BS ISO 18211:2016 pdf free download.Non-destructive testing — Long-range inspection of above-ground pipelines and plant piping using guided wave testing with axial propagation.
1 Scope
BS ISO 18211 specilies a method for long-range testing of carbon and low-alloy steel above-ground pipelines and plant piping using guided ultrasonic waves with axial propagation applied on the entire circumferential pipe section, in order to detect corrosion or erosion damage.
The guided wave testing (GWT) method allows for last inspection of above-ground pipelines, plant piping and cased road crossrngs. giving a qualitative screening and localization of probable corroded and eroded areas. GWT is typically performed on operating piping systems.
BS ISO 18211 is applicable to the following types of pipes:
a) above-ground painted pipelines;
b) above-ground Insulated pipelines;
c) painted plant piping;
dJ insulated plant piping.
NOTE Pipe sections within road crossings with external casings (without bitumen or plastic coating) are a special case of buried pipe where there is no soil pressure on the OD of the pipe. BS ISO 18211 applies to these cased road crossings.
Other types ol pipes not included in the above list need dedicated approaches due to increased complexity.
2 Normative references
The Following documents, In whole or in part, are normatively referenced in BS ISO 18211 and are Indispensable for Its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 9712, Non -destruct Eve testing — Qualification and certification of NDT personnel
3 Terms and definitions
For the purposes of BS ISO 18211, the following terms and definitions apply.
3.1
axial direction
direction along the main axis ofthe pipe
circumferential direction
direction around the circumference of the pipe
3.3
total pipe wall cross-section
TCS
area between the inner and outer diameters of the pipe in a plane perpendicular to the pipe axis
b) The tolerance of range setting shall be agreed upon between the parties (due to the long wavelength used for GWf the tolerance on distance measurenwnt is not likely to be better than ±100 mm).
c) The probe ring coupling to the pipe surface shall be checked according to the procedures and thresholds provided by the manufacturer If the coupling is found not to meet the required specification, then the surface preparation shall be improved, the probe ring re-applied and the data re-sampled.
d) If the equipment permits an absolute amplitude calibration, then It shall be used. Otherwise, calibration of sensitivity, using knowledge of a well-characterized reflector, such as a girth weld, shall be used. The calibration shall also include distance amplitude correction (DAC) or time corrected gain (TCG). in order to compensate the calibration for axial position within the range of the lest. DAC and TCG are to he understood conceptually in the same manner as is established for conventional UT testing; a DAC provides a constant level of sensitivity as a tuncton of range. allowing reflections at varying ranges lobe compared in a consistent manner to a known reference level. The calibration shall be set according to the instructions provided by the manufacturer of the GWT equipment.
e) The signal-to-noise ratio shall be estimated according to the procedure provided by the manufacturer. For adequate interpretation of the test data, the signal-to-noise ratio shall be greater than 6 d small amplitude signals below this value cannot be interpreted reliably and will lead to noise signals being reported as discontinuities. The signal-to-noise ratio is used to determine the range of the test (see for more information on test range).
10 Testing
10.1 PreparatIon of the test ob)ect
jo_i_i Surface temperature
The surface temperature of the pipe shall be within the operating range of the test equipment used.
10.12 Removalof Insulation
Testing on insulated pipes requires the removal of circular bands of insulation at all the points where the probe ring shall be positioned and for a length that is sufficient to allow the fixing of the probe ring directly on to the pipe surface.
10.1.3 Wall thickness assessment
Metal loss at the probe ring location affects the test pertormance of GWT, Visual testing and ultrasonic testing shall be performed to assess the presence of externai or internal metal loss. If metal loss is detected, it is recommended that the probe ring is attached to an alternative location. The wall thickness values shall be recorded.
GWT does not provide Inspection coverage in tht dead zone. One way of providing 100 % pipe Inspection coverage is to perform more than one guided wave test on a piping system where there is sufficient overlap between tests to provIde inspection coverage in all dead zones. If the dead zone Is not inspected with GWT using another test location and if the dead zone is to be tested, ultrasonic testing (or an alternative method) shall be used.
10.1.4 Surface preparation
Testing on well-adhered painted surfaces Is normally satisfactory. Loose or flaking painL superficial corrosion products and other coatings shall be removed at the test location prior to attaching the probe ring if required to achieve the data quality set out in Clause 9. item e).
set to the equivalent of a discontinuity that reflects 5 % of the guided wave sound intensity or —26 dl3 below the reflection from a machined surface normal to the pipe axis. The call level shall be included in the test report.
10.6 Detection sensitivity
The test sensitivity is a function of many variables and depends on the Following:
a) the test equipment. including the ultrasonic instrument and the probe ring;
b) the specific guided wave mode
c) the diameter of the pipe being tested; the same Isolated wall loss discontinuity that is detected in a small diameter pipe may not be detected in a larger diameter pipe:
d) the type of discontinuity in the pipe, as the guided wave reflection coefficient will not be equal for all wall loss discontinuities (see Annex A for more information).
The instructions provided by the equipment manufacturer shall be used for any assessment of sensitivity.
10.7 Visual confirmation
All indications from the GWT test shall be confirmed visually whenever possible. Where possible, the locations of geometric features shall be identified visually and their positions shall be measured and compared with the GWT results.
11 Complementary NDT to support the GWT
The GWT method provides rapid screening of the complete volume of the entire pipe, From which indications are called. However, it does not provide direct characterization of the indications. It also does not provide screening results for certain locations where clear GWT signals cannot be obtained; these Include the material adjacent to large reflectors such as flanges, valves, and branches, and short sections between closely spaced major features where it is not possible to achieve sufficient access.
Therefore, complementary testing using other mcthods and applied according to their relevant standards, shall be used to
— perform follow up inspection of all indications that have been identified by GWT, and
— perform inspection of local areas which cannot be tested by GWT. but nevertheless are required to be inspected by the test program.
Complementary N DT Is necessary to give a coniplete evaluation or the pipe and it is considered to be an essential part of the Inspection.
12 Test report
At the end of the inspection, a test report shall he compiled to document the results or all GWT and
complementary NDT performed. The final test report shall include the following:
a) date and place of test;
b) Identification of client;
c) Identification of pipeline;
d) section of pipeline tested;
e) pipe diameter and thickness.