Subsea Control System 

Further to the EFAT, the Subsea Control System will need to be incorporated with all of the other deliverable components of the SPS package and tested fully as an integrated system. This type of test is called a ‘System Integration Test’ or ‘SIT’.

Planning should be made in the project Schedule for availability of at least one subsea Xmas tree and the template / manifold, so that the overall operation of the system can be verified. (These are not always available at the correct time for 'acceptance testing' of the subsea controls equipment, hence another the reason for the EFAT)

The controls system contract should therefore clearly state the definition of any required system testing and should clarify at what point the equipment is considered 'accepted' from the Supplier. Ideally, this should only be when overall operation of the complete system (including trees, manifold etc) is proven, but this is often difficult to arrange, particularly if the individual schedules are widely separated. In this event, a financial retention is sometimes made, to ensure the eventual testing is performed. In any event, a Warranty Period will cover problems with system operation, but the incentive to correct them in a timely manner must be maintained.

The Client or its Representative should witness the SIT. In order to achieve this, the Supplier must issue a Notice Of Readiness in sufficient time for the Client to mobilise its Representatives, typically, 15 working days is required to mobilise all interested parties for an SIT.

Care should therefore be taken in contractual documentation at the start of a project to ensure these provisions are included, else the Client will find that the last minute changes of schedule and lack of readiness will cause considerable disruption to its other project responsibilities. Similarly, where some tests require the presence of equipment supplied by others, care should be taken to ensure the schedules coincide. Organisation of the SIT is ultimately the contractor’s responsibility, however this test is crucial to verify full and proper communications and functionality of the full Control system when hooked up to Tree and manifold system. Therefore a full understanding of the requirements and a constant overview is required by the client at all times to avoid anything being overlooked.

The SIT is the only opportunity for a Client, its partners, the eventual system Operators and the Installation Contractor, to see all of the SPS equipment operating as it should, prior to being installed subsea. Therefore, significant importance should be placed on the event and the witnessing thereof. Photographs and video records of all aspects of the equipment should be made. All drawings should be checked and marked-up for 'as-built' at this time, as full and correct records will be invaluable once installation commences and for the life of the system. ROV operators in particular should use the opportunity to familiarise their operators with the equipment.

A SIT is usually performed at the manifold / template fabricator's site, or tree supplier, and provision must be made in the respective contracts for access by the controls supplier etc to perform these tests without disruption to the formers' contractual schedule.

At the start of SIT, it is assumed that all equipment has already successfully passed the individual Factory Acceptance Testing (FAT) and system EFAT (the availability of the Test Records should be verified).

Therefore, each item can be assumed to operate correctly and interface with its immediate external interfaces. The emphasis of the SIT is therefore to verify that the overall system operates as expected, especially with equipment that has never been connected together as a system before. In particular, that the equipment interfaces correctly with its Installation aids and can be physically installed into position, retrieved, operated by ROV etc.

In general, equipment should be tested for:

Where equipment is missing from the SIT, Simulators should be employed; care should be taken that these have themselves previously been tested as both functional and fully representative of the unit they are simulating.

The proposed test procedure should be written and submitted to the Client for review and approval. No test should be performed until the document has reached an acceptable status; therefore, the first issue should be submitted to the Client at least 6 weeks before the test. A signed, approved copy of the test procedure should be used to perform the test and the test procedure should not then be modified without written permission from the Client; in any event, a corrected document should be issued.

Previous FAT Results should be available.

The results of the SIT procedure should be recorded in a System Integration Test Report document, usually included as an Appendix to the SIT procedure itself. The Report document should then be supplied with the final project documentation.

It should be signed and dated by all witnessing parties.

The report should be written as concisely as possible. However, care should be taken that actual test values are recorded, as well as a statement of PASS/FAIL for each test, so that the document can be used to check differences between identical units, as evidence of drift in parameters, or be used as reference values for other future tests.

All tests should be witnessed by the Supplier's QA department and test results 'stamped' as official records of events.

Ideally, the Supplier should have performed each test procedure at least once, before notifying the Client to attend, so that errors in the procedure are detected at an early stage.

The following is a summary of parameters that should be tested as a minimum for a subsea control system. They may be some overlap of testing from the EFAT, however this will be the first time the control system has been interfaced with other equipment from the SPS package i.e. manifold and trees. It cannot be exhaustive, as each system will be different, but again, as stated before, the Client will find that the more testing that can be performed onshore before installation, the better the chances of a trouble-free installation and commissioning.

On completion of the SIT, particular attention should be paid to leaving the system in the correct state for installation and / or operation, such as: