Ultrasonic testing

The invention provides apparatus for ultrasonically testing the edges and/or the body of a metallic workpiece, utilizing water as a coupling medium between ultrasonic transducers and a metallic product moving relative to the testing apparatus along a predetermined pathway; which apparatus comprises guide means defining the pathway to be followed by the metal product, one or more reservoirs being the pathway each incorporating a top opening through which water can overflow to contact successive parts of the piece to be tested, located thereabove and a plurality of ultrasonic transducers located in one or more groups within the reservoir or reservoirs and directed towards the edge or body of the piece to be tested so that they may be static, adjustable transverse to the direction of movement of the product along the pathway, or reciprocate in a sinusoidal manner to traverse all or part of the pathway.

This invention relates to ultrasonic testing, and more particularly to the 
ultrasonic testing of the edges and/or the bodies of metallic products 
such as steel plates or steel pipes. Where the edges of steel plates are 
to be subjected to welding, such as in the production of pipe by the 
welding of separate plates together, or the welding of opposite edges of 
spirally wound strip together, detailed inspection of the opposed welding 
edges is necessary to ensure good quality for welding so as to reduce to a 
minimum welding faults during production of the pipe. 
Again, the opposed end edges of tubes and pipes, which are to be connected 
together by welding for example, need to be quality inspected. 
It has previously been proposed to test the bodies of products of this kind 
by moving the product along a line of travel adjacent to a water reservoir 
such that water from the reservoir contacts successive parts of the 
product to be tested. At the same time there is provided in the reservoir 
a beam carrying a plurality of ultrasonic transducers spaced therealong. 
In practice as the product is moved past the reservoir the beam is 
reciprocated axially by means of a pneumatic or hydraulic piston and 
cylinder set, whilst the transducers are activated to transmit pulses into 
the product and receive reflections thereof from the product using the 
reservoir water as an accoustic coupling medium. 
Although apparatus of this kind (hereinafter called "apparatus of the kind 
referred to") is capable of valuable inspection work with respect to 
products such as steel plate, it does incorporate a problem in that the 
beam reciprocation does not in practice perform at constant velocity so 
that a full area inspection of the product as it passes is not always 
exactly obtained. 
It is an object of the present invention to provide for the effective and 
convenient testing of metallic products. 
According to the invention there is provided apparatus for ultrasonically 
testing the edges and/or body of a metallic work piece, utilising water as 
a coupling medium between ultrasonic transducers and a metallic product 
moving relative to the testing apparatus along a generally predetermined 
pathway; which apparatus comprises guide means defining the pathway to be 
followed by the metal product, one or more reservoirs below the pathway 
each incorporating a top opening though which water can overflow to 
contact successive parts of the piece to be tested located thereabove, and 
a plurality of ultrasonic transducers located in one or more groups within 
the reservoir or reservoirs and directed towards the edge or body of the 
piece to be tested so that they may be static or reciprocate in a 
sinusoidal manner to traverse all or part of the pathway and may be 
adjustable transverse to the direction of movement of the product along 
the pathway in order to change the position of the area of inspection. 
In one embodiment of the invention there is provided apparatus for 
simultaneously ultrasonically testing the opposed edges of a metallic 
workpiece utilising water as a coupling medium between ultrasonic 
transducers and a metallic product moving relative to the to the testing 
apparatus along a predetermined pathway, which apparatus comprises guide 
means defining the pathway to be followed by the metal product; one 
reservoir for water having a top opening and so arranged in relation to 
the pathway as to be immediately below one edge of the metal product, a 
second reservoir for water having a top opening and moveably mounted on a 
carriage way transverse to the pathway so as to be capable of positioning 
immediately below the opposed edge of the metal product, water supply 
means to the two reservoirs arranged to provide a continuing supply of 
water thereto so as to overflow in use from the top of the reservoir to 
contact with the metal product passing along the pathways thereabove, and 
a plurality of ultrasonic transducers located within each reservoir and 
directed towards the edge of the metal product passing thereacross. The 
invention includes within its scope a method of ultrasonic testing using 
the apparatus herein defined. 
Another embodiment of the invention provides apparatus of the kind referred 
to including means for reciprocating the beam in operation of the 
arrangement wherein said means is arranged to provide a sinusoidal drive 
for the beam. 
The means for providing the sinusoidal drive for the beam may comprise a 
crankshaft drive. 
In a preferred embodiment the water reservoir has a narrow overhead opening 
through which, in operation, water is allowed to escape. In such an 
arrangement the product is arranged such that its path of travel lies 
across the overhead opening of the reservoir whereby the product impinges 
upon escaping water from the reservoir as it passes thereacross. 
Previous proposals for the use of a pneumatic cylinder for example to drive 
the reciprocating beam theoretically involve the beam in a movement with 
constant velocity so that each ultrasonic transducer describes a saw-tooth 
inspection pattern along the length of the product in operation. We have 
found that in practice however such a cylinder does not provide constant 
velocity, and that in addition, at the beginning and end of each stroke 
there is an inevitable total pause in movement of the beam. The result of 
this is that a significant area of the product is not inspected in 
operation and the saw-tooth pattern described by the transducers is 
considerably distorted. 
By means of a drive according to the invention each transducer on the beam 
describes a sinusoidal inspection path along the surface of the workpiece 
capable of providing a true and even test pattern across the product.

