WO1999022218A1

WO1999022218A1 - Apparatus and method for testing the hardness of a pipe

Info

Publication number: WO1999022218A1
Application number: PCT/US1998/022449
Authority: WO
Inventors: Jack O. Hill; Leroy Fry, Jr.
Original assignee: Hill Jack O; Fry Leroy Jr
Priority date: 1997-10-27
Filing date: 1998-10-23
Publication date: 1999-05-06
Also published as: AU1117299A

Abstract

An apparatus (10) for testing hardness of a pipe (12) including a body (14) having a longitudinal axis, a probe (16) connected to the body and extending transverse to the longitudinal axis of the body, a retaining mechanism (18) connected to the probe and positioned within the body so as to maintain the probe in a fixed position relative to the pipe while the body is moving through the pipe, and a processor connected to the probe so as to convert a signal produced by the probe relative to the hardness of the pipe into a humanly perceivable indication of pipe hardness. The probe serves to contact a point along the inner surface of the pipe while the body is moving continuously through the pipe.

Description

.APPARATUS AND METHOD FOR TESTING THE HARDNESS OF A PIPE

TECHNICAL FIELD

The present invention relates to pipeline inspection devices. More particularly, the present invention relates to pipe inspection pigs which serve to detect the hardness of the pipe at specific locations.

BACKGROUND .ART

Numerous pipe inspection pigs are in existence and have been used in connection with non-destructive inspection of pipelines for gaseous or liquid materials, such as natural gas, liquid hydrocarbons, or water.

Various methods of detecting flaws or defects from the inside of a pipe or pipeline have been attempted with varying degrees of success. Ferromagnetic induction devices have been used as

disclosed in U.S. Patent No. 4,742,298. This invention was directed to determining the presence and the magnitude of surface flaws and to overcoming difficulties encountered in determining the

presence and the magnitude of surface flaws in a pipe. The solution proposed was to use a

cylindrical primary alternating current coil which is coaxially aligned with the pipe to generate a high frequency AC magnetic field in the pipeline, a multiple cylindrical secondary AC sensing coil

where arranged at prescribed intervals in a circumferential direction around the interior of the pipe,

each secondary coil having an axis parallel to the axis of the primary coil. The AC voltage sensed

at each secondary coil is set to be proportional to the density of a parallel component of magnetic flux caused by the AC magnetic field generator.

Eddy current sensing probes have also been used primarily in connection with

non-destructive inspection and testing of relatively thin-walled tubing which is not ferromagnetic

material. Such tubing does exist in steam generators and heating exchangers having been the

primary focus of eddy current probes as disclosed in U.S. Patent No. 4,851,773 which discloses a single direction rotating head profϊlometer. One embodiment of that device discloses an

electromechanical eddy current probe having a rotatable sensing head for sensing the wall thickness and for locating local defects in a tube or conduit through which it is passed. Basically, the

mechanical profilometer probe was designed to detect dents in the interior surface of steam generator tubes. The position of the rotating head is varied along the length of the tubing being

inspected as the probe is drawn through the tubing with a cable.

Another eddy current probe is disclosed in U.S. Patent No. 4,952,875 in which a plurality of pairs of diametrically opposed sensing coils are alternatingly staggered along the longitudinal axis of the test sensor to give complete coverage of the interior pipe surface and are further

permitted to move in and out to accommodate the size differences or constrictions in the pipeline. However, the sensor probe is intended to move longitudinally through the pipeline.

Also, U.S. Patent No. 5.068,608 discloses multiple coil eddy current probe system and an eddy current probe is disclosed in which a defect is first detected when the probe is positioned adjacent the defect and a series of axially spaced probes are activated to sense and detect the

extremities of a crack or other discontinuity. Generally, eddy current probes have not been

particularly successful with respect to underground pipelines constructed of steel or other ferromagnetic materials and having pipeline walls with thicknesses substantially greater than the

normal eddy current penetration depth. However, one attempt to provide an eddy current probe or ferromagnetic pipeline flaw detection was disclosed in U.S. Patent No. 4,107,605.

