API RP 2X:2004(2015) pdf download

API RP 2X:2004(2015) pdf download.Recommended Practice for Ultrasonic and Magnetic Examination of Offshore Structural Fabrication and Guidelines for Qualification of Technicians.
To ensure that the equipment’s internal and external controls function within the accuracies and tolerances of the equipment manufocturer. the operator’s written procedures. and certain nationally or internationally published standards. the equipment should be calibrated to properly set and traceable measurements held at the National Institute of Standards and Technology NIST) or other national standards agency. A standard operating procedure and quality control manual should detail the method adapted to assure traceability. The time interals shown in Table I are recommended for calibration of NDE equipment.
Prior to and at regular intervals during an inspection job, routine performance checks and calibrations (also termed should be carried out. The routine for these, including the equipment used, the frequency of each test, and the course of action if the instrument cannot be calibrated should be described in the inspection companies written procedure. The recommended time intervals for these equipment checks are shown in Table 2.
7.5.3.2 The 11W and lOW Standards
Figure 4 presents the 11W standard, a recognized test reference for evaluating sensitivity, sweep linearity, and shear wave transducer index point and angle. The lOW standard, see Figure 5. is less commonly known hut affords a means of establishing shear wave beam characteristics and profiles. It may also be employed to check the accuracy of the beam index and angle obtained from measurements on the large hole of the 11W block and for assessment of the resolution characteristics of instrument-transducer combinations.
The 11W and lOW standards are available from normal commercial sources hut are simple enough to he fabricated in any well-equipped machine shop; however, a number of rules should be observed when preparing calibration standards. First, the material should be similar in chemical composition and acoustical properties to the material to be examined. For offshore structural examinations, blocks fabricated from straight carbon or carbon-manganese steels are appropriate. The steel should be of the fully deoxidized type and subjected to a hardening heat treatment at l650’F (9(XYC) for 1/2 hour followed by water quenching to room temperature plus subsequent tempering at I 2(XYF (65WC) for 3 hours for the purpose of minimizing “noise” and acoustical anisotrophy. Prior to final machining, the blank stock should be machined on the surIices to be utilized in the finished standard, followed by an ultrasonic examination to ensure that the blank is free of defects or flaws which will interfere with its subsequent usc. Once accepted for final machining, stock removal should be restricted to the surlaces indicated on the drawings or those requiring acoustical coupling in use. Unnecessary machining. plating. and surface treatments result in wall echoes and diminish the usefulness as a reference standard.
7.5.3.3 Check of Horizontal Linearity
lo check the horizontal or (sweep) linearity of the instrumentation. it is necessary to adjust multiple echoes obtained from a longitudinal wave transducer placed on the flat surface of the 11W block to match equal divisions on the overlay grid or horizontal scale of the CRT. The leading edge or left hand side of each echo signal should coincide with the divisions of the horizontal scale (see Figure 6). The preferred number of echoes is four or five, depending on the possibility of dividing the selected range into units that coincide with major divisions of the horizontal scale.
In most instances, it is recommended ihat the highest frequency be utilized as this produces the sharpest indications and improves the accuracy of measurement. It should also be realized that the distance between the initial pulse indication and the first echo signal is alwas greater than the distance between successive multiple echoes; therefore, the alignment should commence with the first echo signal and no with the initial pulse.
After aligning the echoes wih the scale, one should determine the deviation of positions of each echo from the scale mark. The maximum noted deviation should not exceed I percent of the full scale range. Checks Ofl selected ranges of 5 inches (125 millimeters) and 10 inches (254 millimeters) arc recommended.