sists of six four-row sections of heater coils, and one four-row section of tempering coils, the latter designed to raise the temperature of the incoming air above the freezing point before reaching the sprays, but which in general will not be used on account of the large amount of air recirculated. The coils are of the Buffalo standard mitre type. In order to properly adjust the delivery temperature of the water, the pipe connections for the coils are arranged and valved so that they may be connected in series multiple as shown in Fig. 6.

There are over 129,000 lin. ft. of pipe in these heaters or, in other words, if placed end to end, the total length would be about twenty-five miles. The total normal capacity of the fans is 33,000,000 cubic feet of air per hour.

W. E. Wood & Co., engineers and constructors, Detroit, Mich., designed and supervised the installation of this system, the apparatus being furnished by the Buffalo Forge Company, Buffalo, N. Y. and by the Carrier Air Conditioning Company, New York.

Insulating 3,000 Ft. of Underground Steam Piping.

The Berwind-White Coal Mining Company is one of the largest operators in the bituminous field, and in many respects its most interesting operations are in and near Windber, Pa. This town has a population of 12,000 and is situated high in the mountains not far from Johnstown, Windber is practically owned by the coal company and allied interests.

Some years ago the Windber Heating Company was formed and a large power house was built at the entrance of the coal mine. This plant furnished power and light for the operation of the mine, and electric light, power and heat for a large portion of the town. At the present time this heating company is under contract to supply heat for 58,000 sq. ft. of radiation.

In all the early installations the pipe was insulated with wood covering. About a year ago one line was opened up, and the pipe covered with J-M sectional conduit, the construction of which may be noted from the accompanying illustrations. This proved so satisfactory that the company has recently opened up over 2,000 ft. of steam line, taking it from the ditch and relaying it with J-M sectional conduit. Today it has in all a total of 3,325 ft. of the J-M conduit installed.

The recent installation, of which some views are shown herewith, is an 8-in. main line, running from the power house up a steep hill and down a stiff grade to the heart of the town where it connects with the branch mains. There is no return line on

this system, live steam being carried into each building at a low point, so that the return will flow back into a trap, from which it is allowed to go to waste.

Several difficult conditions had to be met with, such as the line passing through coal veins and hard pan, a surface through which water strong in sulphur percolated. This chemical-water rapidly ate the steel pipe away where it came in contact with it and it was necessary to remove a considerable quantity of pipe, although it had only been in

three years. In one place, a hole had been eaten in the pipe nearly 2 in. in diameter.

In laying this pipe line it was originally found necessary to cross under the gutter of a roadway which carried mine water strongly charged with sulphur. In laying the new conduit and pipe at this point, the course of the steam was temporarily diverted while the conduit was laid across its path. A concrete dam was constructed in the gutter with the conduit imbedded in it. This prevented the backfilling from washing away, securely held the conduit in line and kept it free of danger from sulphur water.

As originally laid the pipe was allowed to take the curvature of the ditch, resulting in unnecessary strains being placed on the joints, causing their leaking. In laying the new con

duit care was taken to secure the correct grade. The ditch was dug 3 ft. wide and to the necessary depth. In the bottom of the ditch another ditch 9 in. deep and 12 in. wide was made. In this was laid a 6-in. diameter sub-drain, the bottom of which was covered with 6 in. of crushed stone of rather coarse grade. Upon this was laid a layer of hne chip stone, to form a fairly even bed for the bottom half of the conduit.

At every fifth section of tile was a supporting tee, with the bell of the branch down, and the base filled to the flow line of the conduit with rich concrete, as will be noted in the illustration (Fig. 1). In this concrete were set J-M roll frames with exactness as to height. These frames are designed to carry the entire weight of the pipe and permit it to move under expansion and contraction without placing any strain on the tile conduit shown in foreground of Fig. 1.

