14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



tunity to absorb the heat, so that excess heat would pass up the stack. 

 Thus, a temperature recording device may be an indicator both of the 

 heat producing and heat absorbing functions of the furnace. 



Limitations 



Recording devices whatever their nature do not in themselves 

 provide the requisite control of furnace operations but simply sub- 

 stitute exact data for guess-work to guide the operator. Accord- 

 ingly, the installation of any system of control will be effective only 

 in proportion as the data are intelligently interpreted and applied. 



The case comes to mind of a large central heating plant with a 

 wide-awake chief engineer, cognizant of fuel wastes and means for 

 their elimination, who equipped each one of his mechanically stokered 

 boilers with draft gages, a permanently installed flue gas analyzer 

 and a recording thermometer, and with this apparatus established his 

 standards. His firemen were apparently brought to the point of 

 seeing the advantages to themselves of making use of the equipment 

 and were fully instructed as to the meaning of it all. In spite of this, 

 on several occasions the engineer has come upon a fireman closing a 

 hole in the fuel bed by firing coal through the two-foot cleaning door 

 on the side of the setting, thus allowing volumes more of air to enter 

 the furnace than could possibly enter even through the hole in the 

 fuel bed, and in spite of the warnings, the engineer to-day is not sure 

 but that, when the occasion arises, the firemen will repeat the same 

 operation. In short, the human factor must be considered. 



There are two general types of control apparatus, namely, indicat- 

 ing and recording. The former type is of value only as providing a 

 guide to the fireman and is no safeguard against his failings. The 

 recording type, however, in furnishing an uninterrupted register, 

 serves not only as a guide to the fireman but also as a record of 

 efficiencies for the operator. 



Costs 



The simple form of Orsat gas analyzer, designed along the lines 

 of the sketch shown on page 11, may be purchased for around 

 40 dollars. It is a portable outfit and properly used, can make a 

 carbon dioxide analysis in about a minute's time. There is also the 

 fixed installation equipped with gas collector ready at any time to 

 make analyses. Another device is in the form of a continuous indi- 

 cator with or without the further refinement of a permanent record. 



