TO:ISO/TC 67/SC 4 P-members

COPY TO:ISO/TC 67/SC 4 O-members

ISO Central Secretariat

RE:Ballot of interpretation

In December of last year, ISO/TC 67/SC 4 received a request for interpretation concerning sub-clause 10.2.2 of ISO 13628-5:2002, Petroleum and natural gas industries — Design and operation of subsea production systems — Part 5: Subsea umbilicals. In accordance with TC 67 N 435 Annex G, the request was forwarded to ISO/TC 67/SC 4/WG 6 to develop a response.

Further to the requirements of N 435 Annex G, the request and the rationale are being distributed to the sub-committee P-members for ballot. Please note that in order for the interpretation to be approved at least 50% of the P-members must respond and 75% of the votes received must be for approval.

Please fill out the attached ballot form and return it to me either by e-mail or by fax no later than 10 June 2005.

Regards

Jennifer Kelly

For the Secretariat of ISO/TC 67/SC 4

Ballot of interpretation

ISO 13628-5:2002, Petroleum and natural gas industries — Design and operation of subsea production systems — Part 5: Subsea umbilicals

Sub-clause 10.2.2

Question 1

In section 10.2.2, when undertaking the final part of the tensile test (fifth paragraph) are the electrical tests(10.2.1: i.e. measuring of electrical resistance) stopped when the safe working load is reached?*

Interpretation developed by ISO/TC 67/SC 4/WG 6:

Answer #1: No.

Question 2

If No, are the electrical measurements continued until ' mechanical failure occurs, or when the minimum breaking load is reached ' ?

Interpretation developed by ISO/TC 67/SC 4/WG 6:

Answer #2: The electrical measurements need to be continued until mechanical failure occurs.

Discussion: By testing until mechanical failure occurs, one establishes an understanding of the margins that exist between failure and the specified loads for the test specimen. This margin is important to establish.
A new work item for revision to 13628-5:2002 has recently been approved. The requirement for measurements until mechanical failure occurs will be clarified in the revision.

*relevant clauses are attached for information

We approve this interpretation

We disapprove this interpretation for the reasons stated

Member body voting:

Date: Name:


67/SC 4 N 321 Annex A

Clauses taken from ISO 13628-5:2002

10.2.1 General

Verification tests shall be undertaken to validate the performance of the umbilical. This process can be undertaken using a separate length manufactured prior to main production, or, if the risk is small, using sample(s) from the production length.

If the umbilical contains electrical cores, the following electrical tests shall be performed as an integral part of the mechanical tests:

a) continuous monitoring of the conductor path with each conductor in the umbilical connected in series. The measured DC conductor resistance value shall not exceed the value defined in 7.7.3 at the beginning and end of the test;

b) insulation resistance shall be measured during and after completion of the mechanical testing. The measured value shall comply with the requirements of 7.7.4.

If the umbilical contains optical fibres, light-signal monitoring shall be performed as an integral part of the mechanical test.

If tests require the umbilical to be tensile-loaded, the mechanical means of anchoring shall employ the same design principles as for the service umbilical system.

NOTE 1 Umbilical verification tests to be performed and specified in 10.2 are summarized in annex B.

10.2.2 Tensile test

A representative length of the completed umbilical, which takes account of end effects and pitch lengths of the umbilical components, shall be subjected to a two-stage tensile loading programme.

The first stage shall involve three load cycles to establish the permanent set and residual twist of the umbilical design, up to the maximum design working load. Stage two shall involve a further loading to establish the load at which the components within the umbilical cease to function, and the ultimate tensile strength of the umbilical.

Both ends of the sample shall be terminated in such a manner that for armoured umbilicals the armour wires are gripped, and for unarmoured umbilicals the internal components are firmly gripped. When loaded into the test rig, the specimen shall have freedom to rotate under the action of the tensile load. During tensile testing umbilicals containing hoses/tubes shall be pressurized to their specified installation pressure (for static umbilicals), or to the value defined in the manufacturer's written specification (for dynamic umbilicals). Electrical testing, if applicable, shall be performed in accordance with the requirements of 10.2.1. Optical fibres shall be monitored for optical continuity.

The tensile load shall be applied in a minimum of 10 increments up to the maximum design working load and at each load level, the load, extension and rotation shall be recorded. On reaching the maximum working load, the load shall be reduced and the same procedure utilised during load-down. The procedure shall be repeated for the second and third cycles.

Following completion of the three load cycles, and with the pressure removed, the load shall be increased until mechanical failure occurs, or minimum breaking load is reached, whichever is the sooner. Any prior functional failure of the umbilical shall be noted. At the conclusion of the testing, the umbilical specimen shall be stripped down and visually examined in the event of premature failure of functional components.