FOREST UTILIZATION 45 



Water space should be divided into sec- 

 tions, an arrangement improving the 

 circulation of water and reducing the 

 severity of any explosion. 



7. Modern boilers are tubular boilers, 



which have the largest heating sur- 

 face. Diameter of tubes is measured 

 outside, including metal. 



8. Combustion chamber should allow of 



full combustion of fuel and gases. 

 Draft area should be one-eighth of 

 grate area. Return flues pass the gases 

 to the entrance of the combustion 

 chamber. 



Heating surface should be as nearly as 

 possible at right angles to the current 

 of escaping gases. 



9. Very best water gauges, safety valves, 



injectors and steam gauges are pre- 

 requisites. All boiler fixtures should 

 be readily accessible. 



10. Safety valves must be tried once daily. 



The water level should be controlled 

 by gauge cocks, glass gauges alone 

 being unreliable. 



11. Cold water should not be fed directly 



into boiler and should never come in 

 direct contact with the boiler metal. 

 Steam injectors will not lift hot water 

 as well as cold water. 



12. Steam pressure gauge must stand at zero 



when pressure is off. 



13. In case of low water and danger of ex- 



plosion, cover fire with wet earth. 



14. If fire is fed from mill refuse, steady 



heat can be retained only with boilers 

 of large water capacity. The larger 

 the boiler the greater the fuel econ- 

 omy, 

 (b) Pointers about engines. 



I. Horsepower of engines is: 



Sectional area of piston in sq'uare inches 

 times pressure times velocity in feet 

 over 550. 



Deduct 10% to 20% for friction. 



Pressure on the piston is not much 

 over one-half of pressure in the boiler 

 (60%). 



