For the manufacture of 16 x stainless steel separators for Sasol
ND Engineering was awarded the order to design and manufacture 16 out of 24 tar separators in what as known as the Sasol Separator Replacement Project.
The procurement selection process for the manufacture of the separators was handled by Fluor SA and Sasol Technologies on behalf of Sasol and proved to be an exceptionally stringent process.
The willingness by Fluor SA and Sasol to keep this work local must be commended,especially since this was a high priority project within the organisation and, as it turned out, would prove an opportune time to prove the true capabilities of South African fabricators.
In short, the task that ND Engineering was faced with boiled down to the manufacture of 16 tar separator vessels within a 12-month period. This meant ordering, testing, preparing,forming, assembling, and welding more than1 000 tons of 2205 duplex stainless steel.
To achieve this mammoth task, both ND Engineering’s main workshop and the Bayside workshop were utilised in a production line type process. The company’s main workshop assembled various components of the vessels in jigs with the completed sections being sent to the Bayside workshop for complete trial assembly, inspection and release for final assembly and welding on site in Secunda.
The resources in both of these workshops were fully committed to this project for 9 months. Six months into manufacture, ND Engineering’s site team established operations in a specially designated site area in Secunda. At this point the company had over 300 resources working 7 days a week on the project across the 3 work areas.
An average of 91 000 hours were being worked on this project per month, and over the 12 month period, approximately 750 000 hours were clocked up without a single lost time injury being recorded. From the onset, this was a project like no other that ND Engineering had ever worked on. Sasol and Fluor SA had a very specific goal that they set out to achieve with the fabrication of these separators.
This was to extend the required inspection intervals on these vessels, thus reducing inspection and maintenance downtime and improving output. To achieve this, they set up one of the most advanced technical scopes and developed supplementary material standard requirements, making this project one of the most complex and advanced fabrication projects a South African company has ever had the privilege of working on.“An absolute premium was placed on planning and scheduling and every step of the manufacturing and testing process was laid out in an extremely detailed execution plan,” says ND Engineering’s owner Elvis Green.
This plan was used as a daily tool tomonitor progress against what was required to meet end delivery. As the pictures included with this submission show, these separators were highly complex in terms of the detailed internals and the multitude of cone, shell, and roof nozzles which had to be absolutely spot on in terms of their position and elevation. They were replacement vessels that would be going into a live plant, so there was no room for errors in terms of the nozzle positions.
The positions were verified by laser scanning of the completed vessel,. This included the staircases, ladders, and platforms. All were laser scanned and found to be in complete compliance.In addition to the complexity of the separator vessels, there were also very complex welding standards that required an unprecedented number of Production Weld Test Plates (PTPs) over the period of the project.
A total of 128 PTPs were completed to ensure that the results achieved during shop and site welding were in line with the project approved welding procedures and required parameters. Due to the complex features of the design, combinations of design standards were needed to evaluate the designs. Additional detailed FEA analysis was also conducted in order to assess each of the vessels’ specific design parameters.In addition to having to meet the design parameters, the 8 Tertiary Tar Separators had to be fully redesigned to operate as a part of a pressurised system, and the 8 Tertiary Tar Separators needed to be redesigned to include 9 access covers on the roof of the vessels to accommodate more access openings and the loading of the platforms on the roof.
Extending the life cycle costing
The existing separators were fabricated from carbon steel and were required to be inspected annually. This entailed shutting down the plant to inspect and / or carry out the necessary repairs due to stress corrosion cracking. The client used dual certified, duplex stainless steel with specific properties so as to extend the inspection intervals and reduce the impact of the product on the Separator shell and cones. The Risk Based Inspections (RBI) expectation is expected to be between 5 and 10 years.
Quality produced on time
To meet the delivery deadlines set for the project meant that ND Engineering needed to implement all of the carefully thought-out strategies to fast track the manufacturing process whilst maintaining the set quality objectives. The client’s expectation and specific requirements far exceeded the standards listed above. To satisfy these requirements ND Engineering carried out extensive NDE testing on the welded components. The site built for the project will now form part of a workshop extension of the pre-existing workshop.
In order to meet the tight schedules a total of approximately 320 people were actively involved in the fabrication either in the workshops or on site in Secunda. This overall project will continue to offer employment for the foreseeable future as the installation phases will run for another two years.
ND Engineering – 031 464 0510