Document 1gweddrYEVQKLREn0J9vnevyE

HEATINC VENTILATINC AIR CONDITIONING CUIDE 1942 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. Chapter 13 RADIATORS AND CONVECTORS Heat Emission of Radiators and Convectors, Types of Radi ators, Output of Radiators, Heating Effect, Heating Up the Radiator and Convector, Enclosed Radiators, Convectors, Selection, Code Tests, Gravity-Indirect Heating Systems THE accepted terms for heating units are: (1) radiators, for direct surface heating units, either exposed, enclosed, or shielded, which emit a large percentage of their heat by radiation; and (2) convectors, for heating units having a large percentage of extended fin surface and which emit heat principally by convection. Convectors are dependent upon enclosures to provide the circulation by gravity of large volumes of air. HEAT EMISSION OF RADIATORS AND CONVECTORS Most' heating units emit heat by radiation and convection. The re sultant heat from these processes depends upon whether or not the heating unit is exposed or enclosed and upon the contour and surface charac teristics of the material in the units. An exposed radiator emits less than half of its heat lay radiation, the amount depending upon the size and number of sections. When the radiator is enclosed or shielded, radiation is further reduced. The balance of the emission is by conduction to the air in contact with the heating surface, and the resulting circulation of the air warms by convection. A convector emits practically all of its heat by conduction to the air surrounding it and this heated air is in turn transmitted by convection to the rooms or spaces to be warmed, the heat emitted by radiation being negligible. TYPES OF RADIATORS Present day radiators may be classified as tubular, wall, or window types, and are generally made of cast-iron. There are two types of tubu lar radiators available, that known as large-tube which has a spacing of 2% in. per section, and that known as small-tube which has a spacing of 1% in. per section. The tubes in the latter type of radiator are materially smaller than those in the large-tube type. Small-tube radiators occupy less space and are particularly suited for installation in recesses. In 1939, after a complete study of the demand for various sizes of radiators, the Institute of Boiler and Radiator Manufacturers, acting for the manufacturers, in cooperation with the Division of Simplified Practice, National, Bureau of Standards, established Simplified Practice Recom- 253