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Chemical tanker inert gas compliance

The Naval Architect: November 2018Inert gas

You only have to glance at Chapter 17 of the IMO’s IBC Code to get a sense of the complexity of the chemical tanker segment. The chapter lists the minimum requirements for the safe carriage of almost 200 chemicals, with notes pertaining to the fire protection measures, gauging equipment, and tank vents, etc., needed in each case.


The hazardous nature of many chemical tanker cargoes necessitates such stringent vigilance, especially given the highly variable nature of the chemical segment; some vessels change cargoes often, whilst others carry a single product throughout their lifetime. To coin an apt phrase from Rune Damsgaard, business director at Air Products: “the chemical trade is specialised in diversity.”


As with any shipping segment, however, there are regulations pertaining to common safety issues that apply across the board. In contrast to the listings in the IBC Code, which relate to the properties of specific chemicals, these universal regulations are often drawn up or amended in response to actual or forecasted incidents deemed severe enough to warrant an intervention by the IMO and its Marine Safety Committee (MSC).


One recent example regards the installation of fixed inert gas systems. This common piece of equipment delivers inert gas – usually nitrogen – to cargo tanks in order to keep the oxygen level below a percentage at which combustion is possible, preventing explosion. On chemical tankers, inerting can be undertaken after loading but must be done before unloading, at which point inert gas is constantly applied until all flammable vapours have been purged.


Until 1 January 2016, the only tankers required by SOLAS to have fixed inert gas systems were oil tankers above 20,000dwt, which face the risk of self-ignition. However, a series of incidents – including the tragic explosion on Odfjell Seachem’s chemical tanker Bow Mariner in 2004, which killed 21 crew members – prompted an inter-industry working group to come together and make recommendations to improve tanker safety.


These were debated at MSC 92 in 2013, one crucial recommendation being that fixed inert gas systems be required on all tankers above 8,000dwt – keel-laid after 1st January 2016 – when transporting low flashpoint cargoes (<60*C). The amendment was accepted by MSC, and was written into SOLAS II-2/4.5.5 and II-2/16.3.3, coming into force on 1st January 2016. Further amendments included the lowering of the oxygen limit in inert gas from 8% to 5%.


The significance of these new amendments is that the majority of new chemical tankers must now be fitted with an inert gas system, in almost all cases using nitrogen. Vessels solely transporting vegetable oil are not technically required to do this, but would be restricted from transporting low flashpoint cargoes in the future. Given the changeable operating patterns alluded to above, the amendments have therefore resulted in almost universal installation of inert gas systems on newbuild tankers above 8,000dwt.


However, as the amendments only affect vessels built from 2016 onwards, there is now what some consider to be an unfair imbalance between older vessels and newer vessels. Pre-2016 vessels, even when transporting the same flammable cargoes as newbuilds, are fully compliant without a system on board. This has an impact on operating costs, as newer tankers must burn more fuel to run the tank inerting system, and may therefore be less attractive to prospective charters. As Damsgaard puts it: “It’s rather unfair that ships could be better off taking on cargoes and offloading them without having the extra cost of paying for and operating a nitrogen system. The rules favour less safety-minded operators.”


The fact that the amendments don’t apply retrospectively isn’t unusual in legislative terms. However, in this case the problems are exacerbated due to the unusually long life-span of chemical tankers, which according to Damsgaard can be up to 35 years. Older, less safe vessels will eventually be phased out, levelling the playing field, but for those built in 2015, this could take up until 2050.


Ultimately, the force majeure of commercial pressure may offer its own solution. Damsgaard points to “market demand for safer vessels with inert gas systems installed,” taking an example from the oil industry of Repsol’s requirement that ships loading/unloading at its terminals be fitted with inert gas systems, regardless of size (other well-known oil majors, by contrast, only recommend the use of inert gas at their terminal at present). It is certainly possible that chemical producers may similarly require all vessels, even if they are exempt, to be fitted with an inert gas system.


Operators voluntarily retrofitting an inert gas system will also benefit from greater peace of mind, the value of which is easy to understate. As Damsgaard says: “If you inert the tank, it will forgive human error.” Whatever size or age a chemical tanker may be, simple mistakes can easily be made when seafarers are faced with an ever-changing cast of chemicals. By reducing the explosion risk, operators similarly reduce the chance of explosive consequences.