Rather, this response is tailored to address specific statements made in this announcement concerning underwater burning safety and the role oxygen and hydrogen play in any underwater burning operation, regardless of where it occurs.

Of major concern are the following statements:

• "As no oxygen is necessary, the potential explosive dangers involved with conventional exothermic (oxy-arc) cutting are completely removed and the hazards to the diver are significantly reduced, especially when cutting into tanks, cylinders, pipes and any other sealed compartments."
• "When conventional oxy-arc (exothermic) cutting is regarded as a safety hazard to the diver, or no oxygen is available, these electrodes offer a safe, convenient and cost-effective alternative, without any hazards to the diver."

Oxygen and Hydrogen
Oxygen by itself is not flammable but supports combustion. Referencing the published Material Safety Data Sheets for oxygen, one finds the following description: "Oxygen is a colorless, nonflammable and odorless gas. Oxygen sustains combustion of many materials that cannot burn in air. Oxygen supports combustion and/or increases the combustion rate of flammable materials" (emphasis added). This is not in any way to say that oxygen is a benign or harmless element in underwater burning, only that another element must be present that combines with oxygen to create the potential for a flammable reaction.

This second element can be trapped gases or vapors that are already present, or hydrogen created by the underwater burning process.

Hydrogen is a "colorless, odorless, flammable gas, the lightest of the elements, that combines chemically with oxygen to form water." It is generally known that whenever hydrogen gas occupies between seven and 13 percent of any given volume, it becomes a very explosive gas. If oxygen was added to this volume and an explosion occurred, the explosive force of the hydrogen would be greatly intensified and magnified with this addition. In addition, because such an explosion occurred underwater, the water pressure would add another layer of magnitude to the force of the explosion.

However, oxygen need not be present for hydrogen to explode. During underwater burning operations, hydrogen is a constant presence created by the use of an electrical current, and the high temperature in the kerf (cut-line in the steel). Additionally, flammable gases (such as methane from decayed marine growth inside an abandoned pipeline or ballast tank of a barge) or petroleum residue may also be present and combine with the hydrogen.

Fred C. Hess's book, Chemistry Made Simple, informs us that there are several methods used by commercial gas producers to manufacture hydrogen. The first method is based on a law of physics: that by putting an electrical circuit in the water, such as in underwater burning operations, the negative terminal (in this case, the cutting rod) will disassociate hydrogen from the water. This method of producing hydrogen is referred to as electrolysis. This can be seen anytime a dive station is set up for burning. The polarity of the cutting rig is verified by using the infamous "bucket test" - the ground clamp is placed in a bucket of water and the knife switch is made hot while sticking the tip of the cutting rod in the water near the ground clamp. If bubbles start to come off the end of the cutting rod, then the welding machine is set correctly. You have direct current electrode negative (DCEN), or straight polarity. The bubbles are, in fact, minute hydrogen bubbles. It is highly recommended that a plastic bucket be used for this test rather than metal.

Whether a diver is using steel tubular electrodes or exothermic rods, electrical current is required to ignite the rod or produce the energy (heat) to cut the steel. Because of extreme safety considerations, no diver or diving contractor ever uses an AC power source, only DC with straight polarity, or electrode negative.

Referencing Chemistry Made Simple again, another method for producing hydrogen is the action of flowing water or low-pressure steam over white-hot steel. In the case of underwater cutting, hydrogen and oxygen are being liberated from the water because of the extremely high temperature of the steel being cut as well as the tip of the rod doing the cutting. This phenomenon always occurs when cutting underwater regardless of the cutting process employed. In addition, if a diver is using shielded metal arc cutting (SMAC) electrodes, some of these type of electrodes have elements in their flux that, when burning, produce oxygen. In this case, SMAC electrodes would produce hydrogen naturally and, by flux additives, produce oxygen.

More bluntly put, anytime a diver using an underwater burning apparatus - whether steel tubular electrodes with oxygen, exothermic rods with oxygen, or a shielded metal arc electrode with no oxygen - hydrogen gas is being created at the tip of the electrode as well as from the molten metal. This hydrogen, freed from the water, of course takes the form of an expanding gas bubble (it was created under pressure) and will rapidly rise and expand.

In addition, any burning operation where steel is being heated, melted, and burned away creates sparks or hot cinders, which are nothing more than small bits of white hot steel. These sparks become trapped in the bubble column and also rise. When the sparks contact a large enough concentration of trapped gas, an explosion will occur. These can range from small pops or "finger slappers" to explosions that produce enough force to injure or kill the diver.

Dangerous Business
Quite often, diving contractors using exothermic rods will employ a power source to only ignite the rod and then rely on the oxygen being fed to the burning tip to keep the rod hot and cut steel, without any electrical power source. However, the tip of the rod is still burning at around 7,500 degrees Fahrenheit, which is more than enough to raise the temperature of the steel to be cut (at the kerf) to 3,000 degrees Fahrenheit - which is the temperature that steel melts or becomes liquid.

The temperature required to disassociate hydrogen molecules from water is only about 2,000 degrees Fahrenheit. What happens when you take steel (or any object, for that matter) that is white-hot and place it in water? Steam is produced (water in a gaseous form) and it is still comprised of two parts hydrogen and one part oxygen. For a manufacturer to state that, with shielded metal arc cutting, "the potential explosive dangers involved with conventional exothermic (oxy-arc) cutting are completely removed and the hazards to the diver are significantly reduced, especially when cutting into tanks, cylinders, pipes and any other sealed compartment" is extremely hazardous itself! Cutting into any tank, cylinder, pipe or sealed compartment with any method that produces extreme heat or uses an electric arc has always been and will continue to be, an extremely dangerous operation underwater. It would be a tragic catastrophe if a diving contractor were to accept that the "potential explosive dangers" have been completely removed when using SMAC underwater and attempted an underwater burning operation on a sunken barge or abandoned pipeline because it "offers a safe, convenient and cost-effective alternative, without any hazards to the diver" (emphasis added).

There are many examples of accidents that have occurred both underwater and topside where divers or welders have cut into or welded on compartments or pipelines containing flammable fumes from hydrocarbons or methane gas from decaying marine organisms. These accidents involved neither hydrogen nor oxygen, but were the consequences of arcing or cutting into an object that contained gas vapors under pressure.

The only truly safe underwater cutting operation is where the cutting is of a "cold" nature; that is, no induced fire and heat that are supported by an electric arc. Systems that employ semi- or full automatic HP water cutting with entrained grit, or hydraulic diamond wire cutting, for example, pose no potential explosive hazards. And, divers are not manually operating these complex systems, either! None of the above comments are intended to claim that divers should never cut into a tank, cylinder, pipe, or sealed compartment with a burning torch using steel tubular, exothermic, or SMAC rods.

Underwater cutting with oxy-arc or SMAC can be performed safely by following the proper procedures for flooding, venting, and verifying the areas are gas-free. This type of underwater burning operation goes back to the salvage of the ships sunk in Pearl Harbor in 1941, and for every severe accident to a diver doing this type of burning operation, there are probably thousands of similar operations done safely and efficiently.