Manufacture of Cfment Pipe 



89 



inches and the capacity of the machine is from 1000 to 2000 feet per 

 nine hours, according to the size. 



The manufacturers state that they have made internal pressure 

 tests on their machine-made pipe, and found 8-inch pipe to with- 



Fig. 13. — Filling the ordinary hand molds with a pneumatic tamper. There are six 

 plants in California where these tampers are used successfully. 



Stand from 65 to 85 pounds per square inch, 10-inch pipe a maximum 

 of 77 pounds, 16-inch pipe 65 pounds, the pipe being made of 1 : 3^ 

 mixture. They state also that tests on 1 : 5^4 pipe showed strength 

 about 60 percent of the above figures. 



The first of these machines w^as installed at Van Nuys, Cali- 



