2011X54 Explosion on tanker SURF CITY

Explosion on tanker SURF CITY
Report No. Mars04-SURF CITY

We, at The Nautical Institute, are grateful for the receipt of copies of Official Government Accident Reports. From time to time it is planned to reproduce extracts from these reports in this column in order that they will reach a wider audience than would otherwise be possible.
Summary of events
On February 20,1990, the reflagged 760-foot long U.S. tanker SURF CITY loaded with naptha and automotive diesel oil, departed Kuwait en route to discharge ports in southern Europe. At 1012 on February 22, the master and the chief mate were standing at the No. 4 starboard water ballast tank (4SWBT) access trunk when an explosion occurred in the tank. The tank and area aft to the deckhouse on the starboard side were immediately engulfed in flames. The crew abandoned ship in the port lifeboat and were rescued by the U.S.Navy frigate USS SIMPSON. A helicopter recovered the master's remains but the chief mate was never found. The fire burned for 2 weeks and 196,985 barrels of the 602,215 barrels of cargo on board were lost. The damage loss resulting from this accident was $31.53 million.

The safety issues looked at by the investigators were:

* Ballast tank entry procedures.
* Extension of the inert gas system to include ballast tanks.
* Ballast system integrity.
* Repeated stress related fatigue fracturing in cargo/ballast tanks.
* Location of fire foam monitor.
* Retrofit or replacement of primary lifesaving equipment.

The Safety Board made recommendations addressing these issues to the U.S. Coast Guard, the International Chamber of Shipping, the International Association of Classification Societies, and the Gleneagle Management Company, Inc., and through the U.S. Coast Guard to the International; Maritime Organisation. Many of these recommendations have now been adopted.

 

The Accident
On the morning of February 22 the chief mate decided that he would inspect the automatic draft gauges which were located in each of the ballast tanks to attempt to get them to work again. He asked the 4-8 watch ABs to put water driven air blowers on 4P and 4S water ballast tanks at the end of their watch.
One of the ABs opened the forward and centre tank cleaning (Butterwoth) cover plates on 4SWBT ballast tank. He then collected from the store 2 high speed / high volume Jetfans and 2 electrically bonded hoses to connect the fans to the fire main. He inserted the fans into the Butterworth openings and then opened the access trunk cover.
The second AB then arrived to assist, he was accompanied by an ordinary seaman (OS). The OS obtained 2 more jetfans but could only find one further grounded hose, they therefore used an ungrounded hose to connect one of the jetfans to the forward opening of 4PWBT. According to the second AB, the chief mate inspected the ungrounded hose and "said.....it was O.K."
The first AB stated that he had noticed "a very clear naptha smell on deck", but added that it was not strong enough to cause him to become alarmed, he had assumed that the smell was coming from the cargo vents and being blown across the deck from the port bow to the starboard quarter by the relatively light wind. He mentioned the smell to his watch partner, but not to the mate.
The crew members installed the jetfans on the port side and then opened the access trunk. The second AB then telephoned the engine room to ask them to start the fire pump. At about 0900 they opened the valves on the fire main connected to the jetfans and noticed the fans appeared to be operating at full speed and blowing air into the tanks. They then returned to the accommodation.
Two ratings on the 8 - 12 watch (the helmsman/lookout in the wheelhouse and the boatswain, who was acting as lookout, on the bridge wing) said that they saw the master and the chief mate on deck near 4S access trunk entrance at about 0945, then saw them lean over and peer into the access and jerk their heads back and hurriedly away. One of them also said he could see fumes coming out of the access and smelt them on the bridge wing, he also said the fans were operating. The master and mate were seen to confer for a short time, the mate then went aft. At about 0950 the third mate received a telephone call from the mate asking where the breathing apparatus was. As he did not know, he handed the call over to the boatswain who told the mate where it was located.
According to the witnesses, when the chief mate rejoined the master at the access trunk, he brought with him a 10 minute Emergency Life Support Apparatus (ELSA), and had something in his hand, possibly a gas analyser. The mate was seen to enter the access wearing the ELSA and whilst the blowers were still working, he emerged about 5 minutes later, "panting for air", and sat on the deck to catch his breath.
The master and the mate then shut off all the fans, removed the 2 blowers from 4SWBT and laid them on the deck. The boatswain then said the master and mate stood forward of the access trunk and used a mirror (generally made of steel), to reflect sunlight down and aft through the Butterworth openings and the access trunk into the ballast tank. The boatswain explained that the tanker personnel who carry a mirror usually keep it in their back pocket on a string to ensure they do not drop it into a tank. He did not see where the mate put the mirror he had been using.
The master was standing next to the access trunk and the mate was apparently preparing to re-enter the tank when an explosion erupted from 4SWBT. Almost immediately the deck area from 4S ballast tank aft to the deckhouse on the starboard side of the vessel was engulfed in flames.

