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The Ultrasonic Testing Standard of Composite Plate for Pressure Vessel

The Area of Application of The Standard

This article is applicable to the ultrasonic testing and quality grading of stainless steel, titanium and titanium alloy, aluminum and aluminum alloy, nickel and nickel alloy, copper and copper alloy composite plates for pressure vessels with the thickness of base plate more than or equal to 6mm. Base plates are typically carbon steel, low alloy steel, or stainless steel. Using YUT Series Ultrasonic Flaw Detectors can perfectly reach the testing standards and get accurate inspection results.

 

The Selection of Ultrasonic Probes

For the various thickness of the plates, inspectors generally select the probes according to the principle showed as below:

Thickness (mm)

Adapt probe type

Frequency (Mhz)

Element size (mm)

6-20

Dual-element Straight Beam Probe

4-5

Circular wafer diameter:10-30mm

Side length of square wafer:10-30mm

20-40

Single-element Straight Beam Probe

5

φ14mm-φ20mm

40-250

Single-element Straight Beam Probe

2.5

φ20mm-φ25mm

The performance requirements of dual-element straight beam probe of ultrasonic flaw detector shall meet the following requirements.

 

Distance-amplitude characteristic curve
Use the test block in Fig. 2 of this part to measure the echo height (unit: dB) on each thickness. The characteristic curve as shown in Figure A.1 shall be made, which shall meet the following conditions:
a) The difference between the echo height on the thickness of 19mm and the maximum echo height shall be within 3dB~6dB.
b) The difference between the echo height at 3mm and the maximum echo height shall also be within 3dB~6dB.

 

Surface echoes height

The height of the surface echoes tested by direct contact method shall be 40dB lower than the maximum echo height. 

Detection Sensitivity

 

Move the probe and make it align with the 5.6mm flat-bottom hole of the test block shown in picture. The difference between the echo height and the maximum echo height should be -10dB~+2dB.

 

Inspection Surface

The inspection surface can be carried out from the surface of substrate or composite plate.

 

Coupling Mode

The coupling mode can be direct contact method and water immersion method.

 

Scanning method

A) Scanning method can be 100% scanning or parallel line scanning along the width direction of steel plate with an interval of 50mm.

B) Other scanning forms can also be used according to the requirements of the contract, technical agreement or drawings.
C) 100% scanning shall be carried out within 50mm on both sides of the groove reservation line.

 

Determination of Reference Sensitivity

Place the probe of ultrasonic flaw detector at the fully combined part of clad steel plate, and adjust the height of the first bottom wave to 80% of the full scale of the fluorescent screen. This serves as the baseline sensitivity.

 

Determination of Unconnected Area

When the height of the first bottom wave is lower than 5% of the full scale of the fluorescent screen and there is obvious unbonded defect reflection wave (≥ 5%), this part is called unbonded zone. Move the probe so that the first bottom wave rises to 40% of the full scale of the screen, with the probe center as the boundary point of the unbound zone.