Apr 182012

Australia’s Transport Safety Bureau found that an injured third officer aboard the K-Line woodchip carrier Universal Gloria was so poorly trained that he was unaware of the difference between oxygen and air. The officer, on his first assignment as third, was badly burned when the air compressor he was using to fill a cylinder for an oxygen breathing apparatus, OBA, set, exploded.

During routine checks the third officer found that the pressure in one of the OBA cylinders in the fire locker was about 7 MPa, well below the normal 20 MPa, so he decided to remove the cylinder and take it to the steering compartment so he could use the compressor to re-fill it.

The third mate tried to screw the compressor discharge hose connector into the OBA cylinder, but it did not fit. He found an adaptor in the box next to the compressor that fitted both the OBA cylinder and the compressor discharge hose connector. He fitted the adaptor to the hose connector and then fitted it to the OBA cylinder.

The third mate checked all the connections and opened the OBA cylinder valve. Then, as he reached over the compressor to switch it on, the compressor discharge tube exploded. During this process, it is likely that the temperature of the oxygen-rich environment within the discharge hose and tube had dramatically increased due to adiabatic compression.

The heat of the oxygen rose beyond the auto-ignition temperature of the oil in the system, resulting in the explosion. The third officer was engulfed in a ball of flame. He jumped to his feet, regained his composure, and ran out of the steering compartment.

The AB reported the fire, which continued to burn on and around the compressor, to the bridge watchkeeper. He then went to the engine room to get a portable fire extinguisher. He quickly returned with an extinguisher and discharged its contents onto the fire, extinguishing it.

There are internationally recognised colour schemes used in industry so that high pressure cylinders containing different gases can be easily identified.

There are also a number of different types of engineering controls that prevent a high pressure cylinder from being connected to an incompatible system. An oxygen/acetylene welding set is an example where such engineering controls are used. The threads on the oxygen cylinder are right handed, whereas the threads on the acetylene cylinder are left handed. Therefore, the cylinders cannot be incorrectly connected to the welding set.

All ‘K’ Line ships were supplied with Kawasaki OBA sets and either Sabre or Kawasaki BA sets. The cylinders used in all these sets were colour coded. The BA cylinders were pale green in colour, signifying that they contained air and the OBA cylinders were black, indicating that they contained oxygen. The OBA cylinders were also labelled ‘oxygen’ (in Japanese only) and stamped with the molecular formula for oxygen ‘O2’.
The Sabre cylinders had a European standard threaded connection that was different to that of the Kawasaki air and oxygen cylinders. Therefore, the Kawasaki air and oxygen cylinders could not be connected to a Sabre BA set or an air compressor fitted with a European standard connection.
The Kawasaki cylinders were manufactured to conform to the Japanese standard for high pressure gas cylinder valves. However, the threaded connections on both types of Kawasaki cylinders were the same and there were no other engineering controls in place to prevent a Kawasaki oxygen cylinder from being connected to a Kawasaki BA set or an air compressor fitted with a Kawasaki type threaded connection.

Therefore, it was possible for a Kawasaki OBA cylinder to be inadvertently connected to an air compressor fitted with a Kawasaki type threaded connector.

The third mate did not understand that the pale green colour of the BA cylinders signified that they were filled with air, or that the compressor would re-fill them with air. Furthermore, he did not understand that air is a mixture of 78% nitrogen, 21% oxygen and other trace gases. In fact, he thought that oxygen and air were the same thing.

The ATSB investigation found that the explosion occurred as a result of a fire that started within the compressor when oil ignited in the hot oxygen-rich environment.

The investigation identified three safety issues. The crew were not appropriately trained or drilled in the operation and maintenance of the ship’s OBA sets; the ship’s safety management system did not provide the crew with appropriate guidance in relation to the operation and maintenance of the OBA sets; and there were no engineering controls in place to prevent the inadvertent connection of an OBA cylinder to the air compressor.

Fortunately, Universal Gloria had not suffered a serious fire: The ship’s fire fighting manual referred exclusively to fire fighting in the vehicle decks of a car carrier and, hence, was of little assistance to the crew on board a woodchip carrier.
ATSB Report

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