IACS History File + TB Part A UI SC140 Secondary Means of Venting Cargo Tanks Part A. Revision History Version no. Approval date Implementation date when applicable Rev.3 (Jan 2011) 28 January 2011 1 July 2013 Rev.2 (Nov 2005) 17 November 2005 - Rev.1 (June 1999) No Record - NEW (Oct 1998) 09 October 1998 - Rev.3 (Jan 2011).1 Origin for Change: Other (Suggestion by OCIMF).2 Main Reason for Change: OCIMF has been working with IACS for the last several years in order to resolve differences between IACS UI SC140 and OCIMF SIRE VIQ Inspector Guidance notes on the correct interpretation and application of SOLAS Reg. II-2/11.6.3.2. OCIMF are of the opinion that their guidance notes most accurately reflected the correct interpretation of the SOLAS secondary venting requirements for tankers. Accordingly, it was agreed that IACS would amend UI SC140 in order to clarify any differences with the OCIMF guidance..3 List of non-iacs Member classification societies contributing through the TC Forum and/or participating in IACS Working Group:.4 History of Decisions Made: Feedback was received from OCIMF regarding their views on UI SC140 in respect of secondary venting and valve arrangements. Discussions at Machinery Panel meetings and between Panel Chairman and OCIMF have demonstrated that revisions to UI SC140 are necessary. Form A submitted by the Machinery Panel was approved by GPG on 28 March 2008. Panel Chairman submitted the draft revised UI SC140 and its HF&TB concerning Secondary Means of Venting Cargo Tanks to GPG on 12 January 2011. GPG, after further discussions, approved the revised UI SC140 on 28 January 2011..5 Other Resolutions Changes.6 Dates: Original proposal: March 2008 Made by: Machinery panel Page 1 of 3
Panel Approval: 12 January 2011 GPG Approval: 28 January 2011 (Ref. 6041_IGn) Rev. 2 (Nov 2005) The references to SOLAS within the UI were updated so that the references were corrected in respect to the updated SOLAS and FSS Code. Rev. 1 (June 1999) The fourth paragraph was added to the UI, which is currently paragraph 4 of the Rev. 3 version. New (Oct 1998) The UI included three paragraphs which are currently paragraphs 1, 2 and 3 of the Rev. 3 version. Page 2 of 3
Part B Part B. Technical Background List of Technical Background (TB) documents for UI SC140: Annex 1. TB for Rev. 3 (Jan 2011) See separate TB document in Annex 1. Note: 1) There are no separate Technical Background (TB) documents for UI SC140 New (Oct 1998), Rev.1 (June 1999) and Rev.2 (Nov 2005). Page 3 of 3
Part B, Annex 1 Technical Background for UI SC140 Rev.3, Jan 2011 1. Scope and objectives Feedback from OCIMF regarding views on UI SC140 in respect of secondary venting and valve arrangements highlighted discrepancies between their documentation and IACS interpretation. Discussions at Machinery Panel meetings and between the MP Chairman and OCIMF have demonstrated that revisions to SC140 are necessary. Therefore, the objective was to revise current version of SC140 to reflect feedback from OCIMF on the practical application of SC140 and reported tank damages due to valve operation/mal-operation during cargo handling. 2. Engineering background for technical basis and rationale OCIMF believes that vessels utilising a common gas / vapour system as the primary means of venting which is isolated from a cargo tank by a valve, or other means, which is shut due to the normal operation of the vessel (such as in the case of a vessel carrying parcel cargo with non compatible vapours) are not in compliance with the requirements of SOLAS Reg. II-2/4.5.3 unless they have a second independent means of venting which can not be isolated from the cargo tank. After careful consideration, the OCIMF concerns were discussed during the 9 th IACS Machinery Panel meeting and the agreed consensus was the UI SC140 was applicable to arrangements involving homogenous or compatible cargo vapours (such as ships with groups of tanks with each group having a secondary venting arrangement, etc.) and the UI would be amended to identify this. For tanks with non-compatible cargoes, independent secondary venting arrangements shall be provided. OCIMF also believes that the Human Element should be considered when approving the secondary means of venting for a cargo tank as there have been some cases where personnel have inadvertently left valves in the incorrect position when completing filling/discharging operations. The machinery panel also discussed this point at the 9 th IACS Machinery Panel meeting and it was identified that paragraph 4 of the UI already clearly addressed the IACS position on this issue, as follows: Inadvertent closure or mechanical failure of the isolation valves required by SOLAS Reg. II-2/4.5.3.2.2 and the FSS Code, Ch. 15, paragraph 2.3.2.2 need not be considered in establishing the secondary means since: a) The valves are operated under the control of the responsible ship s officer and a clear visual indication of the operational status of the valves required by SOLAS Reg. II-2/4.5.3.2.2, as amended, and b) The possibility of mechanical failure of the valves is remote due to their simplicity. However, the machinery panel agreed to include the clarification for homogeneous cargoes to paragraph 4.
Based on experience with certain chemical tankers it was suggested that IACS should also make clarifications on the required settings of the P/V -alarms that are generally accepted as an alternative means to secondary venting, such as for ships that do not have P/V-breakers and/or do not carry homogenous cargoes. It is understood that the purpose of the alarms is to warn the crew in the event the P/V-valves (being the primary means of venting on these ships) have malfunctioned. The panel agreed and therefore, a new paragraph 5 was added to the UI as follows: For ships that apply pressure sensors in each tank as an alternative secondary means of venting as per SOLAS Reg. II-2/11.6.3.2, the setting of the overpressure alarm shall be above the pressure setting of the P/V-valve and the setting of the under-pressure alarm shall be below the vacuum setting of the P/V-valve. The alarm settings are to be within the design pressures of the cargo tanks. The settings are to be fixed and not arranged for blocking or adjustment in operation. The matter was further discussed at the 12 th Machinery Panel meeting and the consensus was that at the introduction of UI SC140 in 1998 it was clearly communicated that due to the locking arrangements and requirement to visual indication of position for cargo tank isolation valves, inadvertent closing of these valves was not assumed to be a failure mode. As such therefore this is seen as an operational matter and should further amendment be required this must be directed through flag administrations to IMO. 3. Source/derivation of the proposed IACS Resolution - SOLAS Reg. II-2/4.5.3 Cargo Tank Venting - SOLAS Reg. II-2/11.6 Protection of cargo tank structure against pressure or vacuum in tankers - OCIMF SIRE Vessel Inspection Questionnaire 8.3 Are SOLAS secondary venting requirements being complied with? 4. Summary of Changes intended for the revised Resolution: - To identify that this UI is only applicable for homogeneous or cargoes where the vapours are compatible and do not require isolation. - To include requirements for the setting of P/V alarms where they are used in lieu of a secondary means of venting. 5. Points of discussions or possible discussions 6. Attachments if any