spray systems may be potentially superior to CO9 apphcations and may replace halon environments such as telephone central offices and computer rooms. In the fine spray dehveiy system, water is delivered at relatively high pressure (above 100 psi [0.689 MPa]) or by air atomization to generate droplets significantly smaUer than those generated by sprinklers. Water flow from a fine spray nozzle potentially extinguishes the fire faster than a sprinkler because the droplets are smaUer and vaporize more quickly. Preliminaiy information indicates that the smaller the droplet size, the lower the water flow requirements and the less chance of water damage. 

NFPA 16 Standard for the Installation of Foam-Water Sprinkler and Foam-Water Spray Systems, 1999 edition. National Fire Protection Association, Quincy, MA. 

The team suggested mitigations. For example, the consequences of an ammonia release could be markedly reduced by a reliable and quick-acting water spray system. The probability of damage due to ship collisions could be reduced by a f tor of five by a speed limit of eight knots. Evacuation of the potentially affected is practicable and effective. 

A device called an air washer is also used for humidification and dehumidification, It consists of a chamber incorporating a water spray system, a collection tank, and an eliminator section. The eliminator plates are necessary to reduce the incidence of water droplets that are carried out of the plant into the duct run. 

Regarding fires, water is the primary extinguishing agent, and it should be available in adequate supply and pressure at all of the locations in the plant. The layout for various types of installations and the appropriate recommendations are found in the standards of the National Fire Protection Association. Fire hydrants, hose lines, automatic sprinkler and water spray systems should all be a part of the permanent equipment facilities of the plant. 

Water spray systems. Tliese are used for exposure protection of buildings, tanks, and control of Class B flaimnable liquid fires. 

The usual protection for large installations is to provide a water-spray system. For small bulk storage, fire hoses or monitors are often adequate. However, for installations over 50 tons of storage (and all major cylinder-filling plants) it is accepted that a fixed water-spray system needs to be provided which is automatically initiated by a system capable of detecting a fire threatening the vessels... 

Automatic equipment promptly detected the hazardous vapor and operated the automatic high-density water-spray system, which was designed to wash the ethylene from the atmosphere. The leak was too large for the spray system to handle. 

Water spray systems have been demonstrated to assist in the dispersion of vapor releases. The sprays assist in the dilution of the vapors with the induced air currents created by the velocity of the projected water particles. They cannot guarantee that a gas will reach an ignition source but do improve that probabilities that dispersion mechanisms will be enhanced. 

American Petroleum Institute (API), Publication 2030 Guidelines for Application of Water Spray Systems for Fire Protection in the Petroleum Industry. First Edition, API, Washington, D.C., 1987. 

An active fire protection system requires some action to occur before it functions per its design intent. This action may be taken by either a person or control system. Examples of active fire protection systems are monitors, water spray systems, foam systems, emergency isolation valves, and ESD systems. 

Processes susceptible to a runaway reaction during fire exposure shall be protected by water spray systems and fire monitors. 

Bare pressure vessels in a process unit protected by vapor depressuring usually do not require protection by fixed water spray systems. 

Water is not suitable for electrical (Class C) fires, but is effective on all combustible (Class A) and many flammable liquid (Class B) fires. Water can be applied by hose streams, monitors, sprinklers, water spray systems, or as water curtains for such purposes as ... 

A hazard analysis may be performed to review reductions in the suggested separation distances. Increased risk can be mitigated by providing additional safeguards, such as fireproofing, automatic water-spray systems, emergency shutdown systems, or additional firefighting equipment. 

For example, if LPG vessels are considered to be within a fire-scenario envelope, they require fireproofing unless protected by a fixed water spray system. API Standard 2510, Design and Construction of Liquefied Petroleum Gas Installations (API, 2001) recommends fireproofing pipe supports within 50 ft (15 m) of the LPG vessel, or within the spill containment area. 

The time required to apply adequate, reliable cooling from fixed water spray systems or fixed monitors, including response time for personnel to operate them. 

Structures with equipment on two or more levels, not protected by water spray or deluge systems, should be counted as double the grade area beneath the multilevel structure plus the areas as noted above. Where fixed water spray systems are provided, their water requirements should be added to the fire water demand. Water demands for other areas within a plant may include ... 

Sufficient sectional block valves should be provided so that sections of the underground system can be taken out of service for repairs without undue interruption of the fire water protection. For example, the sectional block valves should be located so that a combination of no more than five resources, such as hydrants, monitors, water spray systems, etc. would be out-of-service at any given time. Sectional block valves should be provided at no more than 800 ft (243 m) intervals for long runs of pipe. 

The last two applications, while convenient and initially appealing, require more maintenance and inspection than a simple, ground level monitor. Significant reactive forces can be generated and, therefore, the support structures must be properly engineered. Elevated monitors also require support and hydraulics to be protected by a water spray system if exposed to fires. An elevated monitor is shown in Eigure 7-12. 

Fixed installations, such as water spray systems, halon systems, sprinkler systems, carbon dioxide extinguishing systems, explosion suppression systems, and other fire protection installations are often provided with flow and trouble detection switches connected to transmitters. A signal indicating the condition of the system should be sent to the attended location(s). 

A deluge sprinkler system is a sprinkler system designed to NFPA 13 with open sprinkler heads. A water spray system is hydraulically designed with open spray heads to protect a specific hazard. Water spray systems are discussed in Section 7.4.8. 

Fixed water spray systems are most commonly used to protect flammable liquid and gas vessels, piping and equipment, process structures and equipment, electrical equipment such as transformers, oil switches, rotating electrical machinery, and openings through which conveyors pass. The type of water spray will depend on the nature of the hazard and the purpose for which the protection is provided. 

The design densities to be used in designing water spray systems are given in Chapter 8. 

The design of water spray systems should be in accordance with NFPA 15. Highlights and exceptions to NFPA 15 are ... 

Water spray systems should be provided with a water flow alarm installed in accordance with NFPA13, Installation of Sprinkler Systems. Electrically oper-... 

At least one remote manual actuation device independent of the manual actuation device located at the system actuation valve should be installed for all automatic water spray systems. 

Foam-Water Deluge and Water Spray Systems... 

The quantity of flammable liquids or gases or heated combustibles can be indicative of the need for fixed water spray fire protection. Table 8-4, developed from FM Data Sheet 7-14, suggests quantities of flammables where fixed water spray fire protection should be considered based on one insurance provider s guidance. Some company internal guidelines and practices allow up to 5,000 gal (18,927 I) in the largest vessel before water spray protection is recommended. Additional guidance on fixed fire protection is available in API Publication 2030, Application of Water Spray Systems for Fire Protection in the Petroleum Industry, (API, 1998). 

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