The most popular and currently most useful sensors for ferromagnetic pipeline inspection have been magnetic flux generators and magnetic flux leakage sensors which are positioned circumferentially around an inspection pig which is moved longitudinally through the pipeline.

Examples of such sensors are disclosed in U.S. Patent Nos. 4,105,972, 4,310,796, 4,444,777 and

4,458,601. The operation of such magnetic flux detection probes is described in U.S. Patent No. 4,789,827 in connection with a magnetic flux detection probe in which the sensors are intentionally

spaced at different radial distances or spaced at different distances from the interior pipe surface in an effort to obtain greater accuracy with respect to the location of the flaw or defect on the inside or the outside of the pipe wall.

Some attempts have been made to detect defects at different angular orientations in connection with testing and inspecting pipes as they are being manufactured. U.S. Patent No.

3,906,357 discloses an exterior pipe testing device in which there are two external sensor sections, one having a plurality of fixed sensing shoes circumferentially spaced around the pipe to be inspected which depends upon linear movement of the pipe therethrough for detecting flaws or defects primarily oriented circumferentially around the pipe. A second inspection unit is provided

which has a pair of opposed magnetic sensing shoes which is rotated rapidly around the outside of the pipe to be inspected in an effort to detect longitudinal cracks which might otherwise go

unnoticed with the fixed shoe sensing unit. Complex circuitry is used to coordinate the sensor input from each of the sensing units with a rotating magnetic pulse generator geared to the linear motion

of the pipe being manufactured. A purpose of this device is to actuate one or more spray cans at the linear and the circumferential position where a manufacturing flaw is detected either by the linear

inspection unit or the rotary inspection unit. Application of such a testing device to on-site underground pipelines has not been demonstrated.

.Another exterior pipe testing device has been disclosed in U.S. Patent No. 4,439,730, in

which pairs of north and south poles of magnets are held adjacent to the exterior wall of a pipe at

uniformly spaced apart positions circumferentially around the pipe. The north and south poles are

positioned between the north and south poles of longitudinally spaced apart circular magnets around

the pipe. The circumferential spaced apart magnets are rotated at a high rate of speed so that

orthogonically directed resultant magnetic field is produced on opposite sides of the pipe between the north and south pole of the rotating magnets. Pairs of flux detectors are interposed on opposite sides of the rotating magnet. The magnets are rotated at a sufficiently high rate of speed relative to the longitudinal motion of the pipe since the flux field interruptions in the same incremental area of the pipe. Again, complex circuitry is required in order to coordinate the sensor input from each

of the sensing units because of the high rotational speed (320 revolutions per minute in the example

set forth in 730) in order to keep track of the sampled signals from the two overlapping sensors and further, to coordinate them to a longitudinal position along the pipe. At a longitudinal travelling speed of 80 feet per minute as set forth in the example, the device must make four complete

revolutions during every one foot of travel, which is consistent with the sensor field slightly over three inches long, so that 100% of the pipe surface can be covered.

Pipeline flaw detectors for use inside of existing pipelines have also provided rotary

mechanisms for rotating sensing shoes helically through the pipeline as the detector is moved linearly therealong. One such device is disclosed in U.S. Patent No. 3,238,448 which, upon

detecting a flaw, actuates a strong electromagnet to magnetize the corresponding portion of the pipeline so that the position of the defect can be detected from aboveground with magnetic sensors. This device rotates two opposed search units in a single direction such that only very large flaws

can be accurately detected and locating any such detected flaws is dependent upon a second careful

searching action for the magnetized pipe section from above ground.

Another pipeline inspection apparatus is disclosed in U.S. Patent No. 4,072,894 which produces a circumferentially directed magnetic flux field as flux leakage detection sensors are

resiliently held against the pipe wall surface and helically moved through the pipe to pass

transversely across any longitudinally extending anomalies in the pipe wall.

