Document GK7X3y2zQ6Zd3xo2bE6o1bkVn

American Society of Heating and Ventilating Engineers Guide, 1935 Table 9. Proposed Dimensions of Steel Welding Neck Flanges for Maximum Steam Service Pressure of 150 Lb per Sq In. (Gage) at a Temperature of 500 F, and 100 Lb at 750 F NoPmipineal Silt i m 1H 2 m 3 m 4 5 6 8 10 12 14 O. D. 16 0. D. 18 O. D. 20 0. D. 24 O. D. Diameter Flaonpge Thickness op Flo. Min. Diameter op Hub Hub Diam. Beginning op Chamber Length Thru Hub 0 0X Hy m4M 5 6 m7m 9 10 11 13M 16 19 21 23H 25 27H 32 Ha H He % 'He H 'He 'He 'He 1. 1H lHe m1M lHe lHe mI'He I'He 2He 2He 3He 3He 4H 4'He 5He 6He ?He 9'He 12 14H 15H 18 19H 22 26X 1.32 1.66 1.90 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 2 He 2 He 22%H 2H 2'He 3 3H 3H 4 4 4H 5 5 5H S'He 6 Diam. for Standard Pipe A 1.05 1.38 1.61 .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 Diam. op Bolt Circle 3H 3H m 4H 5H 6 7 mmm HH 14H 17 18H 21H 22H 25 29H No. Size OP Bolts op Bolts 4 4- lA A 4H 4 4 4 v% 8 ys 8 8 M 8H 8H 12 12 14 12 i 16 l 16 20 1VH/t 20 iH All dimensions given~in inches. A raised face of % in. is included in thicbuu offlange minimum. --- It is recommended that the taper o! the hub should not exceed 6 degrees for a reasonable distance bach of the chamfer in order to reduoe the heat transfer while welding. are shown in Fig. 1. They are made in pipe sizes % to 24 in., standard and extra heavy, in steel, wrought iron, brass, copper, and special alloys. Socket welding fittings shown in Fig. 1 are commercially available. A proposed American Standard containing dimensions of steel welding-neck flanges for pressures up to 1500 lb per square inch has been developed in A.S.A. Sectional Committee B16. Tables 9 and 10 give these dimensions for welding-neck flanges suitable for 150 and 300 lb pier square inch gage pressure. VALVES Valves are made with both threaded, and flanged ends for screwed and bolted connections just as are pipe fittings. The material used for valves of small size is generally brass or bronze for low pressures and forged steel for high pressures, while in the larger 592 Chapter 34--Pipe, Fittings, Welding 'zes either cast-iron, cast-steel or some of the steel alloys are employed, practically all iron or steel valves intended for steam or water work are bronze-mounted or trimmed. Brass, bronze, and iron valves are generally designed for standard or extra heavy service, the former being used up to 125 lb and the latter up to 250 lb saturated steam working pressure, although most manufacturers also make valves for medium pressure up to 175 lb steam working pres sure. The more common types are gate valves or straightway valves, elobe valves, angle valves, check valves and automatic valves, such as reducing and back-pressure valves. Gate valves are the most frequently used of all valves since in their open position the resistance to flow is a minimum. These valves may be secured with either a rising or a non-rising stem, although in the smaller sizes the rising stem is more commonly used. The rising stem valve is desirable because the positions of the handle and stem indicate whether the valve is open or closed, although space limitations may prevent its use. The globe valve is less expensive to manufacture than the gate valve, but its peculiar construction offers a high resistance to flow and may prevent complete drainage of the pipe line. These objections are of particular importance in heating work. Check valves are automatic in operation and permit flow in only one direction, depending for operation on the difference in pressure between the two sides of the valve. The two principal kinds of check valves are the swing check in which a flapper is hinged to swing back and forth, and the lift check in which a dead weight disc moves vertically from its seat. Valves commonly used for controlling steam or water supply to radi ators constitute a special class since they are manufactured to meet heating system requirements. These valves are generally of the angle type and are usually made of brass. Graduations on the heads or lever 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 11. Automatic control of steam supply to individual radiators can be 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 jfj-in. hole through the web forming the seat to insure sufficient circulation to prevent freezing when the valve is closed. Valves made particularly 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 in 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 593