inside the boiler at the highest point, and is supported at the ends by iron straps bb, bolted to the boiler shell. It is

connected to the steam pipe in such a manner that the steam can only enter the steam pipe by passing through the slots, the ends of the pipe being closed. The combined area of the slots, or perforations, in the dry pipe is usually made equal to that of the steam pipe connected to it. A small hole should be drilled into the bottom of the pipe to allow any water entering the dry pipe to drain out of it.

SEPARATORS.

795. A separator is an apparatus designed to remove the entrained water, or the oil, dirt, or other impurities from a current of steam flowing through a pipe. When the separator is intended to free the steam from water simply, it is placed on the main pipe leading from the boiler to the engine, and as close as possible to the latter. When it is desired to remove the grease and dirt from the exhaust steam before condensing it and feeding it back to the boiler, the separator is placed in the exhaust pipe leading from the engine to the condenser.

796. The Stratton separator is shown in Fig. 222. It consists of a chamber with a steam inlet and outlet, and containing a vertical pipe a. Steam enters by the inlet c, and is deflected by a curved partition, which gives it a spiral motion about the pipe a. The particles of water or oil are thrown off by centrifugal action, and run down the walls to the bottom of the chamber. The steam passes up through the pipe a and out of the outlet d in a practically dry condition. The separator is provided with a drip pipe / for

the removal of the water, and a gauge glass g. The wings b,

STEAM AND STEAM BOILERS.

(CONTINUED.)

BOILER FITTINGS—Continued.

FEED APPARATUS.

798. The Surface Condenser. The steam generated in the boiler, after performing its work in the engine, is usually discharged into a vessel known as the condenser. The surface condenser will be treated of here only in so far as it relates to the feed apparatus, but will be further dealt with in the section on Steam Engines when considering the general question of condensers. (See Arts. 1085 to 1097.)

799. The condenser shown in Fig. 223 consists of a closed vessel B provided with numerous smail brass tubes C, C fitted air-tight into the tube-sheets C', C'. The steam from the engine enters the condenser through the exhaust pipe A, strikes against the baffle plate H, and is distributed through the condenser, as shown by the arrows.

The steam comes in contact with the outside of the tubes, which are kept cool by water passing constantly through them. The cooling water is taken from the sea by the circulating pump, not shown in the figure, and forced through the main injection pipe D into the chamber E; thence through the tubes C, C into the chamber F, whence it returns to the chamber E', passes into the outboard delivery pipe G, and is discharged overboard.

The exhaust steam coming into contact with the cold surface of the tubes is condensed, that is, turned into water again. This water flows by gravity down the sloping bottom. J of the condenser and into the lower end of the air pump K. For notice of the copyright, see page immediately following the title page.

This is usually a bucket pump and worked by means of a lever from the engine. Its construction and operation are described later. (See Art. 1094.) Its purpose is to keep up the vacuum due to the condensation of the steam, which vacuum would otherwise soon be destroyed by the air and vapor arising from the hot water of condensation. It also removes the water from the condenser as fast as it is formed, delivering it into the hotwell L. Connected to the bottom. of the hotwell are the suction pipes n, n' of the feed apparatus, which consists either of pumps, or injectors, or both. The feed apparatus is supposed to take the water from the hotwell as fast as it is pumped in; should it fail to do so, the hotwell will speedily fill. An escape for the water is formed by attaching an overflow pipe M, provided with a cock, to the side of the hotwell, the pipe leading the water to the bilges. Generally, one or more plunger feed-pumps, which are shown at N, are bolted to one side of the air pump and worked from the same connection from which the air pump is worked.

The feed-pumps are connected to the hotwell by their suction pipes and n', the feed-pipes being shown at n, and n The suction pipes are provided with stop-valves or cocks, in order that each pump may be shut off, if desired. Z is the suction pipe for the auxiliary pump. There are two bilge pumps, one of which is shown at 0, the pipe o leading from the bilge, and the bilge water being thrown overboard through the pipes T, T'.

That part of the condenser which is filled with the condensing water is called the water end; that part which is filled with vapor, or the water of condensation, is called the

steam end.

800. The construction of the feed-pump is shown in Fig. 224. A is the plunger, made of Muntz metal. It is cored out to lighten it, and it passes through a stuffing-box and gland lined with white metal. The pump chamber Bis bolted to the side of the air pump. A valve chamber C, containing the suction valve Dand delivery valve E, is bolted to