4-2.1 Oxygen-Arc and Shielded Metal Arc Equipment. Underwater oxygen arc cutting and shielded metal arc cutting and welding are performed with basically the same equipment. A typical arrangement of this equipment is illustrated in Figure 4-1; additional accessories not shown include scrapers and wire brushes which are used for both underwater cutting and welding operations. The equipment is also listed in Table 4-1.
4-2.2 Diving Equipment. The standard Navy MK 1, MK 12 or Superlite-17 helmets will be used while conducting underwater cutting or welding operations. These helmets have wide fields of view and a welding shield can be attached, as shown in Figures 4-2, 4-3 and 4-4.
Specific technical information necessary to operate the diving equipment is addressed in Operation and Maintenance Instructions for the MK 1, Mod "0" Lightweight Diving Outfit (NAVSEA SS520-AE-MMA-010/ DIV OST); for the MK 12 SSDS (NAVSEA 0994-LP-018-5010); for the Superlite 17b-Mod "0" Helmet (S6560-AG-OMP-010/SL17B/NS-DS118B); or, for the Superlite 17B-Mod "1" Helmet (S6560-AG-OMP-010/SL17B/NSI).
4-2.2.1 Welding Shields. The MK 12 welding shield is secured to the helmet by two spring clips which hook to the forward edge of the side viewport retainers. A rubber cushion on the rear of the shield body helps to hold it in place. The lens is clip-mounted in a hinged section. The hinged section can be flipped up or down and is held in position by a flat detent spring. The replaceable lenses, made of gold foil laminated with polycarbonate, are supplied in #4, #6 and #8 commercial shades of light density. Darker shades are available but are seldom required.
Close up views of the welding shields with parts identification are illustrated in Figures 4-5 and 4-6.
S0300-BB-MAN-010 Table 4-1. Recommended Equipment for Underwater Arc Cutting and Welding Category Item
Diving equipment MK 12, MK 1 or Superlite 17B Surface Supported Diving
System with Welding shield and assorted welding lens
Heavy-duty rubber gloves and Playtex-type or surgical gloves
Cutting and welding equipment DC welding power source 400 amperes
Safety switch rated at 400 ampers, 250 volts
Welding cables, sizes 1/0 and 2/0 with bolt-together cable connectors and necessary bolts and nuts
"C"-type ground clamp
Amperage tong meter
Electrician's DC volt meter
Cutting equipment Underwater cutting torches
Manifold to connect the cylinders; if more than one is to be used
2-stage, high flow, high volume regulator Leak detector - LEAK-TEC or soap suds Welding equipment Electrode holder
Weighted wire brush Chipping hammer Scraper
Ultrasonic thickness and flaw detection device Dye Penetrant test kit
Specific technical information necessary to operate diving equipment is addressed in the appropriate surface supported diving system technical manual.
4-2.3 Power Supply Requirements. The preferred power supply for underwater cutting and welding is a 400 amp or larger, engine driven DC welding generator with a minimum of 60 percent duty cycle. The generator shall have independent voltage and amperage controls. Figure 4-7a shows control panel of a typical generator. A welding power source with a minimum capacity of 300 amperes is acceptable, however, cutting time is considerably longer whenever power is reduced. 400 amp and over are required for some operations. DC generators, motor generators and rectifiers are acceptable power supplies. In an emergency, a 200-ampere machine set for peak or near-peak load may be sufficient for short periods of time; rectified or motor driven type machines may also be used.
4-2.3.1 Power converters. Power converters are just what the name implies; the input alternating current (AC) primary power is passed through a circuit breaker to a rectifier, where the input is transformed to DC power. Portable power converters, though somewhat limited, are particularly useful for salvage work when ship or shore power is available. Figure 4-8 shows one such unit which weighs only 70 pounds and will deliver a maximum of 80 volts open circuit with an adjustable current range of 30 to 375 amps. Power converters should not be used when the work is deeper than 100 FSW or with more than 200 feet of welding lead. To work beyond these boundaries would overwork the machine. This type machine will support cutting operations using the exothermic technique for short periods of time, however, for long burning jobs where power is to be used, a welding generator is recommended. This type of unit will not accommodate cutting operations using the steel-tubular electrode. When using electric-driven machines, ensure that the primary power supply cables are laid separately and away from welding supply cables.
