Ring Joint Flange Inspection

Problem: Inspection for cracking in the ring joint area of the flange.

Technique: The application of an ultrasonic method applying a pitch-catch technique assisted by a simple manipulator.

Calibration: Longitudinal ultrasonic transducers are used with calculated probe roof angles. The roof angles are optimized for the range of the sound depending on the diameter of the flange being inspected. Special consideration has been made to adjust the angle such that cracks behind the boltholes are readily detected.

Two, 1/2 “, 5 MHz, composite probes are mounted in special low angle shoes to look at the specified

 

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The Inspection for cracking in the ring joint area of the flange was done in two different methods at two different temperatures. The first using special slightly angled 0 degree probes to look between the bolt holes, and the second using low angled shear wave probes to see behind the bolt holes. Once completed during its ambient stage the flange was heated up to 200Deg. F and the tests were repeated. Both tests were looking for a notch that was only 0.050” deep. The notches could be seen both at the ambient and the elevated temperatures. There are pictures of the setup as well as the screen images. The following information has been collected on each technique.

 

Method One:

Looking between the boltholes for cracking in the ring joint area has proved the easiest technique so far. Two, half inch, 5 MHz, composite probes are mounted in special low angle shoes to look at the specified area. The probe shoes are spaced 0.1” apart to eliminate the cross talk between them. The instrument used was a Panametrics Epoch IV. Instrument settings were as follows:

	Cold	Hot
Gain	62.5dB	70.7dB
Velocity	0.2266	0.2266
Zero	15.41	15.41
Range	2.499	2.499
Frequency	5MHz	5MHz
Angle	0	0
Thick	0	0
Energy	Low	Low
Damp	50	50
Notch Amplitude	94%	94%

 

The settings may seem unusual, but they are optimized to give the best A-Scan image to the technician to distinguish signals from actual notches from other signals. With these settings, the notch signal shows up at 6.25 screen divisions and the backwall signal shows up at 8.75 screen divisions.

Method Two:

The second method uses 25-degree radiused shear waves. Mechanical Integrity use 2 transducers held in a special adjustable frame to inspect behind the boltholes for cracking. The settings for the second method are the same as the first method except for:

 

	Cold	Hot
Gain	49.8dB	49.8dB
Velocity	0.2303	0.2303
Zero	0	0
Angle	25°	25°
Energy	Max	Max
Range	Max	Max
Notch Amplitude	26%	26%

 

This technique enables the signal from the 0.050” notch in the ring joint area to be seen between the 4th and 5th screen divisions. As with any inspection, the screen range and probe delay may be changed to optimize visibility on the A-scan to operator preference as long as they do not hinder the visibility of the ultrasonic signals.