Document B52Z0mb0yYOwrV4zEQpL251pk

390 CHAPTER 15 . 1952 Guide i' return piping preventing return of condensation; (c) valve closed in return line; (d) connection of bottom of water column into a very active section or thin waterway; and (e) improper connections between boilers in battery permitting boiler with excess pressure to push returning condensation into boiler with lower pressure. 4. Water is carried over into steam main. This may be caused by: (a) grease and dirt in boiler; (6) insufficient steam dome or too small steam liberating area: (c) outlet connections of too small area; (d) excessive rate of output; and (e) water level carried higher than specified. 5: Boiler is slow in response to operation of dampers. This may be due to: (a) poor draft resulting from air leaks into chimney or breeching; (6) inferior fuel; (c) inferior attention; (d) accumulation of clinker on grate; and (e) boiler too small for the load. 6. Boiler requires too frequent cleaning of flues. This may be due to: (a) poor draft; (6) smoky combustion- (e) too low a rate of combustion; and (d) too much excess air in firebox causing chilling of gases. 7. Boiler smokes through fire door. This may be due to: (a) defective draft in chimney or incorrect setting of dampers; (6) air leaks into boiler or breeching; (c) gas outlet from firebox plugged with fuel; (d) dirty or clogged flues; and (e) improper reduction in breeching size. 8. Low carbon dioxide. This may be due on oil burning boilers to: (a) improper adjustment of the burner; (6) leakage through the boiler setting; (e) improper fire caused by a fouled nozzle; or (d) to an insufficient quantity of oil being burned. Cleaning Boilers . All boilers are provided with flue clean-out openings through which the heating surface can be reached by means of brushes or scrapers. Flues of solid fuel boilers should be cleaned often to keep the surfaces free of soot or ash. Gas boiler flues and burners should be cleaned at least once a year. Oil burning boiler flues should be examined periodically to deter mine when cleaning is necessary. The grease used to lubricate the cutting tools during erection of new pip ing systems serves as a carrier for sand and dirt, with the result that a scum of fine particles and grease accumulates on the surface of the water in all new boilers, while heavier particles may settle to the bottom of the boiler ahd form sludge. These impurities tend to cause foaming, preventing tiie generation of steam and causing an unsteady water line. This unavoidable accumulation of oil and grease should be removed by blowing off the boiler as follows: If not already provided, install a surface blow connection of at least 1J in. nominal pipe size with outlet extended to within 18 in. of the floor or to sewer, inserting a valve in line close to boiler. Bring the water line to center of outlet, raise steam pressure, and while fire is burning briskly open valve in blow-off line. When pressure recedes, close valve and repeat process adding water at intervals to maintain proper level. As a final operation bring the pressure in the boiler to about 10 lb, close blow-off, draw the fire or stop burner, and open drain valve. After boiler has cooled partly, fill and flush out several times before filling it to proper water level for normal service. The use of soda, or any alkali, vinegar or any acid is not recommended for cleaning heating boilers be cause of the difficulty of complete removal and the possibility of subsequent injury, after the cleaning process has been completed. Insoluble compounds have been developed which are effective, but special instructions on the proper cleaning compound and directions for its use, as given by the boiler manufacturer, should be carefully followed. Care of Idle Heating Boilers Heating boilers are often seriously damaged during summer months due chiefly to corrosion resulting from the combination of sulfur in the f t r- F tj fe' I Heating Boilers, Furnaces, Space Heaters' 391: soot with the moisture in the cellar air. At the end of the heating season the following precautions should be taken: v 1. AU heating surfaces should be cleaned thoroughly of soot, ash and residue, and the heating surfaces of steel boilers should be given a coating of lubricating oil on the fire side. 2. All machined surfaces should be coated with oil or grease. 3. Connections to the chimney should be cleaned, and in case of small boilers, the pipe should be placed in a dry place after cleaning. 4. If there is much moisture in the boiler room, it is desirable to drain.the boiler to prevent atmospheric condensation on the heating surfaces of the boiler when they are below the dew-point temperature. Due to the hazard that some one may in advertently build a fire in a dry boiler, however, it is safer to keep the boiler filled with water, particularly in residential installations. Air can be excluded from a steam boiler by raising the water level into the steam outlets. A hot water system usually is left filled to the expansion tank. 5. The grates and ashpit should be cleaned. 6'. Clean and repack the gage glass if necessary. 7. Remove any rust or other deposit from exposed surfaces by scraping with a wire brush or sandpaper. After boiler is thoroughly cleaned, apply a coat of preservative paint where required to external parts normally painted. 8. Inspect all accessories of the boiler carefully to see that they are in good work ing order. In this connection, oil all door hinges, damper bearings, and regulator parts.' WARM AIR FURNACES Warm air heating furnaces of a number of types and a wide range, of sizes are listed and illustrated in the Catalog Data Section. Warm air furnaces may be classified in several different ways: 1. According to method of heat distribution--these are either gravity or me chanical (blower) furnaces. 2. According to fuels for which the furnaces are designed--these are coal handfired or stoker-fired, oil, gas, or wood. 3. According to materials of construction--they are cast-iron, low carbon steel, and occasionally high temperature steel alloys. 4. According to design or construction, such as drum and radiator, tubular, horizontal, etc. Gravity Warm Air Furnaces A gravity furnace is one in which the motive head producing air flow depends upon the difference in density between the heated air leaving the top of the casing and cooled air entering the bottom of the casing. Since . this gravity head is relatively low, the furnace must have low internal re sistance to the flow of air, and relatively large areas must be available for free circulation within the furnace casing. It hrcommon practice to pro vide approximately 50 percent free air area through gravity type furnaces. Furnaces for gravity type systems are available in designs suitable for central heating, pipeless furnace, or unit floor furnace installations. Booster fans are sometimes used in conjunction with gravity design systems, to in crease air circulation. Where a fan is to be used with a furnace casing sized for gravity air flow, some form of baffling must be emplpyed to re strict the free area within the casing and to force impingement of the air against the heating surfaces. Where square casings are used, the corners must be baffled.