02 December 2021
The procurement and arrival in South Africa next week of an Inert Gas System and a specialist excavator operator from Europe is expected to relieve pressure and provide enhanced safety to management efforts of transferring an unstable chemical cargo off a constrained vessel currently docked in St Helena Bay.
That is according to the South African Maritime Safety Authority (SAMSA) in a statement in Pretoria on Thursday confirming the docking yet again of the Marshall Island flagged bulk carrier, NS Qingdao, back at St Helena Bay on Tuesday, after days spent off shore due to its unstable chemical cargo.
The saga with the vessel, according to SAMSA, began on 23 October 2021 in Durban where it had docked to offload its chemical cargo, but had to be sent back offshore and rerouted to St Helena Bay after her cargo suffered a chemical reaction, releasing toxic fumes into the atmosphere.
According to SAMSA, redirecting the bulk carrier, now under constant escort, to St Helena Bay on the country’s west coast (Atlantic Ocean) was intended to provide it with protected anchorage, “with the advantage of being in close proximity to the Vissershok waste deposal site where the cargo could be safely discharged and neutralised.”
However, with stormy, wet weather unrelenting, said SAMSA: “Last week (25 Novembe)r the vessel was instructed to sail offshore (again) under tow to help ventilate her No3 cargo holds after the hold was closed due to a change in weather conditions causing an increase in hot spots in the hold and fumes to enter the engine room through the engine room vents.”
In the meantime, said SAMSA that all non-essential personnel were removed as a safety precaution, with only a minimum crew onboard. In the intervening period, plans were made to procure a special Inert Gas System and a specialist excavator operator from Europe. SAMSA said the Inert Gas system would be used to blanket the cargo with an inert gas to prevent any further reactions in the cargo.
However, the discovery of and an announcement in South Africa about a new Covid-19 variant, Omnicron, which almost immediately sent several countries abroad in a tailspin of panic, followed by the closure of borders and bans on international flights to the country, “delayed operations slightly,” said SAMSA, adding that the salvage crew was, however, “optimistic” that the Inert Gas System would arrive in St Helena Bay by Tuesday next week (07 December 2021).
MarineInsight.com contextualises the use of an inert gas system as follows: “Inert gas system is the most important integrated system for oil tankers for safe operation of the ship. Inert gas is the gas that contains insufficient oxygen (normally less than 8 %) to suppress the combustion of flammable hydrocarbon gases. The inert gas system spreads the inert gas over the oil cargo hydrocarbon mixture which increases the lower explosion limit LEL (lower concentration at which the vapours can be ignited), simultaneously decreasing the Higher explosion limit HEL (Higher concentration at which vapour explodes).
“When the concentration reaches around 10%, an atmosphere is created inside the tank in which hydrocarbon vapours cannot burn. The concentration of inert gas is kept around 5% as a safety limit.”
Meanwhile, in Pretoria on Thursday, SAMSA further reiterated its earlier assurance that the toxic fumes emitted from the vessel do not pose any danger either to humans or the oceans and coastline environment. Providing specific detail of the bulk carrier’s water sensitive and reactive chemical cargo, SAMSA said: “SAMSA would like to assure the public that this is a controlled event and neither the environment nor any person is at risk at this time and that all safety precautions are taken to prevent the situation from escalating.
Of the cargo’s nature, the agency said: “The bulk cargo consists out of a mixture of Sodium Metabisulphite, Magnesium Nitrate Hexahydrate ,Caustic Calcined Magnesite, Electrode Paste, Monoammonium Phosphate, Ferrous Sulphate Monohydrate, Zinc Sulphate Monohydrate, Dicalcium Phosphate, Sodium Sulphite Anhydrous and Calcium Chloride.”
With the recall of the vessel to dock at St Helena Bay on Tuesday, said SAMSA: “The cargo is being discharged into skips to remove all hot spots in the cargo hold to help neutralise the chemical reaction and gases under the watchful eyes of experienced salvors and chemical experts.
“The first two skips were discharged yesterday morning in the care of SPILLTECH for transportation to Vissershok under controlled conditions. SAMSA would like to reaffirm that there is no immediate risk to any person ashore and that all persons involved in the operation onboard is using all the required personnel protective equipment.”
However, just to be sure, extra measures undertaken since the rerouting of the vessel from Durban to St Helena Bay have included the constant watchful eye of a tug UMKHUSELI that, according to SAMSA “will remain on site to act as a static tow while the vessel is at anchor and ensure that any toxic gases are blown offshore during the operation.
“The ship owner is cooperating with SAMSA, DFFE, TNPA, Salvage Team and local authorities.SAMSA would like to assure the public that this is a controlled event and neither the environment nor any person is at risk at this time and that all safety precautions are taken to prevent the situation from escalating,” said the agency.