One of the most popular and currently the most widely used state-of-the-art internal magnetic flux gas pipe inspection devices comprises a pipeline pig which has sealing cups around the exterior perimeter to both center the apparatus and to drive it by differential gas pressure along

the pipeline. A magnetic flux is generated by multiple circumferentially spaced magnets with north and south poles axially spaced apart and a magnetic flux sensor interposed therebetween, m operation, the pig travels linearly through the pipeline and sensory input data from each sensor is

recorded as a function of distance of travel. When a defect, void, or other anomaly in the pipe is

indicated by sensing an interruption of a smooth longitudinal magnetic flux, then such an anomaly is recorded on a graph as a function of time or distance. A major drawback of this device is that the longitudinal, or axially aligned, magnetic flux cannot always detect longitudinal voids or defects such as a unifoπn deterioration along a continuous welded seam of the pipeline. Resolution is

determined by the size of the multiple sensor unit. A second set of circumferentially positioned magnetic flux generators and flux leakage sensors can be positioned at a small staggered distance with respect to the first set so that the space between the flux generator and sensor shoes is covered

by the second set of sensors.

One of the regulations that both state and federal agencies have is a requirement that each

length (joint) of pipe installed in a pipeline be documented as to the "grade" of steel used in the making of the joint of pipe. The records of many pipelines have been lost or poorly kept. The

Federal Department of Transportation (DOT) has, as of 1997, given the pipeline owners five years to bring their records into compliance. Line pipe is identified by size, wall thickness and grades.

Intelligent pigs, as described hereinbefore, presently measure thickness, joint length, geographic position and other physical parameters. Pipe grade is controlled by the steel mill which produces

the pipe. It is confirmed by testing. The grade can be confirmed by pressure tests and tensile tests.

Over the years, mill records for joints of pipe may be lost and/or undocumented joints may be

placed in the pipeline. Should a pipeline contain one or more undocumented pipe joints, the DOT regulations require that the pipeline be operated at pressures assuming the pipe grade is 24,000 p.s.i. This would require that many pipelines lower their operating pressure to uneconomical levels.

Many pipelines in the U.S. are operating in excess of the legal allowable pressures.

In order to "document" the grade of the pipe joints, two techniques can be employed. First, coupons may be cut from the line at various intervals. These coupons are then tested by pulling to yield so as to determine tensile strength. This method requires that the line must be removed from

service. As such, this is a costly approach. Furthermore, this method can produce damage which may accelerate pipeline failure.

An alternative technique is to show that the pipe is of the grade the pipeline is rated at by a preponderous of evidence. To establish the grade of the pipeline, it is important to note that grades of pipe made at approximately the same time (year) have the same basic properties of: (1) chemical composition; (2) density (velocity of sound); (3) magnetic (eddy current field) and (4) hardness (Vickers B indentation). By measuring one or more of these properties in a documented joint of pipe in a line, other joints can be compared to this "standard". In this manner, each joint can be confirmed to be the same or different than the "standard" joints of pipe. This method allows for an

intelligent inspection tool (i.e. the pig) to be designed to compare the grade of each joint of pipe. When coupled with the information from another tool, such as a Geopig, its location in the pipeline, its geodetic position, and the grade of each joint can be verified.

Presently, tests of density (speed of sound), and magnetism (conductivity) can be achieved

with the pigs of the prior art, as described herein previously. A hardness test may be made with a

MICRODUE (MIC 10). This established hardness tester operates according to the ultrasonic

contact impedance method. This method enables quick and easy measurements by positioning the probe and reading off the value. This operational ease is achieved because Vickers diamond indent

in the material's surface is electronically measured and instantly displayed as a hardness value without using the cumbersome optical evaluation of the microscope normally associated with Vickers hardness testing. The MIC 10 is a very easy instrument to use. It is a hardness tester that can be transported anywhere for testing components at any location. The small narrow probe can

even enable one to make measurements at positions that are difficult to access, such as tooth flanks or roots of gears. It can be measured in any direction, e.g. in the horizontal or overhead position.

