Note

The thermic lance will operate on oxygen pressures from 80-120 psi. If the pipe burns faster than the filler rods, use more pressure. If the filler rods burn much faster than the pipe, use less pressure.

Figure E-2. Thermic Lance Holder Assembly.

A. THERMIC LANCE-INSERT TORCH INTO HOLDER (B)

B. THERMIC LANCE HOLDER

C. CONNECTING HOSE FOR REGULATOR ASSEMBLY (E)

D. COUPLING TO ATTACH (C) TO (E) - UNIT (D) CONSISTS OF A COUPLING AND A HOSE CLAMP

E. TWO STAGE REGULATOR CAPABLE OF PRODUCING A HEAD PRESSURE OF AT LEAST 200 P.S.I

F. SUPPLY OF OXYGEN

Figure E-3. Standard Thermic Lance Equipment Set Up.

E-3.4 Material Consumption.1 One Thermic lance will penetrate 24-inches of reinforced concrete producing a hole 2-1/2 inches in diameter using 60 cubic feet of oxygen in 5 minutes.

E-4 MAPP GAS CUTTING

MAPP Gas cutting is the only oxygen-fuel underwater cutting process approved for use by the Navy. It is used only when oxy-arc cutting equipment is not available or when there is an absence of sufficient electric power to conduct oxy-arc cutting.

MAPP gas is a mixture of stabilized methylacetylene propidene.

MAPP gas cutting is performed with a gas torch rather than with a cutting electrode. The technique for underwater cutting is exactly the same as oxygen-acetylene cutting topside. However, a great deal more skill is required using the MAPP gas process as opposed to Oxy-Arc underwater cutting.

Like Kerie Cable, this process is useful in ship salvage operations especially in areas where stringing long electrical power leads is difficult. Also, the necessary equipment can be carried in a small boat. The standard acetylene oxygen cutting torch is approved for Navy use. A spacer sleeve is attached over the cutting tip which aides the diver in maintaining the proper stand-off from the metal to be cut.

E-4.1 Principles of Operation. The principle of cutting metal underwater with a gas torch is virtually the same as that employed topside, except that the acetylene has been replaced with MAPP gas. The torch mixes the MAPP gas and oxygen which burn and generate sufficient heat to melt the metal to be cut. A small area on the metal is heated to a molten puddle and then oxygen is directed at that point. The oxygen instantly converts the molten puddle into a gaseous and chemical state, while simultaneously blowing it away. The flame is angled slightly in order to preheat the metal ahead of the cut, thus allowing the cut to continue.

1. These figures are manufacturer's estimates

E-4.2 Equipment and Material. The equipment generally required for underwater MAPP gas cutting is listed in Table E-2. Only approved equipment shall be used. Prior to use, it shall be examined, tested and determined to operate properly. The entire assembly, from cylinders to torch is essentially one complete functioning unit. The condition of internal cleanliness and repair of regulators, gauges, manifolds torch and hoses will govern the overall operating efficiency. A fleck of dirt in a regulator topside can cause complete failure at depth.

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