SAFETY IN WELDING

Group 16

Ilham Romadhona(13/02858)Arga Prasetya (13/02896)Weny Faradita (13/05463)

General safety refers to condition as they

apply to all phase of welding and cutting. Specifically it deals with :

Ventilation Clothing Equipment

General Safety

Three factors govern the amount of

contamination to which welders may be exposed: Dimensions of the space Number of welders Possible evolution of hazardous fumes

Management must ensure welders have proper protection and ventilation

Ventilation

Natural and Mechanical Ventilation

Must not be restricted by screens Sufficient to keep concentrations Mechanical ventilation required for:

Metals not described here Spaces <10.000 feet per welder Rooms with ceilings lower than 16 feet Confined spaces or areas with barriers to

natural cross ventilation

Contaminant

should travel away from breathing zone.

Local exhaust ventilation may be more effective.

Poor Fair

Good Best

Welding zone Minimum air flow CU Ft/ Min Duct Diameter in

4” to 6” from arc or torch 150 36” to 8” from arc or torch 275 3 ½8” to 10” from arc or torch 425 4 ½

10” to 12” from arc or torch 600 5 ½

Exhaust hoods

Woolen clothing is preferable to cotton because it does not ignite as readily and protects the skins better from temperature change

Protective Clothing

Equipments

Basic Rules for Oxy-acetylene Welding : Ensure the safety fuse plug or disk is functional Attach regulator Stand to one side of regulator Open cylinder valve slowly Not more than 150 psi Purge oxygen and acetylene lines Light the acetylene Never use oil or grease near oxygen Do not use oxygen to clean or blow off dirt or clothing Keep your work area clean

Safety in Oxyacetylene Welding

1. Never lift cylinders by the service valve or

valve protection (use slings, net, or other approved means)

2. Keys, handles, and hand wheels must be present

3. Use the proper regulator4. Open acetylene valve no more than 11/2 turns5. If in doubt about a cylinder, don’t use it

Gas Cylinders Safety

Use Protective Devices

Pressure relief valves, backflow preventers or check valves

Flash back arrestors Fuel gas hose—red

(sometimes black) Oxygen hose—green Hose protection

required Pressure-reducing

regulators

Store Gas Cylinders

Safety The storage area must be well ventilated Keep fuel cylinders 20 feet or more from

combustibles Close valves, ensure valves are protected Limit inside storage to 2,000 cubic feet Store cylinders in the upright position and

secured from falling Separate oxygen from fuel gas

All pipig and fittings used to convey gases from a

central supply system to work stations must withstand a minimum preasure of 150 psi

Oxygen piping can be of black steel, wrought iron, brass or copper, and only oil free compounds should be used on oxygen threaded connections.

Piping for acetylene must be of wrought iron.

Piping

Joints and hoses should be checked for leaks before any

welding is attempted. Whilst acetylene may be detected by its distinctive smell (usually at levels of less than 2%) oxygen is odourless.

Leak detection is best carried out applying a weak (typically 0.5%) solution of a detergent in water or a leak detecting solution from one of the gas supply companies. It is applied to the joints using a brush and the escaping gas will form bubbles. On curing the leak, the area should be cleaned to remove the residue from the leak detecting solution.

Testing for Leaks

Lighting a TorchFirst - before you attempt to light the torch follow these checks: Make sure regulator pressure adjustment screws are backed out! Make sure torch valves are closed! Stand away from front of regulator Separately and slowly open the oxygen and acetylene cylinder valves Adjust regulator p/a screws to tip pressure settings Open/close torch valves separately and fine tune pressure settings on

regulators Depress cutting lever and adjust pressure if necessary

Lighting and adjusting the torch (with a positive/equal

pressure mixer): Separately purge both oxygen and fuel gas lines Open fuel gas valve 1/2 turn Ignite flame with striker Increase fuel gas flow until flame leaves end of tip and

no smoke is present Decrease until flame goes back to tip Open oxygen valve and adjust to neutral flame Depress oxygen lever and make necessary

adjustments

Shutting down the torch (with a positive/equal pressure mixer): Close oxygen torch valve Close fuel gas torch valve

If the torch/regulators and gases are done being used for a while, follow these procedures: Close oxygen and fuel gas cylinder valves Separately purge oxygen and fuel gas lines Make sure all regulator gauges read 0 Back out regulator pressure adjustment screws! If you are using in a commercial environment, report any damage,

etc. to your supervisor

Shutdown a Torch

Backfires occur when the torch flame burns back into the

blowpipe, sometimes it can continue burning back to the point where oxygen and the fuel gas are mixed causing a potentially serious situation.

Flashbacks are caused by a reverse flow of oxygen into the fuel gas hose (or fuel gas into the oxygen hose) – this then produces an explosive mixture in the hose. The flame can then burn back through the blowpipe, into the hose and may even reach the pressure regulator and the cylinder. This can result in damage or destruction of equipment, and could even cause the cylinder to explode. This could end in serious injury (or worse) and severe damage to property.

