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10322 Chemical accident in Arabian gulf with naphtha
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General accident information
Class/Quality * * * * *
Year 1990
Summary Explosion on tanker "surf city" caused fireball,
Fire, explosions and 11 casualties
Country ARABIAN GULF
Activity NAVIGATION (MARINE)
Location SEA
Chemicals Diesel oil/Fuel, Naphtha, Naphtha
Cause Unknown-cause
Fatalities/Injuries 2 / 9
Occurrences or events Burst/Rupture, Burst/Rupture, Corrosion, Damage,
Drive, Evacuation, Explosion, Explosion,
Fatique, Fire, Fire fighting/Emergency response, Fireball,
Human-operations, Human-operations, Human-operations, Ignition,
Insufficient ventilation, Load/Stow, Pump-over, Pump-over,
Release, Remove, Repair, Safety-measures,
Stench-emission, Vaporize, Wrong-action, Wrong-composition
 
 
Full accident information 
download accident report Click here to view a document containing the full accident information

Country: ARABIAN GULF (ARABIAN GULF)
Date : 1990 0222


The reflagged 232/m-long USA tanker ship "Surf city", loaded with 32.875E+3/m3 (cubic meter) of naphtha and 28.413E+3/m3 of automotive diesel oil, exploded and burned in the Persian Gulf. At the loading terminal the tanker discharged all salt water from the segregated ballast tanks. The tanker was equipped with an inerting system which was able to inert cargo tanks, however the fuel oil, double bottom tanks, cofferdams and the four ballast tanks were not provided with inerting facilities.
The tanker was equipped with a remote measuring system with sensors in the forepeak in two ballast tank (4P and 4S) and propeller shaft alley in the engine room. The gauges had not been used for about 3/months. One of the crew members went out on the main deck about 0755 hours and removed the fore ward and center cleaning cover plates, which were bolted to the main deck tank top of the 4S water ballast tank. He inserted a water driven jet fan into each of the 305/mm diameter Butterworth openings. He next opened the access trunk cover and connected one end of the bonded hose to a jet fan and the other end to a valved outlet on the fire main piping. Now tools were taken from starboard to portside to place the same type of equipment to vent the ballast tanks. One of two available hoses was an ungrounded one. This was placed on the jet fan on the foreward Butterworth opening to the fire main. The electrically bounded hose was installed on the jet fan on the centre Butterworth opening of the portside ballast tank.
A clear naphtha smell was noticed on deck at the starboard ballast tank, however, it was considered as not strong enough, according one of the crew members to become alarmed. It was assumed that the vapours would be blown away across the deck from the port bow to the starboard quarter by the relatively light wind. The fumes from the port tank only smelled of dirt and algae.
According to witnesses one of the crew members, supplied with short duration breathing equipment, went via the access trunk to the 4S ballast tank with the blowers operating. After 5/minutes he climbed out of the access trunk "panting for air" and sat on deck to catch his breath. Next the seawater supply to all four jet fans was shut off. Two jet fans were removed from the 4S ballast tank Butterworth openings and laid the blowers on deck. A mirror made of steel was used to reflect sunlight down into the ballast tank through the Butterworth opening and the access trunk in an apparent attempt to locate the naphtha leak. One of the crew members was ready to reenter the tank when an explosion occurred in the 4S ballast tank aft to the deckhouse. The starboard side of the vessel was engulfed in flames. With the exception of the two crew members near the tank and three crew members on the bridge all of the crew were within the accommodation area and were protected from explosion, fragments and fire. A vast fire ball with a blast was observed, smoke and an intense heat radiation from the fireball developed. The ship was abandoned, however starboard life boats could not be used because of the intense heat of the fire. Before the engine room was left the main engine was stopped and the generator was allowed to continue operating. The fire pump was found operating. Because of the heat the foam supply from the foam tank could not be approached. A distress signal was sent out to an escorting USA navy warship, 2.7/km astern. According to bridge watch on the navy ship a massive explosion was immediately followed by two small explosions. Behind the burning tanker a burning slick developed and appeared to be fed by the fuel leaking out of the hole created by the explosion.
One of the crew members lowered the life boat with 20 crew members onboard with some delay because the striking pendant was not removed. One crew member on the life boat was thrown overboard by the shock of the falling lifeboat (fall of a short distance). The propulsion engines of the tanker were stopped, however the speed of the ship was still 13.0-14.8km/h. The original speed before the accident was about 23.1/km/h.
Before the lifeboat was launched one crew member went back into the accommodation house to search for crew members. He only found the radio officer. They went back to the life boat and discovered that the port lifeboat was already launched and moved away from the ship.
These two crew member jumped into the sea with life preservers donned.
All other four crew members who jumped over board or fell into the water were rescued afterwards by the lifeboat.
Of the 25 crew members there were 2 fatalities, 2 crew members seriously injured, 3 moderately injured and 4 had minor injury.
From investigation it appeared that the cargo and the slops tanks were empty and that the ballast tanks were filled with seawater to increase the vessel's sea keeping ability.
For fire fighting first the Sumatra attacked the fire and the Smith Tak BV Insalv Lion, later three other local salvage vessels arrived on the screen.
Investigation showed that naphtha could only have been entered into the ballast tank as a result of either a failure in the ballast system piping or a failure in a ballast tank bulkhead. Investigation revealed that the ballast penetration into ballast tank, the ballast piping and the branch valve were tight, so the ballast piping system did not provide a path for naphtha leakage to the tank. The National Transportation Safety Board (NTSB) could not determine whether the bulkhead fracturing occurred before or after the explosion, however testimony and documentation show that the Surf City had a history of such fractures. It was conclude that a fracture in the transverse bulkhead between the cargo and the ballast tank was the most probable source of entry for the naphtha into the ballast tank.
It could be concluded that the static electricity and lighting could no generate sparks with sufficient energy. Also military activities could be ruled out. Metal-to metal contact is considered as a probable ignition source and the impact or energy release from fracture development and propagation in the tank's internal structural steel. The level indication system could also not generate sufficient energy to create a spark. As external source of ignition to the ballast tank spark or flame entry from the cargo control room via the ballast remote draft gauge manometer piping or an uncontrolled ignition source from the deckhouse or main deck were considered. Although the ignition source could not be identified the NTSB concluded that the most likely source was within the ballast tank.
The duration of the fire was 2/weeks and 31.318E+3/m3 of the 96.380E+3/m3 of cargo were lost.
The damage loss resulting from this accident was 31.53E+6 USA dollars.

Lessons learned
1.
The accident might have been avoided if the ballast tank was inerted.
However, the inert gas system was effective in preventing the fires and explosions from spreading to the tank ship's forward cargo tank.
2.
The two fire monitors on the "Surf City" aft of the cargo tanks on the main deck subjected them to damage and to heat exposure from an explosion or fire.
3.
Routing of ballast piping through cargo tanks and cargo piping through ballast tanks should be prohibited.
4.
Lifeboats, also those which were built after 1 July 1986, should be totally enclosed.
5.
Guidance should be issued for crew members with respect to ventilating or entering cargo and ballast tanks.
With ballast tanks it may be preferable to ensure full ventilation has taken place by filling the ballast tank with clean sea water and pumping out to ensure adequate air enters the space. Where possible portable air/water fans should be utilized to increase ventilation in such spaces.
The appropriate tests for oxygen and cargo vapour must be taken before entry is permitted.




 
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