54 ROUGU-AND-TUMBLE ENGINEERING 



inly know that at 5 pounds pressure the damage 

 is not entirely avoided. As long as the iron is hot, 

 the dirt will dry out quickly, and by the time the boiler 

 is cold enough to force cold water through it safely, 

 the mud is dry and adheres closely to the iron. Some 

 of the foreign matter will be blown out, but you will 

 find it a difficult matter to wash out what sticks to the 

 hot iron. 



I am aware that some engineers claim that the boiler 

 should be blown out at about 5 pounds or 10 pounds 

 pressure, but I believe in taking the common sense 

 view. They will advise you to blow out at a low pres- 

 sure, and then, as soon as the boiler is cool enough, to 

 wash it thoroughly. 



Now, if you must wait till the boiler is cool before 

 washing, why not let it cool with the water in it? 

 Then, when you let the water out, your work is easy, 

 and the moment you begin to force water through it, 

 you will see the dirty water flowing out at the manhole 

 or hand hole. The dirt is soft and washes very easily; 

 but, if it had dried on the inside of the boiler while you 

 were waiting for it to cool, you would find it very diffi- 

 cult to wash off. 



You will observe, I said to force the water through the 

 boiler, and to do this you must use a force pump. No en- 

 gineer ought to attempt to run an engine without a 