In order for the MIC 10 probe to be properly used, it must remain relatively static relative to the item to be tested. Once the reading is obtained, the data can be transmitted via an RS232C port to a master data memory located at a desired location.

It is an object of the present invention to prove a method and apparatus for the testing of the hardness of an interior surface of a pipeline.

It is another object of the present invention to prove a method and apparatus which allows an MIC 10 probe to remain static during the movement of a pig through the pipeline.

It is a further object of the present invention to prove a method and apparatus which facilitates the determination of the grade of the pipeline by a preponderance of evidence.

It is a further object of the present invention to prove a method and apparatus for the

measurement of the hardness of a pipe which allows for the documentation of the grade of pipe joints.

It is still a further object of the present invention to prove a method and apparatus for the measurement of pipeline hardness which is easy to use, easy to install, easy to manufacture, and relatively inexpensive.

These and other objects and advantages of the present invention will become apparent from

a reading of the attached specification and appended claims.

SUMMARY OF THE INVENTION

The present invention is an apparatus for testing the hardness of a pipe which comprises a body having a longitudinal axis, a probe connected to the body and extending transverse to the

longitudinal axis, a retention device connected to the probe and positioned within the body so as to maintain the probe in a fixed position relative to the pipe while the body is moving in the pipe, and processor connected to the probe so as to convert the signal from the probe into a humanly

perceivable indication of pipe hardness. The probe serves to contact the inner surface of the pipe so as to produce a signal relative to the hardness of the pipe.

In the preferred embodiment of the present invention, the body comprises a first cup, a

second cup, and a guide rod(s)connected to the first cup at one end and to the second cup at another end. The probe is connected to the guide rod(s). The probe comprises a housing which is received by the guide rod(s) and extends transverse to the longitudinal axis of the guide rod(s), and a probe member mounted within the housing and extending transversely to the guide rod(s). An actuation means is connected to the housing for selectively urging the probe member outwardly of the housing so as to contact the pipe. Specifically, the actuation means includes a solenoid connected to the

probe member for causing the probe member to move outwardly of the housing in response to a

signal from a remote location. The actuation means also includes a return spring connected to the probe member so as to return the probe member to a home position when the solenoid is deactivated. In the preferred form of the present invention, the retention device includes a brake

shoe which is affixed to the probe member. The brake shoe is engagable with an inner wall of the pipe so as to resist longitudinal movement of the probe member along the pipe. The retention device further includes a stop member affixed along a length of the guide rod(s). A spring extends

between the stop member and the housing. The spring serves to urge the housing to a home position

following the contacting of the probe with the inner surface of the pipe. The housing is slidable

along the guide rod(s) between the home position and the stop member during the contacting of the probe with the inner surface of the pipe. In an alternative form of the present invention, the probe includes a wheel which is rotatably

mounted to the body. The wheel has a rim with a surface suitable for contacting the inner surface

of the pipe. A probe holder is slidably mounted within the wheel. The probe holder serves to move radially outwardly and inwardly along a slot in the wheel relative to a rotation of the wheel. A probe member is mounted in the probe holder. The retention device is an arm which is slidably and

pivotally connected to the body. The arm is pivotally connected at another end to the probe holder. The body has a slide bearing slidably receiving the arm such that the arm is slidable within the slide bearing when the probe contacts the inner surface of the pipe. The wheel has an axis of rotation transverse to the longitudinal axis of the body. The wheel has a hub portion and a rim portion. The

rim portion has an elastomeric outer surface. The probe holder is connected to the hub portion and is offset from the axis of rotation of the wheel. A ball-and-socket joint may be used to connect the probe holder to the hub portion.

The present invention is furthermore a method of testing the hardness of the pipe which comprises the steps of: (1) forming a body having a size suitable for fitting within the pipe; (2)

moving the body longitudinally through the pipe; (3) extending a hardness probe outwardly of the body so as to contact a point on an inner surface of the pipe for a desired period of time while the

body moves longitudinally through the pipe; and (4) producing a signal relative to a hardness of the pipe at that point. The body moves continuously longitudinally through the pipe while the hardness

probe contacts the point on the inner surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a cross-sectional side view showing the pig of the present invention as installed

within a pipeline. JO- FIGURE 2 is a cross-sectional view of the present invention as taken across lines 2-2 of

FIGURE 1.