Backfires and Flashbacks

Backfire or flashback procedure After an unsustained backfire in which the flame is extinguished: close the blowpipe control valves (fuel gas first) check the nozzle is tight check the pressures on regulators re-light the torch using the recommended procedureIf the flame continues to burn: close the oxygen valve at the torch (to prevent internal burning) close the acetylene valve at the torch close cylinder valves or gas supply point isolation valves for both oxygen

and acetylene close outlets of adjustable pressure regulators by winding out the

pressure-adjusting screws open both torch valves to vent the pressure in the equipment close torch valves check nozzle tightness and pressures on regulators re-light the torch using the recommended procedure

If a flashback occurs in the hose and equipment, or fire in the hose, regulator connections or gas supply outlet points:

isolate oxygen and fuel gas supplies at the cylinder valves or gas supply outlet points (only if this can be done safely)

if no risk of personal injury, control fire using first aid fire-fighting equipment if the fire cannot be put out at once, call emergency fire services after the equipment has cooled, examine the equipment and replace defective

components

When a backfire has been investigated and the fault rectified, the torch may be re-lit. After a flashback, because the flame has extended to the regulator it is essential not only to examine the torch, but the hoses and components must be checked and, if necessary, replaced. The flashback arrestor should also be checked according to manufacturer's instructions and, with some designs, it may be necessary to replace it. BCGA Code of Practice CP7 recommends that non-return valves and flashback arrestors are replaced every 5 years.

All containers should be considered unsafe for welding or

cutting unless they have been rendered safe, or declared safe by a qualified person. When welding or cutting containers, there is the possibility of explosions, fires, and the release of toxic vapors or fumes. Containers include jacketed vessels, tanks, drums, covered parts or other equivalent situations. Seemingly empty containers might have materials hidden in cracks and crevices, which will release hazardous fumes when heated by welding or cutting. And the flammable and explosive materials include gasoline, light oil and many others

Safety in Welding and Cutting Containers

There are some cleaning method : Cleaning the container that has held combustibles is necessary in all cases

before any welding or cutting is done. This cleaning may be supplemental by filling the container with water or an inert gas both before and during such work. Treat each compartment in a container in the same manner, regardless of which comparment is be welded or cut.

Water Cleaning water-soluble substances can be removed by repeatedlv filling and draining the container with water. Water-soluble acids, acetone, and alcohol can be removed in this manner. Diluted acid frequently reacts with metal to produce hydrogen; care must be taken to ensure that all traces of the acid are removed.

An accumulation of air or gas in a confined area will expand when heated and the internal preasure may build up to cause an

explosion

Hot Chemical Cleaning, there are some procedure recommended:1. Flush out any remaining residue of the container with water and drain.2. Dissolve 2-4 ounces of trisodium phospate or commercial caustic cleaning compound

into a gallon of boiling water. Pour this solution into the container and fill the water.3. Attach a steam line to the container and admit steam to maintain the solution at a

temperature of 170o-190o for 15-20 minutes, during the steaming periode add water to allow discharge of volatile. At the end of the prescribed periode, drain the container.

Steam Cleaning, There are the procedures:1. Blow steam into the container, preferably through the drain, for a period of time to be

governed by the condition or nature of the flammable substance previously held by the container

2. Continue steaming until the container is free from odor and the metal parts are hot enough to permit steam vapors to flow freely out of the container vent or similar opening.

3. Thoroughly flush the inside of the container with hot, preferably boiling, water.4. Drain the container.5. Inspect the inside of the container to see if it is clean. To do this, use a mirror to reflect

light into the container6. Close the container openings. In 15 minutes, reopen the container and test with a

combustible gas indicator. If the vapor concentration is in excess of 14 percent of the lower limit of flammbility, repeat the cleaning procedure.

Safety in Cutting

Never use a cutting torch where sparks will be a hazard If cutting is to be over a wooden floor, clean the floor and wet it Keep a fire extinguisher nearby whenever any cutting is done Whenever possible perform cutting in wide open areas so sparks

and slag will not become lodged in confined cracks. If cutting is to be done near flammable material and the

material cannot moved, suitable fire resisting guard In plants where a dirty or gassy atmosphere exists extra

precaution should be taken to avoid explosions resulting from electric spark or open fire during cutting or welding operation.

Arc welding includes shielded metal-arc, gas-

shielded arc and resistance welding. Only general safety measures can be indicated for these areas because arc welding equipment varies considerably in size and type.

Safety in Arc Welding

Safety practices which are generally common to all types of arc welding operations are as follows:

1. Welding can be safe when sufficient measures are taken to protect yourself and others from potential hazards

2. Students should read and understand the following before welding: Warning Labels Material Safety Data Sheets (MSDS)

3. Students should also be familiar with the following information Safety in Welding, Cutting, and Allied Processes’ (ANSI Z49.1) Lincoln Electric’s ‘Arc Welding Safety’ (E205)

4. Fumes and gases can be hazardous to your health5. Keep your head out of the fumes6. Use enough ventilation, exhaust at the arc, or both, to keep fumes

and gases from your breathing zone and the general area7. See product labeling and MSDS for ventilation and respirator

requirements

8. Only manual electrode holders which are specifically designed for arc welding and cutting, and

are of a capacity capable of safely handling the maximum rated current required by the

electrodes, shall be used

9. Any current-carrying parts passing through the portion of the holder which the arc welder or

cutter grips in his hand, and the outer surfaces of the jaws of the holder, shall be fully insulated

against the maximum voltage encountered to ground

10. Only cable free from repair or splices for a minimum distance of 10 feet from the cable end to

which the electrode holder is connected shall be used. Except that cables with standard

insulated connectors or with splices whose insulating quality is equal to that of the cable are

permitted)

11. All ground connections shall be inspected to ensure that they are mechanically strong and

electrically adequate for the required current

Sekian

Terima Kasih