SAFE PRACTICES WHILE WELDING, GAS CUTTING, DRILLING AND GRINDINGMade By – Mohammad Kashif

GAS CUTTING

Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the U.S.) and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut metals, respectively. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903. Pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the work piece material (e.g. steel) in a room environment. A common propane/air flame burns at about 2,000 °C (3,630 °F), a propane/oxygen flame burns at about 2,500 °C (4,530 °F), and an acetylene/oxygen flame burns at about 3,500 °C (6,330 °F)

GAS CUTTING

Regulator- controls pressure from tank to the required pressure in the hose. Then operator controls the flow using needle valve.

Gas hoses – they are specifically color coded for use.

Torch – there are two different types of torch for welding and cutting purpose.

Regulators – they are used to regulate the output pressure. There are 2 gauges one shows the cylinder pressure other the o/l pressure.

Check valve – it is designed to allow gas to flow in one direction.

Flashback arrestor – it prevents the shock wave from downstream coming back up the hoses and entering the cylinder.

SAFE PRACTICES PERTAINING TO GAS CUTTING

Gas cylinder must be prevented from sharp impact with one another or the ground.

Acetylene cylinder must always be kept upright.

Cylinders should be stored in a well protected, well ventilated dry location, well away from highly combustible material

Moving cylindersNever use gas without proper pressure regulators

One should not smoke where cylinders are stored

Cylinder valves should be closed after completion of work

Do not tamper with number and marking on cylinder

Keep all cylinders chained, they should be chained individually and not as group

Before connecting the pressure regulator to a cylinder valve, the valve should be opened slightly and closed. This is called cracking and is done to remove dirt.

To test for leak soap solutions should be used.

Never attempt to mix gases in a cylinder

GAS TORCH AND TIPS

Never use a gas torch as a hammer or a lever.

A spanner and not a plier should be used for changing tips.

The slag accumulated at the blow pipe should be frequently removed by either hard wood stick or brass wire.

HOSE AND GAS TUBINGS

Use the correct color hose for oxygen(green/ black) and acetylene (red).

Always protect hose from being trampled upon.

If dirt goes into the hose blow through (using O2 not C2H2 ) before connecting to valve and regulator.

FIRE HAZARDS

Damaged insulation can cause local arcing between cables and near by grounded metal.

Sparks, molten metal gobules and hot slag falling on flammable material lying in weld /cutting area.

Leaking valves on fuel gas cylinders and blow pipes.

Back fire from blow pipes. To work around the above

conditions fire extinguishing equipment should be maintained in a state of readiness.

OTHER GENERAL PRECAUTIONS

Remove any combustible material before starting welding.

Do not weld in confined spaces without adequate ventilation or individual respiratory equipment.

When welding inside boiler cylinders must be kept outside and hose and its attachment tested for leakage.

Keep a fire extinguisher ready for emergency use.

Use goggles with non flammable lenses and frames.

Do not weld painted or galvanized surfaces in a badly ventilated place.

Never attempt to relight a blow pipe that has blown out without first closing both the valves.

If cutting is to be stopped for a long time, close the cylinder valves and then release all gas pressure from the regulator by opening torch valves momentarily

ARC WELDING BASICS

Arc welding is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes

WELDING MACHINES

In welding the Voltage is directly related to the arc length and Current is related to amount of heat input.

Constant current machines are generally used for manual welding as voltage may change due to arc length but power given wont change.

Positive charged anode has more heat concentration so for consumable electrode DCEP gives deeper penetration and greater weld speed as electrode will burn off quickly

PRECAUTIONS DURING USING WELDING M/C

When no welding is being performed remove electrode from holder and machine must be disconnected from power source.

Do not change the polarity switch when machine is under load. The arching due to high current can burn the contact switches.

Never strike an arc on a compressed gas cylinder.

ELECTRODE HOLDER

They should be of adequate rating for the maximum welding current.

Electrode holder shall be provided with discs or shields to protect the hands of the welder from heat of the arc.

Hot electrode holders must not be permitted to dip in the water because retaining moisture may cause an electric shock.

WELDING CABLES

They should be completely insulated and flexible type.

The cable should be free from repair or splices up to 3 mtr from the electrode holder.

Welding cable should be kept dry and free from grease and oil to avoid premature breakdown of insulation

SAFETY RECOMMENDATIONS IN WELDING AND CUTTING OPERATION

One should not look at an electric arc with the naked eye. Use a hand shield or helmet.

Eye trouble caused by arc flashes may be soothed by bathing with the following solution

Na2 CO3 343 g

Purified water freshly boiled & cooled 1000 ml

Welder should not leave the electrode holder on the table or in contact with a grounded metallic surface.

Adequate ventilation should be there while welding.

Welding should not be carried out in closed containers or on containers that have held combustible material.

PROTECTION FROM WELDING RAYS

Welding arc, in addition to being very bright, is a source of infrared and ultra violet radiation also; consequently the operator must use either a helmet or a hand shield fitted with special filter glass.

Exposing the eyes & face to infra red rays would lead to the face becoming uncomfortably hot and it might induce serious eye troubles. Excess UV light can cause an affect similar to sun burn on the skin

PROTECTIVE CLOTHING

Gloves protect the hand of a welder.

For overhead welding, some form of protection for the head is required. Leather skull cap or peaked cup will do the needful.

Leather jackets and leather leggings are also available.

Safety boots are necessary to protect the feet of the welder from hot slag and in particular, from falling off cuts.

VENTILATION & HEALTH PROTECTIONFumes are produced • At the arc in metal arc

welding with covered electrodes and in arc cutting

• When the being arc welded is galvanized.

Fumes are very injurious to health due to fluoride or high chromium content.

So either work outdoor or keep a ventilator while working

VENTILATION & HEALTH PROTECTION

Gases are present at the place of welding as a result of

• Application of heat to certain metals.

• Combustion (CO), the absorption of O2 in the process of combustion, and the oxidation of N2 in the air.

• The escape of gases used for combustion in welding and cutting blowpipes.

DRILLING

Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of circular cross-section in solid materials. The drill bit is a rotary cutting tool, often multipoint. The bit is pressed against the work piece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the work piece, cutting off chips (swarf) from the hole as it is drilled.

SAFETY MEASURES WHILE DRILLING

Do not support the work pieces by hand, use a holding device.

Never make any adjustment when the machine is running.

Never clean away chips using hands use a brush.

Keep all loose clothing away from turning tools.

Ease up on the feed as the drill breaks through the work to avoid damaged tools or workplaces

Always wear eye protection while operating any drilling machines.

Make sure that cutting tools are running straight before starting the operation.

Drill bit should be of correct size

GRINDING

Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.

Grinding practice is a large and diverse area of manufacturing and tool making. It can produce very fine finishes and very accurate dimensions; yet in mass production contexts it can also rough out large volumes of metal quite rapidly. It is usually better suited to the machining of very hard materials than is "regular" machining (that is, cutting larger chips with cutting tools such as tool bits or milling cutters), and until recent decades it was the only practical way to machine such materials as hardened steels. Compared to "regular" machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft’s diameter by half a thousandth of an inch or 12.7 um.

SAFETY PRECAUTIONS WHILE USING PORTABLE GRINDER

Guard must be adjusted to protect the user.

Ensure that the machine will not operate when unattached by checking the dead man switch.

Wear safety glasses or shield to protect from flying chips.

Do not use wheels that are cracked or vibrating excessively.

Use both hand while using the grinder.