The drums for all pressures are of two sheets of sufficient thickness to give the required factor of safety. The longitudinal seams are double riveted b.u.t.t strapped, the straps being bent to the proper radius in an hydraulic press. The circulating tubes are expanded into the drums at the seams, the b.u.t.t straps serving as tube seats.
The drumheads, drum fittings and features of riveting are the same in the cross drum as in the longitudinal types. The sections and mud drum are also the same for the two types.
Cross drum boilers are supported at the rear on the mud drum which rests on cast-iron foundation plates. They are suspended at the front from a wrought-iron supporting frame, each section being suspended independently from the cross members by hook suspension bolts. This method of support is such as to allow for expansion and contraction without straining either the boiler or the brickwork and permits of repair or renewal of the latter without in any way disturbing the boiler or its connections.
The following features of design and of attachments supplied are the same for all types.
FRONTS--Ornamental fronts are fitted to the front supporting frame.
These have large doors for access to the front headers and panels above the fire fronts. The fire fronts where furnished have independent frames for fire doors which are bolted on, and ashpit doors fitted with blast catches. The lugs on door frames and on doors are cast solid. The faces of doors and of frames are planed and the lugs milled. The doors and frames are placed in their final relative position, clamped, and the holes for hinge pins drilled while thus held. A perfect alignment of door and frame is thus a.s.sured and the method is representative of the care taken in small details of manufacture.
The front as a whole is so arranged that any stoker may be applied with but slight modification wherever boilers are set with sufficient furnace height.
[Ill.u.s.tration: Cross Drum Boiler Front]
In the vertical header boilers large wrought-iron doors, which give access to the rear headers, are attached to the rear supporting frame.
[Ill.u.s.tration: Wrought-steel Inclined Header Longitudinal Drum Babc.o.c.k & Wilc.o.x Boiler, Equipped with Babc.o.c.k & Wilc.o.x Superheater]
[Ill.u.s.tration: Automatic Drumhead Stop and Check Valve]
FITTINGS--Each boiler is provided with the following fittings as part of the standard equipment:
Blow-off connections and valves attached to the mud drum.
Safety valves placed on nozzles on the steam drums.
A water column connected to the front of the drum.
A steam gauge attached to the boiler front.
Feed water connection and valves. A f.l.a.n.g.ed stop and check valve of heavy pattern is attached directly to each drumhead, closing automatically in case of a rupture in the feed line.
All valves and fittings are substantially built and are of designs which by their successful service for many years have become standard with The Babc.o.c.k & Wilc.o.x Co.
The fixtures that are supplied with the boilers consist of:
Dead plates and supports, the plates arranged for a fire brick lining.
A full set of grate bars and bearers, the latter fitted with expansion sockets for side walls.
Flame bridge plates with necessary fastenings, and special fire brick for lining same.
Bridge wall girder for hanging bridge wall with expansion sockets for side walls.
A full set of access and cleaning doors through which all portions of the pressure parts may be reached.
A swing damper and frame with damper operating rig.
There are also supplied with each boiler a wrench for handhole nuts, a water-driven turbine tube cleaner, a set of fire tools and a metal steam hose and cleaning pipe equipped with a special nozzle for blowing dust and soot from the tubes.
Aside from the details of design and construction as covered in the foregoing description, a study of the ill.u.s.trations will make clear the features of the boiler as a whole which have led to its success.
The method of supporting the boiler has been described. This allows it to be hung at any height that may be necessary to properly handle the fuel to be burned or to accommodate the stoker to be installed. The height of the nest of tubes which forms the roof of the furnace is thus the controlling feature in determining the furnace height, or the distance from the front headers to the floor line. The sides and front of the furnace are formed by the side and front boiler walls. The rear wall of the furnace consists of a bridge wall built from the bottom of the ashpit to the lower row of tubes. The location of this wall may be adjusted within limits to give the depth of furnace demanded by the fuel used. Ordinarily the bridge wall is the determining feature in the locating of the front baffle. Where a great depth of furnace is necessary, in which case, if the front baffle were placed at the bridge wall the front pa.s.s of the boiler would be relatively too long, a patented construction is used which maintains the baffle in what may be considered its normal position, and a connection made between the baffle and the bridge wall by means of a tile roof. Such furnace construction is known as a "Webster" furnace.
[Ill.u.s.tration: Longitudinal Drum Boiler--Front View]
A consideration of this furnace will clearly indicate its adaptability, by reason of its flexibility, for any fuel and any design of stoker. The boiler lends itself readily to installation with an extension or Dutch oven furnace if this be demanded by the fuel to be used, and in general it may be stated that a satisfactory furnace arrangement may be made in connection with a Babc.o.c.k & Wilc.o.x boiler for burning any fuel, solid, liquid or gaseous.