Motor generator power sources consume large amounts of energy during their entire running period. A welding rectified power supply will require significant energy only during the welding cycle. This may be an important consideration when away from normal logistic support.
Figure 4-7. Typical Welding Generator and Power-Converter Control Panel.
4-2.3.2 Welding Generator, Pre-Setup Inspection. Successful underwater welding and cutting is highly dependent on the efficient running of the power supply unit. Before any underwater work takes place, the welding power source should be fully inspected by qualified personnel. The commutators on motor-generators should be clean. Brushes must not be excessively short or worn. Slack brush rigging springs must be replaced. Operation of a welding generator beyond its capacity and duty cycle will melt the soldered rotor winding connections to the commutator. This will reduce the generator's capacity during future use. If the generator is incapable of achieving rated capacity for its duty cycle, then the interior of the housing should be checked for traces of soldered deposits. All power sources should be checked for confirmation of rated capacity before use. Motor generators designed solely for use with semi-automatic welding equipment are not suitable for underwater applications.
Table 4-1 lists the equipment required for underwater cutting and welding.
4-2.3.3 Polarity. Underwater cutting and welding operations are usually performed with DC ELECTRODE NEGATIVE, i.e., STRAIGHT POLARITY. A typical equipment arrangement is illustrated in Figure 4-8. The cable from the electrode holder is connected to the negative (-) terminal of the DC power supply and the positive (+) or ground cable is connected to the work. The majority of electrode manufacturers call for a DC, ELECTRODE NEGATIVE setup. Occasionally, there may be a requirement for reverse polarity, sometimes referred to as DC, ELECTRODE POSITIVE for a particular electrode or for improved welding as noted in Chapter 3. This will normally be at the recommendation of the electrode manufacturer and will be printed on the electrode box or included in accompanying literature.
4-2.3.4 Polarity test. When the polarity of a welding generator is uncertain; i.e., the terminals are unmarked or not legible, it is necessary to determine the polarity before proceeding with welding or cutting operations.
The procedure for the test is as follows:
a. With the power source dead, connect the ground and welding leads to the terminals.
b. Attach a small, plate to the ground cable; place an electrode in the electrode holder or cutting torch as applicable.
c. Personnel performing this test must be properly insulated from the current.
d. Immerse the plate and the tip of the electrode in a container of salt water and hold them about 2 inches apart.
e. Call for "Switch on," and one of the following will occur:
1) A heavy stream of bubbles will rise from electrode tip. This indicates straight polarity, that is: DC, ELECTRODE NEGATIVE (-). Label the terminals on the welding machine.
2) If bubbles appear from the plate, switch off the current and change the lead connections to the opposite terminals. Repeat test and label the machine terminals for future reference.
f. Once the correct polarity is determined, the ground clamp should then be bolted to the POSITIVE (+) lead and the electrode holder attached to the NEGATIVE (-) lead.
4-2.3.5 Tong Test Ammeter. The Tong Test Ammeter is a portable instrument that will measure current flowing in a circuit without making electrical connections to it. It is a most important tool to have on hand while setting-up for and during underwater cutting and welding operations. This is especially true when there is uncertainty as to the output of a particular welding machine. Costly mistakes and wasted bottom time may be avoided by simply taking a Tong reading before the diver enters the water. This step will eliminate any doubt as to the actual welding generator amperage output. There have been many holes burned in ship's bottoms by divers who assumed the welding machine was functioning properly when in fact it was delivering amperage far in excess of the dial setting. On the other hand, there have been many man-hours wasted by divers trying to weld or burn with too little amperage.
