Fire Detection and Suppression Chapter 3 Water Supply

Characteristics of Water Compound of two parts hydrogen and one part oxygen (H20) Liquid between 32F and 212F (0C and 100C) Solid below 32°F (0C) Gas above 212°F (100°C) Incompressible Weight for fire protection purposes=62.5 lb/ft3 or 8.33 lb/gal (1 kg/L) Water Supply

Extinguishing Properties of Water The law of specific heat: the specific heat of any substance is the ratio between the amount of heat needed to raise the temperature of a specified quantity of a material and the amount of heat needed to raise the temperature of an identical quantity of water by the same number of degrees. (Continued) Water Supply

Extinguishing Properties of Water (cont.) The law of latent heat of vaporization The latent heat of vaporization is the quantity of heat absorbed by a substance when it changes from a liquid to a vapor. 1 gallon of water will absorb 9,346 Btu (1,266 + 8,080) of heat if all the water is converted to steam. (Continued) Water Supply

Extinguishing Properties of Water (cont.) Surface area of water: the speed with which water absorbs heat increases in proportion to the water surface exposed to the heat. Expansion ability Smothering ability (Continued) Water Supply

Extinguishing Properties of Water (cont.) Specific gravity: the density of liquids in relation to water Liquids with a specific gravity less than 1 are lighter than water and therefore float on water. Most flammable liquids have a specific gravity of less than 1. Water Supply

Water’s Advantages as an Extinguishing Agent Greater heat-absorbing capacity Large amount of heat required to change water into steam Easily expanded surface area Plentiful supply Water Supply

Water’s Disadvantages as an Extinguishing Agent High surface tension Reactivity Low levels of opacity and reflectivity Freezes at 32F (0C) Conductivity Water Supply

Water Pressure and Velocity Pressure: force per unit area on a liquid or gas expressed in psi or kPa Force: simple measure of weight Velocity The speed at which fluid travels through hose or pipe Result of pressure exerted on the fluid at its source (Continued) Water Supply

Water Pressure and Velocity (cont.) Principles of pressure First Principle: fluid pressure is perpendicular to any surface on which it acts. Second Principle: fluid pressure at a point in a fluid at rest is the same intensity in all directions. Third Principle: pressure applied to a confined fluid from without is transmitted equally in all directions. (Continued) Water Supply

Water Pressure and Velocity (cont.) Principles of pressure Fourth Principle: the pressure of a liquid in an open vessel is proportional to its depth. Fifth Principle: the pressure of a liquid in an open vessel is proportional to the density of the liquid. Sixth Principle: the pressure of a liquid on the bottom of a vessel is independent of the shape of the vessel. (Continued) Water Supply

Water Pressure and Velocity (cont.) Types of pressure Atmospheric pressure: pressure exerted on the earth by the atmosphere itself Head pressure Height that a pressure can lift a column of liquid Height of a water supply above the discharge orifice is called the elevation head. Static pressure: stored potential energy available to force water through pipe, fittings, fire hose, and adapters (Continued) Water Supply

Water Pressure and Velocity Types of pressure (cont.) Normal operating pressure: pressure found in a water distribution system during normal consumption demands Residual pressure: that part of the total available pressure not used to overcome friction loss or gravity while forcing water through pipe, fittings, fire hose, and adapters Flow pressure (velocity pressure): forward velocity pressure while water is flowing Water Supply

Pressure Loss and Gain Elevation Altitude Center line of the pump or the bottom of a static water supply source above or below ground level Elevation pressure results from differences in elevation of nozzle and pump. Altitude Position of an object above or below sea level Effects of lower atmospheric pressure on drafting above 2000 feet (600 m) Water Supply

Friction Loss That part of the total pressure lost while forcing water through pipe, fittings, fire hose, and adapters (Continued) Water Supply

Friction Loss (cont.) Causes Movement of water molecules against each other Linings in fire hose/inside surface of piping Hose couplings/pipe fittings Sharp bends Change in hose size or in orifice by adapters Improper hose-coupling gasket size/pipe control valves Water Supply

Friction Loss (cont.) Principles of friction loss: First principle: if all other conditions are the same, friction loss varies directly with the length of the hose or pipe. Second principle: when hoses are the same size, friction loss varies approximately with the square of the increase in the velocity of the flow. Third principle: for the same discharge, friction loss varies inversely as the fifth power of the diameter of the hose. (Continued) Water Supply

Friction Loss Principles of friction loss (cont.): Fourth principle: for a given flow velocity, friction loss is approximately the same, regardless of the pressure on the water. Other factors affecting friction loss: diameter and length of hose or pipe Reducing friction loss Water Supply

Water Hammer Energy surge that results from suddenly stopping or starting water moving through hose or pipe Can damage the pump, appliances, hose, or the municipal water system itself Water Supply

Municipal Water Supply Systems Components Source of water supply Means of moving water Water processing or treatment facilities Water distribution system, including storage (Continued) Water Supply

Municipal Water Supply Systems (cont.) Sources of water supply Public water supply system Surface or ground water Means of moving water Directing pumping system Gravity system Combination system (Continued) Water Supply

Municipal Water Supply Systems (cont.) Water processing or treatment facilities The fire department’s main concern regarding treatment facilities is that a maintenance error, natural disaster, loss of power supply, or fire could drastically reduce the volume and pressure of water available for fire fighting operations. (Continued) Water Supply

Municipal Water Supply Systems (cont.) Water Distribution System Dead-end hydrants Circulating feed or looped lines Grid system Primary feeders Secondary feeders Distributors Water Supply

Water Distribution System Variables Piping materials Pipe diameter Piping arrangement Simple loop One inflow point and one outflow point. Exactly two paths between the inflow and outflow points. (Continued) Water Supply

Water Distribution System Variables Piping arrangement (cont.) Complex loop (grid) More than one inflow point More than one outflow point More than two paths between inflow and outflow points (Continued) Water Supply

Water Distribution System Variables Piping arrangement (cont.) Valves Function in system Location in system Access Indicating Nonindicating Gate valves Butterfly valves (Continued) Water Supply

Water Distribution System Variables Piping arrangement (cont.) Hydrants Dry-barrel and wet-barrel Water Supply

Water Distribution System Variables Piping arrangement (cont.) Distribution and location Maintenance Color coding: Less than 500 gpm: Red 500999 gpm : Orange 1,0001,499 gpm: Green 1,500 gpm or more: Light Blue Water Supply

Private Water Supply Systems Purposes To provide water strictly for fire protection purposes To provide water for sanitary and fire protection purposes To provide water for fire protection and manufacturing processes Potential problems for fire fighting purposes (Continued) Water Supply

Private Water Supply Systems (cont.) Water supply requirements for standpipe and hose systems NFPA 14, Standard for the Installation of Standpipe and Hose Systems Class I service Class II service Class III service (Continued) Water Supply

Private Water Supply Systems (cont.) Water supply requirements for automatic sprinkler systems NFPA 13, Standard for the Installation of Sprinkler Systems Pipe schedule systems Hydraulically designed water-based extinguishing systems (Continued) Water Supply

Private Water Supply Systems Water supply requirements for automatic sprinkler systems (cont.) Duration of water supplies See Table 3.5 in manual NFPA 231, Standard for General Storage Water Supply