UT Equipment Calibration Procedure [PDF]

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INDEX Clause Ref... 1 2 3 4 5 6 7 8 9 10 11 12

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Scope Reference Documents Personal Test Equipment and Auxiliaries Surface Condition and Preparation Couplant Calibration Block Calibration Interval Equipment Controls Calibration Procedure Documentation Safety

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Annexure - 1

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1. Scope: 1.1. This procedure describes routine calibration of ultrasonic flaw detectors using conventional pulse echo method for the detection and evaluation of flaws in metallic components and product forms. 1.2. Only pulse-echo A-scan type instruments based on piezo-electric principle of generating and receiving sound waves have been covered. Both the Analogue and digital out put equipments are in the scope of this procedure. However, this procedure may be used for other types of instruments e. g. B-scan and C-scan types, if permitted by the relevant codes/ specifications and subject to any additional requirement stated therein. 1.3. This procedure shall not be used for calibration of ultrasonic flaw detectors with sound generation and reception based on other principles like Synthetic Aperture focusing, EMAT, Phased Array, ToFD etc. 1.4. The procedure described here is limited to the verification of linearity and calibration of A-scan type display. Calibration of electrical components is not under the purview of this procedure and shall not be used for that purpose. 2. Reference Documents: 2.1 The following documents are referred: 2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 3

ASME Section V Ed 2013 Edition: AST|M E 317. ASME Section VIII Division 1; Ed 2013 Edition. ASME B 31.1,31 2013 Edition. ASME Section I; 2013 Edition. ASNT SNT TC 1A 2006 edition.

Personnel: 3.1 All personnel performing calibration of UT equipment using this procedure shall be qualified to a minimum of Level II. (Refer 2.1.6) 3.2 Personnel performing Examination shall have vision, with correction if necessary, to enable to read Jaeger Type No. 2 Standard Chart at a distance of not less than 300mm, and differentiate the contrast between the colors and shades of gray, and records of such vision test shall be maintained by company. Vision tests shall be conducted annually and be current during examination. 3.3 Each calibration of ultrasonic equipment shall be witnessed and approved by a NDT Level III in the

relevant method. 3.4 Personnel conducting Ultrasonic Examination should be aware of the safe-practice requirements during examination. 4

Test Equipment and Auxiliaries: 4.1 The pulse-echo type instrument capable of operation at frequencies over the range of at least 1 MHz to 5 MHz and equipped with a stepped gain control in units of 2.0 dB or less are subject to the calibration on annual basis. 4.2 Search Units (Transducers) shall be either Single Crystal or Twin Crystal types. The nominal frequency shall be from 1 MHz to 5 MHz 4.3 The search units’ materials & construction shall be capable of producing either longitudinal or shear waves into the test component. Generally designated normal (0) probes should be capable of producing longitudinal waves into test component while angle probes should be capable of producing refracted shear waves in to test component at angles 45, 60, and 70 (in steel). 4.4 The nominal cross-section sizes of normal probes shall be between diameters 10 mm to 25 mm, while the cross-section sizes of angle probes shall be 8 mm x 9 mm to 20 mm x 22 mm. 4.5 Co-axial cables connecting search units with the equipment shall be of length between 1.5m. & 4m. and shall have end adapters capable of secured connections at ends; where, required adopters of various types shall be used to secure connectivity.

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Surface condition & preparation: 5.1 As the calibration block used for the purpose of instrument calibration is integrally attached to the probe supplied for calibration, surface preparation is not required. 5.2 In cases, where a separate calibration not integrally attached is used, the surface shall be prepared in such a way that areas to be scanned shall be free of all dirt, paint, loose particles, loose mill-scale, temporary attachments or any obstructive materials that could interfere with the examination.

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Couplant: 6.1 Couplants are not required when using integrally attached blocks. 6.2 For non-integral blocks, couplants are used to eliminate the air gap between the transducer and the test surface to assure maximum ultrasound transmission. The couplants will normally be a wetting agent (polycel) in water, liquid soap, sodium CMC or any other suitable couplant medium. Glycerin, light machine oil or grease may also be used.

