Document 3ep43r6ZR7XYKmo6D95ZadyXa

American Society of Heating and Ventilating Engineers Guide, 1937 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 piping 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 and form sludge. These impurities have a tendency to cause foaming, preventing the 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 1% 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 pres sure 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 fife 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 because 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 in a boiler, as given by the boiler manufacturer, should be carefully followed. It is common practice when starting new installations to discharge heating returns to the sewer during the first wek of operation. This prevents the passage of grease, dirt or other foreign matter into the boiler and consequently may avoid the necessity of cleaning the boiler. During the time the returns are being passed to the sewer, the feed valve should be cracked sufficiently to maintain the proper water level in the boiler. Care oi Idle Heating Boilers Heating boilers are often seriously damaged during summer months due chiefly to corrosion resulting from the combination of sulphur from the fuel with the moisture in the cellar air. At the end of the heating season the following precautions should be taken: - 1. Alf'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 of some one inadvertently building 460 Chapter 25--Boilers a fire in a dry boiler, however, it is safer to keep the boiler filled with water. 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 working order. In this connection, oil all door hinges, damper bearings and regulator parts. BOILER INSULATION Insulation for cast-iron boilers is of two general types: (1) plastic material or blocks wired on, cemented and covered with canvas or duck; and (2) blocks, sheets or plastic material covered with a metal jacket furnished by the boiler manufacturer. Self-contained steel firebox boilers usually are insulated with blocks, cement and canvas, or rock wool blankets; HRT boilers are brick set and do not require insulation beyond that provided in the setting. It is essential that the insulation on a boiler and adjacent piping be of non-combustible material as even slow-burning insulation constitutes a dangerous fire hazard in case of low water in the boiler. REFERENCES A.S.H.V.E. Code of Minimum Requirements for the Heating and Ventilation of Buildings. A.S.H.V.E. Standard and Short Form Heat Balance Codes for Testing Low-Pressure Steam Heating Solid Fuel Boilers (Codes 1 and 2). ` A.S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers (Code No. 3). A.S.H.V.E. Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers. Heating, Ventilating and Air Conditioning, by Harding and Willard, Revised Edition, 1932. A.S.M.E. Boiler Construction Code for Low Pressure Heating Boilers. Heating, Piping and Air Conditioning Contractors National Association Standards (boiler selection tables). House Heating, published by American Gas Association. Handbook of Oil Burning, published by American Oil Burner Association. Heating and Air Conditioning, by Allen and Walker (fourth edition). Selecting the Right Size Boiler, by Sabin Crocker (Healing, Piping and Air Con ditioning, February, March, April, 1932). PROBLEMS IN PRACTICE 11 What basic requirements of boiler design are to be accomplished with a combination boiler and oil burner unit? Combination units vary widely but in general, the basic requirements of design depends., upon a combustion chamber of proper design and arranged for the flame shape with adequate heating surface for the complete combustion of the fuel. * 2 Name the construction materials that distinguish two types of low pressure heating boilers'. a. Cast-iron, k Steel. 461