FIGURE 3 is a cross-sectional side view showing an alternative foi of the apparatus of the present invention.

FIGURE 4 is a plan view of the apparatus as shown in FIGURE 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGURE 1, there is shown at 10 the apparatus of the present invention for the testing of the hardness of a pipe 12. As shown in FIGURE 1, the apparatus 10 includes a body 14 having a longitudinal axis, a probe means 16, and a retention means 18. The body 14 is formed by a first cup 20, a second cup 22 and at least one guide rod 24 extending between the first cup 20 and

the second cup 22. Specifically, the guide rod 24 is connected to the first cup 20 at an end 26 and is connected to the second cup 22 at another end 28. Each of the cups 20 and 22 has an outer diameter which is suitable for fitting within the inner diameter of the pipe 12. The guide rod 24 can be used to house the electronics and processing means so as to receive the information from the

probe 16.

In normal use, the body 14 will be installed in the pipeline 12 and moved continuously

through the annules of the pipeline 12 when a pressure of liquid or gas is pumped behind the second cup 22. This propels the body 14 forwardly continuously through the pipeline 12 in the direction

30. As will be described hereinafter, the guide rod 24 is actually three guide rods that are positioned

centrally of the body 14 and offset from each other by 120°. The guide rod 24 extends

longitudinally in the pipe 12 and generally in axial alignment with the pipe 12.

In FIGURE 1 , it can be seen that the hardness probe 16 extends transversely to guide rod 24.

Specifically, the housing 32 of the probe 16 is received slidably by the guide rod 24 and extends transversely to the guide rod 24. A probe member 34 is mounted within the housing 32 and also extends transversely to the longitudinal axis of the guide rod 24. A more detailed illustration of the probe member 34 is shown in FIGURE 2.

The housing 32 can suitably contain the electronics for the probe member 34. As was recited herein previously, the probe member 34, and associated electronics, are associated with the MIC 10 probe. A processor can be connected to such a probe so as to convert the signals as transmitted by the probe member 34 relative to the hardness of the pipe 12 so as to produce a humanly perceivable

indication of the pipe hardness. These signals can be retained in memory within the body 14 of the apparatus 10 or the signals can be transmitted outwardly of the pipeline 12 for receipt in a remote location.

A solenoid switch 36 is received by the housing 32. Solenoid switch 36 serves to actuate the probe member 34 at a desired point in time. When the solenoid switch 36 actuates the probe member 34, the probe member 34 will come into contact with the inner surface 38 of pipe 12. As

such, the hardness at the point 40 can be suitably measured by the probe member 34. Since it is a requirement to maintain the probe member 34 in static contact with the inside wall 38 of the pipe 12, a structure is formed so as to allow for this static contact even though the body 14 is moving continuously through the interior of the pipe 12. The design of the apparatus 10 of the present

invention holds the probe 34 in static contact normal to the access of the pipe 12 for approximately 30 milliseconds (approximately one inch of travel of the body 14). Typically, the body 14 will be moving in pipe 12 at approximately two miles per hour.

The present invention maintains the static contact by the incorporation of a stop member 40

and a spring 42. The stop member 40 bears on one end of the spring 42. The spring 42 extends around the guide rods 24 and has an opposite end contacting the surface of the housing 32. When the probe member 34 contacts the inner surface of pipe 12, the movement of the housing 32 is temporarily "braked". This will momentarily cause the housing 32 to slide along the guide rod 24 toward the stop 40. After a measurement has been suitably taken, the solenoid switch 36 will cause

the probe member 34 to be retracted back into the housing 32. The spring 42 will then return the housing 32 to its home "position". This action occurs even though the body 14 is moving continuously through the interior of the pipe 12. Another stop 44 is provided on the guide rod 24

so as to limit the forward movement of the 32 and to serve as a limit as to the "home" position. The hardness measurements are taken as the housing moves from stop 44 to stop 40.

