Frequently Asked Questions

  • NEPSYS

  1. What are the depth limitations of NEPSYS?

    Projects have been completed at over 30m depth and the system has undergone testing at the Aberdeen hyperbaric centre to just over 80m. Potentially NEPSYS could be used at greater depths but SAT diving is required for anything below 50m and for efficiency SAT may be considered at shallower depths.
  2. How does NEPSYS compare to wet welding?

    The mechanical properties of a NEPSYS weld are equal to those of a dry weld and it provides a permanent structural weld, unlike a wet weld. As an example dry welding typically achieves over 20% elongation of the weld when tested to destruction in an “all-weld tensile test”. NEPSYS has been tested and found to achieve 25% elongation whereas wet welding consumables are only rated to a maximum of 17% and typically wet welding only achieves 7-10%.
  3. How does NEPSYS compare to hyperbaric welding?

    Hyperbaric welding is extremely costly and usually requires very long lead times while the hyperbaric chambers are designed and constructed. Also hyperbaric chambers can contain high humidity levels which may permit the absorption of hydrogen into the weld. NEPSYS however can be rapidly mobilized at a fraction of the cost and provides a dry hydrogen-free environment ideal for welding.
  4. How does NEPSYS compare to a cofferdam repair?

    A cofferdam repair does not remove the moisture and humidity from within whereas NEPSYS provides a controlled environment of heated inert gas ideal for welding inside the customized habitat. NEPSYS provide a permanent structural weld.
  5. What welding process can be used in NEPSYS?

    At this point in time, MMAW is used. Our R&D is working towards semi-automatic processes so that TIG, MIG & FCAW are all available.
  6. Can NEPSYS weld aluminum?

    Not at this time – this is currently part of our R&D process though
  7. What materials can be welded?

    Currently NEPSYS uses the MMAW process and so all materials that can be welded using this process can potentially be welded by NEPSYS. We are currently working on developing a semi-automatic/continuous wire capability which will enable a greater variety of alloys etc to be welded.
  8. Can NEPSYS weld a full double-sided insert plate?

    Yes, we have successfully performed complete insert plates (welding both sides) on Australian Navy vessels in the past.
  9. How big is the habitat?

    The habitat can be fabricated to suit any project and a variety of shapes and sizes has already been used. Usually it is fabricated just large enough to enclose the weld area, although in some instances the weld may be performed in stages, in which case the habitat may not need to enclose the whole of the weld.
  10. What pressure is in the habitat?

    The habitat pressure is adjusted to keep about 1 bar pressure above the hydrostatic pressure of the surrounding sea water.
  11. What if the habitat leaks?

    Although the aim is to completely seal the habitat, a perfect seal is not required. The positive pressure within the habitat ensures that if there is any minor leakage, the gas will leak out rather than water leaking in.
  12. What about smoke buildup in the habitat?

    A constant flow of heated inert gas into and out of the habitat ensures that any smoke is purged away from the weld area and out of the habitat as it is produced.
  13. How does the habitat attach onto the area to be welded?

    The habitat can be attached by any of a number of methods. On a flat surface it is usually attached with magnets or suction. On pipes and complex shapes it may be attached with studs that are welded to the parent material or it can be secured with metal straps. Alternatively if the habitat fully encloses the pipe it will typically be fabricated in sections that bolt together around the pipe.
  14. What effect does the heated gas have?

    Initially heated air is pumped into the habitat to purge it of water and dry out the area to be welded – it also provides pre-heating. When the inert gas is introduced, it continues to heat inside the habitat but it also provides a hydrogen-free environment ideally suited to welding
  15. How long does it take to mobilise?

    Mobilisation can be achieved in only a few hours if suitable habitats are already available (e.g. ship repair). If however a complex customized habitat needs to be designed & fabricated then time to complete the habitat is needed.
  16. Has NEPSYS got Class Approval?

    Globally we have approval from DNV, Lloyds, ABS and BV on a case by case basis.
  17. How long does NEPSYS take to weld say, 1 metre of weld?

    This depends on the configuration of the joint, material thickness and other issues like diver access and complexity etc. But as an example NEPSYS was recently used to join a diagonal to a jacket leg in a K-node configuration on an oil rig in the Gulf of Mexico. The circumferential weld was approximately 2 metres around and the material was approximately 10mm thick. This full-penetration weld was completed in 2.75 days from start to finish including full inspection and NDT. Simpler configurations can be completed even more quickly.
  18. Do you get any quenching effect on the weld?

    The heated gas environment within the habitat prevents the quenching and cooling effect of the surrounding sea water.
  19. What different configurations can you weld?

    All joint types can be welded using NEPSYS.
  20. Does NEPSYS use special welding rods?

    A special water proofing is applied to the electrodes but otherwise the rods are commercial off-the-shelf.
  21. Do you work globally?

    Yes, Neptune Marine has worked throughout the Asia region and in the USA as well as all around Australia. We are able to mobilize to all other parts of the world as required from our US division or from the Australian division.
  22. Is NEPSYS patented?

    NEPSYS is patented in Australia and the USA. European patents are still pending.