1998 - Bahamas

Year 1998
Vessel Bahamas
Location Rio Grande, Brazil
Cargo type Bulk
Chemicals SULPHURIC ACID (spent)

Summary

On July 1998, the Maltese registered chemical tanker M/T "Bahamas" was loaded with sulphuric acid in Australia and after leaving, moored in Durban, South Africa on July 21 to take on fuel oil and then continued the voyage to Rio Grande, Brazil. During this last passage, the vessel experienced heavy seas and pitched and rolled severely. The vessel arrived at the Trevo Terminal at the Rio Grande on August 24 in a loading condition that was within its stability and stress limits. It arrived loaded with 19,616.3 tons of 95% sulphuric acid. The general arrangement of the vessel can be seen in Figure 1 whilst Figure 2 shows the port area of Rio Grande. Pumping of sulphuric acid of cargo tanks 6P and 6S commenced and ended the following day. On the morning of August 25, the vessel started to discharge from tanks 11P and 11S. The pumpman had however mistakenly closed, rather than opened, a valve leading to a centrifugal discharge pump as the cargo was being unloaded. When the suction valve was closed with the pump running, the sulphuric acid heated, boiled and then flashed, destroying the pump seals because of high temperature and corrosivity.

The Chief Officer detecting the pumpmans' mistake half an hour later, donned personal protective clothing and entered the pump room. He opened the valves, noticed the leak and ordered crew members to pump the spilled acid into an empty cargo tank. The liquid could not be completely removed.

The vessels' cargo tanks were stainless steel but her structure was mild steel. Mild steel is vulnerable to a 95% sulphuric acid solution which was the ships' cargo. Diluted with water to concentrations of 80% to 40%, the acid becomes extremely corrosive creating serious problems for mild steel components.

At the end of the discharge process, in order to trim the vessel, it received ballast water in ballast tanks 4S and 4P, however the liquid began spewing from a ballast line of tank 4S. At this moment, the solution of acid and water had already gone into the cargo tunnel which contained all but two of the vessels' cargo pumps. The crew tried and failed to pump all
the spillage into cargo tank 9S, which was empty at the time. Nonetheless, after finding no loss from the cargo tanks, the crew thought that the problem had been solved and the ship proceeded to its next destination, the Petrobras Terminal (Figure 2), still in the Rio Grande. However, acid had disabled the hydraulic system that drove the cargo pumps. The pumpman was dismissed from his job for posing a danger to the vessel and to the environment.

On August 26, the vessel took on more hydraulic oil but the low pressure of the hydraulic oil-driven-cargo-system only allowed 676 tons of acid to be discharged. On August 28, the vessel was ordered by Petrobras to move to Porto Novo, a wharf near the entrance of the harbour, since it was affecting the terminal's schedule. Once alongside Porto Novo, the vessel began discharging from two cargo tanks 11P and 11S which had independent electric pumps. The master had justified the delay of the vessel as a problem with the hydraulic oil system and, up to that moment, the authorities were not informed of any problem with the ship.

In the early hours of August 29, the crew notified the captain that the vessel was listing to starboard. Cargo tank 11P was shut down and the vessel started to receive ballast in cargo tank 12P through the fire monitor.

The level in cargo tank 2P then fell whilst the level in cargo tank 2S rose. The list of the ship changed rapidly to port. The crew found liquid in ballast tanks 2S and 2P which previously had been empty. In the pump room, acid had reached the top of the cargo pump valves. The Chief Officer tried to operate them in order to drain the liquid to the cargo tanks, but vapours and low visibility did not make this possible. Efforts by the crew to correct the list lasted for two days.

On August 30, a port sentinel informed the Harbour Master's office that the ship was listing. A port officer sent to the scene was informed by the Master that the problem was under control and no external help was necessary.

On August 31, the acid had made its way into the engine rooms and had reached the main generators. The engine room bilge pumps failed. By early morning, the crew abandoned the vessel by order of the Master due to the risk of explosion of the ship.

Narrative

On July 1998, the Maltese registered chemical tanker M/T "Bahamas" was loaded with sulphuric acid in Australia and after leaving, moored in Durban, South Africa on July 21 to take on fuel oil and then continued the voyage to Rio Grande, Brazil. During this last passage, the vessel experienced heavy seas and pitched and rolled severely. The vessel arrived at the Trevo Terminal at the Rio Grande on August 24 in a loading condition that was within its stability and stress limits. It arrived loaded with 19,616.3 tons of 95% sulphuric acid. The general arrangement of the vessel can be seen in Figure 1 whilst Figure 2 shows the port area of Rio Grande. Pumping of sulphuric acid of cargo tanks 6P and 6S commenced and ended the following day. On the morning of August 25, the vessel started to discharge from tanks 11P and 11S. The pumpman had however mistakenly closed, rather than opened, a valve leading to a centrifugal discharge pump as the cargo was being unloaded. When the suction valve was closed with the pump running, the sulphuric acid heated, boiled and then flashed, destroying the pump seals because of high temperature and corrosivity.

The Chief Officer detecting the pumpmans' mistake half an hour later, donned personal protective clothing and entered the pump room. He opened the valves, noticed the leak and ordered crew members to pump the spilled acid into an empty cargo tank. The liquid could not be completely removed.

The vessels' cargo tanks were stainless steel but her structure was mild steel. Mild steel is vulnerable to a 95% sulphuric acid solution which was the ships' cargo. Diluted with water to concentrations of 80% to 40%, the acid becomes extremely corrosive creating serious problems for mild steel components.

