Part 33 (1/2)
As already stated, the volu less than in the case of coal, makes it evident that the area of stacks for oil fuel will be less than for coal It is assuases to be handled, and this volume for oil may be taken as approxi stacks for oil fuel there are two features whichpractice there is rarely danger of tooof oil, however, this may play an important part in the reduction of plant econo more apparent where the load on the plant may be reduced at intervals The reason for this is that, aside froht decrease in temperature at reduced loads, the tendency, due to careless firing, is toward a constant gas flow through the boiler regardless of the rate of operation, with the corresponding increase of excess air at light loads
With excessive stack height, econo loads is almost impossible with hand control With autoh to take care of known peaks, under lighter loads this economical operation beco a stack for a plant where the load is known to be nearly a constant is easier than for a plant where the load will vary over a wide range While great care must be taken to avoid excessive draft, still more care must be taken to assure a draft suction within all parts of the setting under any and all conditions of operation It is very easily possible to h low draft, by the losses due to setting deterioration, resulting from such lack of suction Under conditions where the suction is not sufficient to carry off the products of co brickill cause its rapid failure
[Illustration: 7800 Horse-power Installation of Babcock & Wilcox Boilers, Equipped with Babcock & Wilcox Chain Grate Stokers at the Metropolitan West Side Elevated Ry Co, Chicago, Ill]
It becoht for oil-fired boilers is one which ner, on the one hand, ainst the evils of excessive draft with the view to plant econoainst the evils of lack of draft from the viewpoint of upkeep cost
Stacks for this work should be proportioned to give ample draft for the maximum overload that a plant will be called upon to carry, all conditions of overload carefully considered At the saured liberally enough to insure a draft suction within the setting under all conditions, care ainst the installation of a stack which would give more than this maximum draft
TABLE 56
STACK SIZES FOR OIL FUEL
ADAPTED FROM C R WEYMOUTH'S TABLE (TRANS
A S M E VOL 34)
+----------------------------------------------------+ |+--------+-----------------------------------------+| || | Height in Feet Above Boiler Room Floor || ||Diameter+------+------+------+-----+--------------+| || Inches | 80 | 90 | 100 | 120 | 140 | 160 || |+--------+------+------+------+------+------+------+| || 33 | 161 | 206 | 233 | 270 | 306 | 315 || || 36 | 208 | 253 | 295 | 331 | 363 | 387 || || 39 | 251 | 303 | 343 | 399 | 488 | 467 || || 42 | 295 | 359 | 403 | 474 | 521 | 557 || || 48 | 399 | 486 | 551 | 645 | 713 | 760 || || 54 | 519 | 634 | 720 | 847 | 933 | 1000 || || 60 | 657 | 800 | 913 | 1073 | 1193 | 1280 || || 66 | 813 | 993 | 1133 | 1333 | 1480 | 1593 || || 72 | 980 | 1206 | 1373 | 1620 | 1807 | 1940 || || 84 | 1373 | 1587 | 1933 | 2293 | 2560 | 2767 || || 96 | 1833 | 2260 | 2587 | 3087 | 3453 | 3740 || || 108 | 2367 | 2920 | 3347 | 4000 | 4483 | 4867 || || 120 | 3060 | 3660 | 4207 | 5040 | 5660 | 6160 || |+--------+------+------+------+------+------+------+| +----------------------------------------------------+
Figures represent noood for 50 per cent overloads
Based on centrally located stacks, short direct flues and ordinary operating efficiencies
Table 56 gives the sizes of stacks, and horse pohich they will serve for oil fuel This table is, in modified form, one calculated by Mr C R Wey to the subject, and will ordinarily give satisfactory results
Stacks for Blast Furnace Gas Work--For boilers burning blast furnace gas, as in the case of oil-fired boilers, stack sizes as suited for coal firing will have to be modified The diameter of stacks for this work should be approxiases would be slightly greater than froiven stack, but such a decrease due to voluher teases
Records show that with this class of fuel 175 per cent of the rated capacity of a boiler can be developed with a draft at the boiler damper of froht of stacks to one which will give this draft as a round, will produce such a draft and this height should ordinarily not be exceeded Until recently the question of econoas has not been considered, but, aside frouarded against in order to lower the upkeep cost
Stacks should be ht to produce a draft that will develop the maximum capacity required, and this draft decreased proportionately for loads under the as fed to a boiler for any given rating is a fixed quantity and if a draft in excess of that required for that particular rate of operation is supplied, econo is materially increased Excess air which is drawn in, either through or around the gas burners by an excessive draft, will decrease econoain, as in oil-fired practice, it is essential on the other hand that a suction be , in this case not only to provide against setting deterioration but to protect the operators froerous Aside froas and air or a ”laneing” action erous explosions within the setting, , may increase the exit te out dahly essential, therefore, that the furnace be properly constructed to meet the draft which will be available
Stacks for Wood-fired Boilers--For boilers using wood as fuel, there is but little data upon which to base stack sizes The loss of draft through the bed of fuel will vary over limits even wider than in the case of coal, for in this class of fuel the moisture may run from practically 00 per cent to over 60 per cent, and theare radically different for the different classes of wood (see chapter on Wood-burning Furnaces) As econoh stack tee quantities of excess air are supplied due to the eneral, it may be stated that for this class of fuel the diareat as for coal-fired boilers, while the height ning a stack for boilers using wood fuel to consider each individual set of conditions that exist, rather than try to follow any general rule
One factor not to be overlooked in stacks for wood burning is their location The fine particles of this fuel are often carried unconsuh the boiler, and where the stack is not on top of the boiler, these particles may accumulate in the base of the stack below the point at which the flue enters Where there is any air leakage through the base of such a stack, this fuel nited and the stack burned
Where there is a possibility of such action taking place, it is well to line the stack with fire brick for a portion of its height
Draft Gauges--The ordinary for 35, which consists of a U-tube, containing water, lacks sensitiveness in ht pressure differences as usually exist, and for that reason gauges which multiply the draft indications are35 U-tube Draft Gauge]
[Illustration: Fig 36 Barrus Draft Gauge]
An instruiven excellent results is one introduced by Mr
G H Barrus, which multiplies the ordinary indications as36, and consists of a U-tube er tubes, or cha a diameter of 2 inches Two different liquids which will not mix, and which are of different color, are used, usually alcohol colored red and a certain grade of lubricating oil The movement of the line of demarcation is proportional to the difference in the areas of the cha them The instrue