Document MGBk9x99ENmveb0Ma1rz8rMXj

American Society of Heating and Ventilating Engineers Guide, 1937 handles are often supplied to indicate the relative opening of the valve in any position. Standard roughing-in dimensions for angle-type valves are given in Table 12. Automatic control of steam supply to individual radiators can be Table 11. Proposed Dimensions of Steel Welding Neck Flanges for Maximum Steam Service Pressure of 300 Lb per Sq In. (Gage) at a Temperature of 750 F Chapter 34--Pipe, Fittings, Welding for use in hot water heating systems are of less complex design, one type consisting of a simple butterfly valve, and another of a quick opening type jn which a part in the valve mechanism matches up with an opening in the valve body. In one-pipe steam-heating systems, automatic air valves are required at the radiators. Two common types of air valves available are the vacuum type and the straight-pressure type. Vacuum valves permit the expulsion of air from the radiators when the steam pressure rises and, in addition, act as checks to prevent the return of air into the radiator when Table 12. Standard Roughing-in Dimensions Angle Type Valves Nominal Pipe Size *2 234 3 334 4 5 6 S 10 12 14 O. D. 16 U. D. 18 O. D. 20 O. D. 24 O. D. Dtam or Flange Thick ness of Flange Min. 0Q Diam. OF Hub x Hub Diam. Beginning of Chamfer Length Thru Hub . Diam. FOB Standard Pipe HYA Diam. FOR Extra Strong Pipe Diam, of Bolt Circle A m634 9 10 11 1234 15 1734 20M 23 25J4 28 3034 36 34 354s m1 3^6 454 13ie 534 13i 354 ml 54 7 Gde 1034 134 1254 2 1454 234 . 1654 2*4 19 254 21 m234 2334 2754 2.38 2.88 3.50 4.00 4.50 5.56 6.63 8.63 10.75 12.75 14.00 16.00 18.00 20.00 24,00 254 3 334 394 354 354 354 454 434 534 554 554 634 654 654 2.07 2.47 3.07 3.55 4.03 5.05 6.07 7.98 10.02 12.00 13.25 15.25 17.25 19.25 23.25 1.94 2.32 2.90 3.36 3.83 4.81 5.76 7.63 9.75 11.75 -- 5 534 654 734 734 934 1054 13 1534 >1754 2034 2234 2454 27 32 No. OF Size OF Bolts Bolts 8 54 8 54 8 54 8 54 8 54 8 54 12 54 12 34 16 1 16 '134 20 134 20 134 24 , 134 24 134 24 134 For sizes below 2 in. use dimensions of 600 lb flanges. All dimensions given in inches. A raised face of H# in. is included in thickness offlange minimum. It is recommended that the taper of the hub should not exceed 6 deg for a reasonable distance back of the chamfer in order to reduce the heat transfer while welding. effected by use of direct-acting radiator valves having a thermostatic ' element at the valve, or near to it. The direct-acting valve is usually an angle-type valve containing a thermostatic element which permits the flow of steam in accordance with room temperature requirements. These valves usually are capable of adjustment to permit variation in room temperature to suit individual taste. Ordinary steam valves may be used for hot water service by drilling a J'js-in. hole through the web forming the seat to insure sufficient circulation to prevent freezing when the valve is closed. Valves made particularly 640 Thread Standard, AJ5.A. No. B2--1919. The standardization of the Roughing-in Dimensions of Angle Steam and Hot Water, and Modulating Radiator Valves was made possible by the cooperation of the Manufacturers Standardization Society of the Valves and Fittings Industry. a vacuum is formed by the condensation of steam after the supply pressure has dropped. Ordinary air valves permit the expulsion of air from the radiator when steam is supplied under pressure, but when the pressure dies down and a vacuum tends to be formed the air is drawn back into the radiator. A system operating continuously or intermittently and supplied with" vacuum valves will generally heat more quickly than one provided with non-vacuum air valves; thus, it .will effect considerable economy of fuel because the idle period during which no heat is delivered is shortened. In those cases, where a system is equipped with vacuum air valves and which has been cold for several days, the system will probably have an 641