For Practical Workers 



How to Make an Efficient 

 Boiler-Patch 



THE usual method of patching a 

 boiler cannot be relied upon for 

 high efficiency. Suppose there is need 

 of a patch at the check-\alve hole of a 

 locomotive-boiler. The radial cracks, 

 most often along 

 the length of the 

 plate, start out 

 from the hole. If 

 a disk of boiler- 

 plate is applied 

 with a single row 

 of ri\ets, as shown 

 in F"ig. I, there is 

 danger of tearing 

 the boiler-plate or 

 the patch, be- 

 tween the rivets; also of shearing the 

 rivets. 



The more rivets are used, the weaker 

 the i)atch, since e\ery hole weakens the 

 plate. This may be seen by examining 

 Fig. 2. The first piece of cardboard is 

 solid all the way across ; the second has a 

 hole in it, making the resistance to tear- 

 ing just that much less. The only way 



Fig. 1. The usual 

 form of boiler-patch 



Fig. 2. Obviously the hole in the plate 

 shown at the right weakens it 



to prevent shearing the rivets is to add 

 more rivets opposite the defect, but this 

 increases the number of holes and actual- 

 ly weakens the plate. 



This difficulty can be avoided by the 

 use of a patch like the one shown in Fig. 

 3. Two rows of rivets are used. The 

 additional number of holes does not 

 weaken the patch, howev'er, because the 

 force tending to pull the plate apart does 

 not act at right angles to the line of 



Fig. 3. An improved patch can be made 

 by placing the rivets so as to prevent the 

 strain from acting at right angles to them 



rivets. The component of this force is 

 to be reckoned with and the greater the 

 angle of the rivets the less this force will 

 be. By multiplying the number of 

 rivets it is possible to mass more metal 

 opposite the defect than there would be 

 in the original plate, and the efficiency 

 in shearing will be e\en greater than one 

 hundred per cent. The obsersance of 

 this simple expedient, which simpK- takes 

 into consideration a princii)lc of physics, 

 will result in far less danger from weak 

 s[)ots in a boiler. 



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