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The Stellar Daisy Loss: Understanding Cargo Liquefaction Risks

 

by Kaivan H. Chinoy, Petro Inspect / The Bunker Detectives


It is extremely sad to see the loss of bulk carriers, particularly Very Large Ore Carriers (or VLOCs) making headlines in this day and age. While the cause of the disappearance of the Stellar Daisy is still a speculation, the evidence of an oil slick suggest the vessel has sunk.

           

Stellar Daisy may have been a 24 year old bulker (built 1993, source: VesselsValue); but surely under a strict enhanced Class Survey regime comprising of regular inspections to detect potential structural weakness and areas of corrosion, and being operated under new SOLAS rules that cover survivability and structural requirements for bulk carriers of 150 metres and upwards to prevent them from sinking easily if water enters the ship for any reason - vessels these days just don't disappear into thin air!

Large bulk carriers, due to their length (to put it in perspective Stellar Daisy was approx. over 3 footballs fields long!) are susceptible to extreme stress or cyclic loading where some parts are exposed to fluctuating loads (structures under stress) more than others. Under the right conditions, the ship could literally break it's back and sink like a rock with no time for the crew to abandon ship. Other reasons could be cargo shift due to liquefaction, collapse of a hold compartment due to combination of adverse weather conditions / flooding / fatigue failure etc. That said, sinking may have been attributed to a single cause.

A lot has been written about these large ore carriers and numerous P&I safety bulletins issued in way of liquefaction of ore cargo (which may well be one of the causes) along with emphasis on MSBC code regarding Flow Moisture Point (FMP) and Transportable Moisture Limit (TML).

So what is Liquefaction? It's a known issue with most ore cargoes include coal. The key issue is whether the solid bulk cargo that is to be loaded is liable to liquefaction? The cargo may appear to be relatively dry when loaded; however, it may still contain sufficient moisture to become fluid under the stimulus of the compaction and vibration that occurs during a voyage (caused by recurring cycles or cyclic forces, such as the movement of the ship and rolling/pitching/pounding etc.) resulting in a potential loss of the ship's positive stability from a reduction in metacentric height (GM). The effect on a ship can be sudden and dramatic causing the vessel to capsize! Essentially when the cargo is loaded with moisture content in excess of its TML the cargo may reach a fluid-state (liquefaction). For this reason we must determine / understand, the limits of Moisture Content (MC) and Transportable Moisture Limit (TML) for the cargo in question. The Canadian Code of Safe Practice for Solid Bulk Cargo which is essentially the same as the IMSBC Code (SOLAS 1974 and its Protocols) sets out the internationally agreed provisions for the safe stowage and shipment of solid bulk cargoes, including cargoes that may liquefy.

TML is defined as 90% of the Flow Moisture Point (FMP). TML represents the maximum moisture content of the cargo which is considered safe for carriage in ships (regulation 1.7.27 of IMSBC Code Ed 2013). TML can be explained as a ref value against which MC is measured.

FMP of any cargo is considered to be the percentage of MC at which the cargo would behave like a fluid and develop a flow state (i.e. liquefying). The FMP depends on the characteristics of cargo; the environment in which it is kept (e.g. stored out in the open exposed to the environment like rain, snow etc.) and should be measured experimentally in a laboratory environment The bottom line is that any such cargo may liquefy if shipped with MC in excess of their TML.

In other words, for the cargo to be acceptable for loading the MC should be less than it is TML. The Code also states that the shipper must provide the Master with written evidence that the MC does not exceed the TML. This is usually in a form of a certificate/declaration (there is no prescribed format) and the analysis should have been recently done (less than 7 days). As a minimum the certificate of the MC / TML should bear the following:
1. Duly signed and dated
2. MC test conducted with the last 7 days from the date of the certificate
3. Note TML tests could be valid up to 6 months (see frequency of TML/MC testing Regulation IMSBC Code Reg 4.5.1 /4.5.
4. Declaration by shipper that the moisture content is, to the best of his knowledge and belief, the average moisture of the cargo at the time the declaration is presented to the Master.

Failure to provide with such a certificate declaration the Master should not load the cargo and has the right to reject the cargo. Given the heavy rain falls in Brazil, the MC for ore cargoes transported or stored out in the open can be very different from what is stated on the declaration. Some time ago AVA Marine published its own version of LP Bulletin to provide guidance to Masters regarding these issues. The Bulletin could be found here: https://media.wix.com/ugd/88422b_1433d3d62b964272a813df0d27bed058.pdf

There is a well know case of deliberate grounding of a vessel off the coast of India due to cargo shift in order to save the vessel from capsizing (https://www.skuld.com/topics/cargo/solid-bulk/cargo-liquefaction/deliberate-grounding-due-to-shift-of-liquefied-cargo/ ). This shows how serious liquefaction problem really is. Our thoughts and prayers go out to the families of those who may have perished in this unfortunate incident.

 

About Petro Inspect and The Bunker Detectives

 

 

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