150 COMMERCIAL ROSE CULTURE 



fusible plug is placed at the low water line in a boiler; this is 

 a few inches above the top of the tubes; if the water gets below 

 this the plug will melt and, through the escaping water or steam 

 behind the boiler, an alarm would be given to the fireman. The 

 manhole at the top of the boiler is for the purpose of entering 

 to examine and clean, inspect or repair it. The hand holes 

 are the small openings for cleaning and inspecting the boilers. 

 These should be opened every season and the bottom of the 

 boiler inspected and swabbed out with a cloth or brush on a 

 pole, and washed out with a nozzle on the end of the hose. The 

 heating surface of a boiler is the portion exposed to the fire 

 which must, of course, always be covered with water. If any 

 dirt accumulates on the bottom of a boiler the water is kept 

 away and the fire will burn this part, causing a sag or uneven 

 place in the plate; this, in turn, makes a hollow place for the 

 dirt to lodge and has to be watched very carefully or the boiler 

 will soon be ruined. 



THE GRATE 



From four to five feet in length of grate bars gives the best 

 results with this type of boiler, and shaking grates are much 

 better than stationary ones, from the fact that they break up 

 the fire and do not allow of clinkers being produced and, most 

 important, being operated without opening the fire doors to 

 admit so much cold air, they do not cause such a cooling off 

 of the boiler plates. The fire is also kept more level on the 

 grate, as it should be. On some of our largest places the station- 

 ary grates are being torn out and shaking grates installed in 

 their place; the saving in fuel in one or two seasons is said to 

 offset the outlay. 



The horse power of a boiler is three times the square feet 

 of grate surface with natural draught. The space left over the 

 bridge wall under a return tubular boiler should be eighteen 

 square inches of space per horse power of the boiler. The area 

 of the chimney should be about one-eighth the area of the grate. 



