The Case Of The Benzene Bomber

 
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An explosion aboard a ship carrying flammable cargo is a master’s nightmare. This nightmare will really make your hair stand on end.

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We’re alongside berth number 1 in Santa Clara oil terminal, Brazil on 17th January 2001. Our ship is the Emilia Theresa, a 3,336 gross tonne chemical tanker managed by Unifleet and flagged in the Isle of Man. She’s loading benzene into her twelve wing tanks, six starboard, six on the port side.

Example of Sampling and Ullage arrangements for each tank. (Behind is the open ullage port with the easy open handles in front is the restricted ullage / sampling port)

Next to each tank lid are two ports, an open ullage port with threaded easy-open handles and a closed ullage port. Cargo data sheets are posted as they should be, with warnings in English that samples should be taken using only the closed ullage port. Special equipment is needed to take samples from the closed, or restricted, ullage ports, and it’s kept in the ship’s aft pumproom.

It’s 1252 and the Emilia Theresa’s Houtin screw pumps have filled eight tanks. Now the filling of the last tanks, number one tanks port and starboard, begins.

About four and a half hours later with loading almost complete, the cargo surveyor comes aboard. His name is Jorge Santos. There isn’t a lot of conversation with the officers or crew of the Emilia Theresa; the cargo surveyor is Brazilian; he speaks Portuguese but his English is patchy while the ten officers and crew of the ship are a mixture of Finnish, Russian, Polish and Ukrainian.

Chief Officer used on board sampling equipment

At 1630 the loading of number one port tank is complete and being topped off. The Chief Officer takes a final reading using an MMC gauge through the closed ullage port.

Jorge talks to the Chief Officer for a moment, then the Chief Officer disconnects the MMC gauge. As the pumpman closes the tank inlet he moves to number six port tank and again takes a reading through the closed ullage port with the MMC gauge.

Finally the Chief Officer goes to the cargo control room, contacts the terminal personnel and tells then that the ship is ready ready for them to blow through the lines.

View forward from the bridge

With all the hustle and bustle of getting ready for departure, and a total crew of only 10, no-one was left to supervise the cargo surveyor, Jorge.

From his position by the valve manifold located midships on the walkway the pumpman sees Jorge walk along the deck to the aft tank covers. He can’t see quite what Jorge is doing, or using.

What happened next we have to recreate from the evidence because nobody knows for sure, but it must have gone something like this:

Jorge goes to port tank six. He sets out a glass sample bottle beside the tank lid and takes out his sample equipment: a brass can attached to a two to three metre length of synthetic rope. He unscrews the handle of the open ullage port drops in the metal can with the sample bottle in it, hauls out the sample, caps the bottle and sets it down beside the tank lid, and moves to number six starboard tank. There he repeats the sampling and moves to tanks five port and starboard, then on to tanks four port and starboard, working his way forward leaving a wake of glass sample bottles.

By about 1650, twenty minutes after he started sampling, Jorge is beside the last tank, number one port wing tank.

Jorge opened the Open Ullage Port...

Again, he opens the open ullage port. Again he drops his metal can on the end of its synthetic rope through the port. Then there’s a brilliant flash and concussion and he’s thrown back in a blast of heated gas and flame. The tank lid is blown up into the air and falls to the deck with a loud clang.

For the master in his cabin and the Chief Officer in the cargo control room, the blast was certainly a sound they hoped they’d never hear but they were prepared. From the cargo control room window the Chief Officer flames from the forward part of the ship and sounded the general alarm.

The Master made his way to the starboard side aft muster station. The crew were already there waiting for instructions. He ordered the Chief Engineer to supply foam to the deck monitor system, selected a crewmember and went to the forward foam monitors.

Working together on the two monitors the two men attacked the fire, dousing it in less than three minutes.

Four minutes after the fire is out the local fire brigade arrived but there is nothing for them to do.

Part of the burned rope. The rest of the evidence was taken away by Intertek Testing Services and not available to investigators.

Jorge, the cargo surveyor, is given first aid and sent to hospital.

Looking around afterwards, the master and chief officer find the length of synthetic rope, blackened and stiff for half its length, and the brass sample can surrounded by pieces of broken bottle.

Later, Jorge’s company, Intertek Testing Services retrieved the sampling can and the rope, which the master had taken into custody but had cut a length of a metre from the burnt end which he kept. He did not get a receipt from Intertek.

What happened is that benzene vapour in the space between the surface of the cargo and the top of the tank ignited and caused an explosion. The source of ignition was certainly static electricity.

