Method and apparatus for eddy current inspection of hot test pieces with means to cool the detector and to purge the test path of contaminants

DETAILED DESCRIPTION This invention provides eddy current flaw inspection apparatus which overcomes the problems of prior proposals including those problems which have been described.
This apparatus is especially suited for the inspection of steel pipe while it is still hot from fabrication.
The apparatus will determine the presence of defects in the pipe so that quality can be checked continuously as pipe is produced.
Accordingly production of imperfect pipe is minimized.
Essentially, there are two embodiments of the invention.
In an embodiment which is preferred when flaw inspection is immediately after pipe fabrication, the detector assembly is endless and surrounds the workpiece.
For inspection of selected portions such as a pipe weld and where manufacture permits space between the pipe forming machine and a detector, a segmented detector arrangement is preferred.
The endless inspection apparatus is used with pipes and bars of a wide range of sizes.
Pipe sizing operations used to form relatively small-sized workpieces cause the probability of a cobble to be relatively high.
Accordingly, a rugged endless inspection apparatus is fixed to a sizing machine to serve as a guide to direct pipe out of the machine.
In this manner the danger of a calamity resulting from a cobble is minimized.
Where the manufacturing operation permits the detector to be spaced from a pipe welder or sizer, the detection coils are positioned in movable groups in the manner described more completely in the DETECTOR CASE.
This group arrangement not only minimizes the danger of cobbles, but also facilitates repair or replacement of elements of the detection system.
There are further advantages to the multiple group arrangement which will be described presently.
One of the outstanding advantages of the present invention is the discovery that a nonmagnetic, metal heat shield may be interposed between a workpiece and a detection coil without any appreciable loss in flaw detection sensitivity.
This discovery permits the construction of a detection assembly in which excellent heat transfer characteristics are achieved