Document G5Lw3oMvxD97qDDw8895EMD4r

American Society of Heating and Ventilating Engineers Guide, 1934 Chapter 32--Steam System Piping To blast trap Fig. 28. Heating Unit Return Connection without Separate Air Line (Central Fan System) TO FWD LDCTHC - UUOW.V A BY 00USIANT EDO AUOLE B- Fig. 32. Constants for Determining Proper Length of Offset Pipe acceptable nethoo pbefebed metkoo Fig. 33. Acceptable and Preferred Methods of Taking Branch from Main * of Dripping Main Where It RisestoHigher Level fNote.--Suitable for vapor and atmospheric systems. Fig. 30. Looping Main Around Beam Fig. 34. Dirt Pocket Connection oBY OETUQM SUPPLY MAW Q Fig. 31. Looping Dry Return Main Around Opening Note.---Suitable for any dry return line and any return line carrying air. GEDUCNG COUPLING- Fig. 35. Dripping End of , Main into Wet Return Note.--Suitable for vapor systems. 468 WTM UNE Fig. 36. Dripping End of Main into Dry Return. (A Gate Valve is Recommended at the Inlet Side of the Trap) Fig. 37. Dripping Heel of Riser into Dry Return. (A Gate Valve is Recommended at the Inlet Side of the Trap) The pipe sizes would then be based on the length of the run and the pressure drop desired, as in the case of radiators. It generally is considered desirable to place the in direct heating units on a separate system and not on supply or return lines connected to the general heating system. DRIPPING Any steam main in any type of steam heating system may be dropped to a lower level without dripping if the pitch is downward with the steam flow. Any steam main in any heating system can be elevated if dripped. (Fig. 29). Steam mains also may be run over obstructions without a change in level if a small pipe is carried below the obstruction to care for the condensation (Fig. 30). Return mains may be carried past doorways or other obstructions by using the scheme illustrated in Fig. 31; in vacuum systems it is well to have a gate valve in the air line. Offsets in steam and return piping should preferably be made with 90-deg ells but occasionally fittings of other angles are used, and in such cases the length of the diagonal offset will be found as shown in Fig. 32. Branches from steam mains in one-pipe gravity steam systems should use the preferred connection shown in Fig. 33, but where radiator condensa tion does not flow back into the main the acceptable method shown in the same figure may be used. This acceptable method has the advantage of giving a perfect swing joint when connected to the vertical riser or radia tor connection, whereas the preferred connection does not give this swing without distorting the angle of the pipe. Runouts from the steam main are usually made about 5 ft long to provide flexibility for movement in the main. Dirt pockets, desirable on all systems employing thermostatic traps, should be so located as to protect the traps from scale and muck which will interfere with their operation. Dirt pockets are usually made 8 in. to 12 in. deep and serve as receivers for foreign matter which otherwise would be carried into the trap. They are constructed as shown in Fig. 34-. On vapor systems where the end of the steam main is dripped down into the wet return, the air venting at the end of the main is accomplished by an air vent passing through a thermostatic trap into the dry return line as shown in Fig. 35. On vacuum systems the ends of the steam mains are dripped and vented into the return through thermostatic drip traps opening into the return line. The same method. may be used in atmos pheric systems. The cooling leg (Fig. 36) is for cooling the condensation 469