The Case of the Forgotten Assassin


David lay on the jetty as they waited for the ambulance. Underneath the fire blanket that covered him, 60 per cent of his body had suffered second degree burns. His left arm was fractured. His last words were “I can’t believe I have been caught like this”. He was a victim of the forgotten assassin.

And he was an expert.


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We’ll call him David, not his real name but he was a real person. After completing an engineering apprenticeship he decided to go to sea and over the next 17 years aboard ship, reaching the rank of chief engineer. He spent another 20 years as a service engineer selling cleaning chemicals, mainly to the maritime industry then set up on his own as a consultant.

Now, in 2003, he’s 61 and an expert.

Like David, his client, Harris Pye Marine Ltd is known for its expertise, it is considered a leader in boiler repairs and he is its preferred chemical cleaning sub-contractor.

He’s been at the Grand Bahamas Shipyard at Freeport since 26 September working on the 96,235 gross tonne, 1975-built, LNG carrier Hilli, owned by Golar Hilli and flagged in the UK.

There had been two fuel-related explosions in the starboard boiler in April and June, 2003. There was significant damage so temporary repairs were made pending major repairs scheduled for August at Grand Bahama Shipyard. Hilli finally berthed there on 4 September on just the port boiler because a number of starboard boiler tubes had failed and the boiler itself had to be shut down.

After repairs are complete, it is David’s job to chemically clean the boilers. It’s a finely-judged procedure: it involves corrosive acids that, if not done expertly, can eat away the boiler steel and shorten its life and weaken components in a reaction that generates hydrogen.

image By 3 October, with an interruption due to a hurricane, 190 tubes had been replaced in the starboard boiler. Those repairs involved hotwork, cutting and welding and ordinary halogen worklamps were used. There was no need for these to be intrinsically safe or explosion proof. The boiler was successfully pressure tested.

imageMeanwhile, David underwent safety training with the shipyard’s Health and Safety Department. Training included the use of Permits to Work, entry into confined spaces and accident reporting procedures. He also set up his chemical cleaning equipment to clean the starboard boiler in the same configuration as he had previously used in Spain, where he’d worked on the Hilli before after the second explosion.

Over the next few days David set to preparing the equipment to clean the starboard boiler. The first of two surprises came about 4 October when a consignment of Unitor Descalex arrived. He was expecting another product, Ashland Drew SAF Acid, which he knew well because he’d worked for the company. According to the Golar purchasing department the Ashland Drew cleaner wasn’t available in time and the Unitor Descalex was an acceptable alternative.

imageLike household kettles, ships’ boilers build up scale, mainly calcium and magnesium carbonates as hard deposits that reduce efficiency and blocks pipes. Unitor Descalex uses sulphamic acid to remove the scale and includes an inhibiter to prevent the acid corroding good steel but it doesn’t last forever so it includes a dye that changes colour according to the acidity.

This is the first time David has used this particular product. We can’t be completely sure, but he probably did read the Material Safety Data Sheet, MSDS. It seemed familiar enough, it was, after all, a very similar product to the SAF Acid he usually used and he didn’t notice that one, small bit of information was not in the Unitor Descalex MSDS but which was in the MSDS for SAF Acid.

Now it’s 9 October and David degreases the starboard boiler drum and tubes and goes back to his hotel to rest.

The next morning, there’s a second surprise. Golar Management has brought in a second boiler cleaning expert, from Moss Varmetiknikk in Denmark, to supervise David on its behalf. They haven’t told David or Harris Pye Marine. We’ll call him Stan. He had no formal training in chemistry, marine engineering or boiler cleaning. His knowledge had been passed on from his father in the form of “on the job training”. Most of his chemical cleaning experience had been in the offshore industry. This included cleans on boilers, pipe systems and heat exchangers. He also had some experience in cleaning boilers on board steam-driven frigates of the Royal Norwegian Navy.

Stan checked into his hotel on Grand Bahama at about midnight on 9 October.

imageIn his bags he had a packet of pH papers to test the boiler water acidity, comparator strips to test the water iron content, and steel wool. The steel wool was for a simple test: If the inhibiter in the boiler cleaner was still doing its job to protect the steel then the steel wool would sink. If the inhibiter was not working, then the acid in the cleaner would attack the steel, generate hydrogen, and the bubbles trapped in the steel wool would make it float.

David, on the other hand, did not have, or at least didn’t use, equipment or indicators to test whether or not the inhibitor was still working but, unlike Stan, who was almost half his age, he did have a lot of experience and training behind him.

The next morning Golar management’s technical superintendant met with the Harris Pye personnel. It was agreed that there would be no hotwork carried out in the engine room while the cleaning was going on but nothing was said about the use of naked lights and entry into the steam drum of the boiler.

