INSULATION OF PARTITION WALLS IN CELLARS

If both adjoining cellars have nearly the same temperature, anŷ kind of material will do, and no insulation is necessary, but when on one side of them is a warm room or stairway, the same care must be taken to insulate them as the outer walls. Under no circumstances should hollow bricks only be used, and if the difference in temperature is not very great, they can be filled with pitch, and will then be fairly well protected.

Under no circumstances should sawdust be put on a floor above a cooled room, as is frequently done. The moisture of the atmosphere will penetrate it, and when the moisture strikes that part of the sawdust which has the temperature which is the dew point of the air, it will condense, make the sawdust moist, and convert it into a good conductor, besides spoiling the floor. This can be easily proven by examining such layer of sawdust, which has been used for a summer, at the end of the season, when the weather is still hot. The sawdust will in such case be found very wet.

INSULATION OF COLD PIPES.

The same considerations prevail here as in the protection of cold surfaces. But care should be taken never to cover the pipes when they are cold or sweating, as this will spoil the insulation right at the start.

Any kind of insulating material can be used, for instance, felt, magnesia, or paper cells, anything, in fact, which is a nonconductor, as air spaces cannot well be built around the pipes, and it is therefore just as cheap to use a filling material. The chief consideration here is again that the insulation is air and water-tight on the outside. Covering the material with good canvas well sewed on and coated with three coats of good elastic paint, will make the insulation air and water-tight. Especial care should be taken to get tight finish for the ends. It is likely that a puncture of the canvas will occur, which would spoil the whole insulation under the same cover. It is therefore better not to take the insulating material very thick, but to make two, or still better, three distinct air and water-proof insulations, one over the other. If the first one is punctured and spoiled, the rest remain intact, and no harm is done, while the punctured layer still affords a little protection, although less than one not "nctured.

The pipes should first be well painted. A tar paint is best for this purpose, if the smell while putting it on is not objectionable. Then a layer of felt or any other good non-conductor should be wrapped tight around the pipes and tied with wire. Copper wire is considered best for this purpose. Over this, a layer of good insulating paper, as tar paper, which is pliable, is laid, and then the whole coated with one or two coats of good elastic paint. Then again felt or other insulating material is wrapped tight with copper wire, still another layer of tar paper, and the latter coated with paint as before. It is best to tie the tar paper also, as it will give a more compact insulation, not so easily destroyed by knocking against it. If it is not thought necessary to add another layer of felt and tar paper, the canvas should be put on tight and well painted, as explained.

Another form of insulation, and the best where it can be used again, is made with pitch. The pipes are layed in boxes upon rests giving at least a three-inch space from outside of pipe to inside of box. The box is closed tight with a lid, and pitch poured in. This insulation can easily be removed by opening the box and knocking or melting out the pitch, and when the pipe is repaired, closing the box and putting in hot pitch, which will join the new and the old insulation. This process can be assisted by slightly warming the box on the outside where the insulation is to be joined.

If pipes are laid under ground, the box should either be made of cast-iron or impregnated wood, and the wood should be at least two inches thick. Clay pipes can also be used to lay the pipes in.

If the pipes are above ground, galvanized pipes made of thin iron can be used and the cold pipes held in place therein by wooden, or any better, insulating material which can be found, as a spacer. Pitch is then poured in through openings left for this purpose. The single lengths of pipes are joined by soldering, and special form pieces made for fittings. This insulation can also be easily removed and repaired, and is the very best, preserving at the same time the cold pipes and saving their paint. IRREGULAR BODIES, AS PUMP CYLINDERS WITH CHAMBERS.

The best method is to use material which can be applied in a plastic state, in sufficient thickness, and then to protect

the outside of the parts in question as thoroughly as possible by painting or by putting on air-tight plaster or placing canvas over it and painting well, always bearing in mind that the outside must be air and water-tight.

WATER COOLING TOWERS OR GRADIR WORKS.

Where water is required for ammonia or steam condensers, and the well supply is insufficient, or where it is too expensive to use city water, the only help is to erect a water cooling tower. The only natural cooling agents are water and air. To use air directly for condensing purposes would need too cumbersome an apparatus, and be too expensive in first cost. But we can cool the water first with air, and do it cheaply and efficiently, the water in this case not being wasted, but used as a medium to carry the heat of condensation to the air.

The principle of the cooling tower is to allow air and water to come into close contact and to exchange heat thereby, and, further, to evaporate a small part of the water, the air absorbing the moisture, and the heat necessary to evaporate this part of the water being abstracted from the remaining water, cooling it in this manner lower than the air could do by contact alone.

