June 3, 2022. It is one of the last days of the turnaround. For weeks now, the Schwechat Refinery has been bustling with activity during this legally required general overhaul. “It was the very last day, the very last water-pressure test in the course of the turnaround”, recalls Karl Graf, VP Refining Asset Management. The pressure test is a standard process in which water is fed into a column to check its load-bearing capacity. Suddenly, damage appeared on the outer skin of the column. It is the main column of the crude oil distillation unit and one of the largest in Europe: Over 50 meters high and reaching 9 meters in diameter in places.
What followed was a high-speed tour de force – accomplished in only 16 weeks thanks to the dedication of the OMV experts and the active support of reliable partner companies.
The first step: Crisis team comes together
The hastily established office next to the crude oil unit was manned continuously from June 3. The task force consisted of about 15 people who were set to work in shifts 24/7 for the next few weeks. They were the staff and engineers with the most experience in the field of mechanical engineering, welding technology, inspection, plant construction, process engineering, as well as those with the management skills needed to master such an exceptional situation.
A total of about 50 OMV colleagues and up to 320 other experts from various technical departments and partner companies from Austria and Europe were deployed.
In parallel, a team took care of establishing an alternative supply system to continue supplying the markets and customers served by the Schwechat Refinery – you can read about how this was achieved here.
The second step: Static safety measures
“We didn’t know how stable the column was in that state, so our first move was to secure the area of the unit in question. Immediately after the first crisis meeting, a small team carried out static investigations on the column and evaluated the situation on site”, Karl Graf describing the first measures to make safe the site.
Then it was a matter of finding out what all the damage actually involved. “It wasn’t clear how extensive the damage to the outer skin was in the lower area of the column below the frame – the area was inaccessible. The danger of other parts falling down from inside the column was simply too great”, says Karl Graf. Together with external experts, the damage to the foundation and steel structure was examined, the column design was analyzed, the unit was measured by means of 3D scans, and the data and material analyses were all completed. This phase took about a week.
At the same time, an independent team got started on investigating the accident by first preserving the evidence, supported by external experts and employees of TÜV Süd and the University of Leoben.
The third step: The repair concept
In parallel, the team worked to develop a sophisticated repair concept while applying the highest safety standards. What parts are damaged? Who will handle the mechanical work, the inspection, the scaffolding, the insulation, the cleaning? What do we need in terms of materials and which companies can deliver that quickly and reliably? All these questions had to be clarified. Only three days after the incident and the concept was ready.
Another four days later, it was clear which materials were needed and in what quantities – a lot. The orders had been placed and everyone knew what had to be done.
The fourth step: The head has to come off, crane needed
What followed was the erection of 200 tons of scaffolding around the entire column. The column was then stripped, cleaned and inspected from the outside. All this was done by a team working in shifts, day and night. At the same time, a 70-meter-high crane was erected. “Normally there are waiting times of over a year for cranes of this size”, says Karl Graf, “but one of our partner companies got it to us within just a few days”. After this, vacuum rings could be welded on to stabilize the column. This was needed for what followed on June 19, one of the big milestones in the repair plan: Cutting off and lifting down the column head – a part weighing 100 tons. Why was this complex work step needed? The damaged column internals and the damaged column sump (as the lower part of a column is called) could only be removed safely and efficiently from above. After the successful lift, the team was able to get an overview of the enormous damage inside the column for the first time – and start the clean-up work.
The fifth step: Clean-up work – bringing in the Spanish industrial climbers
All the fallen parts from inside the column could now be extracted through the opening that had been created. This was done by a group of 17 Spanish industrial climbers. More than 120 tons of scrap and steel were recovered using winches and a crane. The first parts had already been removed in the preceding days via “manholes” – access openings of about half a meter in diameter. However, taking off the large column head made for much faster progress.
“All this work came in the middle of summer”, says Karl Graf, “so we installed an air conditioning system to cool the air in the steel column and ensure safe working conditions. This was then complemented by a sophisticated ventilation and lighting concept”.
On July 3 – exactly one month after the incident – the results were visible: The damaged parts had been removed and only the outer shell of the column was still standing. There was now a clear path to reach the section in the column’s sump that had a 25-metre-long crack running through it.
The sixth step: Thorough inspection
The inspection program that now followed in the interior of the column, including 3D measurements and laser scans, required a 60-ton interior scaffold: “We needed to examine more than 8 kilometers of weld seams to identify even the smallest cracks. We also inspected the column for any further deformation. In total, we came up with 10,000 inspection points and 400 repair points”, Karl Graf describing the scale of the work.
We had 210,000 accident-free working hours - and that with mostly critical work in a very small space. What the team has achieved here is really enormous."
Karl Graf, VP Refining Asset Management
The seventh step: Repairs in the sump and placing interior column parts
“As it turned out, the entire sump area was destroyed. It had to be cut out and replaced. The fact that we managed to do this work within a few weeks and that all the necessary material was available to us is also thanks to the tremendous support of our partner companies”, says Karl Graf.
voestalpine, for example, immediately freed up production slots to produce more than 100 tons of roll-clad steel in various wall thicknesses. The individual components were prefabricated at one of our equipment manufacturing partner companies, delivered to Schwechat, and welded on site. Among them was a ring connecting the frame to the cone. “We have improved the design on this so-called ‘brim’. This now makes the column even more stable and increases its future useful lifetime”, explains Karl Graf.
While welding was underway in the sump, support beams were installed at different levels in the upper area. These beams serve as a base for the 39 separating trays that divide the column into several sections and are needed for the distillation process. “We have also improved the design of the individual trays. In future, deposits will no longer form so easily here, leading to an increase in efficiency”, says Karl Graf.
While all this work was still in full swing, with not a moment to lose – and as a sign that the repairs were nearing completion – the column head was lifted safely back into place and secured. Another important milestone was thereby met on August 19.
The eighth step: Completion of the work and successful water-pressure test
The big day finally arrived at the end of September: All the work was completed and the column was ready for a new water-pressure test. Was the tension among the team just as high? “We had inspected everything thoroughly, knew the repair method inside out, had all the calculations, had made multiple improvements – no, actually our team wasn’t nervous”, says Karl Graf. And this calmness turned out to be justified: The water-pressure test was successful and the column could now be handed back to the operations team. After being inspected by TÜV as well, the Schwechat Refinery has been running at full capacity again since October 7.
With all the work and the time pressure, the top priority naturally was the safety of every employee. “We had 210,000 accident-free working hours – and that was with most of the work classified as critical and taking place in a very confined space. What the team has achieved here really is colossal”, says Karl Graf.