The five most common causes of commercial diver deaths, as reported to The Divers Association International: how to find these hazards, identify them and avoid them.
By Hal Lomax, Reprinted With Permission from the Divers Association International
Hazards to the Working Diver
The dictionary definition of the word HAZARD is as follows: danger; risk; peril; threat. To further break this down, there are inherent (natural) hazards, and then there are hazards created by external forces. The inherent hazards to a working diver are fairly obvious to those with even a basic knowledge of the diving industry: drowning (since the work takes place underwater) and pressure related illness (since the human body is designed to breathe air only at sea level). The diving industry has tried and tested methods of dealing with the inherent hazards to the diver.
With the inherent hazards to the diver addressed, we will move on to the external hazards. A survey of the causes of commercial diving deaths over any recent period of years will show a few recurring causes. The top five causes of commercial diver deaths world-wide, in order of frequency are as follows:
- Use of improper diving mode (SCUBA)
- No lockout on energized equipment
- Stored energy
- Differential Pressure (also known as Delta P or ΔP)
- Hydrogen gas explosion (underwater cutting or welding)
The first thing that should occur to anyone looking at the list above is that every single hazard listed here is an avoidable hazard. That means every single death caused by these hazards was avoidable.
Use of Improper Diving Mode (SCUBA)
The inappropriate use of SCUBA in commercial work accounted for between 43 and 44 percent of the diver deaths reported to The Divers Association in 2014 and 2015. This is a very alarming statistic. In a 2010 study of inshore diving deaths worldwide, the International Oil and Gas Producers (IOGP) found that 29 percent of overall deaths were due to the inappropriate use of SCUBA. If the numbers in the IOGP study and the numbers reported to the Divers Association represent what is actually happening, the number of deaths due to the use of SCUBA equipment is increasing by roughly 10 percent each year. Another alarming aspect of this is it appears that many of the divers killed in SCUBA were trained commercial divers who should have been taught that SCUBA equipment is unsafe to use for working.
SCUBA equipment will not likely ever be seen on an offshore worksite today as the two primary offshore diving contractor associations, ADCI and IMCA, ban it outright. Virtually all of the reported incidents occurred inland or near the coast, but alarmingly two were on government jobs.
The primary reasons that SCUBA is not a safe mode of diving for commercial work are as follows:
- the diver’s air supply is limited to what he can carry, and there is no significant back-up
- the diver’s breathing, and the amount of air supply remaining cannot be monitored on surface
- although the diver can wear a safety line, the restricted air supply makes the line itself a hazard
- the diver typically does not have any form of head protection
- the diver’s depth cannot be monitored on surface for decompression
- the diver’s ascent, ascent rate, and required decompression stops cannot be monitored
- the diver does not have hard-wired communications and wireless communications often fail
- the diver does not have surface monitored video, so the supervisor is uninformed of events
A reputable diving contractor will never consider asking a diver to work in SCUBA. Where the problem seems to arise is when questionable contractors take contracts by cutting prices to the point that they cannot perform the work properly. They look at the difference in price between sending SCUBA divers on a job or sending a proper surface supplied diving crew out and go with SCUBA. Another reason often heard given to justify the use of SCUBA is that the work cannot be done safely in surface supplied gear.
In many inland jurisdictions today, SCUBA is illegal in the workplace because it is unsafe. Among those jurisdictions are the UK and most of Canada (with the exception of fisheries or scientific work). In addition to that, all ADCI, IMCA and IOGP projects totally ban SCUBA. So when there is pressure from the employer to work in SCUBA, how does a diver ensure that he will not end up as a statistic, dying in SCUBA equipment? A safer option is a SCUBA Replacement Pack or Mobile/Portable spread (see photo below).
No Lockouts on Energized Equipment
Five of the 30 deaths reported or roughly 17 percent of them were attributed to “no lockout on energized equipment.” That description “energized equipment” can refer to pumps, propellers, impellers, gates, valves or any machine or equipment that can itself move or cause the movement of water that will or may result in injury or death to a diver. The number of deaths due to failure to lockout equipment over the years led to many changes, one of these being the “Permit to Work” or “PTW” system found on most oil platforms and most power generation plants. But we still see diver deaths occurring every year.
Many industrial facilities require water to operate, so they have both water intakes and waste water outfalls. Both fresh and salt water share one common trait: marine growth tends to spread, restricting flow in intake and outfall pipelines. Some of these facilities may operate for years without requiring a diver. When they do require a diver, the knowledge of how to safely have divers work on the facility simply does not exist. Some of these facilities do not even have a PTW system in place, and if they do, you will see no reference to divers in the paperwork.
