OF THE 

 COLLEGE OF 



lines in order that the safe pressures recommended above be not excee 

 and all sudden stresses or pulsations which are likely to occur where air is 

 allowed to accumulate in the pipe line must be prevented by providing 

 ample air vents or air inlets at all summits in the pipe line. These air in- 

 lets can be formed by cutting a hole ;n the pipe and cementing to it a ver- 

 tical stand pipe made of several sections of cement pipes, the lower end of 

 which is cut to saddle around the hole and the upper end extending above 

 the height to which water will rise. 



1. Manufacturing Hand Tamped Cement Pipes. 

 Mixtures used. 



The best proportion to use depends on the material available. With 

 .good clean pit gravel containing about 50 to 60 per cent, sand, less cement- 

 can be used than with sand alone. The mixtures commonly used are 1 part 

 of cement to 4 parts of pit gravel and sand for pipes up to 18 inches in 

 diameter, and 1 part of cement to 3 parts of gravel and sand for larger 

 pipes. If crushed rock or screened gravel is used, a good mixture is 1 part 

 of cement to 2 of sand and 3 or 4 of gravel or rock. No gravel or rock 

 larger than one-half the thickness of the pipe should be used. To make 

 the pipe more water tight 5 per cent, of the weight of cement in hydrated 

 lime is added. The sand and gravel must be free from dirt or organic 

 matter. 



Mixing materials. 



The mixing is very important. It is usually done by hand and in small 

 batches, but for a large plant concrete mixers are advisable. The ma- 

 terials are mixed by means of a hoe or with a shovel; they should be mixed 

 three times dry and three times wet. While it is desirable to use as much 

 water as possible, only sufficient water is added to the mixture to give the 

 consistency of damp earth which will retain its shape when squeezed in the 

 hand. When too much water is added the mix will stick to the mould 

 and the pipe will collapse when the mould is removed. In order to make 

 the ends smoother, some manufacturers use for the ends a finer and richer 

 mixture made of 1 part of cement to 2% or 3 of screened sand. 

 Process of moulding. (Pigs. 36, 37, 38). 



The moulds consist of a set of base rings which are bevelled to form the 

 base of the pipe, an inside core, an outside jacket, a funnelled sheet iron 

 hopper, a rimmer or cast iron ring which fits around the inside core and 

 levelled on the inside edge, a tamping bar and a feeding scoop. The pipe 

 is usually made on a solid platform or levelled area. To set the mould in 

 position the inside core is placed inside of the base ring and clamped tight 

 to it by turning a lever, the outside jacket is placed around the base ring 

 and contracted by turning a lever. The hopper fits on the top of the out- 

 side jacket. The mortar is fed in the moulds and spread in thin layers of 

 one to two inches thick. Each layer must be carefully and uniformly 

 tamped all around the inside core in order that the core be not shifted and 

 the pipe made unequal in thickness. When the last layer has been tamped 

 a little extra material is placed all around the top and the hopper is re- 

 moved; the rimmer is then placed around the inside core, is jammed down 

 and revolved, at the same time pressing down on the pipe . The inside core 

 is now contracted and removed; the rimmer is taken off. If the pipe has 

 been made on a platform it is now carried by means of lifting hooks with 

 the jacket still clamped on the base ring and placed on level ground. The 



