26 Factory Acceptance Testing (FAT)

26.1 General

Every deliverable component of the Subsea Control System should be subjected to a formal test procedure, before acceptance from the Supplier for shipment to the delivery location.

This type of test is usually termed a ‘Factory Acceptance Test’ or ‘FAT’.

The proposed test procedure should be written and submitted to the Purchaser 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 Purchaser 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 Purchaser; in any event, a corrected document should be issued.

The Purchaser or its Engineering Representative should witness every FAT. Sole QC is inadequate for this Engineering function which requires knowledge and understanding of the system and system components to observe the system test and to note and question any irregularities.

In order to achieve this, the Supplier must issue a Notice Of Readiness in sufficient time for the Purchaser to mobilise its Representative, typically, 5 working days is required.

Care should therefore be taken in contractual documentation at the start of a project to ensure these provisions are included, or else the Purchaser 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.

26.2 Test Requirements

In general, equipment should be tested for:

Mechanical completion and conformance to drawing dimensions.
Interfaces with other equipment.
Functional operation over the complete range of specified parameters.
Of particular concern should be Hyperbaric testing, particularly in deepwater applications where equipment has not previously been fully qualified for the design working pressure. All subsea equipment must be tested inside a hyperbaric chamber and be surrounded by the test medium. This is not always easy to achieve; equipment is sometimes tested at modular level and later connected together and care should be taken to ensure that there does not remain an interface that has never been subjected to hyperbaric pressure.
Each item of equipment should be tested using Simulators for inputs and test boxes for outputs.
Figure 26.1 - Subsea sensor simulator

Testing against other deliverable items is done at a later stage (see "System Integration Testing" section Chapter 28, System Integration Testing (SIT)). It is also advisable to perform 'low-level' testing on complex items, such as the subsea telemetry protocol, using the Supplier's Design Specifications, on at least the first deliverable unit, to verify that all sub-units are operating correctly and, in particular, perform correctly with applied 'fault' conditions.
Care should be taken that the Simulators have themselves previously been tested as both functional and fully-representative of the unit they are simulating.
Other environmental testing should also be performed on at least one of every design of deliverable equipment. This should include vibration and shock testing, load tests. This "Qualification Testing" may form a separate part of the overall QA Plan and Contract; it should only be granted a 'waiver' if the Supplier can demonstrate similar testing on identical equipment from an earlier project.

26.3 Documentation

Before commencing the test, always ensure that the latest, Customer-approved version of the Test procedure is to be used.

Verify that the item to be tested has been correctly manufactured in accordance with the Suppliers normal manufacturing procedures and documentation and is fully complete.

The results of the FAT procedure should be recorded in a Factory Acceptance Test Report document, usually included as an Appendix to the FAT procedure itself. The Report document should then be supplied with the Unit and in any event, it should form part of 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 type of test procedure at least once, before notifying the Purchaser to attend (typically called an in-house FAT), so that errors in the procedure are detected at an early stage.

Parameters appearing outside of the specified test limits are cause for rejection of the complete unit; a re-test should only be held once the problem has been found, corrected, and a report made to, and accepted by the Purchaser.

This is then an incentive for a 'dry-run' test to be performed by the Supplier before notifying the Purchaser. If so included in the Contract, a Purchaser may be entitled to reclaim its costs of attendance following an aborted test, unless due to unforeseen events.

26.4 Test Parameters

The following is a summary of parameters that should be tested as a minimum for each type of subsea control system component described in this Chapter of the Data Book. It cannot be exhaustive, as each system will be different, but the Purchaser will find that the more testing that can be performed at the factory, or onshore before installation, the better the chances of a trouble-free installation and commissioning.

