The UK Health and Safety Executive has issued a safety alert for ballast water treatment systems using electrolytic chlorination units, after an explosion of a Headway OceanGuard* system in a semi-submersible.
The warning comes after “an electrolytic unit catastrophically failed on a semi-submersible installation operating on the UK Continental Shelf (dimensions: 1376mm x 501mm x 386mm and weighing around 330kg). The failure resulted in the commercial loss of the unit, and produced projectile debris which had sufficient force to cause significant damage to surrounding cabling and equipment,” the HSE safety bulletin states.
Electrolytic chlorination applies an electrical current to the ballast seawater. The process is likely to generate Chlorine, Sodium Hypochlorite, Sodium Hydroxide, Hydrogen and other chemical compounds within a chamber through which the ballast seawater passes, making pressure safe operations vital.
Owners and operators that use these and similar units, or are planning to install them, should undertake a suitable and sufficient assessment of the risks from using the equipment, such as via a detailed hazard and operability study (HAZOP).
Apart from the usual considerations (temperature, flow rate, pressure), operators should also be aware that this unit’s electrodes can operate under low / no ballast water flow during maintenance/calibration activities, overriding the flow sensors. Their operation may continue if the systems are not re-set. “Under such conditions, electrolysis and overheating is likely to continue to such an extent that in the unit could fail from overpressure and/or internal explosion in the absence of adequate over-pressure relief. Awareness of such a developing situation will be difficult in the absence of temperature and pressure indication,” HSE warns.
Headway’s published a statement, outlining the results of an investigation into the incident:
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Source: HSE