To determine the exact amperage output of the welding generator, take a tong meter reading. Wait until the diver has established an arc and is welding and simply encircle the welding lead with the tongs of the test ammeter and close them. A clear, accurate reading will instantly register on the scale. This will be the closed-circuit reading. The tongs open by a slight pressure of one finger on the trigger and are self-closing (see Figure 4-9)
Do not rely exclusively on the values indicated by the control panel knobs or on installed meters. The meters are not intended for exact current or voltage measurements. The tong test ammeter will read the actual current passing through the welding cable.
4-2.3.6 Amperage and Voltage. An understanding welding of electricity and of the interrelationships of amperage and voltage is important for the diver involved with underwater cutting and welding. An electrical arc welding circuit is the same as any other electrical circuit. There are three factors in a simple electrical circuit:
a. Current — flow of electricity b. Pressure — force needed to effect current flow c. Resistance — force used to regulate the flow of current
Current is a "rate of flow." Current is measured in amperes. The term ampere is the amount of current that flows through a circuit per second. Amperage is also the current that provides the heat necessary to melt the base metal.
Pressure is the push or force that causes the current to flow. The measure of pressure is the volt. Voltage measured in machine out-put and across an arc are essentially the same. Before the arc is struck or if the arc is broken, the voltmeter will read the voltage across the
machine with no current flowing in the circuit. This is known as the open circuit voltage and is higher than arc voltage when current is flowing (closed circuit voltage, also referred to as arc voltage).
Resistance is a restriction to current flow in an electrical circuit. Every component in the circuit, including the conductor, (welding and ground leads) offers resistance to current flow. Current flows through some conductors easier than others. Resistance depends basically on the material and the thickness (cross sectional area) of a conductor. Welding leads are made of copper since it has the lowest electrical resistivity of common metals.
There are a number of variable factors affecting welding machine settings. These include size and type of electrode, thickness of metal to be welded, type of joint and the skill and technique of the diver. Current ranges as published by assorted manufacturers vary considerably for the same classification and size of electrode. The underwater welding or cutting operation should be started using the settings listed in Tables 2-1 and 3-3 and adjusted as necessary to produce the desired effect.
4-2.3.7 Diesel Driven Welding Generator Amperage and Voltage settings. In addition to setting up for the desired polarity, the machine must also be set for the correct amperage and voltage. Setup procedures for welding machines vary according to the type of machine and according to the manufacturer. Therefore, the manufacturer's operating manuals and instructions for the particular machine should be consulted and closely followed.
Most diesel driven welding generators have two control dials, one for adjusting desired amperage and one for voltage adjustment. There are several types of welding generators in use throughout the Navy and the commercial industry. The overall functions and operating setup are essentially the same.
The dial on the operator's left is the Amperage Range or Course Amperage Control. The range of each switch position is displayed on the nameplate. The amperage range is set before welding begins and is not to be adjusted while actual welding is in progress. The dial on the right is the Fine Adjustment Control and selects a welding amperage and open-circuit voltage between the minimum and maximum values of the coarse range selected by the Range Switch. The scale surrounding the Fine Adjustment control is calibrated in percent and does not indicate an actual amperage value. The Fine Adjustment control may be adjusted while welding. The procedure is:
EXAMPLE: Setting up a Typical Welding Generator.
With the Amperage Range set at the 100 to 220 position and the Fine Adjustment set at 0 percent, the welding generator would produce 100 amps and 24 to 26 closed-circuit volts. By moving the Fine Adjustment to the 35 percent position, the generator would produce 140 amps and 28 to 30 closed-circuit volts. Should more closed-circuit voltage be desired with the same amperage, the Amperage Range can be moved to the 65 to 140 range and the fine current adjusted to the 100 percent position. This arrangement would cause the machine to produce 140 amps and 34 to 36 closed-circuit volts. This setting is often chosen to produce smoother beads, less arc blow and better penetration, however it can increase undercutting due to the increased voltage (pressure). Notice that the Amperage Ranges overlap. This allows amperage and voltage adjustment throughout the machines range.