26.4.1 Master Control Station

All mechanical Details; all components/serial numbers recorded.
All required documents and drawings at approved status
Operation over power supply range.
All memory passes functional test.
Operating software installed onto newly formatted / de-fragmented hard disc.
Start up (and shutdown) operates smoothly and does not cause fluctuations in digital or serial outputs.
All displays match the design specification.
Each display to be tested for correct system operation (e.g. EPU display shows all necessary EPU/HPU parameters, can control all outputs etc, all maintenance displays operational, 'help' files correctly installed.)
All ESD inputs cause the correct ESD sequence.
Interfaces to FPSO/Platform SCADA system operate correctly.
Date/time synchronisation with PCS.
Subsea Telemetry matches its design specification, operates correctly with a 'real' SCM, can detect all types of fault without loss of data to other operational SCMs. (Test equipment should simulate a complete field, rather than just one SCM).
All interlocks and overrides operate correctly and do not cause unexpected actions when released.
MCS operates correctly when 'fully-loaded' i.e. with a full subsea system attached, interface to SCADA operational, ESD inputs activated.
MCS operates correctly when some of the subsea SCMs are inoperative (faulty or removed).
Of particular interest in testing an MCS is its ability to handle 'unexpected' events, such as particular failure modes in the subsea telemetry, error-codes in the various serial interfaces, unexpected key-presses during other operations, activation of a higher-priority ESD signal during a lower-priority one etc.
Where a dual-redundant system is employed, the changeover to the backup unit is 'bumpless' i.e. does not cause any unexpected actions, changes of state of digital outputs, operation of any subsea valves etc. Similarly, the return to the main unit should also be 'bumpless'.
Historical data recording system operates correctly over a wide time period. Verify data can be downloaded to disc/ other equipment as per specification.
Operates correctly over full range of ambient temperature. A 'heat-soak' test should be performed.

26.4.2 Electric Power Unit

All required documents and drawings at approved status
Operation over full range of input voltage, frequency, loads, start up surges.
Visual checks on workmanship, cable marking etc.
Insulation testing cores to ground and each other.
Continuity testing.
Earth continuity tests.
Circuit breaker tests.
Line Insulation monitoring tests (particularly as regards usage with subsea umbilicals and long-term Testing)
Heat soak tests / Burn in period.

26.4.3 Uninterruptible Power Supply (normally supplied by others)

Operation over full range of input voltage, frequency, loads, start up surges.
Heat soak tests / Burn in period.
Visual checks on workmanship, cable marking etc.
Insulation testing cores to ground and each other.
Continuity testing.
Earth continuity tests.
Circuit breaker tests.

26.4.4 Hydraulic Power Unit

All required documents and drawings at approved status
Mechanical details correct, including correct identification of all hand valves, gauges etc per P&ID.
Certified lift tests performed on pad-eyes.
Correct pre-charge in accumulators.
Correct operation of safety valves.
Correct generation of output pressures.
ESD solenoid valve operation.
Adjustment of output pressures (where regulators available).
All electrical system operational, including all outputs to remote display at MCS (may be a serial data link), emergency stop circuits, remote/local control of pumps, flowmeters.

26.4.5 Subsea Control Module and Mounting Base

Correct mechanical details
- All required documents and drawings at approved status
Correct interface with stabplates, connectors (correctly polarised and marked), Mounting Base.
Telemetry system operating as per design specification; test all electronic commands for correct operation on at least the first unit.
Hydraulic outputs operate correctly; maintain output until LP supply lowered to specified value and then all close.
No hydraulic leakage to vent port
No outputs affect other outputs when operated.
All sensor inputs operate correctly and are calibrated correctly.
Heat soak test (at high and low temperatures)
Hyperbaric test on each unit.

26.4.6 Subsea Accumulator Module

All mechanical details correct as per specification
All required documents and drawings at approved status
Correct pre-charge in accumulators
All valves operate correctly, marked correctly.
Pressure and volume test.

26.4.7 Subsea Distribution Unit

All mechanical details correct as per specification. Markings correct and visible.
All required documents and drawings at approved status
Correct interface with stabplates, connectors (correctly polarised and marked), Mounting Base, ROV connectors,
All block/bleed valves operate correctly; no leaks
All electrical outputs operate correctly and wired correctly.
Current limit functions operate correctly, where included.
Hyperbaric test on each unit. This is usually impossible on the whole unit due to its size, however, where an SDU contains an electrical distribution unit (EDU), this is usually small enough to be Hyperbarically tested, and this should be insisted upon.

26.4.8 Subsea Umbilical Termination Unit

All mechanical details correct as per specification. Markings correct and visible.
All required documents and drawings at approved status
Hyperbaric testing is usually impossible on these units due to their size. However, pressure testing of field-installable electrical connectors must be performed as a minimum.

26.4.9 Topsides Umbilical Termination Unit

All mechanical details correct as per specification.
All required documents and drawings at approved status
Markings correct and visible.
Pressure & leak test all pipes and valves
Lift test