6.3 The couplant should be selected so that its viscosity is appropriate for the surface finish of the material surface to be examined (Examination of rough surfaces generally requires high viscosity couplant). Temperature of the material surface can change the couplant’s viscosity. 7

Calibration Blocks: 7.1 Integrally attached block: N 30 calibration standard: Aluminium block of 48mm long and 38.5mm diameter (Solid cylindrical shape) attached to a 24mm diameter 2MHz longitudinal wave transducer shall be used. This block and probe assembly is supplied by Krautkrammer, manufacturer of ultrasonic flaw detectors. Refer to figure 1. 7.2 Other calibration blocks like IIW V1 or IOW standard blocks may be used. Refer to figure 2 for block details.

8. Calibration interval: Screen Height Linearity and Amplitude Control Linearity of the equipment shall be periodically evaluated; such periodicity shall be at intervals not to exceed three months for Analogue type instruments and one year for Digital type instruments or prior to first use thereafter. Results of such evaluations shall be recorded and records to be maintained.

9. Equipment controls: 9.1

Any instrument control, which affects instrument linearity (e.g. filters, reject, or clipping), shall be in the same position for calibration, calibration checks, instrument linearity checks, and examination. If the instrument has a damping control, it may be used if it does not reduce sensitivity of examination.

9.2 The reject control shall be in the “off” position for all examinations, unless it can be demonstrated that it does not affect the linearity of the examination. 10. Calibration Procedure: 10.1 Horizontal linearity: Using N30 calibration block: Place the transducer block assembly to the UT instrument socket. Keep the distance range to 500mm. Adjust probe delay to mark the first echo from 50mm of steel (48mm of Al). Measure the successive echoes at 50mm intervals. There shall not a deviation of the readings more than 5% of the measured range. Using the IIW V1 block, keep the probe at position (a) as shown in figure 3. Change the instrument distance range to 250mm so that 10 successive back wall echoes can be viewed can be seen in the display. Adjust the first back echo to 25mm and subsequently measure the echoes at 25mm intervals. There shall not a deviation of the readings more than 5% of the measured range.

10.2 Vertical Linearity: Using N30 calibration block: Place the transducer block assembly to the UT instrument socket. Keep the distance range to 200mm. Choose any two echo who make almost 2:1 ratio. Increase the gain in 2 dB steps from 20% FSH of the highest echo to 80% FSH of the highest. The increase of the lowest echo shall be in the same proportion so that the ratio between the two is within + 5% of 2:1. Using the IIW V1 block, keep the probe at position (b) as shown in figure 3. Change the instrument distance range to 200mm, so that 2 sets of back wall echoes can be viewed can be seen in the display. Follow the same procedure stated above. Alternately, Position an angle beam search unit on a calibration block similar to that shown in Fig. 4 so that indications from both the ½ and ¾ T holes give a 2:1 ratio of amplitudes between the two indications. Adjust the sensitivity (gain) so that the larger indication is set at 80% of full screen height (FSH). Without moving the search unit, adjust sensitivity (gain) to successively set the larger indication from 100% to 20% of full screen height, in 10% increments (or 2 dB steps if a fine control is not available), and read the smaller indication at each setting. The reading shall be 50% of the larger amplitude, within 5% of FSH. The settings and readings shall be estimated to the nearest 1% of full screen. 10.3 Amplitude Control Linearity: Using N30 calibration block: Place the transducer block assembly to the UT instrument socket. Keep the distance range to 200mm. Choose any echo from the back wall. Increase the gain in 6 dB steps from 20% FSH of the highest echo to 80% FSH of the highest. Similarly, decrease the instrument gain by 6dB steps from 80% to 20% FSH. The resulting values shall be within the range as given the following table. Using the IIW V1 block, keep the probe at position (c) as shown in figure 3. Change the instrument distance range to 100mm. Follow the same procedure stated above. Alternately, position an angle beam search unit on a basic calibration block, as shown in Fig. 4 so that the indication from the ½T side-drilled hole is peaked on the screen. Adjust the sensitivity (gain) as shown in the following table. The indication shall fall within the specified limits. Alternatively, any other convenient reflector from any calibration block may be used with angle or straight beam search units. The settings and readings shall be estimated to the nearest 1 % of full screen. Srl no.