FIGURE 2 shows an illustration of the housing 32 and the probe 34. The housing 32 has a generally circular form with semi-circular indentations 50, 52 and 54 spaced evenly therearound.

The solenoid switch 36 is positioned generally centrally of the housing 32. It can be seen that holes

56, 58 and 60 serve to receive the guide rods 24. The holes 56, 58 and 60 should have a suitable diameter so as to allow the housing 32 to easily slide along the guide rods 24. The holes 56, 58 and 60 are offset from each other by approximately 120°.

The probe 36 includes an electronic solenoid 62 that is connected to the solenoid switch 36. The solenoid switch 36 serves to actuate the solenoid 62 so as to push the end of the probe 36 outwardly of the outer edge 64 of housing 32. A brake shoe 66 is affixed to the end of the probe 34. Brake shoe 66 is contoured so as to engage the inner surface 38 of the pipe 12 and also so as

to hold the housing 32 static relative to the pipe 12. The end of the probe 34 is pushed through a

hole in the brake shoe so as to carry out the hardness test. The solenoid switch 36 serves to activate the solenoid 62 so as to cause the end of the probe 34 to extend outwardly so as to contact the inner

surface 38 of the pipe 12. A spring 68 extends around the solenoid 62 so as to urge the end of the

probe 34 back within the housing 32 when the solenoid 62 is deactivated.

It is important to note that the housing 32 contains hardness probes 34, 70 and 72 located

at 120° to each other. Each of these probes 34, 70 and 72 are simultaneously actuated by three separate solenoids 62 associated with each of the probes. The switch 36 will serve to actuate each

of these solenoids so that each of the probes 34, 70 and 72 are pushed outwardly of the outer surface

64 of housing 32. Each of the probes 70 and 72 have a configuration identical to that of probe 34.

The static time required to obtain the test is the time that the pig apparatus 10 takes to travel the distance between on/off stops located on the guide stops 44 and 40 on the guide rods 24. The distance between the on/off rods can be adjusted to obtain the optimum static time of the sensor

housing relative to the pipe for the hardness tester to make a valid measurement. The measurement is digitally recorded on the on-board memory and after each cycle of the apparatus 10.

It is important to note that the body 14 and/or the housing 32 can incorporate various other sensors, such as eddy current, magnetism, sound velocity.

FIGURE 3 shows an alternative embodiment of the hardness testing apparatus 100. As can be seen in FIGURE 3, the hardness testing apparatus 100 includes a wheel 102 having an elastomeric outer surface 104 that rides along against an inside wall 106 of a pipeline 108. A probe holder 110 is mounted within a slot 112 in the wheel 102 such that a probe tip 114 contacts the

surface 106 during the rotation of the wheel 102.

The wheel 102 of a proper diameter is mounted on a cantilevered axle 116 mounted to the body 118 of the pig apparatus 100. The wheel 102 has an inside diameter 104 which is set such that it is in contact with the inside wall 106 of the pipeline 108. The axis of the wheel is set to follow the axis of the pipeline 108. The slot 112 is cut into the rim 120 of the wheel 102 so as to allow

access to the pipe wall 106 by the probe 114. The rim 120 of the wheel 102 is wide enough to

permit the contoured hard rubber tire surface 104 to maintain smooth contact with the pipe wall 106 as the slotted section 112 is rotated past the pipe wall. Guide mount rods 122 and 124 are connected

to the probe holder 110 so as to facilitate the fixing of the position of the probe 114 during the

continuous movement of the pig apparatus through the interior of pipeline 108. Probe 114 includes instruments 126 for recording and obtaining signals relative to the hardness ofthe pipeline 108. The

probe holder 110 will move upwardly and downwardly in slot 112 relative to the rotation ofthe wheel 102. A ball-and-socket joint 128 is connected between the probe holder and the hub 120 of

the wheel 102 so as to facilitate the upward and downward movement ofthe probe holder 110. The probe holder 110 and the slot 112 serve to convert the rotational movement ofthe wheel 102 into rectilinear movement. A spring 130 is provided on the end ofthe probe instrument 126 so as to urge the probe 114 outwardly.

