PHMSA has issued guidance on guided wave technology used for integrity management direct assessment. These target items are for guidance only and do not require that notifications contain only this material. Where operators have alternatives to this guidance, it is suggested that they include it along with any justification in their notification. PHMSA will review each notification on the merits of the individual submittal. Topics addressed in the guidance include:
- Generation of Equipment and Software – G-3 for GUL and Rev 3 for Teletest.
- Inspection Range – 60 ft. to 100 ft., 80 ft probably good max. to use
- A 20% Overlap needs to be provided or alternative such as several shots with different starting location.
- Sensitivity – threshold of 5% Cross Sectional Area for Go-No Go.
- Frequency – can be 15 to 50 kHz, normally 20 to 40 kHz
- Signal or Wave Type – torsional and longitudinal
- DAC – required for each inspection
- Dead Zone – 3 to 6 ft. from collar
- Near Zone – function of frequency – 1 to 2 ft. out from dead zone
- Coating type- inspections have been on coal tar enamel, FBE, wax, extruded with some girth welds coated with tape and shrink sleeves, have not affected results.
- End Seal – always remove end seal and visually inspect 1st 2 to 5 feet of pipe in casing.
- Weld Calibration – good method to set DAC curve. The weld has to be excavated and measured either before or after the calibration shot.
- Validation of Operator Training – Level II minimum
- Equipment – should be traceable from vendor to contractor.
- Calibration, Onsite – diagnostic test on site and system check on site. Prior to shipment owner to perform calibration checks.
- Use on shorted (either direct or electrolytic) casings is not permitted.
- Direct examination of all indications above the testing threshold is required.
- Timing of direct examinations of indications above the testing threshold.
For a full copy of the guidance document, contact Jessica Roger.