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ULTRASONIC WELDLINE INSPECTION |
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| Arctic's weldline vans are self sufficient installed with ultrasonic components for any size of diameter pipe along with its own couplant (water with wetting agent). This mobile unit can go anywhere or inspect weldline at our facility. | |||||||||||||||||||||||||||||||||||||||||||||
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| Procedure: | |||||||||||||||||||||||||||||||||||||||||||||
| This procedure covers the ultrasonic weldline inspection (UTWL) of electric resistance welded (ERW) pipe. All procedures
will be in compliance with API Spec. 5CT unless the customer specified otherwise. Ultrasonic instruments shall be a pulse echo type utilizing an A-scan presentation with an operating frequency range of 1 to 5 MHz. A gate will be used to monitor distance sufficient to detect discontinuities located on the outside and inside surfaces of the pipe. A chart recorder may be used as a reorder on all inspections. Transducers will be 2.25 MHz ½" in diameter, wide band from a certifiable manufacturer. Transducers will be used at their rated frequencies. All transducers will be mounted in wedges contoured to the OD of the pipe with a beam exit point to produce a 45° shear wave angle. Couplant used will be water with a wetting agent added in sufficient volume of flow to conduct ultrasonic vibrations. Reference standards shall be prepared from a suitable length of pipe of the same diameter, wall thickness, surface condition, and heat treatment if at all possible as the material to be inspected. Reference standards will contain an ID notch and an OD notch in compliance with API Spec. 5CT. The systems shall be calibrated on reference standards as specified above. The sensitivity of the unit shall be adjusted by "peaking up" on the reference standard to gain maximum amplitude. This maximized signal shall then be adjusted to 80% of FSH. This gain setting now becomes the reference level to which all indications are evaluated. The gate shall be adjusted to cover indications of the ID and OD notches and alarm set to 70% of screen height. The chart recorder shall be adjusted to produce a permanent record of notable indications (i.e. those above 70% screen height). Unit sensitivity shall be verified at the beginning of each inspection, after 50 pieces and anytime power is interrupted, and at the end of each shift. Pipe will be visibly marked on both ends, rolled to the 12 o'clock position. If weld is straight, a chalk line will be snapped on the length for unit to track. If the weld is spiraled, the unit will start at one end and continue to make subsequent passes to cover the entire weld area, in either case a minimum of two (2) passes will be made to ensure complete coverage of the welded area. Any indication signal greater than 70% screen height will be marked for further evaluation. The operator, at his discretion, may evaluate indications less than 70% amplitude. |
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