Area of Tubes.

across the corcumference at any point and measure from center of line to circumference.

The usual rule to apply for boiler braces is to allow 2" space around the head and tubes that do not need bracing.

To find the area for the braces, find the area of segment of the space above the tubes and subtract the 2".

O

2"

Fig. 100. Showing area of inches.

Fig. 101.

The area of a circle is .7854 of the square of the diameter. Fig. 101.

Doubling the diameter increases the area four times, as shown in Fig. 100.

Real Boiler Economy.

When filling a boiler or emptying it without pressure, there should be a vent. Mr. P. H. Bullock puts a check in a vertical pipe 3/4 inch in diameter, the check opening in. When there is no pressure, the check is always open and prevents a vacuum in the boiler when water is running out, and will let air out when water is running in. It will close itself when steam is raised to about 2 pounds.

When economy, ease of taking care, first cost, etc., are concerned, it is a difficult matter to beat a tubular boiler. When it comes to space occupied, long life, high pressure and large units, it is of necessity supplanted by the water tube. The water tube, correctly designed and honestly built, is also much safer than the tubular.

Where the tubes are put into manifolds, or headers, and suspended from the drums by short tubes, these short tubes should be two sizes heavier than the tubes in boiler. For instance, a 4-inch tube is made from No. 10 metal, and the short tubes should be No. 8. All of them should be full size in the thinnest part, and should be made from wrought iron.

Grates under a boiler should last as long as the boiler, and this can only be done by keeping them cool. When a fire is cleaned by shutting the ash pit doors the grates become red hot. This will be more effectually done if the ash and small coal be left in the ash pit, especially at night. When iron is heated to a red heat the grain becomes coarser under expansion and does not return to its original size when cooled. This process continued causes the iron to swell in places where the heat

About Grate Bars.

has been most intense and distortion occurs, bringing some portion up into the fire and the grates then go pretty fast.

It is the better plan to have the ash pit made with a place to hold water 8" to 10" deep and keep water in it during the time there is fire on the grate.

The ash pit doors should not be closed so long as there is fire on the grates, and the regulation should all be done by damper in the flues.

It is sometimes necessary to take the ash pit doors off when the firemen persist in closing them.

There are numerous forms of grate bars, but the form shown at A, Fig. 102, will give the best distribution of air, while that at B will come next. Either of these types can be made lighter, and a furnace full will cost less than with a straight bar.

Bars set with the rear end raised or lowered will give better results than if placed level.

Shaking grates are of service only for relieving the finer ash, while they are valueless for removing clinker and the coarser ash. The better grate is that made after the plan of A and put in with front and rear sections, so that the front or rear can be dumped separately.

A soft patch for a boiler is a patch made to fit, and either lead putty with iron borings or some form of sheet packing put under to make a joint after the manner of making a flange joint, and the patch is screwed up with counter-sunk bolts. Generally the piece of boiler

Boiler Patches.

is not cut, which leaves two thicknesses of iron, so that that nearest the fire, not being protected by water, is burned.

A hard patch is a patch where the iron is cut out of the boiler, a piece fitted to cover it, holes drilled and riveted on, chipped and caulked and made tight.

The soft patch is liable to get to leaking and is dangerous. The hard patch is safe, although over the fire it would be better to put in a new fire sheet entire to avoid a double thickness and rivets where the fire is intense.

Drilled holes are better than punched, because the fiber of the iron is not disturbed as in punching.

Laying out Gaskets.

To lay out a gasket for the regular shaped manhole or handhole, find the length of the plate and divide it by three. On the line A B and with 3 as radius and with centers at C and D lay off the two circles.

Should the length be 15′′, set the dividers at 5′′ and lay off the two circles. Then with the center at E lay off the arc G, and with the center at the intersection of the circles at F lay off the arc H. With the same centers the outside circle can be laid out. This will make a regular II"X15" gasket.

There will sometimes be found a plate, where, instead of the small arcs G. and H, there will be a straight line drawn from the same points.

Foaming.

Foaming is the raising of the water with the steam. It is caused by grease or dirt that prevents a free separation of the steam. In one case where the engineer

had not kept his boiler clean there was a large amount of deposit. It became necessary to raise the front end three inches and this changed the circulation within the boiler and stirred up the deposit so much as to set up a dangerous foaming until the boiler was cleaned.

Soap, or any substance like an alkaline boiler compound when grease is present, salt water put into fresh water, too little steam room or not sufficient area at top of water, or a strong draft of steam that causes the water to raise, will produce foaming.

It is dangerous by drawing too much water from boiler and also by getting water into the engine which washes off the oil and may break something.

Boiler Braces.

There are two general forms of braces the crowfoot, where both ends are riveted to the boiler, and the