NDT and inspection are crucial for large offshore oil and gas rigs. Image by <a href="https://pixabay.com/users/catmoz-4975455/?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=2191711">C Morrison</a> from <a href="https://pixabay.com//?utm_source=link-attribution&utm_medium=referral&utm_campaign=image&utm_content=2191711">Pixabay</a>

NDT and inspection are crucial for large offshore oil and gas rigs. Image by C Morrison from Pixabay

According to a report published by global management consulting firm McKinsey in April last year, Global Energy Perspective 2022, the continuing increase in fossil-fuels demand will see a peak for oil demand in the next five years while gas remains the most resilient fossil fuel at present. As a result, DEKRA Industrial SA, which has been involved in non-destructive testing (NDT) and inspection in the oil and gas sector — locally and pan-Africa — will continue to expand their presence in this area.

This trend is evident from the high level of activity off the coast of Africa, for example TotalEnergies’ pivotal liquid natural gas project offshore in Northern Mozambique.

DEKRA Industrial managing director Johan Gerber explains: “Offshore oil and gas rigs present potentially hazardous working conditions while the crew members carry out the required drilling. Rig teams are dealing with highly combustible materials, on an ocean-based platform where cranes are swinging heavy equipment overhead and other large-scale moving parts are also a constant presence in the immediate environment.”

Johann Dorfling, DEKRA Industrial’s Western Cape branch manager, notes: “We are active in the oil and gas and maritime sector both on- and offshore; and have carried out ‘before and after’ NDT welding integrity inspections around Africa, such as Las Palmas in the Canary Islands, Ghana, Angola and in Mozambique.”

“On oil rigs we do crane and slew bolt inspections and work extensively on drilling risers, which form the connection between the subsea field developments and production and drilling facilities. An extremely high level of welding is required to ensure that the longevity and structural integrity of the components, structure and pipework on the risers is maintained, as many of these items undergo extreme pressure during their service. NDT and inspection help to prevent the failure of these critically important elements.”

The role of NDT and inspection on drilling risers

MC Liebenberg, NDT Level 3 technician at DEKRA Industrial, clarifies: “Similar to pipelines or flowlines, risers act as conduits to transport produced hydrocarbons, as well as production materials, such as injection fluids, control fluids and gas lift. The cost of a marine drilling riser system can be tens of millions of dollars, but the cost of operational downtime associated with a riser loss or failure can exceed more than one hundred million and this therefore needs to be prevented. In non-destructive testing, there is not one method which is superior to another, and the methods complement each other. In offshore inspection, we most commonly see the use of magnetic particle (MT) and visual inspection (VT), as well as thickness gauging.”

Dorfling adds: “We have performed eddy current, MT and VT inspections, liquid penetrant testing (PT), volumetric as well as ultrasonic UT and phased array ultrasonic testing (PAUT) welding inspections on drilling risers. It is of vital importance to ensure that these risers are in class and do not fail in service as the result of a leak can be catastrophic for the environment and general safety.”

Flexible inspection results

Liebenberg clarifies: “Depending on the acceptance criteria of the inspection, NDT can determine if all areas of inspection are in or out of class, and reported on, detailing the extent of wear, corrosion or defects discovered.”

“DEKRA Industrial does not determine if a vessel is out of class or not, this is determined by the results of our NDT inspection which are presented to the client, who then makes the decision on whether to replace the component or repair it to conform to class standards.”

Rope inspections – A competitive differentiator

Dorfling explains that DEKRA Industrial offers rope access inspection across multiple NDT methodologies, including advanced disciplines such as PAUT. “DEKRA’s capabilities in performing NDT offshore with rope access competitively differentiates us from a number of our competitors, and this is of great importance in this industry — as is the ability to provide a diverse offering,” he enthuses. “We are proud to be able to perform advanced inspection using rope access, as building scaffolding on a rig is not a viable option.”

Gerber concludes: “DEKRA Industrial in South Africa has played a major role in the fields of NDT and inspection locally across a wide range of industry sectors for the past 40 years and we are proud to include this important area — NDT and inspections in the oil and gas arena — in our field of expertise. We anticipate doing even more maritime-related work in the future.”