The gases of combustion evolved in the furnace above described are led over the heating surfaces by two baffles. These are formed of cast-iron baffle plates lined with special fire brick and held in position by tube clamps. The front baffle leads the gases through the forward portion of the tubes to a chamber beneath the drum or drums. It is in this chamber that a superheater is installed where such an apparatus is desired. The gases make a turn over the front baffle, are led downward through the central portion of the tubes, called the second pa.s.s, by means of a hanging bridge wall of brick and the second baffle, around which they make a second turn upward, pa.s.s through the rear portion of the tubes and are led to the stack or flue through a damper box in the rear wall, or around the drums to a damper box placed overhead.
The s.p.a.ce beneath the tubes between the bridge wall and the rear boiler wall forms a pocket into which much of the soot from the gases in their downward pa.s.sage through the second pa.s.s will be deposited and from which it may be readily cleaned through doors furnished for the purpose.
The gas pa.s.sages are ample and are so proportioned that the resistance offered to the gases is only such as will a.s.sure the proper abstraction of heat from the gases without causing undue friction, requiring excessive draft.
[Ill.u.s.tration: Partial Vertical Section Showing Method of Introducing Feed Water]
The method in which the feed water is introduced through the front drumhead of the boiler is clearly seen by reference to the ill.u.s.tration.
From this point of introduction the water pa.s.ses to the rear of the drum, downward through the rear circulating tubes to the sections, upward through the tubes of the sections to the front headers and through these headers and front circulating tubes again to the drum where such water as has not been formed into steam retraces its course.
The steam formed in the pa.s.sage through the tubes is liberated as the water reaches the front of the drum. The steam so formed is stored in the steam s.p.a.ce above the water line, from which it is drawn through a so-called "dry pipe." The dry pipe in the Babc.o.c.k & Wilc.o.x boiler is misnamed, as in reality it fulfills none of the functions ordinarily attributed to such a device. This function is usually to restrict the flow of steam from a boiler with a view to avoid priming. In the Babc.o.c.k & Wilc.o.x boiler its function is simply that of a collecting pipe, and as the aggregate area of the holes in it is greatly in excess of the area of the steam outlet from the drum, it is plain that there can be no restriction through this collecting pipe. It extends nearly the length of the drum, and draws steam evenly from the whole length of the steam s.p.a.ce.
[Ill.u.s.tration: Cast-iron Vertical Header Longitudinal Drum Babc.o.c.k & Wilc.o.x Boiler]
[Ill.u.s.tration: Closed Open
Patented Side Dusting Doors]
The large tube doors through which access is had to the front headers and the doors giving such access to the rear headers in boilers of the vertical header type have already been described and are shown clearly by the ill.u.s.trations on pages 56 and 74. In boilers of the inclined header type, access to the rear headers is secured through the chamber formed by the headers and the rear boiler wall. Large doors in the sides of the setting give full access to all parts for inspection and for removal of acc.u.mulations of soot. Small dusting doors are supplied for the side walls through which all of the heating surfaces may be cleaned by means of a steam dusting lance. These side dusting doors are a patented feature and the shutters are self closing. In wide boilers additional cleaning doors are supplied at the top of the setting to insure ease in reaching all portions of the heating surface.
The drums are accessible for inspection through the manhole openings.
The removal of the handhole plates makes possible the inspection of each tube for its full length and gives the a.s.surance that no defect can exist that cannot be actually seen. This is particularly advantageous when inspecting for the presence of scale.
The materials entering into the construction of the Babc.o.c.k & Wilc.o.x boiler are the best obtainable for the special purpose for which they are used and are subjected to rigid inspection and tests.
The boilers are manufactured by means of the most modern shop equipment and appliances in the hands of an old and well-tried organization of skilled mechanics under the supervision of experienced engineers.
[Ill.u.s.tration: Cast-iron Vertical Header Cross Drum Babc.o.c.k & Wilc.o.x Boiler]
ADVANTAGES OF THE BABc.o.c.k & WILc.o.x BOILER
The advantages of the Babc.o.c.k & Wilc.o.x boiler may perhaps be most clearly set forth by a consideration, 1st, of water-tube boilers as a cla.s.s as compared with sh.e.l.l and fire-tube boilers; and 2nd, of the Babc.o.c.k & Wilc.o.x boiler specifically as compared with other designs of water-tube boilers.
WATER-TUBE _VERSUS_ FIRE-TUBE BOILERS