EPOCH 1000 Series ProcedurePhased Array DGS/AVG

PA DGS/AVG Feature OverviewThe EPOCH 1000i offers the DGS/AVG sizing feature standard for

phased array mode:

Standard EPOCH onboard DGS/AVG setup menu

Applies DGS/AVG curve at 0°, 45°, 60°and 70°focal laws

Quick setup using modified GAIN calibration tool

Interpolated image TVG for easy detection across soundpath range

Use PA probe ID and wedge information to establish curve characteristics

Required Items

Test Block– EP1000-PABLOCK-1

Couplant– D-12

Transducer and Wedge– 5L16-9.6X10-A10P-P-2.5-OM probe– SA10P-N55S wedge

Feature Activation Proper calibration is required prior to activation of the DGS/AVG feature for

precise measurements

Feature Activation The DGS/AVG activation is located in the SIZING OPTION menu group under [P2] (DGS)

The DGS/AVG menu is used to establishthe following DGS setup parameters:

– Reflector Type

– Reflector Diameter

– Delta Vt

– Registration Level

– Warning Level

– ACVSpecimen

– ACVCalBlock

– Delta Vk (radius only)

Note that due to PA probe automaticrecognition and wedge selectionduring Beam setup, probe informationdoes not need to be configured inthe DGS/AVG screen

DGS/AVG Parameters

DGS/AVG setup includes up to 8 parameter selections/adjustments before the operator can begin inspections:

Reflector Type – A single reference reflection is required to build the DGS curve(s) on the EPOCH 1000i – this can be from a Backwall**, Flat-Bottom Hole (FBH), Side-Drilled Hole (SDH), K1/IIW Block Radius*, or K2/DSC Block Radius*

Reflector Diameter – When a Reflector Type of SDH or FBH is selected, the operator must indicate the size of the reference hole.

Delta VT – Also known as Transfer Correction, Delta VT is a calculated value the accounts for an overall attenuation difference between a reference/calibration block and the actual inspection piece (typically caused by surface conditions or subtle material variation)

Registration Level – The value of the “critical” reference reflector for the inspection. This defines the relative height of the DGS curve and the comparison to unknown flaw reflections for rejection/acceptance criteria.

*used only with Angle Beam probe **used only with Straight Beam probe

DGS/AVG Parameters

Warning Level – DGS/AVG allows for one Warning Curve in addition to the main DGS curve. This can be set from +6.0dB to -14.0dB below the main curve, or to 0.0dB to turn this curve off.

ACV Specimen – An attenuation compensation value for the inspection piece. This value is used to adjust the DGS curve, which is based on attenuation in an “ideal” or “perfect” carbon steel, to reflect accurate attenuation response in a “real-world” test piece. This is especially important for longer sound paths. The calculation for this attenuation adjustment is defined in the code EN 583 and other documents.

ACV Calibration Block – An attenuation compensation value for the calibration block. This value serves the same purpose as ACV Specimen, but is used when capturing a reference reflector from the calibration block.

NOTE: ACV Specimen and Calibration Block values are single values applied to all curves

Feature Activation When using the Aluminum PA Demo Block for demonstration, use the DGS/AVG menu to

establish the following DGS setup parameters:– Reflector Type = SDH

– Reflector Diameter = 1.5mm

– Delta Vt = 0.0dB

– Registration Level = 1.00mm

– Warning Level = 0.0dB

– ACVSpecimen = 0.0dB/m

– ACVCalBlock = 0.0 dB/m

– Delta Vk (radius only) = NA

After hitting ESC, the unitwill provide the following prompt. Select NO for fullprocedure.

Acquiring DGS Setup Point As with the conventional DGS/AVG feature, one of the main advantages of this

technique is the requirement of only one reference reflector to perform full curve setup

Place the 5L16 probe on top of the demo block, over the second most shallow SDH, and facing the closest side of the block

Acquiring DGS Setup Point (cont.) After exiting the DGS/AVG activation menu, the instrument will default

to the PA CAL group, with the Calibration type DGS active

Use the same procedure as GAIN calibration to acquire the first SDH as the DGS reference reflector:– Set reference cursor to 45 degrees

– Position Gate 1 to capture an amplitude measurement from the SDH across all angles

– Use AUTO 80% to bring the SDH reflection to 80% at 45 degrees

– Press [P1] (ADD) to begin point calibration

– Press [P2] (DONE) after successful acquisition of point

DGS/AVG Reference Point Collection

DGS/AVG Menu Once the DGS reference reflector has been acquired, the DGS group menu

appears beside [F3] (DGS) in group 4/5– P1 – Live adjustment of registration level– P2 – Live adjustment of transfer correction (Delta Vt)– P3 – Toggles scanning gain on and off– P4 – Toggles sector scan interpolated TVG on and off– P7 – Turns DGS function OFF without entering a setup menu

Sector Scan Image Correction A unique feature of Phased Array DGS/AVG on the EPOCH 1000i is the ability

to interpolate image gain correction across all angles and soundpaths based on the reference reflector

This gain correction allows the DGS/AVG user to gain the benefits of higher probability of detection through the sector scan image while still maintaining mathematically correct DGS/AVG curves at standard A-scan angles for sizing.

Phased Array DGS/AVG and the EPOCH 1000i When adjusting focal laws/angles in DGS/AVG mode

– Coarse adjustment switches only to focal laws with curves applied to the A-scan (0°, 45°, 60°and 70°)

– Fine adjustment allows access to all focal laws, but curves are only displayed for A-scans at 0°, 45°, 60°and 70°

PA DGS/AVG curves may also be used with fixed angle linear scans at 0°, 45°, 60°and 70°

Important Phased Array DGS/AVG Notes ERS Measurement: Remember that the digital ERS (equivalent

reflector size) measurement in DGS/AVG is not the same as dB to Curve in DAC mode! – Each curve represents attenuation of sound using a Flat Bottom Hole

target

– The digital ERS measurement of a live signal rates the signal as if it were a FBH. This means that if the operator sets the curve registration level to 1.5mm and sizes a 1.5mm side drilled hole, the echo will not meet the level of the DGS curve, and the ERS measurement will not be 1.5mm!

Material: The DGS/AVG curves are based on clean steel. Especially when using the Aluminum PA Demo Block, the echo will not align with the DGS curve properly. The PA Demo Block is for general demonstration of this feature only!