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Risk of Chemical spill via Annex II overboard line

Responsible officers must check cargo tank cleanliness for foreign materials after man entry to tanks and at final inspecction for cleannliness before loading. Where vesssels are not provided dismountable spools, the double isolation valves which isolate the cargo system from the sea shall be air pressure tested prior to each cargo operation for integrity and deck log entry to be made.

Overboard connections to sea are usually provided with spectacle blinds or dismountable spools and blanks. These lines are to be positively isolated at all times when not in use by putting the blanks in line or by removing spools and blinding.

chemical tanker navigation at sea
A critical operation checklist should be implemented when the slop tanks are used for cargo or the overboard is put into use which includes:

*crew familiarisation / instruction *unused / idle valve lashing & sealing *over-board valve testing and line blanking.
Cargo hose connection
Fig: Cargo hose connection area

Incident of a contained spill onboard a Chemical Tanker

Brief account of Event:
The vessel was engaged with mandatory pre-wash of cargo MARPOL Annex II Cat “X” – Benzene. On completion of the pre-wash, the hose was blown by air into the barge. The hose provided from the slop barge was connected to ship’s hoses and the connection was approximately 2.5 metres below manifold level.

The Pumpman decided to open a drain cock at the manifold to verify no water and pressure was left in the line, however the line was not completely blown and a cargo/water mixture sprayed on to his arm sleeve. This mixture also spilled on to the deck.

What Went Well:

The Pumpman took an emergency shower on deck and was examined by the duty officer to ensure there were no chemical burns on his skin. His boilersuit was removed outside of the accommodation and sealed in a plastic bag for proper disposal.

What Went Wrong ( Critical Factors ):

1) The persons involved in hose disconnection must take in to consideration that air blowing for a set period of time may not be sufficient to declare the line free of residues and act accordingly. In this case the Pump man opened the drain too early. He did not check the pressure gauge prior to hose disconnection.

2) There was no direct supervision – officers were preoccupied with completing departure checks as the pilot was on his way to the vessel.

3) Inadequate Leadership : No cargo specific instructions given by the Master or C/O in respect of handling Benzene as required by the MCS Circular 1095 (Min safety standard – Benzene).

4) The Pumpman did not wear the correct PPE, Chemical Goggles, during hose disconnection. The consequences of a corrosive cargo splash would have been much more serious as compared to toxic one in this case.

5) Ships’ Risk Assessment did not reflect all requirements of IBC Code for Toxic cargo and preventive measures.

Related Info:

Tank cleaning fatality- case study & lessons learned

Pre-cleaning /washing of cargo tanks

Final cleaning of cargo tanks prior loading

Tank cleaning and posoning hazards

Testing of tanks and cargoes

Practical tank cleaning methods for various noxious liquid cargo

Special tank cleaning method

Determining proper tank cleaning by acid wash method

Supervision of all tank cleaning and gas freeing operations

Disposal of tank washings, slops and dirty ballast - safe method

Type & condition of tank coatings - maintenance guideline

Static electricity -How they generate & required safety precautions

Cargo tank damage during pigging operations

Tank explosion case study

Following reference publications provide useful guidance and international regulations for carrying hazardous chemicals at sea.

Our detail pages contain somewhat larger lists of resources where you may find more useful information.

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