Static electricity is all around us. Put your arm near a television screen and you’ll feel the hairs on your skin stand on end. Comb your hair and put the comb near pieces of paper and it will attract the paper. Just walking over a synthetic pile carpet can build up so much static electricity that you can get a spark and a painful shock if you touch something, or someone, that’s grounded. Then there’s lightning.

How does static electricity get into a cargo tank? Static electricity is a complex phenomena but, basically, when liquid is sprayed into a tank, and the liquid can just be water, one can end up with the liquid carrying a positive static charge and the material of the tank carrying a negative charge.

Given time, these charges will quietly cancel each other out with no harm done. But put a metal object into the tank which touches, or nearly touches, the surface of the liquid and the sides of the tank, then the charges can combine all at once with enough energy to cause a spark.

The tanks Jorge sampled first had been settled for several hours and the static electrical charge had dissipated. By the time he tried to take a sample from number one port tank only twenty minutes had passed since it was loaded, not enough time for the positive and negative charges to dissipate. As he took his sample the conductive brass can tocuhed the surface of the benzene and the side of the tank at the same time and created a spark. And a spark was all it took to turn the Emilia Theresa into a potential benzene bomb.

Of course, we’d expect a cargo surveyor, particularly one working in an oil terminal, to be properly trained and knowledgable about the cargoes being measured and how, where and when measurements should be made. Most of the time, those assumptions are correct, but they only need to be wrong once to create a potential disaster.

Emilia Theresa regularly visited Santa Clara, previously without incident. There was not reason to think that he might blow up the ship.

Damage from the explosion is evident

Jorge used, or was supplied with, the wrong equipment for the job. Synthetic materials must never be used where there’s an explosion or flammable vapour around. Unlike the chief officer’s MMC gauge, Jorge’s brass can and synthetic rope were not gounded to the ship’s hull, which is why a spark was created.

That’s why the International Safety Guide for Oil Tankers and Terminals, ISGOTT, bares the lowering of synthetic ropes into tanks at all times.

His English was not good so he probably didn’t pay much attention to the Enlgish language warning signs that instructed him to use the closed or restricted ullage ports rather than the open ports he did use.

Jorge was well aware of when number one port tank was loaded because he was there when it finished. He might not have known of the danger of static electricity and the need to let sufficient time pass to allow the charge to disssipate.

Two possible scenarios for ignition through static electricity

He would not have known that in that the ship’s International Safety Management manual bans the use of metal cans for ullaging and sampling for thirty minutes after loading is complete.

The crew did, but nobody was supervising Jorge. According to the master he didn’t have enough people on board even have someone posted at the gangway or escort visitors to the ship, even though it did not comply with the ship’s ISM system.

That also means that the ship didn’t carry enough crew to provide the ship with even basic security while in port. Unrealistically low minimum manning requirements have contributed to piracy. Unadequate manning opens the way to acts of sabotage, stowaways and, as in this case, avoidable accidents.

Investigators from the Isle of Man insist that the company must improve its surpervision of shore side personnel particularly when in the cargo area. They suggest that, at minimum, notices should be posted telling visitors to report to the cargo control room and wait for the officer in charge. Additional personnel should be carried to provide that security.

Communication between shore side personnel and ship staff should also be improved, says the official report.

Emilia Theresa became a ‘benzene bomb’ because of poor communications, poor training of the surveyor and insifficent manpower to provide supervision.

What could we do about it?

Of course, we want to leave port as quickly as possible but preferably in one piece, so think safety first.

Do not allow ullaging or gauging to begin until sufficient time has passed for static electricity to dissipate in the last tank loaded. In this case, that would have been 30 minutes.

Since the time of the last loading is recorded it would be simple enough to add 30 minutes to that time and chalk it on the lid of the tank – no ullaging or gauging until that time.

Communications were poor, but Santa Clara was a regular port of call. It would be easy enough to create a small card to be given to the cargo surveyor coming on board, saying, in Portuguese, “Only use closed/restricted ullage port. No sampling for 30 minutes after last tank loaded”.

A simple photograph of the tank ullage ports with an X over the open ullage port might make the point just as well.

If Jorge had used the closed port he could not have used his metal can and synthetic rope at all and would have had to use the ship’s equipment.

All Unifleet tankers carry the right ullaging and gauging equipment. There no reason to wait for the cargo surveyor to ask for it. Offer it to him when he comes on board.

Finally, here’s a thought. It took around 20 minutes for Jorge to sample 11 tanks. That’s about two minutes for each tank. It would have taken just two minutes for the chief officer to watch Jorge take the first sample and make sure that he was using the right equipment and procedures, before he went to the cargo control room. It’s hard to argue that there wasn’t enough time to do that.

There is always time for safety.

This is Bob Couttie wishing you safe sailing.

Isle Of Man Report