Marine growth accumulates on the hulls of vessels, increasing fuel consumption and decreasing speed. Marine growth also restricts flow in vessel seawater intakes. The only alternative to dry docking the vessel is to have a diver clean the marine growth. In addition to the marine growth problem, vessels will often require divers to clear ropes or other debris from their propellers. This is not something that happens every day, so often there is no system in place to protect the diver. Lockout Tagout prevents the machine from starting — insist on LOTO or do not dive, period.
Stored energy accounted for 3 diver deaths in 2014 — 2015, or 10 percent of reported deaths. More accurately put, the rapid release of stored energy caused three diver deaths. Many different materials when stretched, bent, or otherwise deformed will return to their original shape, even years after they have been deformed. This return to the original shape is often very sudden and violent. When this happens underwater, the density of the water will slow the movement slightly, but depending on the material and the circumstances, there is more than enough energy released to severely injure or kill a diver as the material returns to its original shape.
Most divers today are aware of the stored energy in a cable, rope, or chain under strain. Still, divers are killed or injured almost every year. On an offshore salvage project in Europe in 2011, a chain under strain parted, and a diver (on deck at the time) was killed. This author has a good friend who was hit by a 2 inch nylon rope that parted, breaking both his legs. Many of us have stories about lines under strain. But what a lot of divers, supervisors and contractors do not realize, is that pipelines, risers, dock pilings and structural members of platforms can also contain stored energy. A steel piling driven deep and pulled to one side before being welded will usually retain that stored energy, and spring back when cut, even after several decades in place.
In drawing “A” below, a steel piling on a dock structure was warped (pulled to the side) before being encased in a poured concrete cap. If the piling shown were to be cut, it would spring violently to the left, due to stored energy.
The higher on the piling, the more pronounced the movement. Drawing “B” shows a subsea pipeline, a jacket leg, and a riser. The riser was warped when it was installed in the riser clamps. If the riser clamps are cut or released, the riser will spring violently back to its original shape, due to stored energy. The higher up on the riser, the more pronounced the movement.
The method to avoid a stored energy incident involving ropes, wires and chains under heavy strain always is the same: stay away until the strain is relieved. Remember that a rope or wire under strain always whips out to the side, then back on itself when cut or parted; a chain always flies straight back on itself.
The method to avoid a stored energy incident involving a piling or a riser is as follows: 1) cut or release the member in a location where the movement will be minimal (if possible), and 2) restrain the member from movement with rope, chain or lifting slings and lever hoists prior to starting the cut.
When holding a piling with a crane while cutting, if the crane has an upward strain, the pile will fly up rapidly, and then drop back down toward the diver in an energy release. Avoid this hazard by only picking the slack out of the crane wire when cutting off pilings. Never keep an upward strain on the crane wire while cutting piles underwater.
Differential Pressure (ΔP)
Differential pressure, the next hazard on the list, comes in at 7 percent of the deaths reported. Actually, it is likely somewhat higher, but one or two incidents involved the inappropriate use of SCUBA equipment, and were listed in that category. At least one diver dies each year due to ΔP; and in 2016 alone, five deaths were reported to the Divers Association where ΔP is the suspected cause.
Whenever the conditions are such that a body of water is adjacent to an area not filled with water, or filled with water to a lower level (as in a water storage tank or dam), the potential exists for a ΔP incident.
In a ΔP incident, things always happen very quickly. By the time the diver realizes there is a problem it is already too late to help him. Almost every ΔP incident ever recorded has been a fatality, indicating just how serious this condition is, and how little can be done once the diver is caught. To calculate ΔP, we use the following formula: A x DW x psi/ft (water) = DP; where A = area of the hole, DW = difference in water depth on the two sides of the structure, and DP = the differential pressure exerted.
To determine if there is a threat from ΔP, the trick is to establish if there are areas adjacent to the dive area that are de-watered or have different water levels. If the answer to that is “yes” there is a ΔP threat.
In the case of a dam gate, look at the dewatered side if possible. If there is leakage that shows more flow than a small hose, have the gate re-set and look again. There is the option of sending in an ROV or a drop camera with a stick and a ribbon to look for flow. Other methods are hanging a weighted plastic jug, or a half sack of sand on a rope as a tell-tale. Flow due to ΔP will draw the tell-tale into the high flow area. If a diver is working in an area that could possibly have flow due to ΔP, have him carry a long prod with a ribbon on it. A ribbon will indicate even the slightest amount of flow. If you cannot be absolutely sure that any flow is safely workable the answer is simple, do not proceed with the work.
To actually work in the vicinity of ΔP flow, there are a few methods. The most obvious of these is to first eliminate the source of the ΔP threat. This involves filling the de-watered area with water. In the case of a hydro dam stop-log, place the head gate and fill the space between them with water to the elevation of the headpond. In the case of a subsea hose or subsea pipeline, fill them with water prior to performing any work with a diver. Both of these are examples of eliminating the threat altogether.
