Feb 172016

Hazards in confined spaces can reach out and touch you even if you haven’t taken a sniff inside. MAC has warned more than once to beware of ‘confined spaces that aren’t’ and here’s another one from the International Association of Drilling Contractors site, IADC, to add to them.

Vessel maintenance was being conducted on an accommodation barge. Preparation was being made to enter a tank at the base of a column to undertake quarterly planned maintenance of the leakage detection system. The injured party removed a manhole cover to gain vertical access into tank at the base of the column. Within one minute of removing the manhole cover the gas detector alarm sounded and the IP lost consciousness on the floor of column next to the open tank hatch.

Not that the IP had not even entered the ballast tank.

Although the IP fully recovered with no residual ill health effects, the incident was rated High Potential Incident, Medical Treatment Case, Lost Time.


  • Subsequent gas sampling during the investigation was undertaken and recorded unexpectedly high levels of hydrogen.
  • The presence of hydrogen resulted from electrolytic reaction between the sacrificial anodes and the steel within the ballast tank.
  • There was no review or analysis of the abnormal alarm for CO gas reading in the column the day before the incident.
  • Warning signs from the readings taken from the column were not acted upon.
  • The potential for hydrogen accumulation had not been identified or mitigated against.

Physical arrangements within the column did not allow for ventilation without first opening the tank lid, therefore, the generic confined space entry procedure could not be wholly applied, such as forced ventilation.


To address this incident, this company did the following:

1. Company management is to review current documented procedures and vessel practices associated with confined space entry, particularly given the potential presence of hydrogen.

2. The vessel management are to review and mitigate against the risks associated with build up of hydrogen within ballast tanks and other freely-communicated pathways. This shall include risks from fire and explosion, as well as potential inhalation risks.

3. Company and vessel management are to explore options of mitigating against confined space entry into ballast tanks
 Engineered solution regarding alternative leak detection systems.
 Engineered solution regarding air monitoring techniques.

4. Company management is to review task risk assessment and incident reporting procedures, to ensure
that all unusual, potentially hazardous situations are reported and acted upon as appropriate.

5. Client to review its processes for engaging with and sharing key aspects of its HSSE Management System with its contract partners. Particular emphasis to be placed upon their published Life Savers and supporting standards and Knowledge Management / Safety Alerts.

6. Both the company and Client should take the learning from this incident to review and improve their safety systems such that the risks from confined space entry are more effectively and proactively managed.

Here’s the safety alert

And don’t forget:


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