For dry underwater welding projects, the right provider will custom design a habitat to secure the weld area and create an environment that fully encloses and isolates the weld zone.
Benefits of Using NEPSYS®
NEPSYS® has revolutionised underwater welding with a range of benefits including:
- No rework required saving time and costs
- Safer than alternative methods
- Work completed in-situ, no need for dry docking or hyperbaric repairs
- Superior quality results equal to dry environment welding
- Portable and flexible system
Project: First North Sea NEPSYS® Repair, UK
Problem: Full penetration crack in a column to sponson joint configuration at a depth of -15 metres.
Solution: NEPSYS® dry underwater welding technology was used to grind out the defective weld then weld the joint externally using a NEPSYS® habitat and internally using rope access. Before any work began in the North Sea, all aspects of habitat design, fabrication and testing, welding procedure preparation, international class approval, diver/welder and rope access welder qualification and testing were completed at the NEPSYS® training and testing facility in Perth, Western Australia.
Outcome: The repair complied with the D1.1 standard set by AWS (American Welding Society). Neptune’s first NEPSYS® European project met the rigorous standards imposed on North Sea operations and the client was completely satisfied with all aspects of the project.
Project: Tension Leg Platform (TLP) Repair, Gulf of Mexico
Business Units Involved: Subsea Design, Engineering, Fabrication, Commercial Diving and Welding.
Problem: Five transverse indications located at depths up to (-29 metres) on the pontoon to base node connections and one transverse indication on one of the tendon porches were in need of repair.
Solution: After consulting with the TLP operator, Neptune recommended a cost effective repair solution that complied with the American Bureau of Shipping (ABS) permanent repair requirements. Working in conjunction with the TLP’s construction engineering firm, Neptune recommended using the NEPSYS® permanent solution on the project in-situ. Dry docking and conventional welding processes were not viable solutions.
Before repair work commenced, Neptune completed a pre-project inspection of the damage to determine the size and scope of the required repairs. Measurements and video footage of the damage were also obtained to ensure the unique weld habitats could be engineered and fabricated to exact specifications.
Over five days, a team of eight ABS approved diver/welders used E7016 specially coated electrodes and two separate habitats to perform weld repairs to both 90° and 130° connections.
Outcome: The entire welding procedure (3G Vertical Up) was approved by ABS as Class A, compliant with the standards set by AWS D3.6.
The repairs were independently examined and tested and non-destructively tested (NDT) using the magnetic particle inspection and the Ultrasonic Shear Wave Testing methods. Both tests returned results that confirmed full penetration welds of the highest standard.
This project was the first of its kind to be applied to a TLP and the first in the Gulf of Mexico to gain ABS approval. The NEPSYS® process is included in the ABS Attending Surveyor’s Training Update Program at ABS Americas in Houston, Texas.
Project: Hurricane Damaged Repair, Gulf of Mexico
Problem: Following Hurricanes Katrina and Rita, several oil and gas assets in the Gulf of Mexico were in need of repair.
Solution: A major operator in the Gulf asked Neptune to propose a timely cost effective repair to a platform which had severely damaged vertical and horizontal cross braces. Neptune and Cal Dive International were commissioned to complete the work after a demonstration of NEPSYS®.
Neptune Underwater Services (USA), welded the new braces in place using scallop sleeve joints and approved wet welding procedures. The cross braces ranged in size from 18” (46cm) to 26” (66cm) in diameter. A total of 400 ft (122m) of joints required welding. A critical k-node joint on the top cross brace was found to be in need of repair. Due to the location of the joint a permanent, structurally sound repair was required. Using the NEPSYS® technology, a 360° full penetration weld was performed to join a vertical diagonal to the jacket leg at the k-node.
Outcome: The NEPSYS® repair and other welds were assessed by a third party using the magnetic particle inspection method and were found to be 100% compliant. The wet welding was completed to the standards set by AWS 3.6. The NEPSYS® welding met the highest quality requirements of the original fabrication code AWS D1.1.
