1995 - Chung Mu

Year 1995
Vessel Chung Mu
Location Port of Zhanjiang, China
Cargo type Bulk
Chemicals STYRENE MONOMER inhibited

Summary

On the morning of March 8, 1995 at 7.00a.m., the coaster "No. 1 Chung Stone" of Honduran flag collided with the chemical tanker "No. 1 Chung Mu (3,500 tons dwt) at the entrance of the port of Zhanjiang, S. China. This resulted in serious damage to an area of 8m x 2m of the No. 2 wing tank which contained 310 tons of styrene monomer. A breach of several centimetres wide and 80cm long occurred in the damaged area resulting in a loss of 230 tons of styrene.

Styrene is a colourless, oily, flammable liquid which has a sweet odour where pure and a sharp, disagreeable odour where impure. Like many monomers, styrene monomer is an extremely reactive and sometimes extremely unstable hazardous material that must be handled very carefully. Styrene can begin a potentially dangerous process called polymerization. In controlled polymerization, the liquid solidifies, expanding to about five times its original volume. Uncontrolled polymerization or "run-away polymerization" in a tank can be a violent exothermal reaction, powerful enough to rupture the tank, or in the extreme case, even burst the vessel, in a tank ship.

Styrene polymerizes at explosive rates at temperatures above 65ºC, a phenomenon which can cause the tank to rupture. Certain contaminants will readily form peroxides which, in turn, catalyze the polymerization reaction. To prevent this from happening, shipboard cargoes are usually stabilized with 10 to 15 parts per million (ppm) of an inhibitor called tertiary butyl catechol (TBC). However, even with the addition of an inhibitor, when heated above 51ºC, styrene can polymerize with the generation of so much heat that ignition is possible. A ship must therefore possess an inhibitor certificate before loading commences. This certificate indicates the amount and name of the inhibitor that has been added to the styrene monomer cargo; the date the inhibitor was added and its effective lifetime; any temperature limitations qualifying the inhibitor's effective lifetime; and details of action to be taken should the voyage length exceed the inhibitor's lifetime.

Due to its low electrical conductivity, styrene monomer can generate electrostatic charges when subject to agitation or particularly high flow rates. The substance reacts violently with strong oxidants and may be absorbed into the body by inhalation, ingestion or through the skin. It irritates the eyes, skin and respiratory tract, and, in liquid form, degreases the skin. Styrene is also harmful to aquatic life, having a 96hr-LC50 between 1 - 10mg/l. However, it is not a substance considered to bioaccumulate, but there is evidence to suggest that it will taint marine organisms.

Narrative

On the morning of March 8, 1995 at 7.00a.m., the coaster "No. 1 Chung Stone" of Honduran flag collided with the chemical tanker "No. 1 Chung Mu (3,500 tons dwt) at the entrance of the port of Zhanjiang, S. China. This resulted in serious damage to an area of 8m x 2m of the No. 2 wing tank which contained 310 tons of styrene monomer. A breach of several centimetres wide and 80cm long occurred in the damaged area resulting in a loss of 230 tons of styrene.

Styrene is a colourless, oily, flammable liquid which has a sweet odour where pure and a sharp, disagreeable odour where impure. Like many monomers, styrene monomer is an extremely reactive and sometimes extremely unstable hazardous material that must be handled very carefully. Styrene can begin a potentially dangerous process called polymerization. In controlled polymerization, the liquid solidifies, expanding to about five times its original volume. Uncontrolled polymerization or "run-away polymerization" in a tank can be a violent exothermal reaction, powerful enough to rupture the tank, or in the extreme case, even burst the vessel, in a tank ship.

Styrene polymerizes at explosive rates at temperatures above 65ºC, a phenomenon which can cause the tank to rupture. Certain contaminants will readily form peroxides which, in turn, catalyze the polymerization reaction. To prevent this from happening, shipboard cargoes are usually stabilized with 10 to 15 parts per million (ppm) of an inhibitor called tertiary butyl catechol (TBC). However, even with the addition of an inhibitor, when heated above 51ºC, styrene can polymerize with the generation of so much heat that ignition is possible. A ship must therefore possess an inhibitor certificate before loading commences. This certificate indicates the amount and name of the inhibitor that has been added to the styrene monomer cargo; the date the inhibitor was added and its effective lifetime; any temperature limitations qualifying the inhibitor's effective lifetime; and details of action to be taken should the voyage length exceed the inhibitor's lifetime.

Due to its low electrical conductivity, styrene monomer can generate electrostatic charges when subject to agitation or particularly high flow rates. The substance reacts violently with strong oxidants and may be absorbed into the body by inhalation, ingestion or through the skin. It irritates the eyes, skin and respiratory tract, and, in liquid form, degreases the skin. Styrene is also harmful to aquatic life, having a 96hr-LC50 between 1 - 10mg/l. However, it is not a substance considered to bioaccumulate, but there is evidence to suggest that it will taint marine organisms.

Resume

The styrene remaining in the damaged tank was transferred into another tank. Booms on board the tanker were placed around the damaged tanker but were unsuccessful in confining the spill. Wooden plugs were placed by divers to reduce the leak. Tainting tests were carried out to ensure that the seafood had not been affected.

last modified 2020-12-09T12:11:33+00:00