1. Phased Array Ultrasonic Testing Vendor Qualifcation
for a major subsea project
(A risk mitigation strategy)
ABSTRACT
A significant fabrication risk was identified
on the Shah Deniz 2 subsea gas manifolds.
Heavy wall thickness welds needed to be
inspected and the limits of radiography
meant a PAUT vendor had to be qualified in
time for the fabrication of the pipework.
Colin Smith:
https://uk.linkedin.com/in/colinanthonysmith

2. A significant risk had to be addressed if the fabrication site was to avoid using radiography
on heavy wall welds on the high pressure (900bar) gas pipework. The obvious benefits were:
safety (elimination of radiography as the means to NDE the welds), quality – at the 62.5mm
wall thicknesses in the stainless steels it would be difficult to detect crack-like defects in the
root areas with the usual UT and RT methods, and finally productivity; being able to weld &
inspect at the same time in the same vicinity had significant productivity benefits.
There are many NDE contractors who claim that they can PAUT welds and they can if the
welds are ferrous. However, if the welds are nickel based alloys or a stainless steel, then this
significantly reduces the number of NDE contractors with the correct knowhow.
Nickel based alloys and stainless steels are ultrasonically more opaque than ferrous alloys
due to the attenuation of the sound beam. This demands greater energy from the probes
and programming to tailor the beam for the specific application.
An amplitude based PAUT program was initiated by the client – with a goal of qualifying two
PAUT vendors to achieve a competitive tendering situation prior to start of inspection of the
heavy wall pipework required on the Shah Deniz 2, gas production manifold pipework.
These two vendors would then be pre-qualified for the main subsea contractor to choose
for the fabrication phase in Norway. I led this initiative and delivered the successful
outcome.
Scanning a 10” joint – note the finish on the weld caps.
A sized based PAUT program was initially considered but this would have involved
significant engineering to accept non-Code compliant defects justified by FEA. So the

3. amplitude based approach was adopted and ASME allowable defects as the basis of
acceptance. No crack like indications are allowable in the Code.
The qualification program was commenced 18 months before pipework fabrication. Seeded
coupons were manufactured at two locations one in Europe and one in the USA. It became
evident that only one seeded coupon manufacturer could achieve the correct morphology
of the defects that needed to be seeded at the correct depths. Of particular interest was the
location in the root area of 1.5mm crack like indications. These were to simulate lack of
fusion in the root. However the coupon was peppered with various types of defects
throughout the weld thickness. The ultimate acceptance criteria was: zero crack like
indications were allowable. The two seeded coupons were made with four rings of contract
material: 25%Cr super duplex to itself with matching filler, and nickel alloy clad X65 welded
to 25%Cr super duplex with a high nickel filler. These seeded coupons took 12 weeks to
fabricate. Seeding was performed using the thickest sections to be used on site: 62.5mm wt
on the 10” pipework.
The seeded coupons were then shipped to the two preferred PAUT vendors facilities in turn
where the operator was tested using the PAUT vendors procedure. These trials were
witnessed by the client – care was taken to ensure that no collaboration between operators
took place. This served to qualify the operator and the vendors procedure. The output was a
map submitted to the client declaring where the PAUT operator found the defects and they
had to be characterized. This map was compared to the original map. Operator and vendor
either passed or failed the test.
After trialing five potential vendors only two were capable of detecting the crack like
defects in the root area. Some vendors could not detect many of the seeded defects in the
mid thickness of the 62.5mm joints. Final value of the CTR was in excess of $1.5MM.

4. In addition to the seeded coupons (and in parallel) the vendors had to be supplied with
contract material coupons of each size of pipework that was to be tested: in this case 6” x
47.5mm wt , the 10” x 62.5mm wt and the 12” x 38mm wt. Priority was given to the 10”
coupons for the seeding trials.

5. Phased array automatic ultrasonic testing on 10” super duplex joint 62.5mm wall thickness.
Duration from mobilization to demobilization 3 hrs – two scans (one from either side).