The steam pipe was then laid and the expansion joints were placed in the line at proper intervals, to take care of the expansion and contraction of the pipe. All expansion joints were placed in manholes. Then the pipe was subjected to a hydraulic water test of 20 to 60 lbs. according to the steam pressure to be carried in the line where the test was made.

The top halves of the conduit were next

J-M asbesto-sponge filling was packed in the conduit all around the steam pipe (as shown in Fig. 2), after each top section had been secured in place. Crushed stone of medium size was then filled in until the bells of the second half were covered with 3 in. of stone. Then the ditch was filled up and tamped.

The manholes were made with 13 in. concrete foundation walls to a height even with the top of the lower half of conduit. The conduit was brought through the manhole walls, so that the edges of the tile were flush with the inside of the walls. In order that the tile should have bell ends in the manholes, unions were used in laying the first sections on the down grade side of all manholes. Over these concrete foundation walls, brick walls were built and brought in at the top to the proper size to receive the manhole plates. Wherever the tile entered the manholes the pipes were covered with sleeves of J-M sectional asbesto-sponge felted pipe covering and the openings around same closed with a shut

ter.

Cleveland's Municipal Heating Plant.

Mayor Baker of Cleveland, O., in his annual report, has some interesting things to say regarding the experiment being tried in that city of supplying steam for heating purposes from a plant owned by the city. The project, it will be remembered, originated through a request on the part of the trustees of the Cleveland Museum of Art, for the permission of the city to erect in Wade Park a heating plant, so as to avoid the necessity of installing a large smoke-stack in the museum itself. In order to avoid placing a power plant in Wade Park at all, the solution was adopted of installing new boilers and equipment in the Fairmount pumping station in the East End, from which it wa arranged to distribute steam for heating not only the museum but also such private houses, places of business and apartment houses as come within the radius of efficiency for live steam distribution.

"The distributing system of this first municipal heating plant," comments the mayor, "has been installed; work is progressing upon the installation of additional boiler capacity and, in the meantime, steam is being supplied to a number of takers from the old boilers in the Fairmount station, where there is an excess of boiler capacity above the present needs of the water department.

"As yet," he continues, "it is impossible to say what the economy of this plant will be, but I call the council's particular attention to the experiment, both because it is conducted under excellent conditions for deter

of sweepers in operation. This reduction is proportionate, and results in a saving in consumption of power when fewer sweepers than the capacity of the machine are in operation.

The company's reciprocating type vacuum cleaning machines are installed in large office buildings, public buildings, hotels, hospitals, mills, factories, and theatres, and are manufactured in capacities to take care of buildings of any size. The apparatus installed in the New York Post Office is a notable example, this being the largest vacuum cleaning machine in the world.

4-Invincible Vacuum Cleaner.

Invincible vacuum cleaners are built on the centrifugal turbine principle with multistage impellers; in other words, they consist of a system of rotating impellers or fans. In addition, they are equipped with discharge vanes or conversion vanes designed to utilize the kinetic energy due to high velocities at impeller discharge. The introduction of conversion vanes is designed to increase the efficiency, thus obtaining low power consumption. They are all built to operate on moderate vacuum, 6 in. of mercury being the maximum rating.

The stationary machines range in capacity from single sweepers, driven by 12H. P. motors to six sweepers, driven by 15H. P. motors, and still larger sizes when requirements demand them. All stationary machines are horizontal, with impellers mounted directly on the motor shaft and are provided with ring oiled bearings with large oil reservoirs and ball thrust bearings to take up whatever end thrust there may be.

All stationary machines above one-sweeper capacity are provided with combined centrifugal and cloth bag separators in which the centrifugal separator first receives the dirt being designed to separate about 95% of it from the air. The remaining 5% rises to the upper part of the separator and is strained out by means of the cloth separator of large area, allowing the clean air to pass out into the discharge pipe. There is sufficient pulsation in the flow of air at light loads to automatically clean the cloth separator. The dirt collects in a large bucket located at the bottom of the separator, which may be detached from the sepa