4 BULLETIN. 747, U. S. DEPARTMENT OF AGRICULTURE. 



ether words, tlie average of all plants, botli good and bad, between 

 these limits 'shows a variation of about 87 pounds of coal per 1,000 

 pounds of butter, while the poorer plants show a variation of about 

 261 pounds. The better plants, however, show practically no varia- 

 tion in the fuel used per 1,000' pounds between plants of that size. 



The same condition appears in similar curves plotted from data 

 obtained on fuel consumption in other years; hence there must be a 

 definite reason for the variation in fuel cost in the creameries 

 mentioned. 



A careful study of the reports was made to determine, if possible, 

 the reasons for the differences, with the following- conclusions : - 



1. When the annual output was between 250,000 and 350,000 

 pounds of butter the size of the boiler and engine was increased, as 

 well as the length of time of firing the boiler, compared with a* 

 creamery of smaller output. 



2. At about the annual production shown above, the size of the 

 creamery building was increased and the ratio of the coal required 

 to heat the building to the quantity used for making butter is greater 

 than in the smaller plants. 



3. Often when the capacity of the creamery had reached an annual 

 production of between 250.000 and 350,000 pounds of butter an 

 additional helper was employed and the firing of the boiler was 

 intrusted to him. It is probable, however, that he was not so eco- 

 nomical in the use of fuel as the buttermaker. 



4. Frequently when the annual capacity reaches 250,000 pounds it 

 is necessary to make two churnings daily, thus increasing the time 

 of using power. 



.While £>robably there are other reasons why the fuel consumption 

 per 1,000 pounds of butter made does not decrease in proportion to 

 the increase in the capacity of the plant, those mentioned are suffi- 

 cient to account, for much of the discrepancy. 



The curves of figure 2 show the average sizes of engines and boilers 

 for plants of different capacity, and of figure 3 the average number 

 of hours the boilers are fired. That portion of the curves between 

 250,000 and 350,000 pounds of butter made annually should be noted 

 especially. Between these points the average time of firing the boiler 

 is increased from 7.3 to 8.5 hours, or 1.2 hours daily. There is prac- 

 tically no difference in the size of the boiler or the engine, or in the 

 length of time the boiler is fired, between plants where 150,000 and 

 250,000 pounds of butter was made. In creameries below 150,000 

 pounds' capacity, however, both the size of the equipment and the 

 time of firing decrease. Above 350,000 pounds' capacity the size of 

 the equipment and the total time of firing increases, but at a less rate 

 than in the smaller plants. 