At the end of the discharge process, in order to trim the vessel, it received ballast water in ballast tanks 4S and 4P, however the liquid began spewing from a ballast line of tank 4S. At this moment, the solution of acid and water had already gone into the cargo tunnel which contained all but two of the vessels' cargo pumps. The crew tried and failed to pump all
the spillage into cargo tank 9S, which was empty at the time. Nonetheless, after finding no loss from the cargo tanks, the crew thought that the problem had been solved and the ship proceeded to its next destination, the Petrobras Terminal (Figure 2), still in the Rio Grande. However, acid had disabled the hydraulic system that drove the cargo pumps. The pumpman was dismissed from his job for posing a danger to the vessel and to the environment.

On August 26, the vessel took on more hydraulic oil but the low pressure of the hydraulic oil-driven-cargo-system only allowed 676 tons of acid to be discharged. On August 28, the vessel was ordered by Petrobras to move to Porto Novo, a wharf near the entrance of the harbour, since it was affecting the terminal's schedule. Once alongside Porto Novo, the vessel began discharging from two cargo tanks 11P and 11S which had independent electric pumps. The master had justified the delay of the vessel as a problem with the hydraulic oil system and, up to that moment, the authorities were not informed of any problem with the ship.

In the early hours of August 29, the crew notified the captain that the vessel was listing to starboard. Cargo tank 11P was shut down and the vessel started to receive ballast in cargo tank 12P through the fire monitor.

The level in cargo tank 2P then fell whilst the level in cargo tank 2S rose. The list of the ship changed rapidly to port. The crew found liquid in ballast tanks 2S and 2P which previously had been empty. In the pump room, acid had reached the top of the cargo pump valves. The Chief Officer tried to operate them in order to drain the liquid to the cargo tanks, but vapours and low visibility did not make this possible. Efforts by the crew to correct the list lasted for two days.

On August 30, a port sentinel informed the Harbour Master's office that the ship was listing. A port officer sent to the scene was informed by the Master that the problem was under control and no external help was necessary.

On August 31, the acid had made its way into the engine rooms and had reached the main generators. The engine room bilge pumps failed. By early morning, the crew abandoned the vessel by order of the Master due to the risk of explosion of the ship.

Resume

On August 31, when the Harbour Master arrived at the vessels' mooring place, he could observe sprays of liquid coming out from the vents of the cargo tanks and pump room which was later analysed and found to be an acid-water mix. The ship was also drifting to the middle of the channel. The Harbour Master ordered the crew to secure the ship to the dock and stay in the vicinity of the vessel. The Master refused to answer questions put to him by the Harbour Master, arguing that he would only report to the owners of the vessel. The Harbour Master reported to the fire department, the environmental agencies and the Attorney's office.

On September 1, a salvage team from Smit Tak, was hired by the owners of the vessel. When they tried pumping pristine cargo ashore, the acid destroyed the hose, indicating that the acid had become diluted with water. Consultations also began with local authorities.

On September 2, co-ordinated by a local civil defence official, a commission was set up, made up of representatives from: the Harbour Master office, environmental agencies, the local refinery, the local fertilzer industry, the port superintendent and technical experts from the local university.

Among the issues evaluated were:

- the high risk of explosion due to the generation of hydrogen as a result of the chemical reaction of sulphuric acid and vessel structure;
- no tank on shore was able to receive the acid-water mixture (60% acid);
- no suitable ship was available to take the cargo;
- the corrosive process of the vessels' structure could lead to leachate of heavy metals to the environment;
- unabated corrosion could cause an uncontrolled spill in the harbour;
- neutralization was in theory possible but not feasible in practice because not enough material was available at short notice to neutralize the large amount of acid.

The Commission decided to accept the solution of Smit Tak, which was that of slowly pumping the contents of the ship into the harbour on the outgoing tide, with constant monitoring of the pH. If the acidity rose (not less than pH 6.5) in inhabited or environmentally sensitive areas, pumping was to stop.

Smit Tak pumped acid overboard for more than 11 days (Figures 3, 4). In the process, the acidity never exceeded the agreed limits whilst fears of heavy metal contamination, in particular leachate of iron compounds from the hull structure, did not materialize. To prevent further pollution, the fuel oil and lubricant of the ship were removed to trucks. On September 13, a court order interrupted the process citing a report by a chemical engineer of the local university that the risk of explosion was (by then) within acceptable limits. As a consequence, co-ordination of operations was handed over to the judge.

For the next 40 days, the judge held open hearings and delivered writs to protect life, the environment and navigation.

On October 22, with no suitable ship found to take the contaminated acid (10% acid), the judge requisitioned the Panamanian flagged vessel M/T "Yeros" to receive the cargo and discharge it on the high sea at a predefined dumping area established by the environmental authorities in accordance with the London (Dumping) Convention 1972. The "Yeros" made 10 trips and was released on January 20, 1999 when the concentration mixture on board the "Bahamas" was found to be within acceptable limits.

On April 19, the judge ordered Smit Tak to remove the vessel at the expense of the owners and the P & I Club and on April 20, the maritime authority granted Smit Tak a special permit to scuttle the ship at a predetermined position in international waters.

Smit Tak raised the tanker with air bags and towed it to sea. However, the towage was transferred to another tug company on order of the owners. According to the Brazilian Maritime Authority, the two were heading for the African coast. It is reported that the tow was later abandoned by the tug due to non-payment.

The Brazilian Maritime Authority filed a report on April 27 with the office of the London Convention 1972 at IMO stating that the M/T "Bahamas" posed a risk to safety of navigation and to the maritime environment.

last modified 2020-12-09T12:11:31+00:00