4-2.4 Safety Switches. A safety switch, also referred to as "knife switch" and disconnect switch, is required in the electric circuit to protect the diver from electric shock when not cutting or welding. A typical four-pole safety switch used with underwater cutting and welding equipment is shown in Figures 4-1 and 4-8. When a single-pole knife switch is used, it should always be located in the welding-lead side of the electric circuit and must be rated to handle the maximum welding current. Additionally, the safety switch must be mounted vertically on a non-conducting (wood, plastic, etc.) stand. The safety switch has an open circuit potential of some 80 volts across the poles. To prevent accidental contact, the switch should be fitted with a non-conducting slotted cover.
The use of an approved, positive-acting safety switch in the welding or cutting-circuit is mandatory. The switch must be mounted so the handle is in the upper-most position during welding or cutting. If the switch should accidentally fall, the circuit is broken. The switch illustrated in Figure 4-8 shows the correct orientation. The safety switch protects the diver by allowing current flow only when the diver is actually cutting or welding or has the electrode poised and ready. When a single-pole switch is used, special care must be taken that the switch is not being shunted out or bypassed. This can occur if there is a break in the insulation between the welding machine and the safety switch. It is important to remember that wet, bruised or worn cables between the machine and the switch, either single or double pole, can be shorted out by abrading against the frame of the welding machine, hatch combings or lying on a steel deck. Cables in this condition would constitute a potential source of danger.
4-2.5 Power Cables and Connectors. The proper cable size for a particular job depends on the total length of circuit. Size 2/0, extra-flexible welding cable is recommended for work that is a considerable distance from the power source, because the voltage drop is less due to its lower resistance. It should be used where the total length of cable, including the electrode and ground leads, exceeds 300 feet. Where the total length of the leads exceeds 400 feet, 3/0 size cable should be used to reduce resistance. The length of cable attached to an electrode holder, sometimes referred to as the whip lead, may be size 1/0, extra-flexible cable. This will enable the diver to easily maneuver the electrode holder as he welds.
Each additional length of cable and its connectors produce a voltage drop. To prevent excessive voltage-drop in the welding or cutting leads, it is desirable to have various lengths of continuous lead on hand. Welding lead procured in lengths of 50, 100, 200 or 300 feet will prevent considerable current-loss at connections. Excess cable should be laid out in straight lines or large "U"s because coiling sets up an electrical field and reduces cutting or welding efficiency. To compensate for the voltage drop in a welding circuit the open circuit voltage must be increased. The voltage drops for various sizes of cables are shown in Figure 4-10. This voltage drop does not include the effect of contact resistance which can be minimized by making sure all connections are completely insulated by wrapping in rubber tape, applying a layer of scotch cote, then a final wrap with electrical tape. The importance of waterproof connections cannot be over emphasized in underwater cutting or welding. A poorly insulated underwater connection allows a considerable current leak and very rapid deterioration of the copper cable. A poorly insulated connection between the whip (stinger) lead and the welding lead can be extremely dangerous to the diver. Bolt-on connectors are preferred as they are less likely to work loose. The life of any cable is increased by proper coiling when the cable is not in use and by minimizing its exposure to oil.
4-2.6 Gas Manifolds. Manifolds, sometimes referred to as coupler blocks, are used for the purpose of connecting two or more cylinders of the same kind of gas to discharge all of the cylinders through one regulator. The use of manifolds is desirable when it is necessary to furnish an uninterrupted supply of gas or when it is needed to supply gas at greater rates than can be supplied from a single cylinder.
Manifolds, are subjected to full cylinder pressure and they should, therefore, be strongly constructed. Oxygen manifolds should not be made of steel or iron pipe or copper tubing. They should be capable of withstanding a hydrostatic pressure test of 1-1/2 times the working pressure. For example, for use with oxygen cylinders rated at 2,000 psi, the manifold should be tested hydrostatically at 3,000 psi. Extreme care should be taken to see that no oil, grease or solvent is in an oxygen manifold when high-pressure oxygen is connected.
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