Table E5 Recommended Pressure Settings and Hose Size Selection Chart

WATER

MAPP GAS

Hose

Hose

Depth Pressure

Pressure

Diameter

Length

(FSW)

(psi)

(psi)

(in)

(ft)

10

4.5

25

1/4

50

20

9.0

25

1/4

50

30

13.5

25

1/4

50

40

18.0

30

1/4

50

50

22.5

35

5/16

75

60

27.0

40

5/16

75

70

31.0

45

5/16

100

80

35.5

50

5/16

100

90

40.0

55

3/8

125

100

45.0

60

3/8

OXYGEN

Pressure in psig for Plate Thickness of:

Hose

Hose

Depth

Pressure

1/4-1"

1/4-2 3/4"

3-4"

5-6"

Diameter

Length

(FSW)

(psi)

(psi)

(psi)

(psi)

(psi)

(in)

(ft)

10

4.5

60

70

80

90

5/16

50

20

9.0

60

70

80

90

5/16

50

30

13.5

60

70

80

90

5/16

50

40

18.0

65

75

85

95

5/16

50

50

22.5

70

80

90

100

5/16

75

60

27.0

75

82

95

105

3/8

75

70

31.0

80

90

100

110

3/8

100

80

35.5

85

95

105

115

3/8

100

90

40.0

90

100

110

120

3/8

125

100

45.0

95

105

115

125

3/8

125

E-4.7 Lowering the Ignited Torch. The ignited torch may be lowered to the working location in one of two ways:

a. Carrying the Torch Below - In moderate or shallow depths and easily accessible locations, the ignited torch may be carried below by hand. The diver should be prepared to make adjustments to the flame to compensate for increased hydrostatic pressure during descent.

b. Lowering the Ignited Torch - In shallow depths and locations, where it is absolutely certain that the flame can be kept clear of all hoses, lines, diver's dress, helmet and other equipment or personnel, the ignited torch may be lowered directly to a point within reach of the diver. Never lower an ignited torch until it is certain that the diver is ready and watching for it and is in the clear in such a position that the torch flame cannot possibly strike his helmet, suit or umbilical.

It is the responsibility of the diver's tender to see that the correct pressures are maintained at the regulators. When the job has been completed, the diver should shut off the MAPP gas valve first and release the oxygen trigger; however, let preheat oxygen blow until the torch is removed from the water. This will keep the preheat parts from becoming clogged with foreign matter. Clean the torch and tips if it is suspected that clogging may have occurred.

E-4.8 Underwater Cutting. The cut may be started on the edge of the plate or in Figure E-5.

E-4.8.1 Starting the cut at the edge of a plate. To start the cut at the edge of a plate, proceed as follows:

a. Hold the torch head over the corner of the plate so that the preheat flames can heat a spot on the edge. Small sparks flying from the steel will indicate that the metal is hot enough to start the cut (see Figure E-5).

b. Start the cut by pressing on the cutting lever and directing the cutting jet onto the hot spot. Better results will usually be obtained by opening the cutting jet about halfway for a few seconds at the start.

E-4.8.2 Starting the cut at the central portion of a plate. The cut may be started in the middle of a flat plate by "blowing through." The recommended procedure is as follows:

a. Hold the torch tip at one spot on the plate until it is brought to heat. Figure E-6 shows the torch positioned for starting a cut in the middle of a flat, horizontal plate.

b. Turn on the cutting jet gradually, at the same time raising the torch head slightly so that slag will not blow back into the tip. The two motions should be simultaneous.

PREHEAT AREA (a) EDGE STARTING

(b) ADVANCING THE CUT

Figure E-5. Starting the Cut at the Edge of a Plate.

Figure E-6. Starting a Cut in the Central Portion of a Plate.

E-4.8.3 Advancing the cut. The cut is advanced by moving the torch at a steady, uniform rate of speed along the line of cut, fast enough to keep the cut going, but slow enough to cut completely through the metal. When the torch is advanced too slowly, the steel will cool below the ignition temperature and the cutting action will stop. The diver has "lost the cut" and will have to restart the cutting action. When the torch is advanced too rapidly, again the cut will not be completely through. The skipped spots (hangers) will be very hard to cut out. When the cut has been lost, it may be restarted by going back 1/2 to 3/4 inch and start a new kerf to one side of the old cut. As shown in Figure E-7, the purpose of this is to be sure that the cut is complete.

STEEL PLATE

STEEL PLATE

Figure E-7. Restarting the Cut.

E-5 UNDERWATER WELDING

When commercially produced waterproofed wet welding electrodes are not available, surface welding electrodes can be used if waterproofed. Some above-water electrodes will give satisfactory performance underwater if properly prepared and deposited by a skilled diver. The electrodes listed in Table E-6 are suitable for on-site waterproofing. For positional welding underwater, E6013, E7014, E7016 and stainless steel electrodes of 1/8-inch diameter are suitable.

E-5.1 Waterproofing Surface Electrodes. Unlike commercially manufactured wet welding electrodes, it is necessary to waterproof the flux coating of surface welding rods. This is accomplished by dipping the electrode in one of the suitable waterproofing solutions listed in table E-6. One or two dips may be required, depending on viscosity of waterproofing material. Be sure to completely cover all of the flux coating. One or two dips are required because when the waterproof coating is inadequate, water forced into the interstices will turn to steam when the arc is struck and will blow off the coating. The waterproofing coatings must be thoroughly dry before applying additional coatings and also before they are used. The grip ends of the electrodes should be cleaned to prevent the waterproofing material from interfering with electrical contact between the electrodes and holder. It is desirable to send the diver only a few electrodes at a time since waterproofing protects the electrode covering for a limited amount of time.

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