Indication set at % of full screen

01 02 03 04 05

80 40 20 40 80

dB control change 00 -6 dB -12 dB +6 dB +12dB

Measured echo height

Indication limits % of full screen 32 to 48% 16 to 24% 32 to 48% 64 to 96%

Deviation

Remarks

11. Documentation 11.1

For each Ultrasonic equipment calibration as per this Procedure, the following minimum information shall be recorded and suitably addressed in the relevant Report (Refer Annexure I): 11.1.1 11.1.2 11.1.3 11.1.4 11.1.5 11.1.6 11.1.7 11.1.8 11.1.9 11.1.10

Procedure Identification and Revision Ultrasonic Instrument identification (Make / Serial No.) Search unit identification Calibration block identification: Instrument gain adjustment. Damping and Reject settings (when used): Couplant brand name or type when used: Examination personnel identity and qualification level Examination date and time. Equipment calibration status (as appropriate & applicable)

12. Safety: 12.1 All inspection personnel shall be responsible for compliance with applicable safety rules in the use of Test materials. 12.2 Some of the Calibration blocks used in Ultrasonic Testing are fairly heavy in weight, having square edges. They may be become slippery due to usage of couplants and will need to be carefully handled. 12.3

Some test materials such as couplants may cause skin irritation. Use adequate ventilation at all times and avoids prolonged skin contact.

12.4

Test materials shall never be heated above the recommended temperature limits prescribed by the manufacturer.

12.5

The test system has electrical input for the Test equipment and safe practices should be followed to avoid any electrical shocks.

38.5mm dia.

Probe

48 mm length Figure – 1 N30 calibration standard block

Figure – 2

(a) & (c) 25mm

300mm 200mm

100 85 91

(b) Figure – 3 NOTES: 1. Probe position (a): Horizontal linearity. 2. Probe position (b): Vertical linearity. 3. Probe position (c): Amplitude control linearity.

Figure – 4

ANNEXURE – 1 Calibration certificate no. 1. Equipment details: Instrument Model no.

Make

Serial no. 2. Reference Documents: a. ASME BPV Code Sec V; 2013 b. ASTM E 317 c. UT Procedure no. 3. Calibration Block details: a. Block type: N30 b. Calibration Certificate no. 058474 4. Results of calibration: Calibration types a. Vertical linearity Checks b. Horizontal Linearity Checks c. Amplitude Linearity Checks d. Operating Knobs/ buttons e. Alarms/ lights Date of calibration:

Serial no. Date:

Measured deviation See section ‘A’ See section ‘B’ See section ‘C’ Nil Nil

Tolerance Remarks +/- 5% 5% Given at ‘C’ Next calibration date:

This is to certify that the above instrument bearing serial no. has been calibrated in accordance with the requirements of ASME Sec V and ASTM E 317. Calibrated by:

Approved by:

Name:

Name:

Date:

Date:

A. Instrument Vertical Linearity: Calibration block: N30 Instrument: Calibration reference: 50mm thick block; longitudinal wave speed: 5920m/s. Srl no. 01 02 03 04 05 06 07

Instrument Gain (dB) 26.5 24.5 22.5 20.5 18.5 16.5 14.5

Echo Height A (%) 79 64 51 40 32 26 20

Echo height B (%) 38 32 25 20 16 13 10

Ratio

Remarks OK OK OK OK OK OK OK

B. Instrument Horizontal Linearity: Calibration block: N30 Instrument: USM 35 (3298a) Calibration reference: 50mm thick block; longitudinal wave speed: 5920m/s. Srl no. 01 02 03 04 05

Range (mm) 250 250 250 250 250

Echo no. 1 2 3 4 5

Metal path

Difference

Deviation

Remarks

C. Amplitude Control Linearity: Calibration block: N30 Instrument: Calibration reference: 50mm thick block; Longitudinal wave speed: 5920m/s. Srl no.

Indication set at % of full screen

01 02 03 04 05

80 40 20 40 80

dB control change 00 -6 dB -12 dB +6 dB +12dB

Measured echo height 80 41 21 41 79

Indication limits % of full screen 32 to 48% 16 to 24% 32 to 48% 64 to 96%

Deviation

+2.5% +5% +5% +2.5%

Remarks

OK OK OK OK