The Harris Pye team was also told that the chemical cleaning should not start until Stan could review the arrangements. It was the first they’d heard of Stan and what he was supposed to do.

image David returned to the ship at 0800 ready to carry out the cleaning and was only then told to wait for Stan’s arrival. As he waited for Stan to arrive, David used steam from a shoreside boiler to heat up water in a mixing tank on deck and got assistants from Harris Pye to get the dozens of 25 kilo containers of Unitor Descalex ready to add to the tank.

While that was going on, Stan met with Golar’s technical superintendant. Stan had not used inhibited sulphamic acid before and didn’t think that it would remove the boiler scale, but David had used it successfully the last time he cleaned the boiler. He believed that the inhibitor would break down at the temperature at which David intended to use the boiler cleaner.

It’s now about 10 in the morning and David and Stan meet for the first time. David hands over the product and MSDS sheets for the Unitor Descalex and an acid cleaning procedure. It isn’t the procedure recommended by Unitor, it’s for the Ashley Drew product, SAF Acid, but Stan doesn’t know it. Then they walk around the system and check for leaks.

They finish checking for leaks. It’s 1300 and the temperature of the steam-heated water in the tank waiting for the acid cleaner is 57 degrees Celsius, a little less than the recommended temperature in the procedure David gave to Stan, and less than that recommended by Unitor to be used ‘whenever possible’.

Stan is still worried about the breakdown of the inhibitor despite the manufacturer’s recommendations and asks David to turn off the steam. That’s a surprise to David who usually keeps the steam going to maintain the temperature throughout the process, but he does as he’s asked.

The first of the drums of Descalex, are emptied into the reservoir tank on the main deck as Stan goes to the office of the Golar technical superintendant to explain how he plans to monitor the performance of the inhibitor and ensure that the acid is not attacking the steel of the boiler.

He also telephones Denmark to talk to his brother, who works for the same company. Hs he had any experience with Unitor Descalex? His brother has not.

1425 and the last of the 800 kilos of Unitor Descalex has been mixed into the tank. David stands by as it circulates through the boiler system. About 45 minutes later the color coming back out of the boiler and into the mixing tank has changed from clear to red: everything is in order. David positions four monitors to watch for leaks, makes some adjustments, then goes and grabs some rest in a ship’s cabin.

Meanwhile, Stan familiarises himself with the boiler, goes to the technical supervisor’s office for a while then, on his way back to Hilli finds a rusty pipe flange to help him test the efficiency of the inhibitor.

Back on board, Stan and David met up. Stan explains the use of the steel wool and drops the rusty flange into the water/acid tank – if it turns bright and shiny then the inhibitor has stopped working.

Now it’s 1700 and the mixture coming into the tank has turned from red to grey. Stan uses his iron comparator strips, then does the steel wool test on a sample of the mix. The steel wool sinks to the bottom and stays there. The inhibitor is still working.

Over the next four hours Stan repeats the steel wool test until, at 2100, the water in the tank turns a greenish colour. This time the steel wool floats to the surface of a sample, the inhibitor has stopped working.

image David agrees to drain the boiler immediately then open the steam drum and inspect it before flushing through with fresh water. He reconfigures the acid clean system and starts pumping the boiler out to a bowser on the jetty. It will take about an hour.

With the water low in the boiler David asks for the steam drum access door to be opened, which is much what he was planning to do anyway, then goes to the engine control room with Stan for some refreshments.

While David and Stan relax, two workers pick up their tools and a yellow halogen work lamp, go to the steam drum access door, remove the nuts, washers and the dogs, and push the door inwards with some effort. They notice a puff of suction as the door opens but don’t take much notice.image

They finish the job and leave the tools and the halogen lamp ready to put everything back together when David and Stan are finished.

On their way to the steam drum Stan is surprised that the boiler room ventilation fans are not running and there doesn’t seem to be forced ventilation to purge the steam drum of gases. He does not say anything to David about it.

image 2200 and David and Stan get down on their haunches in front of the open accessway, David directly in front, Stan to one side. They’re looking into the mouth of a cannon.

Both men look into the steam drum and notice that the internal surface is clear of scale and corrosion products.

David picks up the halogen lamp and holds it inside the boiler steam drum. There’s a flicker on the lamp and suddenly hot gas travelling faster than the speed of sound punches David 4.5 metres across the room as the gas inside the steam drum detonates, smashing him against a guardrail and a packing crate hard enough to damage them. He’s unconscious; Most of his overalls are burnt off. His trunk and face are badly burned and there are second degree burns over two thirds of his body. He has a fractured left arm. Stan’s sweatshirt and “T” shirt have been partially blown off and there are burns to the left side of his face, to his hands and to the left side of his body. He had not been in the main path of the explosion.

