Marshall (s.) Minneapolis, 2 (s.) New Ulm (s.) Mora (s.) Owatonna (h. w.) St. Paul, 3 (s.) Springfield (s.) Staples (s.) Wisconsin Beaver Dam (s.) Berlin (s.) Burlington (s.) Hartford (s.) Kenosha (h. w.) La Crosse (h. w.) Milwaukee, 5 (s.) Mineral Point (s.) Sturgeon Bay (s.) Waukesha (s.) West Bend (s.) Wyoming Casper (s.) Cheyenne (s.) Evanston (s.) Laramie (s.) Berlin (s.) Brandon (s.) Alexandria (s.) Buhl (s.) Canby (s.) Canada Crookston (s.) Chatham (s.) Dundas (s.) Kingston (s.) London (s.) Montreal (s.) Toronto (s.) Winnipeg (s.) facturers as they are nearly always guaranteed for five years' service. All foreign matter should also be removed from the seat of the valve at the same time. The dirt pockets at the return header on the coils on loop seals and under differential valves should be thoroughly cleaned out. Remove all the foreign matter from the strainer at the vacuum pump and from any strainer at other points in the system-on Vento stacks, pipe coil heaters or on branch returns. Pack all valve stems on the radiators and coils and particularly the valves on the returns and at the vacuum pump. Pack all flanges on the main return and install new gaskets or unions on the return mains. The vacuum pump should have a thorough overhauling. The pistons should be examined, new packing installed and the valves reground. Any other points where air might leak in should be carefully examined. Wherever vacuum systems are used in connection with street steam service, the service company should insist upon its customers taking care of any of the foregoing details for which they are responsible. The service company should also be very particular to see that all points in the main return where air might leak in, such as expansion joints, flanges, valves, etc., are carefully overhauled. The Care of a Vacuum Heating System in the Summer Months By H. S. Many operating engineers in plants where vacuum heating systems are used are under the impression that a vacuum system does not need attention such as is required by the ordinary steam system during the off season, acting on the theory that because there is a vacuum on the system, all obstacles will thereby be overcome. However, a vacuum heating system requires a thorough looking over in the summer months, in order to keep it in the proper condition for efficiency and economical operation. The most important point is to look over each return valve on the coils and radiators. They should be thoroughly cleaned by going around to each one, removing the interior and washing it off with hot water and soap or kerosene, to remove all grease and foreign matter which collect during the heating season. If the valves are of the thermostatic or expansion type, or float valves, they should be examined closely to ascertain if any of the containers or floats are cracked. If so, they should be replaced by new ones. These can usually be obtained from the manu Current Heating and Ventilating Literature. Under this heading is published each month an index to the important articles on the subject of heating and ventilation that have appeared in the columns of our contemporaries. Copies of any of the journals containing the article mentioned may be obtained from THE HEATING AND VENTILATING MAGAZINE on receipt of the stated price. COMBINATION SYSTEM Combining Power, Heating and Ventilation. Ira S. Evans. Ills. 4,000 w. PowerMay 22, 1917. Serial, 1st part. Comparison of the usual blower system and a combination system. 20c. POWER PLANTS Telephone and Telegraph Building Steam Power Plant. Warren O. Rogers. Ills. 2,000 w. Power-May 8, 1917. Officebuilding plant having features out of the ordinary. 20c. Air Moistener Co., Chicago, Ill., has appointed J. W. McAfee, consulting engineer, New York, as its sole selling agent for the eastern and southern states. Mr. McAfee will be glad to forward catalogues and quote trade discounts to the heating and ventilating trade. His headquarters are at 645 West 171st St., New York. are Horizontal return tubular boilers usually set in a brick setting with a fire wall, but without baffles. The products of combustion, created by burning coal on the grate, pass under the boiler shell to the rear, then forward through the tubes in the boiler shell to the front smoke box and out of the uptake into the chimney. A standard brick setting is shown in Fig. 1, this being used for all H. R. T. boilers by one of the most prominent engineering concerns and shows a setting which is guaranteed to prove satisfactory. To provide for expansion of the boiler in the setting the front brackets are set on a bearing plate, but the rear brackets are placed upon rollers; a distance of 1 in. is then left between the rear of the shell and the brickwork. When conditions render such a feature desirable it is entirely practical to arrange the setting of H. R. T. boilers with the smoke uptake located in the rear. This is accomplished by arranging another pass for the gases along the top of the boiler toward the rear, this pass being formed by arching the setting across the shell about 9 in. above the top and supporting the boiler by hangers Steam Blowoff FIG 1. STANDARD BRICK SETTING. from cross beams carried transversely over the top of the setting. This, in fact, is the method used and recommended by the Lukens Iron & Steel Co., one of the oldest tubular boiler manufacturers in the country. % in. added, gives a 3% in. shell and a 3% in. + 1/16 in. or 7/16 in. head. The city of Philadelphia requires the thickness of shell shown on page. 50 for various pressures with 55,000 lbs. tensile strength of steel. The bracing of the heads is accomplished by the expanding of the tubes into the lower portion and by rods or diagonal braces above the tubes. The matter of bracing is often left to the manufacturer with the stipulation of the working pressure and a test pressure of 25% in excess of the working pressure. SIZES AND RATINGS. In rating horsepowers for H. R. T. boilers it is conservative to allow 10 sq. ft. of heating surface per horsepower, heating surface being all the surface of the boilers with water or steam on one side and the fire or gases of combustion on the other. In the H. R. T boiler this consists of the area of the tubes, front and rear heads and the lower half of the outside of the shell. The table on page 51 gives the horsepower for various sizes of H. R. T. boilers. H. R. T. boilers are sometimes set with the smoke box overhanging at the front. Such an arrangement is not desirable as it hinders the fireman in his work close to the fire and ash doors. The blow-off pipe is taken from the rear of the boiler and carried out of the setting by passing through the space in which the gases are travelling. This pipe should be protected from the excessive heat and action of the gases by a baffle or covering of substantial sort; a special asbestos sleeve is manufactured for this particular purpose. Where the steam is taken off of the boiler a dry pipe will give the best results, this consisting of two pieces of perforated pipe one size smaller than the steam nozzle and extended two or three feet along the inside of the shell as close to the top as possible. Sometimes a baffle plate is placed below the pipe to prevent water being drawn up into it. PORTABLE STEEL FIRE BOX BOILERS. A fire-box tubular boiler of the portable type is shown in Fig. 2. The feed water enters this type through the flange in the water leg at the rear of the fire box and just above the ash pit. It gradually ascends in the boiler as it becomes heated, finally becoming vaporized and passing out through the steam nozzle. Based on 10 sq. ft. of heating surface Another type of fire box boiler which is brick set is shown in Fig. 3, the smoke outlet being on the rear in this case. Here all the gases pass through the tubes to the rear smoke box but do not return toward the front through tubes, travelling instead on the outside of the shell along the lower half for the length of the baffle located approximately on the center line of the boiler and extending front almost to the rear of the fire box. Passing around the end of the baffle the gases travel toward the rear again along the top of |