The second method is to diffuse the flow so that the water can flow unimpeded around and past the diver, without harming him. This involves using a robust “diffuser cage” when working near a dam gate, or a large diffuser cap placed on valves used to flood empty subsea structures such as pipelines.
The final hazard we will examine also comes in at 7 percent of reported deaths in 2014 — 2015. This is the hydrogen explosion caused by underwater cutting. Every water molecule consists of two hydrogen atoms and one oxygen atom. There are two methods of separating (disassociating) the hydrogen and oxygen atoms in a water molecule: extreme heat and electric current. Unfortunately for the working diver, the gear we use to cut steel underwater does both. Ultrathermic cutting rods produce temperatures in the range of 10,000 degrees Fahrenheit when burning, which causes disassociation of the hydrogen and oxygen atoms in the water nearest the tip of the rod. In addition to this, the DC current provided by the welding machine to initially light ultrathermic rods also causes disassociation of hydrogen and oxygen atoms in individual water molecules. Therefore, underwater cutting has not one, but two sources of hydrogen.
Hydrogen is extremely explosive. One cubic foot of hydrogen gas has the same explosive potential as one stick of conventional dynamite. Due to the density of water, the shock wave from even a very small explosion is typically lethal to a diver. Even one quarter cubic foot of hydrogen gas, if it explodes, is more than enough to kill a diver. This leads us to the obvious question: what exactly causes a Hydrogen explosion? Look closely at the sketches that follow.
In the drawing on the left, the diver is cutting and the hydrogen and oxygen bubbles are rising up the water column, so there is little risk of explosion. In the drawing on the right, there is an overhang above the diver and his Hydrogen and Oxygen bubbles are collecting. This diver is at risk due to the accumulating gas.
In the sketches below, the diver in the drawing on the top is cutting a pipe and Hydrogen is accumulating inside the pipe. This diver is in very grave danger. The diver on the bottom has ventilated his pipe. The Hydrogen is escaping from the pipe as he cuts, so there is little, if any danger to him, at least as far as a Hydrogen gas explosion goes.
When ventilating enclosed structures such as pipes and tanks, it is best to use a drill or a slug cutter. Drills and slug cutters do not spark, and therefore the chance of igniting an explosion in any entrapped gas is eliminated. To remove Hydrogen gas that is accumulating under an overhang, we purge the overhang area with an air hose until cutting is completed.
The hydrogen gas created by the DC current can be cut back simply by keeping the torch cold while cutting, and only making it hot long enough to light each rod. Many, if not most divers have the amperage set far too high on the machine when cutting — 110 to 130 amperes is sufficient to light a cutting rod. If there are problems lighting with the machine on that setting, it’s either a ground problem, or poorly maintained cutting gear. To reduce the risk, clean the gear, fix the ground, and lower the amperage. Keeping the gear in good condition and securing a good ground on the work allows you to use lower amperage; lower amperage results in less Hydrogen production and less damage to the diving gear due to electrolysis.
We have just discussed the five main causes of diver deaths as reported to the Divers Association during the years 2014 and 2015. The “magic fix” that can eliminate hazards and keep divers safe has been around for quite a few years: risk assessment. A proper risk assessment will identify all of the hazards, including those listed above prior to the work starting. The following are the important points addressed in the first phase of a proper risk assessment:
- Scope of work for the project is identified and expanded to illustrate individual operations
- Identify all inherent risks and hazards to personnel
- Identify all external risks and hazards to personnel
- Prioritize the risks and hazards in order of severity
- Identify mitigation action for each (action to eliminate risk)
- Develop the work plan according to the Risk Assessment results
The initial risk assessment is usually performed by management, with the involvement of the supervisory personnel for the project. The individual workers are involved when the process reaches its second phase, which we know as the Job Hazard Analysis, or JHA. The JHA should address all of the following points:
- The operation is expanded to illustrate individual job steps
- Identify all inherent hazards to personnel
- Identify all external hazards to personnel in each job step
- Identify mitigation factors or actions for each hazard
- Identify personnel responsible for ensuring mitigation
To ensure that each individual job is performed safely, we have to ensure that each job is performed in the exact same way it has been laid out in the JHA. If there is any significant change in the scope of work or the jobsite conditions, work must stop, and the Risk Assessment and JHA process must be repeated. On most projects this will require using the process known as Management of Change.
There are two ways we are going to see a significant change in the number of divers being killed on the job: more stringent regulation and enforcement, and widespread usage of the risk assessment process. All ADCI and IMCA members are required now to follow this process, and the result is an impressive reduction in injuries and fatalities. Every member of this industry, from the newly minted diver to the old, experienced superintendent needs to insist on the use of the risk assessment process on each and every diving project performed, whether it is inland or offshore. That is the very best way to avoid the hazards in diving – we owe that to our families, and to the divers who have lost their lives at work due to these “avoidable incidents.”
Article first published on the Divers Association International website in February 2018.