Offshore supply vessels are those primarily engaged in the transport of stores, materials and equipment to offshore installations; and is designed with accommodation and bridge erections in the forward part of the vessel and an exposed cargo deck in the after part for the handling of cargo at sea.
Definitions 1.2, IMO Guidelines for The Design and Construction of Offshore Supply Vessels, 2006
When Offshore Supply Vessels (OSV) are carrying packaged dangerous goods, they must comply with provisions of IMDG Code.
One of the dangerous goods they carry is Jet Perforating Guns. These are articles consisting of a steel tube or metallic strip, into which are inserted shaped charges connected by detonating cord, without means of initiation.
How Jet Perforating Guns work?
There are two entries in IMDG Code for jet Perforating Guns
| UN Number | Proper Shipping Name | Division | Stowage and Handling |
| 0124 | JET PERFORATING GUNS, CHARGED oil well, without detonator | 1.1D | Category 04: On deck in closed cargo transport unit or under deck in closed cargo transport unit SW1: Protected from sources of heat. |
| 0494 | JET PERFORATING GUNS, CHARGED oil well, without detonator | 1.4D | Category 02: On deck in closed cargo transport unit or under deck SW1: Protected from sources of heat. |
Both entries require Jet Perforating guns to be loaded in “closed cargo transport units” (CCTU) and there is no under deck space in Offshore Supply Vessels (OSVs).
Every cargo handling load/backload on Offshore Supply Vessels (OSV) is a high-risk job. Handling of closed cargo transport units (CCTU) loaded with Jet Perforating guns in it increases risks on these vessels.
Sighting difficulties in achieving the requirements of IMDG Code and the safety of Jet Perforating Guns stowed on deck in tool pallets, cradles or baskets of Offshore Supply Vessels (OSV) United States proposed amendment to IMDG Code to IMO’s Sub-Committee on Carriage of Cargoes and Containers. The proposal was accepted and incorporated into IMDG Code 39th amendment.
IMDG Code 39-18 added a new stowage code SW30 and new provision7.1.4.4.5.
This new provision authorizes transported of Jet Perforating Guns to or from offshore oil platforms, mobile offshore drilling units and other offshore installations to be stowed on deck in offshore well tool pallets, cradles or baskets with certain conditions to be met mandatorily, which are:
- Segregation provisions of IMDG Code
- Securing of guns
- Limitation of explosives in each shaped charge
- Protection of shaped charges
- Pressure release ability in case of fire
- Limitation for total explosive content per well tool pallet, cradle or basket
- Minimum horizontal distance to be maintained between well tool pallets, cradles or baskets
How shaped charges work?
Additional readings
- IMDG Code 39th Amendment
- IMO RESOLUTION MSC.235(82) Adoption of The Guidelines for The Design and Construction of Offshore Supply Vessels, 2006
- IMO RESOLUTION A.863(20) Code of Safe Practice for The Carriage of Cargoes and Persons By Offshore Supply Vessels (OSV CODE)
- OCIMF – Deck Cargo Management Onboard Offshore Vessels
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