TESTS OF THE TENSILE STRENGTH OF WATER PIPE.
SOME interesting tests of the tensile strength of cast-iron water pipes were made some lime since for the city of Newton, Mass., at the United States arsenal at Watertown, the results of which are given in the following report, with accompanying diagram, made by the commanding officer, Major F. H. Parker of the Ordinance Department, U. S. A.:
The pipes, twelve in number, were prepared for testing by dressing the surface of the bore at each end a distance of about four inches, for the purpose of securing a good surface for the leather packings to seal against. It was found necessary to cut off a short section of the spigot end of the pipes before dressing the surface of the bore, removing the metal that was too hard to cut with ordinary lathe tools. In this way the diameters of the bore at the ends of the six-inch and eight-inch pipes were respectively increased to 6.25 Inches and 8.19 inches. The interior pressure acted against about one inch in length of the dressed surface, being that part of the bore covered by the lips of the leather packings.
It was not thought that this method of preparation contributed any tendency to rupture at the ends on account of the small ring of thinner metal which was exposed to the hydrostatic pressure, and this ring was reinforced by the metal of the pipe beyond that which was not directly strained. To dispel any doubts upon this point the eight-inch pipes numbers 3, 5 and 6 were banded with a wrought-iron strap at the spigot end, and the six-inch pipes numbers 7, 8, 9 and 11 were similarly banded with a stout cast-iron ring. An examination of the results would seem to confirm the belief that the bursting strength of the pipes was not influenced by the dressing of the metal of the bore at the ends.
An air rent 1-10 inch in diameter was drilled in each pipe near the spigot end, which was plugged with a tapering steel pin after the pipe was charged with water. None of the fractures occurred through the vent holes.
The testing was done by the gradual increase of hydrostatic pressure in the bore of the pipes till rupture took place, weighing the pressure with the high pressure hydraulic holder gauge of the testing machine.
The thickness of the pipes is given where accessible to measure.
Following are the tabulated results of the tests :
TESTS OF TENSILE STRENGTH OF CAST-IRON WATER PIPE.