Subsea Power Control Unit Structure (SPCUs)

This tender refers to the fabrication of 4 off Subsea Power Control Units (SPCUs) suitable for use underwater to a depth of 20m.  Essentially, they are the pressure hulls to encase the power electronics. Each one of the SPCUs support a single turbine to provide independent power control of each turbine so that the turbines can be controlled independently or ultimately each one can be shut down in the stalled or braked condition.

SCOPE OF WORK

Nesting of all structural parts

All the structural outputs parts and CAD DXF files will be presented to the contractor for them to cut out of the appropriate plate. The minimum of wastage is required. All the parts will be marked and labelled in accordance with the part filename which will then be used in an assembly plan provided.

Design review

The fabrication standards to be used are DNV-OS-C401 but equivalent standards for the yard will be considered.

Review of the overall CAD STEP model files. Progress will be tracked using this CAD file with completed part turning green.

Given the SPCU is considered primary structure, each weld will be traceable with qualifications of welders checked. Each weld will be associated with an individual welder.

Presentation of the build method to ensure quality of production in terms of tolerances and alignments to reduce the amount of rework.

Review of critical stress areas and primary structure where the most stringent quality standards and NDT checks will be applied. The definition of:

1. Critical structural areas will be defined
2. Primary structural areas will be defined
3. Secondary structural areas will be defined
4. Tertiary or typically first fix areas will be defined

Fabrication of 4 off Subsea Power Control Units

Materials used in the fabrication will need to have the correct certificates of compliance with materials grades in accordance with DNV-OS-C401 or equivalent.

Appropriate H&S standards need to be applied during the fabrication of the SPCU cabinets. QED reserves the right to make onsite inspections and will provide the contractor with feedback using Health and safety Observation Records (HORs) where the contractor will be expected to comply with agreed mitigation measures.

Refer to drawing no. QED-TIGER-DWG-00300-01 for SPCU Structure.

Fabrication of First Fix

All hot work on the SPCU needs to be completed prior to painting therefore all necessary brackets and appendages for fixtures and fittings need to be completed in accordance with the design drawings. The tolerance on these systems may be quite tight so appropriate setup time is required and part of the work scope.

The system drawing will be presented on award of the contract. If you require a draft copy for quotation then please let us know. Otherwise we would expect to take a small percentage of the development time.

! WARNING Incorrect positioning of 1^st fix items can lead to significant re-work at the contractors cost unless adequately specified.

Fabrication of the SPCU Cassette

Fabrication of the SPCU cassette which will be inserted into the main structure will be completed as part of this work package to ensure fit up and tight tolerances.

All other processes as above.

Refer to drawing no. QED-TIGER-DWG-00300-02 for SPCU cassette.

This component will be used by the electrical and electronic engineers to mount their equipment on so this component will be prioritised or at least the first on the production line will be required for them to assemble the test equipment on.

Figure 2: SPCU cassette which will house all the electronic equipment

Painting

The whole of the SPCU needs to be painted in accordance with NORSOK M-501 System 7B standards using the Jotun paint or equivalent (colour traffic yellow – RAL 1023).

Suitable preparation of all surfaces is required using the prescribed sand blasting methods.

Suitable ventilation or PPE is required during this process.

A drawing with all the masking details will be provide at the award of the contract.

Iso view of the SPCU main structure, fully assembled

If you wish to apply or have any questions please email us at tenders@qednaval.co.uk and use the tender title above as the subject line. 

Final Expression Of Interest (EOI) date: Monday 26th April 2021

Final submission deadline: this has now been extended to 12:00:00 B.S.T. Wednesday 5th May 2021

Questions submitted:

Q1: The deadline for submission of completed ITT documentation is on 12:00:00 on Monday 3rd May 2021.  Would it be possible to extend the submission deadline?

A1: QED will extend the deadline to 12:00:00 B.S.T. on Wednesday 5 May 2021

Q2:  Origin (QED-TIGER-ITT-00300-05-C4 SPCU) Is there any specific milestone/date to when the first fix and/or all 4 off SPCUs are needed?

A2:  We are looking for 1 cabinet to be built per month but there needs to be a priority to building the cassette first as this needs to go directly to the power electronics lab so that they can assemble it. The aim is to have the 4th cabinet built and delivered to Southampton by Friday 3rd September 2021.

Q3: Origin (QED-TIGER-DWG-00300-01-B1 SPCU GA and QED-TIGER-DWG-00300-02-B1 Sliding Cassette GA)  According to Inyanga’s initial feasibility study on electrical and control system design in a different tender (Function Spec of Subsea Power Control Units), there is a concern regarding a tight fit of componentry within the enclosure/cassette.  Would it be possible to arrange an initial meeting to briefly discuss this prior to the final submission date?

A3: Yes, it would be possible to discuss this matters prior to submission.

Q4: Origin (QED-TIGER-DWG-00300-01-B1 SPCU GA)  The lift eyes are welded to the item 06 (rolled plate) but the supporting stiffener plates (items 7 and 16) and welded using the standard 6mm fillet and have limited access. A preferred option would be to slot the rolled plate and extend the profiles of items 7 and 16 to include the lifting eyes as shown in ‘Note for #4’ sheet. This could also be further discussed in an initial meeting as appropriate.

A4: This has been considered during the initial design and might get changed in the final version. However, there will be a very high safety factor so the current design is still adequate.

Q5: Origin (QED-TIGER-ITT-00300-05-C4 SPCU)  The fabrication will be in accordance with DNV-OS-C401, is attendance of third party surveyors expected, throughout during the build process? Will QED be contracting these services directly?

A5: No, there is no intention to involve a third party surveyor.

Q6:  How is Electrical bonding between main structure (that supports the turbines) and the power control unit structure and the cassette achieved?

A6: This will be determined during the Function Spec of Subsea Power Control Units stage and populated in the final design.

Q7: Is there a requirement for sacrificial anodes?

A7: This has not been decided yet. If yes, then QED will free issue them and there will be a requirements for fixing bolts to be welded.

Q8: Origin (QED-TIGER-DWG-00300-01-B1 SPCU GA and QED-TIGER-DWG-00300-02-B1 Sliding Cassette GA)  Is there a design philosophy for the enclosure that can be shared? There seems to be very limited usable space compared to the external size. Is heat transfer through the domed surface an anticipated design feature?

A8: The enclosure geometry is driven by the heat transfer requirements to ensure that the electrical components operate within their parameters. The design philosophy will be shared with the successful bidder.

Q9: Origin (QED-TIGER-DWG-00300-01-B1 SPCU GA and QED-TIGER-DWG-00300-02-B1 Sliding Cassette GA)  How is the cassette withdrawn / inserted – what supports the weight during this process? Lifting points?

A9: The SPCU will be removed from the Subhub and placed onto a working barge which will have a suitable fixtures for the removal of the cassette.

Q10: If there is an external cooler required for each cassette, are these mounted on the enclosure?

A10: The heat transfer study is going to be carried out before the final design is signed off. This will include any external cooler if required.