In FIGURE 4, it can be seen how the apparatus 100 is mounted within the pig 118. Initially,

it can be seen that an axle 116 extends from the wall of body ofthe pig 118 so as to be rotatably connected to the hub 120 ofwheεl 102. The rim 132 ofthe wheel 102 includes an elastomeric outer surface 104. The ball-and-socket joint 128 connects the hub 120 of wheel 102 to the probe holder

110. Probe holder 110 will move upwardly and downwardly within slot 112 formed in the wheel 102. The probe member 114 is shown as centrally located on the probe holder 110.

Importantly, in FIGURE 4, it can be seen how the apparatus 110 maintains static contact with the inner wall 100 ofthe pipeline 108 as the pig 118 moves through the interior ofthe pipeline

108. As can be seen, a first arm 134 is connected, at one end, to the probe holder 110. Another arm

136 is connected at one end to the opposite side ofthe probe holder 110. The arm 134 is slidably received within a slide bearing 138. Slide bearing 138 is mounted to the inner wall 140 ofthe pig 118 opposite the axle 116. Similarly, the arm 136 is slidably received by slide bearing 142. Slide

bearing 142 is fixedly mounted to the inner surface 140 ofthe pig 118.

As the wheel 102 rotates, the ball-and-socket joint 128 causes the probe holder 110 to

transcribe a circle. The ball-and-socket joint 128 is located approximately one inch from the axis

116 ofthe wheel 102. The holder 110 is constrained by the guides 122 and 124 by arms 134 and 136, respectively. Arms 134 and 136 are held by slide bearings 138 and 142, respectively. These slide bearings 138 and 142 are fixedly mounted to the structure 140 ofthe pig 118. As such, the

arms 134 and 136 can only be moved horizontally. As the ball-and-socket 128 drives the probe holder 110 past the horizontal, the probe 114 is forced to move downwardly. The probe 114 is constrained from rotating so as to push the probe 114 against the wall 106 ofthe pipeline 108. The

spring 130 located on the top ofthe probe 114 allows the probe 114 to be push against the wall 106 ofthe pipeline 108. The combination of the horizontal sliding ofthe guide shoe and the vertical sliding ofthe holder 110 converts the rotation ofthe wheel 102 into rectilinear motion. The spring keeps the probe 114 in contact with the wall 106. The result ofthe above is to place the probe in static contact with the wall ofthe pipeline and to hold it there for approximately one inch of travel

of the pig 118.

Within the concept ofthe present invention, the pig apparatus, in either ofthe embodiments, can incorporate electrical conductivity and velocity of sound as further measurements of the respective pipes. As such, it is possible to further compare unknown joints of pipe to known joints of pipe in a pipeline. The present invention is intended as an improvement and an addition to existing pig apparatus. The improvement is the incorporation ofthe hardness test in a manner which

can easily and simply obtain hardness information as to the nature and quality ofthe pipeline.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details ofthe illustrated construction may be made within the scope

of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.

Claims

CLAIMSWE CL.AIM:

1. An apparatus for testing hardness of a pipe comprising: a body having a longitudinal axis; a probe means connected to said body and extending transverse to said longitudinal axis, said probe means for contacting an inner surface ofthe pipe so as to produce a signal relative to a hardness ofthe pipe;

retention means connected to said probe means and positioned within said body, said retention means for maintaining said probe means in a fixed position relative to the pipe while said body is moving in the pipe; and

processing means connected to said probe means so as to convert said signal to a humanly perceivable indication of pipe hardness.

2. The apparatus of Claim 1, said body comprising:

a first cup; a second cup; and

a guide rod connected to said first cup at one end and to said second cup at another end, said probe means being connected to said guide rod.

3. The apparatus of Claim 2, said probe means comprising:

a housing received by said guide rod and extending transverse to said guide rod; and a probe member mounted within said housing and extending transversely to said

guide rod.

