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Iron melted per minute per square foot cupola area, based on iron down to blast off (54 inches diameter), pounds......

21.82

Iron melted per minute per square foot cupola area, based on iron down

to blast off (50 inches diameter), pounds...

25.45

One pound coke melts how many pounds iron (including bed).

9.02

Blast pressure, ounces....

10.00

Cupola area is how many times twyer area (small end):

At 54 inches diameter cupola.

At 50 inches diameter cupola...

5.98

5.13

Bottom of melting zone above top of twyer, inches

10-14

Weight of iron layer is how many times weight of coke layer. ...

13.33

Time between starting fire and starting blast, hours and minutes.

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Iron melted per minute per square foot cupola area, based on iron down to blast off (54 inches diameter), pounds....

22.95

Iron melted per minute per square foot cupola area, based on iron down to blast off (50 inches diameter), pounds...

26.77

One pound coke melts how many pounds iron (including bed).

9.02

Blast pressure, ounces....

10.13

Cupola area is how many times twyer area (small end):

At 54 inches diameter cupola.

At 50 inches diameter cupola....

Bottom of melting zone above top of twyer, inches

5.98

5.13

10-12

Weight of iron layer is how many times weight of coke layer...
Time between starting fire and starting blast, hours and minutes.

[blocks in formation]

Iron melted per minute per square foot cupola area, based on iron down to blast off (54 inches diameter), pounds ......

23.77

Iron melted per minute per square foot cupola area, based on iron down to blast off (50 inches diameter), pounds. ....

27.73

One pound coke melts how many pounds iron (including bed).

10.02

Blast pressure, ounces. . . . .

10.55

Cupola area is how many times twyer area (small end):

At 54 inches diameter cupola.

At 50 inches diameter cupola..

*5.98

5.13

Bottom of melting zone above top of twyers, inches...

10-12

Weight of iron layer is how many times weight of coke layer...
Time between starting fire and starting blast, hours and minutes.

15.38

2:45

* Iron too dull on account of too small coke charges.

7 During test 9, however, it was noticed that the iron was not at the proper temperature, so for the next test, 10, the coke was increased without altering the blast pressure. This resulted in a decreased melt per hour.

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Iron melted per minute per square foot cupola area, based on iron down to blast off (54 inches diameter), pounds......

23.39

Iron melted per minute per square foot cupola area, based on iron down

to blast off (50 inches diameter), pounds ......

27.29

One pound coke melts how many pounds iron (including bed).

9.49

Blast pressure, ounces....

10.55

Cupola area is how many times twyer area (small end):

At 54 inches diameter cupola..

At 50 inches diameter cupola...

Bottom of melting zone above top of twyer, inches

*5.98

5.13

10-12

Weight of iron layer is how many times weight of coke layer.
Time between starting fire and starting blast, hours and minutes..

* Iron rather dull, coke charge should be increased from 140 to 150 pounds.

14.28 2:30

8 The remainder of the tests which have been made have not been tabulated, but it has been found that a coke charge of 150 pounds, with a blast pressure of 10 ounces results in a melt of between 11 and 11 tons per hour, the iron coming down at the proper temperature.

9 We believe that the changes which are responsible for the increase of our melting rate, were the enlargement of the twyer openings and the decrease of our coke charges, the enlargement of the twyer openings making it possible for us to get the necessary air into the cupola without burning more coal under our boiler, and the decrease of the coke charges resulting in a saving of one-half ton per each 25 tons of iron melted.

10 A close study of cupola action indicates at once why an excess of coke decreases the melting rate. Iron in the cupola is melted in a fixed zone, the first charge of iron above the bed being melted by burning coke in the bed. As this iron is melted, the charge of coke above it descends and restores to the bed the amount which has been burned away. If there is too much coke in the charge, the iron is held above the melting zone above referred to, and the excess coke must be burned away before it can be melted and this of course decreases the economy and the melting speed.

MR. H. M. LANE The discussion of this paper has naturally included cupola practice to some extent, and in the matter given by Messrs. Fortune and Wells a number of points are touched on which it may be well to emphasize.

2 The experiments performed show conclusively that better result were obtained by increasing the area of the twyers. This is in accordance with the facts which might be expected from a knowledge of the principles of the combustion which takes place in the cupola. The only reason that blast pressure has to be used is to overcome the resistance which the gases meet with in passing through the charge, and also to overcome the resistance of the pipes and passages leading to the cupola. The power necessary to overcome this resistance represents an expenditure of energy. The compression of the air to high pressures always absorbs power, and hence if we can arrange to deliver the same number of pounds of air to the cupola at a lower pressure we will save the coal pile in the boiler room and have more uniform results from the cupola.

3 This points to the use of large twyer areas and low blast pressures. With the ordinary height of cupola, however, these pressures will usually run at least ten ounces; hence it is simply a question of practice as to whether a positive or fan blower shall be used. With properly designed twyers, either will give good results. With poorly designed and proportioned twyers the positive blower will give the best results, on account of the fact that it tends to overcome the difficulties introduced by bad twyer design.

THE AUTHOR It was not the purpose of this paper to present the actual results of specific tests; relative performances only are shown as indicative of average conditions and results. Air was not assumed as an incompressible fluid, but allowance is made in the formula for its change of density relatively to the pressure. The significant figures are given because so calculated by the given formula. It is merely a matter of opinion whether round numbers should be substituted. The formula employed and the results given are those generally accepted by blower manufacturers.

1

No. 1176

PATTERNS FOR REPETITION WORK

BY E. H. BERRY, ILION, N. Y.

Associate Member of the Society

A pattern which is run continuously for months, or perhaps years, clearly falls within the limits of this paper as being used for repetition work. And it is just as clear that one which is discarded after a single casting has been made from it should be classed as a pattern for jobbing work.

2 The exact point which marks the division between them depends in a large measure, upon the size of the foundry and the kind of work it handles, and the two classes frequently merge into each other by imperceptible gradations. Without attempting to fix specific limits, we can use the extreme cases cited above to indicate the lines along which the distinction should be drawn, leaving each pattern user to decide for himself as to the precise position on the scale which he assigns to any given pattern.

3 It is this position which usually determines the expenditure that can be permitted in making the pattern, for it is evident that a cost which would be perfectly legitimate for making say a million castings, might be excessive if only ten thousand were required, and entirely prohibitive for one thousand. On the other hand, the circumstances might be such as to justify a high pattern cost, even for a small number of castings, as for instance, in the case of certain master patterns, further reference to which will be made elsewhere in this article.

4 Many of the conclusions reached in this paper may be borne in mind to good advantage even in the case of jobbing patterns. But the very nature of the service for which these are intended is such that the designer must leave most of the details to the judgment of the pattern maker; and if the latter fails to catch every important point, it simply means that the moulder may have to spend some addi

Presented at the New York Meeting (December, 1907) of the American Society of Mechanical Engineers and forming part of Volume 29 of the Transactions.

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