Document R22XV714d8qMBEa5vLEVBLkg7

814 CHAPTER 51 Qs FLOW IN CUBIC FEET PER HOUR 1965 Guide And Data Book l different specific gravity may be obtained by multiplying Fig. 11 capacities by a multiplier obtained from Table 3. - Example 1: A2-in. pipe must carry 3640 cfh of a certain gas with a specific gravity oi 0.50. Find toe pressure drop if the pipe length is 75 ft. Solution: From Table 3 multiply the fiow by 1.10 to correct for the variation in specific gravity from a value of 0.60. Enter Fig. 11 at 4000 cfh and move vertically down tins line until it inter' ' sects the 2-in. line. From this intersection move horn zontally across until it intersects the 75-ft line. From this second intersection move vertically down and read the pressure drop as 4 in. of water per 75 ft of pipe length for the partiimlar gas. Combustion Process ond Adjustments Most domestic gas burners are of the atmospheric injeo- Toble 3 .... Multipliers for Various Specific Gravities (For Utm With Table 2 and Fig. 11) - Spadfk GreWly.. ... MuKpBar. Spadfk Gravity -MUtipBar 0.35 0.40 0:45 : 0.60 . ., - 0.55 0.60 0.66 0.70 - 0.75 0.80 0.85 0.60 ' 1.31 1.23 ' 1.16 1.10 . 1.04 1.00' 0.962 0.926 . 0.895 0.867 0.841 0.817 ' 1.00 1.10 1.20 1.30 . . 1.40 * 1.50 \ 1.60 .*> 1.80 1.90 2.00 2.10 ` ' 0.775 0.740 0.707- ' - 0.680 ' 0.655 , - 0.633 . 0.613 . 0.594 0.577 0.565 0.547 0.535 tion (Bunsen) type in which primary air is introduced and mixed with the gas in the throat of the miring tube. For normal operation of most atmospheric type burners/40 to 60 percent of the theoretical air as primary air will give best operation. Slotted-port and ribbon burners may require from 50 to 80 percent=primary air for proper operation. The amount of excess air required in practice depends upon several factors, notably: uniformity of air distribution and mixing, direction of gas travel from burner, and the height and temperature of combustion chamber.' With power type burners utilizing motor driven blowers to provide both pri mary and secondary air, the excess air can be closely controlled while proper combustion is secured. Secondary air is drawn into gas appliances by natural draft As with other fuels, excess secondary air constitutes a loss, and should be reduced to a proper minimum, which usually cannot be less than 25 to 35 percent, if the appliance is to meet ASA approval requirements. Yellow flame burners depend only upon secondary air for combustion. Hie flame produced by atmospheric injection burners is non-luminous. Air shutter adjustments for manufactured gas should be made by first closing the air shutter until yellow flame tips appear, and then opening the air shutter to a final position at which the yellow tips just disappear. This type of flame obtains ready ignition from port to'port, mid also favors quiet flame extinction. For natural gas, the air adjustment is generally * made to secure as blue a flame as is obtainable without lifting of flames from burner ports. Manufacturers' instructions for burner adjustment should be followed.. Gas-designed equipment does not usually incorporate any means for varying the secondary air supply (and henoe the COO- The amount of effective opening and baffling is de termined by A.GA. tests and cannot be varied. Gas conver sion bumere, however, do incorporate mpana for controlling * ; ' CHAPTER 52 HEATING BOILERS, FURNACES, SPACE HEATERS BOILERS: Construction, Types, Design Considerations, Rating and Testing Standards, Efficiency, Rating, Selection, Space Limitations, Connections and Fittings, Erection, Operation and Maintenance. FURNACES: Types, Components, Ratings, Testing and Rating Standards. SPACE HEATERS: Types Solid Fuel, Oil, Gas; Materials and Construction,- Testing and Rating; Design Considerations,- Installation :j IN presenting the subject of Boilers, Furnaces, and Space Cast-iron Boilers Heaters this chapter is divided into three parts; the first deals with boilers, the second with warm air furnaces, and Cast-iron boilers are generally classified as: the third with space heaters. PART I: HEATING BOILERS 1. Square or rectangular boilers with vertical sections. " 2. Round, square,-or rectangular boilers with horizontal pan cake sections. . Cast iron boilers are usually shipped in sections, ahd> as Steam and hot water boilers for low-pressure hunting are sembled at tiie place of installation. However, some boilers are built of steel or cast iron in a wide variety of types and sizes, shipped factory assembled and as boiler-burner unite' qr many of which are illustrated in the Catalog Data Section. packaged boilers having all components in an assembled unit. The nationally recognized code governing the construction In the majority of boilers the sections are assembled with of low-pressure steel and cast-iron heating boilers is the push nipples and tie rods, but external headers'.and screw ASME Boiler Construction Code for Low Pressure- Heating nipples are also used satisfactorily.1 Many sectional boilers are Boilers. Some states and municipalities have their own codes -provided with large push nipples at top to permit the.circula- which apply locally, but these are usually patterned after the tion of water between adjacent sections at'both the-water - ASME Code. line and bottom of the boiler. This is necessary to permit the The maximum allowable working pressures arc limited by use of an indirect water heater with the boiler for summer- the ASME Code far Low Pressure Heating Baders to 15 psi winter hot water supply. Round and sectional boilers may be for steam and 160 psi for hot water, heating boilers, with a enlarged by the addition of sections and corresponding plate maximum temperature limitation of 250 F. Hot water boilers work. are generally designed for a working pressure of 30 psi, and Sectional type boilere are available with wet-baee or water may be equipped for higher working pressures for either heat backed constiuction; wherein the -ashpit or firebox is com ing purposes or for hot water supply only when designed, pletely surrounded by water-cariying channels,' and thus no tested, and stamped for the higher pressure. separate base is required. This type of construction.permits TYPES OF HEATING BOILERS the boiler to be set directly on a wood or composition, floor 'without danger .of fire. It also allows the incorporation of.a - Heating boilers are classified in a number of different ways, such as:-.. ... 1: According to materials of construction. Most heiatlng boilers are constructed of cast iron or'steel, but honferrous metals are used for some. . permanentrgas-tight seal, permitting forced-draft -firing'of the sectional type cast iron boiler. ' Capacities of cast iron boilere generally range from capaci ties required for the'small residences up' to about 15,000. sq ft of steam radiation, but boilere are made with capacities up to 2. According to the fuels for which the boilers are designed. These are coal, hand-fired or Btoker-fired; oil, or gas. Some boilers approximately 32,000 sq ft of steam radiation.. are designed specifically for. one fuel, but many boilers are designed for more than one fuel. .................. ;3. According to the specific purpose or application for which the boiler is used, such as space heating or domestic hot water supply. 4. According to the design or construction of the boiler/such as sectional, round, fire-tube, water-tube, magazine-feed, Scotch. 5. According to combustion air handling system, such' as Steel Boilers -v Steel boilere may be of tire fire-tube type, in which-the gases of combustion pass through the tubes and the boiler water circulates around them, or of the water-tube type/ in 'which the gases-circulate around the tubes and the water passes through them. Either the fire-tube or water-tube type 'ihay natural draft, induced draft, or forced draft. - be designed with integral water-jacketed furnaces, or' ar __Th* ce&erml nspoBsihQitT (or this chapter if amesed to TC Z.1, Hot Water ana 8t<ma Heating; and TC ZJS, Wan Air Beatinf-Poel Bonus*. ranged for refractory lined brick or refractory lined jacketed furnaces. Those with integral water-jacketed fumaoes are 619