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Fire & Explosion During Tank Cleaning on a chemical tanker

A recent case study onboard a chemical tanker revealed fatality During Tank Cleaning Operations.What has happened? A parcel size chemical tanker was in ballast voyage and was in the final stage of tank cleaning. The next cargo parcels to be loaded, included a grade requiring a high standard of Tank Cleanliness.

The Wall Wash Test taken by the ship crew upon completion of tank cleaning revealed unsatisfactory results. The ship’s crew decided to conduct a spray in the tank with methanol to achieve the required standard of WWT. This was conducted utilizing a portable air driven pump placed on top of the methanol drum on the catwalk in vicinity of the tank. The pump was connected to a PVC hose serving as the discharge hose.
damage to chemical tank bottom
Fig: Damage to chemical tank bottom

Contributing to the above operation, there was hot work on the fire line involving cutting with a grinder and welding of a pre-fabricated piece of about 1m section. No hot work permit had been issued nor any approval taken from company as required by the SMS. The senior officers of the ship and the crew working on deck were aware of both the operations involving the hot work and the tank cleaning operation.

The discharge hose connection to the pump was leaking resulting in a liquid/vapour trail reaching the source of ignition (Hot work on the fire line 29 meters abaft). Upon ignition, the fire flashed back to the area where the drum of methanol was positioned in vicinity of the cargo tank being sprayed with methanol resulting in a subsequent explosion inside the cargo tank.

As a result of the explosion, three (3) crew members involved in the methanol spray operations were directly affected. The first crew member inside the cargo tank and a second crew member positioned on the main deck and in vicinity of the methanol drum, sustained severe burn injuries. The third crew member stationed outside the cargo tank in vicinity of the tank entrance was reported as missing and assumed fallen overboard due to the force of the explosion. The cargo tank, adjacent pair of cargo tank, the double bottom ballast tank and main deck was damaged structurally.

The search and rescue operations for the missing crew member was carried out by the Ship with sea support vessels of the regional rescue centre for the next two and half days without any success. The two (2) crew members with severe burn injuries were medically evacuated by a helicopter to the nearest hospital and subsequently to another hospital well equipped to treat burn patients. Unfortunately the crew members succumbed to their injuries after a few days of the treatment due to the extensive nature of the burns sustained.

What could be the cause?

i) Unsafe conditions – Presence of fuel (from methanol spray) & a source of ignition for combustion occurring concurrently. This completed the 3 sides of the fire triangle. The third side of the fire triangle – oxygen was available in the cargo tank, as the space was gas free prior to the spray of methanol

ii) Unsafe act – The spray of methanol & source of ignition existed due to non-compliance of procedures and operations conducted unbeknownst to the company. The company did not permit Methanol Spraying or the hot work. Hence the existing controls were violated.

Key learning’s

  1. The underlying/root causes derived as a result of this incident deal with human behaviour and each company/organization should undertake their own methods which motivates their workforce to achieve SAFETY, through compliance to their written procedures. Addressing the “Human Element,” is a long term measure and efforts taken should be continual and conducted tirelessly.

  2. Review & reinforcement of the training system should be periodically conducted to monitor its effectiveness.

  3. Consideration to Implement a separate session with senior officers to address leadership & teamwork issues, reinforce Behaviour Based System (BBS) training, and special emphasis on managing Non Compliance.

  4. Importance of intervention of an Unsafe Act - The crew working on deck at the time were aware of both, the hot work and the methanol spray operations but no attempt was made to stop either of the 2 operations being conducted concurrently resulting in a highly hazardous situation.

  5. Effective controls should be in place to increase compliance to the working procedure.

  6. In the trade practice onboard chemical tankers, it is not uncommon that the use of methanol or other chemical/detergents is undertaken to achieve the required standard of cleanliness inside the cargo tank, pipelines, cargo hoses, manifold adaptors/reducers, gauging equipment, etc. Industry publications clearly highlight and caution regarding their use due to their flammability and toxicity hazards. The spraying with Methanol is not supported due to the same.

  7. The easy availability of methanol on board the vessel attributed to this act being undertaken. As an immediate measure, the company decided to remove all flammable solvents/detergents used for cleaning of tanks, hoses and fittings. All existing stock of such solvents/detergents from the fleet has been off landed to shore facilities.

  8. A safer alternative is being sought for use, which is both non-toxic and non-flammable and tests being undertaken for the various commercially available detergents/chemicals for cleaning, achieving the desired results. This may increase the time for tank cleaning but having a safer alternative clearly outweighs the risk being taken to achieve tank preparedness utilizing flammable /toxic solvents.

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

Securing tank lids & safety precautions

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

Tank cleaning fatality- case study & lessons learned

Cargo tank damage during pigging operations

Tank explosion case study

Rubber lined tanks, for the transport of phosphoric acid, waste acids and hydrochloric acid.

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.

Main Info pages!

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