Note that a full body inspection of
an umbilical line can require some additional equipment. A typical umbilical
material is lean duplex 19D, which is 50
percent austenite and 50 percent ferrite.
This grain structure tends to shield or re-
pel the eddy current field. For eddy cur-
rent to penetrate the metal surface, it is
necessary to saturate the tube wall with
a magnetic field. To do this, the setup
requires an electromagnet and a power
source that can generate sufficient mag-
netic field strength.
A secondary test is an offline UT rotary system with three transducers, one
each for clockwise shear, counterclockwise shear, and wall thickness. A water
column maintains coupling between the
transducers and the tubing as the transducers orbit the tube.
A final test is air under water (a common leak test).This three-part test can
find pinholes (penetrators), strip defects,
and weld defects (see Figure 2).
A Setup for OCTG. API specifies the
dimensions, material grades, mechanical
properties, and other requirements concerning steel products used as casing or
tubing for wells in API 5CT. It also estab-lishes the notch dimensions for the various
grades and quality levels, the NDT method, and data collection requirements.
An ultrasonic rotary setup is suitable
for verifying the wall thickness, but some
grades require only 25 percent coverage.
According to API 5CT, section 10. 13. 4,
pipes specified to PSL- 2 and PSL- 3 require 25 percent and 100 percent wall
thickness coverage, respectively. However, some customers have their own
wall thickness requirements.
To achieve full-volume testing, a setup
usually needs at least seven testing directions: one for the thickness and lamination defects, two for longitudinal notches (clockwise and counterclockwise),
two for transverse notches (forward and
reverse), and two for oblique notches
(clockwise and counterclockwise). The
number of transducers also is related to
the production speed—more transducers
are needed for faster line speeds.
Test references include 6-mm, flat-bottomed drilled holes and pipe with a
wall thickness coupon set to the minimum allowable wall thickness.
End Testing by UT
One drawback is that some conventional
NDT methods have limitations in their
abilities to test to the very end of the
product. These untested ends must be cut
off and discarded, resulting in a substan-
tial loss of product and revenue. Further-
more, some users require a higher level
of inspection because the end is to be
flared, threaded, or welded in the field.
An unconventional end inspection
process uses a large number of transduc-
ers in a small area. Under common test-
ing circumstances, crowding the trans-
ducers causes interference. However,
because this system uses a tube rotation
rate that is relatively slow— 3 to 5 revo-
WITH TUBE MANIPULATION MACHINES
November 6–9, 2017
The solution for tubes.