US3675494A - Pipe testing - Google Patents

Abstract

A small segment is sheared from the end of a cast iron pipe and examined for cracks. An uncracked specimen indicates ductile pipe, whereas a cracked specimen indicates that the pipe does not meet American Standards Association standards.

Description

[45] July 11, 1972 [56) References Cited UNITED STATES PATENTS PIPE TESTING [72] Inventor: John H. Becque, Glen Ellyn. Ill.

[73} Asslgnee: AMS'I'ED Industries Incorporated,

3.l8l,352 5/]965 Nakamuraetal.......................73/l01 Chicago lll.

Primary Examiner-Louis R. Prince [22] Filed: Sept. 23, 1970 Assislanl Examiner-William A. Henry, [1

Attorney-Walter L. Schlegel, Jr and Rusell W. Pyle 2| 1 App]. 1%.; 74,559

[57] ABSTRACT em is sheared from the end of a cast iron pipe A small segm and examined for cracks. An uncracked specimen indicates ductile pipe, whereas a cracked specun' en indicates that the [58] lmotsa'd" 73/432 pipe does not meet American Standards Association standards.

dClalmSDrnwlngBgures PIPE TESTING This invention relates to ductility qualifying test for iron castings and more particularly to a non-destructive test for cast iron pipe or the like whereby castings not meeting required physical specifications may be distinguished from those having the required physical qualities.

American Standard specifications have been established for ductile iron pipe, which in general must exhibit a minimum of 60,000 p.s.i. tensile strength, 45,000 p.s.i. yield strength (0.2 percent offset method) and ten per cent elongation. In conventional production line operations, samples are periodically removed and subjected to various tests, including Talbot strip tests, ring tests, full-length bursting tests and deflection measurements, as described in the Handbook of Cast Iron Pipe, published by the Cast Iron Pipe Research Association, Chicago 3, III., and incorporated herein by reference. The ring and strip tests cannot be economically applied to a large percentage of the pipe production because a long ring must be removed from the pipe in order to conduct such tests.

Another test is described in U.S. Pat. No. 3,440,868, wherein a hard ball is pressed into the surface of the pipe by a predetermined load, causing pipe not having proper ductility to fail. This test is convenient and simple, and each casting may be tested on a production line basis. The variables of pipe thickness and the required load on the ball, however, may render such test difficult to administer.

Accordingly, an object of this invention is to provide a simple non-destructive ductility test for cast iron pipe or the like wherein the load imposed upon the sample and the thickness thereof are not critical to the results of the test.

Other objects will become apparent from the following description and appended claims, taken in connection with the accompanying drawing, wherein:

FIG. I is a vertical sectional view showing a punch apparatus for removing a small segment from the end ofa pipe in accordance with the teachings of the presently described test process;

FIG. 2 is an enlarged side view of the punch used in the apparatus shown in FIG. 1; and

FIGS. 3,4, and 5 are illustrations of segments sheared from the ends of respective pipes.

The test herein described involves the shearing or punching of a small segment or notch from the end of the pipe and examining the segment for cracks or particular deformations. The segment removed is of a small size so as not to alter the properties or usefulness of the casting. In general, a segment sheared from a ductile iron casting conforming to required A.S.A. specifications will remain intact, whereas a similar segment from a grey iron or non-ductile casting and not conforming to such specifications will have a crack near the center thereof.

FIG. I shows a punch mechanism that may be employed to conduct the test. The punch includes a housing I0 defining a cylinder 12 and having an arm 14 extending therefrom to which is secured a cylindrical die 16. A piston 18, having a punch connected thereto is slidably mounted in sealing engagement with the cylinder 12. An electrically controlled source 22 of pressurized fluid is connected to the cylinder 12 and is operated by a switch 24, whereby the punch 20 is extended toward the die 16. A return spring 26 is provided between the piston 18 and an abutment 28 within the cylinder, in order to return the cylinder to an unextended position when pressure is released.

The punch 20 and the die 16 are arranged such that the punch, upon extension, is telescopically received in the die. The lower portion of the punch is shaped in the form of a half cylinder segment, thereby exposing a semi-circular punch surface 30 (FIG. 2) that contacts the end of a pipe 34. The adjacent planar vertical surface 32 of the punch serves as a guide to properly align the punch surface 30 with the end of the pipe. The punch surface 30 is preferably slightly V-shaped, with approximately a 3% angle from horizontal on both sides of the V. This feature allows for better shearing action and has been found to give well defined results.

FIGS. 3,4 and 5 illustrate segments removed from the ends of respective pipes. The FIG. 3 segment was taken from a due tile iron pipe having physical characteristics sufficient to meet the ASA. standard, whereas the pipe from which the segment of FIG. 4 was taken did not meet such specifications. It may be seen that the FIG. 3 segment is sound and uncracked, whereas the FIG. 4 segment contains a central crack 37, indicating an unacceptable percentage of grey iron or lack of proper ductility. Both segments were removed from pipes having beveled ends, such as the end 36 of the pipe 34. FIG. Sis an illustration of a segment removed from the unbeveled end of an unsuitable grey iron pipe. In this instance, the segment takes on the appearance of an hour glass configuration, with the sheared side 38 of the segment curving inwardly.

In order to validate the above-described test, 476 pipes were tested, ranging in size from 6 inches in diameter to 24 inches. A ring was removed from the end of each pipe and was subjected to both the ring crush test and the notching test described above. Of the pipe tested, 46l samples passed both tests and 13 failed both tests. One sample passed the ring crush test and failed the notching test and one sample yielded doubtful results in both tests. In terms of the notching test, a slight crack indicated doubtful results, whereas a definite extensive crack in the segment indicated non-ductile pipe.

Micro examinations were made of the pipe that failed either or both of the above tests. All of the pipe that failed the notching test (including the one that passed the ring crush test) were found to contain an unsuitable amount of grey iron. The pipe that was doubtful in both tests proved to have a good microstructure, being percent ferritic matrix and no carbides or pearlite present.

Having thus described the invention, what is claimed is:

l. A nondestructive method of testing a cast iron pipe for ductility comprising shearing off a small segment from one end of the pipe and examining said segment for cracks and deformities.

2. The process of claim I wherein the segment is sheared off with a semicircular punch.

3. The process of claim 1 wherein the end of the pipe from which the segment is removed is beveled and said segment is examined for cracks.

4. The process of claim I wherein the end of the pipe from which the segment is removed is non-beveled and said removed segment is examined for inwardly curved sides.

Claims (4)

1. A nondestructive method of testing a cast iron pipe for ductility comprising shearing off a small segment from one end of the pipe and examining said segment for cracks and deformities.

2. The process of claim 1 wherein the segment is sheared off with a semicircular punch.

3. The process of claim 1 wherein the end of the pipe from which the segment is removed is beveled and said segment is examined for cracks.

4. The process of claim 1 wherein the end of the pipe from which the segment is removed is non-beveled and said removed segment is examined for inwardly curved sides.

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