In FIGS. 1, 2 and 3 of the drawings water reservoirs 1 and 2 have inlets 3 
continuously supplied with water from the pipes 4. Each reservoir has an 
upper or top opening 5 through which water wells up to contact and provide 
accoustic coupling with a steel plate workpiece 6, before draining away 
down the outside of the reservoir, whence it can be collected and 
recycled, after filtration if necessary, to the supply pipes 4. The water 
inlets are controlled by valves 7 so as to give a desired even flow of 
water through the openings. 
The two reservoirs are situated between two sets of rollers 8 and 9 of a 
roller table along which the steel plates 6 can be driven. 
A plate is shown travelling between these two rollers, the top of the 
reservoirs is just below the lower face of the plate as it passes, and 
sufficiently close so that the water welling up from the upper openings 
thereof contacts the plate in a continuously replenished pool. 
It is to be noted that one reservoir 1 is located beneath one side edge 10 
of the steel plate 6, whilst the other reservoir 2 is mounted on a 
carriage 11 moveable by means of a motor 24 transverse to the direction of 
travel of the plate so that it can be located below the other side edge 13 
of the plate or indeed the opposed side edge of a plate of different 
width. 
Within each reservoir is located a plurality of ultrasonic transducers 14 
connected electrically for the transmission of ultrasonic pulses and the 
receipt of echoes thereof from the plate. The transducers are connected by 
insulated electrical connections 15 to a control unit 16 which actuates 
the transducers and monitors their response. The control unit detects the 
presence of a defect in the respective edge of the plate in known manner. 
The second embodiment of the invention illustrated in FIGS. 4 and 5 
utilises the same principles of the first embodiment adapted to the 
testing of the edges of a tube 17. 
In this case, as can be seen, the tube 17 is rotated on rollers 18 and two 
reservoirs 19 and 20 are located below each of the two edges 21 and 22 of 
the tube so that the edges are tested by ultrasonic devices 23 located 
within the reservoirs in like manner to the edges of the plate illustrated 
in FIGS. 1 to 3. 
In FIGS. 6, 7 and 8, a tank 110 has three inlets 111 continuously supplied 
with water from a pipe 112. The tank has a longitudinal slot 115 in its 
top through which water wells up before draining away down the outside of 
the tank, after which it can be collected and recycled, after filtration 
if necessary, to the supply pipe 112. The inlets 111 are spaced along the 
tank and are controlled by individual valves 116 to give an approximately 
even flow of water along the length of the slot 115. 
The tank is situated between two rollers 120 of a roller table along which 
steel plates can be driven. A plate 121 is shown travelling across these 
two rollers. The top of the tank containing the slot 115 is just below the 
lower face of the plate as it passes, and sufficiently close that the 
water welling up from the slot 115 contacts the plate across its whole 
width in a continuously replenished pool 122. 
Directly under the slot 115 and parallel with it the tank 110 carries a 
beam in the form of a stainless steel tube 125 which extends through 
opposite ends of the tank through water seals 126 which permit the tube 
125 to slide axially. A crankshaft drive, comprising a crank wheel 127 and 
link lever 133, is connected to one end of the tube and is arranged to 
reciprocate the tube in the tank. 
Along the top of the tube 125 is affixed an external duct 129 carrying an 
array of ultrasonic transducers 130 directed through the slot 115. The 
length of the array of the transducer is greater than the width of the 
plate by an amount which is sufficient to ensure that at the extreme 
positions of the tube 125 during its axial reciprocation neither edge of 
the plate overreaches either end of the array of transducers. The relative 
positions and orientations of the transducers 130, the slot 115 and the 
plate 121 are such that ultrasonic energy pulses emitted by each 
transducer are reflected back to the same transducer from the plate. 
The transducers 130 are individually connected by insulated electrical 
connections 131 to a control unit 132, which actuates the transducers and 
monitors their response to ultrasonic energy reflected from the plate 121. 
The control unit 132 detects the presence of a defect in the plate in 
known manner. 
The invention can be used in other manners than that specifically described 
above in relation to FIGS. 6, 7 and 8. Thus, it is possible to inspect a 
tube rather than a plate by aligning the tube lengthways over the slot and 
then rotating the tube until its whole circumference has passed over the 
slot. 
In operation the array of ultrasonic transducers 130 describe a succession 
of evenly spaced sinusoidal inspection paths over the surface of the 
product, ensuring good full area inspection thereof. 
It will be understood that in the arrangement of FIGS. 1 to 5 both 
reservoirs 1 and 2 can be arranged for movement transverse to the 
direction of travel of the plate, so that, for example, wander of the 
edges of the plate during travel can be accommodated at both sides. Means 
may be provided, such as edge detecting switches, to enable the or each 
reservoir to follow the associated plate edge. 
By means of the invention we have provided a convenient, effective and 
simple means for testing metal products such as plates or tubes of 
different width or length.