Abandon Ship and Rescue
With the exception of the master, mate and the 3 crew members on the bridge, all hands were in the accommodation and protected from the blast. The boatswain said he saw the master and the mate disappear in a vast fireball as he was knocked over. It was raining shrapnel. The noise and the blast were tremendous, the heat intense, as the ball of fire and smoke rushed over him.
The bridge front windows were blown in and shards of glass and other debris were sent flying into the wheelhouse. The helmsman/lookout was hit on the head, but the OOW was bending over the chart table and consequently partially shielded.
Immediately after the explosion the ship took a 50 list to starboard and the fire alarm sounded. Some crew members attempted to go forward to fight the fire. The hot deck and the heat forward of the deckhouse prevented them from reaching the monitors or the foam room. The crew members who were up and about roused the others. It was impossible to reach the starboard lifeboat, so they all went to the port lifeboat. The radio officer transmitted a distress message at about 1018 to the USS SIMPSON which was in the area acting as an escort to US ships in the Persian Gulf during the Iran/Iraq war.
The attempts to lower the port lifeboat were hampered because no-one had released the after tricing wire prior to starting to lower. When this was realised, and the tricing wire was released, the boat dropped quickly the short length of slack on the wire and an OS was thrown overboard. The second mate was searching the accommodation and found the radio officer. When they got onto the deck the lifeboat had already gone, they jumped into the sea. The boatswain, who had been lowering the boat attempted to climb down a lifeline but his lifejacket caught up on the line, he freed himself and fell into the sea wearing the lifejacket. The SIMPSON picked up all the survivors. The partial remains of the master were picked up by a helicopter, together with the shoes he was wearing and the ELSA vest minus the air bottle.

Damage and Investigation
The bridge and wheelhouse were completely gutted, most of the windows were missing and all the equipment was incinerated, the bridge deck and bulwarks were warped. Fire had also consumed all combustible contents in the forward part of the accommodation and in many of the compartments on the starboard side. The interior aluminium doors to the athwartships passageway had melted. The steel watertight doors were secured in the open position.
The main deck plating was severely warped forward of the deckhouse to the midships deckhouses and the starboard king post was lying transversely across the main deck piping. The 60 foot long pipeline was bent in several places and a 1 foot section of bottom pipeline separated from the remaining pipeline. The deck and hull plating in way of 4SWBT had almost completely disappeared.
As the remaining cargo was discharged into another vessel and the SURF CITY rose out of the water, three previously submerged buckets were found in 4SWBT adjacent to the inboard longitudinal bulkhead. The buckets were hanging from a 6 foot long, 1/4"diameter polyethylene line attached to a vertical section of the remote draft gauge pipeline. One of the buckets was 12" diameter and 16" deep and made of steel. A plastic bucket, also attached to the line, was inside this. Another plastic bucket was suspended above the steel bucket. Neither the buckets or the line showed any signs of flame exposure or other damage.
A fracture, less than a meter long was found between 4SWBT and No.5S tanks about 6 metres from the bottom and 4 metres outboard of the longitudinal bulkhead. Another fracture was found between No.4SWBT and No. 6C cargo tank about 7 metres above the tank bottom. The tanks surrounding No. 4SWBT, which had been dry, had all taken in about 7 metres of water by the time the vessel had been towed to dry dock.

Possible Ignition Sources
The investigators determined that the explosion and fire did not result from adverse weather or static electricity. They also concluded that the jetfans were probably not the source of ignition. Several ignition sources in No.4SWBT could have created a mechanical spark:
* metal to metal impact from an object such as a dropped mirror, tool, or meter striking a structural member of the tank.
* metal to metal impact from the steel ELSA air bottle striking the trunk access opening.
* metal to metal impact from the steel bucket striking a structural member of the tank.
* metal to metal contact from a detached stiffener which had separated along its weld striking another structural member in the tank.
* metal to metal friction from the faces of structural steel fracture rubbing together and producing heat.
* energy release from the fracture development and propagation in the tank's internal structural steel.

Conclusions
1. The explosion and fire in 4SWBT did not result from adverse weather or from an external incendiary device.
2. Based on 3 independent crew observations, naptha vapour was present when the tank was opened.
3. The most likely source of naptha entry was a fracture in the common bulkhead with 5S cargo tank.
4. Because of the extensive damage, it was impossible to determine the source of ignition, the possible sources are listed above.
5. Tests, research and examination of the damage indicated that the ventilation fans, cargo piping, ballast piping, draft gauge piping and tank level piping were unlikely sources of ignition.
6. The inert gas system prevented the fires and explosions spreading to the forward cargo tanks. If the ballast tanks had been inerted the accident might have been avoided.
7. Specific training in tank entry procedure could not be documented in the case of the master, however, both the mate and master were aware of the dangers as evidenced by the attempt to ventilate the tank and don breathing apparatus.
8. The Company Safety Manual, International Safety Guide for Oil Tankers and Terminals, and USCG regulations lacked specific guidelines for ventilating and entering ballast tanks.
9. The location of the two fire monitors aft of the cargo tanks on the main deck subjected them to damage and to heat exposure from an explosion or fire.
10. The open lifeboat exposed the crew to burning cargo, which was being released from the ruptured tanks.
11. The repeated fracturing in the aft area of 4P and 4S ballast tanks indicates a structural design deficiency.
12. Despite being advised that the hose was not electrically bonded, the mate created a risk by using that hose.

The National Transportation Safety Board determined that the probable cause of the explosion and fire was the lack of adequate industry standards regarding ventilation and entry procedures into ballast tanks. Also causal to the accident was the failure by the master and the chief mate to secure the forced ventilation and close the tank after becoming aware of the naphtha in the ballast tank.

A full copy of this report is available from: National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161. U.S.A.