4. The apparatus of Claim 3, further comprising: actuation means connected to said housing, said actuation means for selectively moving said probe member outwardly of said housing so as to contact the pipe.

5. The apparatus of Claim 4, said actuation means comprising: a solenoid means connected to said probe member for causing said probe member to move outwardly of said housing in response to a signal from a remote location; and

a return spring means connected to said probe member so as to return said probe member to a home position when said solenoid means is deactivated.

6. The apparatus of Claim 3, said retention means comprising:

a brake shoe affixed to said probe member, said brake shoe engagable with an inner wall ofthe pipe so as to resist longitudinal movement of said probe member along the pipe.

7. The apparatus of Claim 3, said retention means comprising: a stop member affixed along a length of said guide rod; and a spring means extending between said stop member and said housing, said spring

means for urging said housing to a home position following the contacting of said probe means with the inner surface ofthe pipe.

8. The apparatus of Claim 7, said housing slidably along said guide rod between said home

position and said stop member during the contacting of said probe means with the inner surface of the pipe.

9. The apparatus of Claim 3, said guide rod comprising:

a first guide rod slidably connected to said housing; a second guide rod slidably connected to said housing; and a third guide rod slidably connected to said housing, said first, second and third guide

rods having longitudinal axes in parallel relation to each other, said first, second and third guide rods being offset from each other by 120┬░.

10. The apparatus of Claim 9, said probe member comprising: a first probe member mounted within said housing and extending transverse to said

longitudinal axes ofthe guide rod; a second probe member mounted within said housing and offset by approximately 120┬░ from said first probe member, said second probe member extending transverse to said longitudinal axes ofthe guide rod; and a third probe member mounted within said housing and offset by approximately 120┬░ from said first and second probe members, said third probe member extending transverse to said longitudinal axes of the guide rod, each of said first, second and third probe members being

simultaneously actuable so as to contact the inner surface ofthe pipe.

11. The apparatus of Claim 1, said probe means comprising: a wheel rotatably mounted to said body, said wheel having a rim with a surface

suitable for contacting the inner surface ofthe pipe;

a probe holder means slidably received within said wheel, said probe holder means for moving radially outwardly along a slot in said wheel relative to a rotation of said wheel; and

a probe member mounted in said probe holder means.

12. The apparatus of Claim 11, said retention means comprising:

an arm slidably and pivotally connected to said body, said arm pivotally connected at another end to said probe holder means.

13. The apparatus of Claim 12, said body having a slide bearing slidably receiving said arm, said arm slidable within said slide bearing when said probe means contacts the inner surface ofthe pipe.

14. The apparatus of Claim 11, said wheel having an axis of rotation transverse to said longitudinal axis of said body.

15. The apparatus of Claim 11 , said wheel having a hub portion and a rim portion, said rim portion having an elastomeric outer surface, said probe holder means being connected to said hub portion in a position offset from an axis of rotation of said wheel.

16. The apparatus of Claim 15, said probe holder means comprising: a ball-and-socket means having one end cantably connected to said hub portion, said ball-and-socket means having another end attached to a probe holder, said ball-and-socket means

for moving said probe holder rectilinearly within said slot in said wheel relative to a rotation of said

wheel.

17. A method of testing the hardness of a pipe comprising the steps of: forming a body having a size suitable for fitting within the pipe; moving the body longitudinally through the pipe;

extending a hardness probe outwardly of said body so as to contact a point on an inner surface ofthe pipe for a desired period of time while said body moves longitudinally through the pipe; and producing a signal relative to a hardness ofthe pipe at said point.

18. The method of Claim 17, said body moving continuously longitudinally through said pipe while said hardness probe contacts said point on said inner surface.

19. The method of Claim 18, further comprising the steps of: sliding said hardness probe within said body while said body moves continuously through the pipe.

20. The method of Claim 17, further comprising the step of: processing the signal so as to convert said signal into a humanly perceivable

indication of hardness.