Jointly designed by PH Tool and Holloway NDT, a set of three "Extended Range Variable Wall" (ERVW) Piping Calibration Blocks with Side-drilled Holes has been developed for calibrations in the axial direction for examination of circumferential butt welds. Three conveniently-sized and lightweight blocks cover a wide range of inspection sizes on the pipe schedule chart that would otherwise require a large number of conventional piping calibration blocks.
Design and development of the new blocks was performed concurrently with simulations using CIVA software. The basic design remains compliant with ASME Sec V Article 4, Fig. T-434.3-2 requirements, but with modifications including varying thickness steps on a single block and reconfigured reference reflector locations to optimize size and functionality. The majority of piping examinations are performed on circumferential welds. As a result, the reflectors included on these blocks are oriented in the circumferential direction, for calibration in the axial direction. Side-drilled Holes were selected as the reference reflector type based on enhanced sensitivity vs. notches at a variety of angles, making them ideal for PAUT calibrations.
The blocks have a consistent outside diameter, while providing varying thickness steps on the inside diameter. The OD of each block is machined to span the maximum number of pipe sizes based on ASME criteria. ID thickness steps were customized to span the range of standard pipe schedules. The steps were placed on the ID rather the OD to maximize usefulness of wedge curvature as per the requirements of T-432.2 introduced in 2017.
Blocks used for establishing DAC/TCG calibrations must provide suitable length and strategically placed reference reflectors to avoid conflicting echoes. The dreaded "split-DAC" is often required on shorter blocks which may result in sudden step up/down in the TCG curve. To establish uninterrupted DAC/TCG curves, the segment lengths and reflector positions were modeled to control interfering reflections. Also, block ends were tapered to deflect termination echoes.
Jointly designed by PH Tool and Holloway NDT, a set of three "Extended Range Variable Wall" (ERVW) Piping Calibration Blocks with EDM Notches has been developed for calibrations in the axial direction for examination of circumferential butt welds. These blocks come in three sizes: small (3” to 5”), medium (6” to 10”) and large (12” to 20”). As a set of three, these blocks are kitted in a protective storage case for transportation to inspection sites, offering convenient calibration on over 96 inspection sizes.
The key to the Extended Range Variable Wall series is the "variable" aspect. Only three blocks are needed to cover a large range of pipe sizes, which would otherwise require dozens of calibration blocks. The small block covers 12 pipe sizes, while the medium block covers 29 sizes. The large size covers a massive 55 inspection sizes on the pipe schedule chart. See the chart above for more information about which ERVW Piping Calibration Block can be used with which pipe sizes. Each step is also engraved with the pipe sizes (OD/wall) covered.
The ERVW blocks feature EDM Notches in accordance with T-434.3-1 and -2 for testing circumferential pipe welds. The slanted end cut eliminates corner trap reflections and allows for full DAC/TCG calibrations with conventional ultrasonic testing or phased-array ultrasonic testing. Each block is machine-engraved with a unique serial number and alloy. The surface finish is media-blasted to 125 Ra max to simulate inspection conditions. The steps were placed on the ID rather than the OD to maximize usefulness of wedge curvature in accordance with the requirements of T-432.2 introduced in 2017.
 main images__71723.original.png "PH Tool ASME (DAC) Style ERVW Piping Blocks")