Part 7 (2/2)

In certain boilers, ”superheating surface” is provided to ”dry the stea Such surface is invariably a source of trouble unless the steam is initially dry and a boiler which will deliver dry steam is obviously to be preferred to one in which surface must be supplied especially for such purpose Where superheaters are installed with Babcock & Wilcox boilers, they are in every sense of the word superheaters and not driers, the stea delivered to them in a dry state

The question has been raised in connection with the cross drun of the Babcock & Wilcox boiler as to its ability to deliver dry steam

Experience has shown the absolute lack of basis for any such objection

The Babcock & Wilcox Coo enerated was separated froe to the drum Glass peepholes were installed in each end of a drun, at the pointtubes entered the druht at one of these peepholes the action in the druh the other It was found that with the boiler operated under three-quarter inch ashpit pressure, which, with the fuel used would be equivalent to approxi for stationary boiler practice, that each tube was delivering with great velocity a stream of solid water, which filled the tube for half its cross sectional area There was no spray orthat the steae through the horizontal circulating tubes, which in the boiler in question were but 50 inches long

[Illustration: Northwest Station of the Coo, Ill This Installation Consists of 11,360 Horse Power of Babcock & Wilcox Boilers and Superheaters, Equipped with Babcock & Wilcox Chain Grate Stokers]

These experiments proved conclusively that the size of the stean has no appreciable effect in deter surface, and that sufficient liberating surface is provided in the circulating tubes alone If further proof of the ability of this design of boiler to deliver dry steam is required, such proof is perhaps best seen in the continued use of the Babcock & Wilcox marine boiler, in which the cross drum is used exclusively, and hich rates of evaporation are obtained far in excess of those secured in ordinary practice

Quick Steaes of water-tube boilers as a class over fire-tube boilers in ability to raise steam quickly have been indicated

Due to the constant and thorough circulation resulting from the sectional nature of the Babcock & Wilcox boiler, steam may be raised n

In starting up a cold Babcock & Wilcox boiler with either coal or oil fuel, where a proper furnace arrangement is supplied, steam may be raised to a pressure of 200 pounds in less than half an hour With a Babcock & Wilcox boiler in a test where forced draft was available, steam was raised from an initial terees to a pressure of 200 pounds, in 12the fire The boiler also responds quickly in starting from banked fires, especially where forced draft is available

In Babcock & Wilcox boilers the water is divided into many small streams which circulate without undue frictional resistance in thin envelopes passing through the hottest part of the furnace, the stea surface There is no part of the boiler exposed to the heat of the fire that is not in contact ater internally, and as a result there is no danger of overheating on starting up quickly nor can leaks occur froht be the case where an atte construction

Storage Capacity for Steam and Water--Where sufficient steam and water capacity are not provided in a boiler, its action will be irregular, the stea subject to frequent and rapid fluctuation

Owing to the sreater ie pressure of 180 pounds per square inch, 8 cubic feet of steam, which is equivalent to one-half cubic foot of water space, are required to supply one boiler horse power for onesuch an interval, the pressure will drop to 150 pounds per square inch The volume of steam space, therefore, may be over rated, but if this be too s off will carry water with it in the forreat a water space results in slow stea up; while toosurface and increases the losses from that cause

That the steam and water space of the Babcock & Wilcox boiler are the result of numerous experiments has previously been pointed out

Accessibility--Cleaning That water-tube boilers are more accessible as a class than are fire-tube boilers has been indicated All water-tube boilers, however, are not equally accessible In certain designs, due to the arrange used it is practically impossible to remove all deposits of soot and dirt Frequently, in order to cheapen the product, sufficient cleaning and access doors are not supplied as part of the boiler equipment The tendency of soot to collect on the crown sheets of certain vertical water-tube boilers has been noted Such deposits are difficult to re the sheet may crack and an explosion result

[Illustration: Rear View--Longitudinal Dru Access Doors to Rear Headers]

It is als internally, and in such places also is there a tendency to unsuspected corrosion under deposits that cannot be removed

In Babcock & Wilcox boilers every portion of the interior of the heating surfaces can be reached and kept clean, while any soot deposited on the exterior surfaces can be blown off while the boiler is under pressure

Inspection--The accessibility whichof all portions of the Babcock & Wilcox boiler also provides a h inspection

Drums are accessible for internal inspection by the removal of the e doors furnished for the purpose Rear headers in the inclined header designs may be inspected from the chamber formed by such headers and the rear wall of the boiler In the vertical header designs rear tube doors are furnished, as has been stated In certain designs of water-tube boilers in order to assure accessibility for inspection of the rear ends of the tubes, the rear portion of the boiler is exposed to the at excessive radiation losses In other designs the means of access to the rear ends of the tubes are of a makeshi+ft and unworkmanlike character

By the removal of handhole plates, all tubes in a Babcock & Wilcox boiler th either for the presence of scale or for suspected corrosion

Repairs--In Babcock & Wilcox boilers the possession of great strength, the elimination of stresses due to uneven teer of leaks and corrosion, the protection of the drums from the intense heat of the fire, and the decreased liability of the scale fore on the hottest tube surfaces, all tend to minimize the necessity for repairs The tubes of the Babcock & Wilcox boiler are practically the only part which may need renewal and these only at infrequent intervals When necessary, such renewals may be made cheaply and quickly A sth for the boiler used, is all that need be carried toboilers are difficult at best and frequently unsatisfactory when completed When staybolt replaceet at the inner sheet of the water leg, several tubes must in some cases be cut out Not infrequently a replace is necessary and this is difficult and requires a lengthy shutdown With the Babcock & Wilcox boiler, on the other hand, even if it is necessary to replace a section, this may be done in a few hours after the boiler is cool

In the case of certain staybolt failures the working pressure of a repaired boiler utilizing such construction will frequently be lowered by the insurance coain placed in service

The sectional nature of the Babcock & Wilcox boiler enables it toperiods of tiardless of the nature of any repair that may be required