Document 6bZdMXJMLra4Jn5k87N3bVwGd

American Society of Heating and Ventilating Engineers Guide, 1930 The dimensions of elbows for 125 lb. cast iron flange fittings are shown in Table 6. Testing Pipe Pressure tests of pipe are commonly made in order to show thepresence of flaws or other defects in the weld or body of the pipe. Wrought pipe, Orders or inquiries should specify diameter of bore "B" required. ^Copyright, 1929, by Bailing and Piping Contractors National Association. as distinguished from seamless tubing, is either butt- or lap-welded; sizes up to and including 134 in, being made by the former, and those 134 in. and larger by the latter process. Lap-welded pipe, 1J4 in. diameter, may safely be tested to 2,500 lb. per square inch cold hydraulic pressure, while 12 in. diameter pipe should not be tested to more than 300 lb. per square inch. The makers vary the test pressure in accordance with the diameter so as to produce approximately the same fiber stress in each size of pipe. 308 CHAPTER 19 PUMPS AND TRAPS Boiler Feed Pumps; Automatic Pumps and Receivers; Centrifugal Pumps; Vacuum Heating Pumps. THE pumps used in connection with heating and ventilating instal lations may be classified as follows: 1. Boiler Feed Pumps. 2. Condensation Return Pumps. 3. Return Line Vacuum Heating Pumps. 4. Forced Circulation Hot Water Heating Pumps. 5. Circulating Pumps for Water, Brine, etc. 6. Refrigeration Pumps and Compressors. BOILER FEED PUMPS Boiler feed pumps may be (1) direct acting steam-driven reciprocating pumps; (2) power driven reciprocating pumps; (3) centrifugal pumps; (4) screw or other similar type pumps. Capacities The capacity of a boiler feed pump should be based on 34.5 lb. of water per hour per maximum boiler horsepower served, with a slippage allow ance of 10 per cent in the water cylinders and a factor of safety allowance of two for intermittently operating pumps and one and one-half for continuously operating pumps, to provide for unusual conditions, such as low water in boilers, drop in steam pressure or excessive loads. Piston Speeds and Efficiencies For reciprocating boiler feed pumps the speed should not exceed 10 times the square root of the number of inches in the length of stroke of the water pistons. Direct-acting reciprocating steam-driven or power-driven boiler feed pumps are generally more efficient for smaller installations, especially with widely fluctuating loads as efficiencies of centrifugal boiler feed type drop off very rapidly for the smaller sizes of pumps and for low-load conditions. For this reason centrifugal pumps are not usually employed for installations of less than 1,000 boiler horsepower. The capacities and pressures at which screw pumps will operate is almost infinite. They may be used with good economy for small capacities. Efficiencies range from 60 to 70 per cent. The volumetric, displacement rate of water pistons should not be less than twice the maximum rate of flow of the condensate to be handled. 309