I W O C S U M B I L I C A L SC U R R E N T C H A L L E N G E S

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Fibron have been manufacturing workover control umbilicals for over 20 years.

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CHALLENGES

• Workover/Intervention umbilicals, out of necessity,

have become longer.

• The deployment reelers now require significant deck

space to accommodate the increased footprint.

• Umbilical reliability is key to minimise down time and

allow the operators to meet their commitments

In this presentation I want to draw your attention to

some of the limitations in using the current standard to

rigidly control the design and manufacture of workover

control (WOC) umbilicals.

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ISO 13628-5

• This presentation will focus on the standard 13628-

5:2009 Petroleum and natural gas industries —

Design and operation of subsea production systems

— Part 5: Subsea umbilicals.

• Many of the sections need to be adapted or refined

before they can be applied to IWOCS umbilicals.

• Rather than reviewing the complete standard we’ll

consider how this standard applies to the

subcomponents and then the umbilical verification

tests.

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COMPONENTS - CABLES• Minimum nominal cross-sectional area of the

conductors in the umbilical shall be 2.5mm².

• Minimum DC high voltage test requirement of 5 kV

DC.

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COMPONENTS - HOSES

• Hose reinforcement shall be comprised of one or

more layers of synthetic fibre.

• Hose should have a burst pressure greater than

4x the DWP.

• For high pressure hoses the standard leaves it up

to the umbilical manufacturer to determine the

appropriate DWP to BP ratio.

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BURST/IMPULSE TEST• For HP hydraulic hoses it becomes increasingly

difficult to meet the 4:1 burst to working pressure ratio.

• The impulse test of 1.33x DWP at a rate of .0.5Hz to 1.3Hz is not representative of the actual working conditions

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UMBILICAL QUALIFICATION TESTS

Standard qualification tests are:-

1. Lay-up trial

2. Combined torsion balance and tension

3. Bend stiffness test

4. End termination strength and fatigue

5. Combined tension and bending test

6. Crush test

7. Internal/External friction factor assessment

8. Bundle impact test

9. Fatigue

10.Free flooding rate

11.Hydrostatic test

12.Topside termination interface test

13.Repair splice qualification

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COMBINED TORSION BALANCE AND TENSILE TEST• Braids inherently torque balanced

• Umbilical usually clamped to a riser or lift line

• Subsea terminations can be slimline,

• Surface (reeler) termination is typically a clamp or

cable grip

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BEND STIFFNESS TEST• Stiffness calculated using beam theory.

• Umbilical rotated through 180° and retested.

• Stiffness taken as the average of the 4 rotations.

• Not required for the majority of WOC’s umbilicals

clamped to risers.

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END TERMINATION STRENGTH & FATIGUE

• This test is usually replaced with a proof load test

on the actual subsea termination.

• Test normally carried out using a fibre cable grip

platted over the umbilical outer sheath

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COMBINED TENSION & BENDING TEST

• By convention this test is replaced with a reeling/unreeling test.

• The test is either 1,500 or 3,000 cycles over two deployment roller sheaves.

• 2nd sheave simulates the reverse bend encountered during deployment in heave compensation mode.

• One cycle comprises an outward and return stroke with the section under test passing back and forward through both sheaves.

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CRUSH TEST

• Umbilical clamped between two plates to simulate

over boarding using a hold back caterpuller.

• Should be replaced with a clamp test for WOCS

• Umbilicals clamped to a riser.

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INTERNAL/EXTERNAL FRICTION FACTOR

• This test is used to determine the friction factor

between the umbilical sheath and the holdback

caterpuller pads – the test is not carried out on

workover control umbilicals.

• The friction factors between the components is

not directly measured but the umbilical fatigue

test, described in a later slide, tests the umbilical's

ability to meet the operational requirements.

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BUNDLE IMPACT TEST

• Impact test not normally applicable as the

umbilical is not subject to rock dumping.

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FATIGUE TEST

• By convention fatigue test taken as either 100,000

or 120,000 cycles over the deployment roller

sheave

• One cycle comprises an outward and return stroke.

• The stroke length is taken as a multiple of the

umbilical assembly pitch.

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FREE FLOODING TEST

• To determine the longitudinal flow rate through the

interstices of the umbilical.

• Again this test is not normally carried out on

workover control umbilicals.

• The picture on the right shows an umbilical clamp

attached to the umbilical to test if the clamp

restricts the flow through the interstices.

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HYDROSTATIC TEST

• The interstices of the umbilical are free flooding and so the hydrostatic test is not carried out on the umbilical bundle.

• Hydraulic hoses are either fluid filled or pressure compensated to counteract the external pressure.

• Non-collapse hoses are tested under external pressurised to determine their collapse rating.

• The insulated conductors are subjected to an external pressure test.

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REPAIR SPLICE QUALIFICATION

• IWOC’s umbilicals are deployed from a reeler

– no topside termination to test.

• The umbilicals are dynamic and pass over a

roller sheave. Repair splices are emergency

repairs to complete a task

• Repair splice will usually require the ‘keeper’

rollers to be disconnected from the roller box

and possibly the fleeting mechanism to allow

the repair to pass through to the reeler drum.

I M M E R S EReview, Observation, Assemble Team and Lead Times

S U B M E R G EDesign Review & Issue Specs

E N G A G EManufacture of Product

D E P L O YPacking, Launch and Maintain

I M P L E M E N T AT I O NFactory Acceptance and Qualification Testing