Transport of liquid chemicals in bulk for Offshore Support Vessels (OSVs)

Amendments to the IBC Code will take effect from 1 January 2021. Although the IBC Code regulates the transport of dangerous chemicals in bulk on tankers, it also impacts OSVs transporting chemicals in bulk. Consequently, some important considerations will be needed to keep the vessel fit for purpose. This statutory news summarizes the IBC Code revisions for OSVs.

Transport of liquid chemicals in bulk for Offshore Support Vessels (OSVs) | DNV GL - Maritime

Relevant for owners and managers of OSVs as well as flag states.


  • Most products previously deemed “pollution-only products”, denoted with a “P” in column (d) of Ch. 17 of the IBC Code, have been re-classified to also pose a safety hazard in addition to the pollution hazard, and column (d) has been updated with an “S/P”. IMO Resolution A.673(16), also known as the LHNS Guidelines under which all OSVs are currently certified, is open for waiving certain requirements for tanks solely certified for “pollution-only products”. This implies that with the revised carriage requirements, the basis for the waiver ceases and the range of products will be drastically reduced for these tanks. Typically mud and brine tanks will lose most of the products on the NLS certificate or Certificate of Fitness.
  • The LHNS Guidelines limit the products which may be carried to IMO Ship Type 3 products which are non-toxic. For instance, methyl alcohol, better known as methanol, will be re-classified as toxic with the revised IBC Code. This suggests that methanol may no longer be carried subject to the LHNS Guidelines. The same goes for products which have been re-assessed with a stricter IMO Ship Type requirement than Type 3.
  • The transport and handling of contaminated bulk liquids from an offshore installation to shore, normally referred to as back loading, is currently performed subject to local and shelf state requirements. For this, there are two new entries in the revised IBC Code: “Offshore contaminated bulk liquid P (o)” and “Offshore contaminated bulk liquid S (o)”. Both entries are classified as IMO Ship Type 2 products and the latter as toxic, meaning that they fall outside the scope of the LHNS Guidelines.

Norwegian-flagged OSVs

The Norwegian Maritime Authority (NMA) published a circular (RSV 14-2020) in June 2020 addressing the impact of the amendments, the challenges and solution for Norwegianflagged OSVs. The main message was that OSVs should be modified and re-certified under the new OSV Chemical Code (OSVCC).

The RSV 14-2020 circular has now been revised and superseded by RSV 23-2020, which allows for continued operation under the current LHNS Guidelines for a limited number of products for which the revised IBC Code carriage requirements hinder carriage, namely those products listed in Appendix 1 of the LHNS Guidelines. As such, the revised circular proposes a more pragmatic approach with less effort needed for OSVs that primarily carry these products, typically mud, brines, glycol and methanol. Products not in Appendix I, but which are within the scope of the LHNS Guidelines, i.e. nontoxic Ship Type 3 products, may of course still be carried under the LHNS Guidelines.


The alternative solution for OSVs deciding to continue subject to the LHNS Guidelines is given in RSV 23-2020 and implies the following:

  • Even though the products have been re-classified to also pose a safety hazard, it will still be possible to continue carrying the products listed in Appendix 1 of the LHNS Guidelines in tanks for which the requirements have been waived based on “pollution-only products”.
  • Products listed in Appendix 1 of the LHNS Guidelines which have been re-classified to Ship Type 2 and/or toxic may still be carried, provided that:
    • cargo tanks are inerted when carrying products with a flash point below 60°C, and
    • the OSV meets the relevant special requirements for toxic products, according to Ch. 15.12 of the IBC Code, except 15.12.2 (vapour-return).
  • “Offshore contaminated bulk liquid P (o)” may be included in the certificate despite being a Ship Type 2 entry. NMA is also in the process of proposing a third IBC Code entry for offshore contaminated bulk liquids, covering those that have been treated to remove or prevent the breakout of hydrogen sulphide (H2S), which also may be carried on OSVs certified under the LHNS Guidelines. A precondition for carriage of any back loads subject to the LHNS Guidelines is compliance with Ch. 16 of the OSVCC, implying installation of fixed vapourdetection instruments for H2S and LEL in the venting system.

Please note that other carriage requirements that may have been added should be complied with. This could typically be 15.17, which requires increased ventilation of cargo pump rooms, and “Yes” in column (n), which requires emergency escape sets for every person on board. Please see the overview in Annex 1 to this news showing the current and revised carriage requirements for the products listed in Appendix 1 of the LHNS Guidelines.

Transitional period/issuance of certificate

The revised IBC Code enters into force on 1 January 2021, and NMA has recognized that more time will be needed to sort out the details for every OSV. For vessels continuing under the LHNS Guidelines, a new Certificate of Fitness based on the IBC Code amendments shall be issued prior to 1 January 2022 and kept on board with the existing NLS certificate or Certificate of Fitness. The revised certificate will have the same expiry date as the existing certificate, and is effective and supersedes the existing NLS certificate or Certificate of Fitness on 1 January 2022. A solution for requesting the new certificate will be available in My Services on Veracity. Details on how to request the new certificate will follow later with separate RRs (Retroactive Requirements) issued for each relevant vessel.

Vessels choosing to convert to the new OSVCC will be issued with a Certificate of Fitness under the OSVCC upon completion of the initial survey following the conversion. This should preferably be carried out before 1 January 2022, otherwise a new Certificate of Fitness under the LHNS Guidelines needs to be obtained covering the period from 1 January 2022 until the conversion is completed and a new Certificate of Fitness under the OSVCC has been issued.

Other flags

With NMA leading the way on this, DNV GL will contact other flags seeking their consent for a consistent approach.


In order to make sure that an OSV is fit for purpose, it must be decided whether to continue under the LHNS Guidelines or to convert to the new OSVCC.

For the cases where only those products listed in Appendix 1 of the LHNS Guidelines are to be carried in volumes less than 800 m3, continuing under the LHNS Guidelines may be the most convenient. In that case, some minor alternations may be needed such as:

  • Modifications in order to comply with the relevant parts of Ch. 15.12 of the IBC Code for toxic products
  • Fitting of decontamination showers and eye wash, which is a general requirement for products posing a safety hazard
  • Fitting of fixed vapour-detection instruments for H2S and LEL in the venting system for the carriage of contaminated back loads
  • Fitting of P/V valves on mud and brine tanks in order to comply with the proposed new entry for offshore contaminated bulk liquids that have been treated to prevent the breakout of H2S

Alternatively, if there is a need to carry Ship Type 2 and toxic products not listed in Appendix 1 of the LHNS Guidelines and/ or to carry volumes exceeding 800 m3, a conversion to the OSVCC will be required. Please also note that with the new OSVCC in force, the basis for giving exemptions for products falling outside the scope of the LHNS Guidelines will cease.

Design review

Based on the needs, including which products and what volumes are to be carried, we recommend performing a design review for individual OSVs to determine the scope of conversion. DNV GL may assist with a design review as a separate project.


  • RSV 23-2020 - Carriage of hazardous and noxious liquid substance in bulk on existing offshore support vessels after 31 December 2020


  • Annex I – Products Listed in Annex I of Resolution A.673(16) – LHNS Guidelines (see PDF download page 3-4)


  • For customers: DATE – Direct Access to Technical Experts via My Services on Veracity 
  • Otherwise (including approved radio service suppliers): Use our office locator to find the nearest DNV GL office.
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