GB2125251A

GB2125251A - Ultrasonic inspection apparatus

Info

Publication number: GB2125251A
Application number: GB08220893A
Authority: GB
Inventors: Alexander Mclay
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1982-07-20
Filing date: 1982-07-20
Publication date: 1984-02-29

Abstract

A rotatable ultrasonic inspection head (10) carries ultrasonic transmitters in angled bores (13, 14, 15) and the head has an inclined face (17) to reduce ultrasound reflections which could behave as further transmissions. The face has an absorbing/reflecting plate 19. <IMAGE>

Description

SPECIFICATION Ultrasonic inspection apparatus This invention relates to ultrasonic inspection apparatus.

It is well known to conduct ultrasonic inspection (especially of seam welds) in water tanks so that the ultrasonic head and the article being inspected are immersed in water with a water gap. A generally accepted code requires three inspection angles of the article (+450,00 and 450) with relatively low sensitivities. A more recent code requires nine inspection angles (+600, +450,00, f600 transverse and f450 transverse) and a sensitivity level of 20% DAC (Distance Amplitude Curve).

With known apparatus this recent code cannot be easily met due mainly to secondary reflections from the ultrasonic head and its holder and operating mechanisms behaving as further ultrasonic transmissions.

According to the present invention ultrasonic inspection apparatus providing nine inspection angles is characterised in that three ultrasonic probes are provided in a rotatable head to give respectively 600, 450, and 0 transmissions, and the head is provided with deflecting/absorbing surfaces so as to reduce ultrasound reflections which could behave as further ultrasonic transmissions.

A rotatable head suitable for use with the invention will now be described with reference to the accompanying drawing in which: Figure 1 is a front elevation ; and Figure 2 is a section on the line Il-Il of Figure 1.

The head 10 is carried on a shaft 11 for rotation about an axis 12. The head is of circuiar form, as seen in Figure 1, and has an approximately triangular section, as seen in Figure 2. The head is perforated by ultrasonic head supporting apertures 13, 14 and 1 5. Aperture 13 provides for 0 ultrasonic transmissions, aperture 14 provides for 450 transmission and aperture 1 5 provides for 600 transmissions.

The head 10 has an upper inclined face 1 6 (which serves no direct function except to provide reduction of weight of the head 10), a lower inclined face 17, and a rear face 18. Face 16 makes an angle of 450 and face 17 makes an angle of 170 with the face 18. Face 17 is covered with a thin stainless steel plate 19 having a highly polished reflective surface whilst the remainder of the assembly is of ultra-sound absorbing material (such as that available under the mark "Derlin").

In use, the head 10 is rotated to various angular positions and the plate 19 taken with the inclination of face 17 reduces problems of selecting a relatively weak "genuine" signal from a mass of relatively strong "unwanted" signals which would otherwise arise from reflections from a "vertical" face 1 7. The removal of "unwanted" signals arises from the inclination of the face 17, the reflective surface of plate 19, and the attenuation of plate 1 9.

Testing suggests that five times greater sensitivity is achieved with a head having the inclined face 17 and plate 1 9 when compared with a head having an unplated face 1 7 parallel to the rear face.

The head 10 finds use for inspections inside pressure vessels (such as Pressurised Water Reactor pressure vessels) in the "as clad" or the "ground clad" conditions at manageable water gaps for all main seam welds and cooling water nozzles in the vessels.

Claims (Filed on 30.3.83) 1. Ultrasonic inspection apparatus comprising a rotatable head (10) carrying ultrasonic probes giving respective angles of transmission at least in the range of 00--600 in which the head is provided with deflecting surfaces (1 7) so as to reduce ultrasound reflections from the head which could behave as further ultrasonic transmissions.

2. Apparatus as claimed in claim 1 having a front face (17) which is penetrated by the axis (12) of rotation of the head and is inclined, at an angle greater than the largest angle in said range, to said axis of rotation to reduce reflections.

3. Apparatus as claimed in claim 2 in which the front face carries an attenuating plate (19).

4. Apparatus as claimed in claim 3 in which the exposed face of the attenuating plate is polished.

5. Apparatus as claimed in claim 2 including a further front face (1 6) which is not penetrated by the axis of rotation of the head but is inclined in a manner to reduce the bulk of the head.

6. Ultrasonic inspection apparatus comprising a rotatable head substantially as hereinbefore described with reference to the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Ultrasonic inspection apparatus This invention relates to ultrasonic inspection apparatus. It is well known to conduct ultrasonic inspection (especially of seam welds) in water tanks so that the ultrasonic head and the article being inspected are immersed in water with a water gap. A generally accepted code requires three inspection angles of the article (+450,00 and 450) with relatively low sensitivities. A more recent code requires nine inspection angles (+600, +450,00, f600 transverse and f450 transverse) and a sensitivity level of 20% DAC (Distance Amplitude Curve). With known apparatus this recent code cannot be easily met due mainly to secondary reflections from the ultrasonic head and its holder and operating mechanisms behaving as further ultrasonic transmissions. According to the present invention ultrasonic inspection apparatus providing nine inspection angles is characterised in that three ultrasonic probes are provided in a rotatable head to give respectively 600, 450, and 0 transmissions, and the head is provided with deflecting/absorbing surfaces so as to reduce ultrasound reflections which could behave as further ultrasonic transmissions. A rotatable head suitable for use with the invention will now be described with reference to the accompanying drawing in which: Figure 1 is a front elevation ; and Figure 2 is a section on the line Il-Il of Figure 1. The head 10 is carried on a shaft 11 for rotation about an axis 12. The head is of circuiar form, as seen in Figure 1, and has an approximately triangular section, as seen in Figure 2. The head is perforated by ultrasonic head supporting apertures 13, 14 and 1 5. Aperture 13 provides for 0 ultrasonic transmissions, aperture 14 provides for 450 transmission and aperture 1 5 provides for 600 transmissions. The head 10 has an upper inclined face 1 6 (which serves no direct function except to provide reduction of weight of the head 10), a lower inclined face 17, and a rear face 18. Face 16 makes an angle of 450 and face 17 makes an angle of 170 with the face 18. Face 17 is covered with a thin stainless steel plate 19 having a highly polished reflective surface whilst the remainder of the assembly is of ultra-sound absorbing material (such as that available under the mark "Derlin"). In use, the head 10 is rotated to various angular positions and the plate 19 taken with the inclination of face 17 reduces problems of selecting a relatively weak "genuine" signal from a mass of relatively strong "unwanted" signals which would otherwise arise from reflections from a "vertical" face 1 7. The removal of "unwanted" signals arises from the inclination of the face 17, the reflective surface of plate 19, and the attenuation of plate 1 9. Testing suggests that five times greater sensitivity is achieved with a head having the inclined face 17 and plate 1 9 when compared with a head having an unplated face 1 7 parallel to the rear face. The head 10 finds use for inspections inside pressure vessels (such as Pressurised Water Reactor pressure vessels) in the "as clad" or the "ground clad" conditions at manageable water gaps for all main seam welds and cooling water nozzles in the vessels. Claims (Filed on 30.3.83)

1. Ultrasonic inspection apparatus comprising a rotatable head (10) carrying ultrasonic probes giving respective angles of transmission at least in the range of 00--600 in which the head is provided with deflecting surfaces (1 7) so as to reduce ultrasound reflections from the head which could behave as further ultrasonic transmissions.