Steam Engines. 513 



When cleaning is to be done it is important to make sure 

 that the fire is all out and the steam should be permitted 

 to fall to as low as 10 pounds before the blow-off is opened. 

 If the fire is not all out the flues may be made to leak 

 and if the steam is too hot the mud will be caked on the 

 flues so that it cannot be readily removed. 



In replacing the plates for the hand holes it is important 

 to see that they are clean and that no scale or dirt is on 

 the seat. Sheet lead makes the best packing for these 

 places. The nuts should be turned up tight at first and 

 after steam is up and the metal expanded they may need 

 tightening a little more. 



642. Firing Care and skill are required to do good 

 firing, whether with wood or coal. In firing with wood 

 it is necessary to keep the fire-box nearly full all the 

 time and it will occasionally require "knocking down" 

 but it is a good plan not to use the poker more than neces- 

 sary. The wood should be placed in the fire-box as closely 

 as practicable. 



In firing with coal the grates should be kept as evenly 

 covered as possible with a thin fire, avoiding throwing 

 on large lumps of coal or putting on large quantities at a 

 time. If the coal forms clinkers these must be removed 

 from the grate through the door but it is desirable not 

 to use the poker when it can be avoided. The ashes 

 must be kept removed form under the grate or the bars 

 will be warpeol or melted. 



It is well to allow the safety valve to blow off once a 

 day to note how this and tho pressure gage agree, but 

 good firing will not permit this to occur unless the engine 

 is stopped. 



When the fire is too strong it may be controlled by open- 

 ing the door to the fire-box an inch or less or leaving the 

 damper open. It is not a good plan to open the fire door 

 ami close the damper at the same time when the engine 

 is running. 



643. Foaming. Foaming in the boiler is a dangerous 



