The Marine Safety Forum provides lessons learned from an incident where the crew observed a smell of “rotten eggs” from the bilge tank vent.
The incident
During a routine transfer of bilge water from the engine room bilge wells to bilge water tank, the crew observed a smell of “rotten eggs” from the bilge tank vent. The transfer was immediately stopped.
During measurements at the tank vent pipe with a multi gas meter, a level of 453ppm of H2S (Hydrogen Sulphide) was detected.
Preventive actions were taken to ensure the gasses would not enter the accommodation. The quick response of Vessels crew prevented a serious accident.
Immediate Hazard:
Dangerous atmosphere (high H2S concentration)
- Seawater in (bilge) tanks, especially in ER, mixed with residue and bio-degradable detergents create conditions favourable for the formation of dangerous levels of H2S.
- Not recognising the dangers associated with H2S could have resulted in explosion, intoxication or in worst case scenario death.
Probable cause
Technical:
- Bilge tank was not disposed for a long period due to not reaching capacity
- Unable to inspect the tank on a regular basis
- Several tank corners solid residue which is very difficult to remove
Organisational:
- Lack of knowledge by external parties
- Internal (Vessel Owner) H2S safety procedure available but did not suffice in sudden release, response and
responsibilities
Communication:
As a result of not receiving a clear answer from the external parties on “Plan of Approach” the vessel was unable
to enter port for almost 4 days for final removal of sludge and cleaning of the tank.
Root causes:
- Maintenance/Inspection – unable to inspect
- Inadequate assessment of needs and risks
Recommendations
Initial actions in relation to incident:
- Transfer stopped (Stop the Job) and H2S concentration measured at the tank vent
- Emergency response team and client informed
- Flexible hose connected to the tank vent to ensure gasses guided away from the accommodation
- Assistance requested from local agencies on removal of the bilge residue and tank cleaning
- Constant monitoring of H2S levels by approved measuring device and crew in full respiratory protection
- Removal of bilge water, cleaning of the tank by specialised contractor and Gas Free certificate issued
Follow up Actions & Precautions:
- Regular checking of bilge water handling and arrangement for disposal
- Bilge water disposal to be combined with sludge disposal on a regular basis
- Review of vessels machinery cleaning practices
- Make H2S awareness part of the onboard training programme