The two men are evacuated to the jetty. It was there that David became briefly conscious: “I can’t believe I have been caught like this” he says then lapses back into unconsciousness. He dies nine days later.

How did David get caught?

Throwing Light On An Explosive Subject

When the two workers opened the access door they noticed air being sucked into the steam chamber. That gives us two clues. First, the system was not being fully vented, otherwise the air pressure inside the boiler would have been the same as the air pressure outside. Any gases generated during the cleaning would still be inside. Also, air was mixing with whatever gas was inside the steam drum.

Fire triangle

image Two parts of the classic fire triangle were now present – the fuel and oxygen, all that was now needed was a source of ignition.

That was almost certainly the halogen lamp. The body of this type of lamp and the glass front, the lens, get very hot, the bulb even hotter, more than 200 degree Celsius. It isn’t gas-tight so it’s neither explosion proof nor intrinsically safe.

Heat from the lamp ignited the gas inside the steam drum. That gas was hydrogen, produced by the action of Sulphamic acid on steel, yet the Material Safety Datasheet for the Unitor Descalex referred to it as non-flammable, non-combustible or non-explosive during storage or transit. It did not highlight the potential risk of hydrogen and flammable/hazardous gases evolving during cleaning.

The Hydrogen Hazard

The MSDS for David’s preferred product, SAF Acid, did refer to a risk of hydrogen and his own written cleaning procedures also made mention of the danger of flammable gases. He knew of the importance of ventilating the system to remove explosive gases but since the hydrogen was there whatever ventilation there was didn’t work well enough.

Of course, the steam drum is a confined space. David was certainly aware of the procedures for safety entry, which includes checking whether combustible gases were present. It probably did not occur to him that just sticking his arm inside the steam drum was entering a confined space. The equipment to make the test was available but wasn’t used.

So when he looked into the steam drum, he was looking into the barrel of a cannon that was primed and ready to fire.

There were no risk assessments for the job, or a method statement outlining how the job was going to be done, and nobody asked for them. David was not involved in the daily project meetings so there was little opportunity for the safety question to be examined.

Then there was the relationship between David and Stan. True, it was amicable, yet David did have a man almost half his age, with much less experience, who challenged his judgment and whose concern regarding the inhibitor may have distracted David.

The official report from Britain’s Marine Accident Investigation Board says:”all those involved seemed to have accepted that David was an expert in his field and that it was unnecessary to carry out any checks relating to the method of cleaning the boiler or of related safety procedures.”

Learning from tragedy.

How do we stop tragedies like this happen to ourselves and others around us?

Make sure there is a job risk assessment for every job you do or that others do for you.

Make sure that specific measures are in place to mitigate the risk and that those measures can be verified – it was impossible to be sure what David’s ventilation arrangements were, what he did can’t be verified.

One simple measure would have ensured that there was no explosive gas in the steam drum – filling it completely with fresh water, then draining it before inspection. That’s a precaution that should be mandatory when boiler cleaning but if it isn’t, it’s wise do it anyway.

Confined space entries are one of the biggest killers of seafarers, contractors, stevedores, and others who go aboard ship. The steam drum was a confined space and it’s important to understand what ‘entry’ means: If any part of the body passes through the plane of the accessway then an entry has been made. It’s something that often isn’t mentioned in confined space entry training but should be because whatever deadly hazard is inside the space can reach out and touch you even if you’re not completely inside.image

It wasn’t mentioned in the training that David got at the shipyard, although that has now changed. If David had realised that he was making an entry into an enclosed space then all those safety procedures that are laid down would have kicked in: The atmosphere inside the steam drum would have been checked for explosive gases and adequate oxygen. That didn’t happen, and why I’m telling you this story.

So, always check there’s enough oxygen in a confined space and that the levels of explosive or toxic gases are too low to present a hazard. In this case we’d have been looking for absolutely no more than 10 per cent of the lower explosive limit and preferably 0.1 per cent or less.

Ventilate the space until the readings are ay an acceptable level, and they’ll be given in your ship’s SMS and keep ventilating until the job’s finished.

Finally, safety is everybody’s responsibility. Stan was surprised when he didn’t see much in the way of ventilation. The two workers who opened the steam drum noticed suction that should not have occurred. In both cases something was not quite right but nobody said anything. If you see or hear or smell something not quite right, don’t just shrug your shoulders – speak up, because sometimes even experts get caught by the forgotten assassin.

This is Bob Couttie wishing you Safe Sailing

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