That part of the water which is evaporated must be replaced. But since this is only from 5 to 10 per cent, according to the temperature of the water entering the cooling tower and the capacity of the air for taking up moisture, the amount required is small, and if the well does not furnish it, can be bought from the city, and yet considerable money saved by the erection of a gradir works.

CONSTRUCTION OF COOLING TOWERS.

The construction of the cooling towers varies. That cooling tower is the best which will give the best chance for evaporating water. This can only be done if the water is retarded as much as possible in its downward course and not mixed with the air, but the air allowed to pass over the surface of the water only. For steam-condensing purposes this evaporation is not so important, as the temperatures of the cooling water required for this purpose need not be so low as for condensing ammonia, where a difference of a few degrees in the cooling water cuts a big hole in the coal pile.

The general construction of cooling towers is a cylindrical or square enclosure, made of wood or iron, containing means to distribute the water and to retard it in its downward course, and a large fan for blowing air in the opposite direction over the water. A good cooling tower is made of a square box of white pine, well painted on the inside, and filled with one-inch boards of cypress, arranged far enough apart to allow free passage of the air. On top are placed iron gutters which receive the water and distribute it through pipes to the gutters provided for each portion. In order to retard the water as much as possible, the second row of partitions is arranged perpendicularly to the upper one, and so on, each row being again provided with gutters so as to distribute the water well.

In this manner the water will always run in a thin film over the partitions and have the best chance to evaporate. This crossing of the partitions has another advantage, viz., that it forms square openings for the air to pass, and spreads the air, supplying each particle of water with air.

The fan is placed in an extension built to the structure at the bottom.

Another kind of cooling tower is made, where either galvanized iron tubes of short length and about four inches diameter are placed in the cylinder forming the tower, so as to break joints, or pipes made of clay of about the same dimensions as the iron pipes are used. The latter will last longer than the iron pipes, but are considerably more expensive and heavier, which is a consideration when the cooling tower is placed on the roof.

Some builders put wire screens in the structure, which will soon rust out and make the water unfit for boiler feeding.

All these towers use fans. But there are some made which are open all around and utilize the natural draft of the air, instead of a fan.

The towers which employ tubes or wire screens, with sprinkling devices instead of gutters, cannot be expected to furnish such low temperatures as towers with vertical partitions and gutters, since in the first case the water and air is thoroughly mixed and little chance for evaporation given, while in the second case all facilities for evaporation are afforded.

COST OF COOLING TOWERS.

A 100-ton refrigerating machine would require a cooling tower of 200 X 1440 = 288,000 gallons per day, which requires a fan oi nine feet diameter, making 190 revolutions, and requiring 12 horse-power to drive it.

The cost, complete, will be in the neighborhood of $2,000. It will require, if used for cooling water for ammonia condensers, about 5 per cent of 288,000 gallons a day, to make up for evaporation 14,400 gallons. The 12 horse-power, if a small engine for driving the fan is used, costs about 72 pounds of coal per hour, and if the tower is erected on the roof, so that the water runs by gravity to the ammonia condensers, the pumping will not cost more than to pump the water from the well, as the extra height the water is to be pumped is more than made up by the depth from which the water is generally pumped if taken from a well.

These figures will suffice to calculate whether it pays to buy a cooling tower or not.

The life of the cooling tower must also be considered when figuring on the investment. Iron towers with galvanized iron tubes cannot last long. The tower cannot be repainted on the inside without great cost and without ruining the tubes. It will, therefore, rust through quickly, as will also the tubes. On the other hand, wood, especially cypress, will last for a long time. The tower can be erected on the ground instead of on the roof. But in that case the ammonia condenser floor must be located high enough to allow the water to flow to the gradir work by gravity. A height of about 35 feet is required for this purpose, otherwise the water must be pumped twice.

PUMPS.

CENTRIFUGAL PUMPS.

These pumps are used when large quantities of water are to be lifted to moderate height, that is to say, not to exceed 28 feet. They are cheap pumps, but must be run very fast.

A pump of this kind, delivering 200 gallons to a height of 50 feet, makes 1,200 revolutions per minute, and a pump of the same capacity, lifting the water 30 feet, makes 1,000 revolutions. They require for this 4.25 horse-power and 2.55 horse-power, respectively. A pump lifting 1,000 gallons 50 feet makes 920 revolutions and requires 25 horse-power.