Health and Safety (WELDING)

The gas welding plant consists of the 2 gas cylinders, oxygen and acetylene. The hoses, flashback arrrestors, gauges and the welding tip and torch. The video is a introduction about gas welding.









Safety Protection

When doing gas welding you must always wear safety equipment. As mentioned in the first part of health and safety you must wear proper steel toe safety boots and overalls to suit the job. You must wear 100% cotton overalls as it does not catch on fire from sparks and molten metals flying around. A welding leather apron can also be worn for more protection.


Eye safety is a must when doing gas welding. You must always wear the right type of gas welding goggles when doing gas welding. The goggles will protect your eyes from flying sparks and bursting molten metals. Also protects your eyes from the fumes that come out of the burning metals. I know people who did not use their googles properly and now suffering from very poor eye sight.

Leather gloves can also be worn for more protection to the hands. But I dont like wearing gloves as i dont get a proper fell of torch. For me welding without gloves is more better. But i am very carefull of not to touch hot metals and burning myself. I have burnt myself once when i picked up the filler rod from the hot side. Then i treated it by puting my finger under cold running water for about 10 minutes and it was just fine. So i tink it is a good practice to wear gloves to prevent yourself from burns.


Oxygen Cylinder

The oxygen cylinder is black in colour and the valve outlets are right hand threads.Oxygen cylinder is a solid drawn cylinder out of mild steel or alloy steel. Mild steel cylinder is charged to a pressure of  2000psi and alloy steel cylinders to  2500psi.Because of the possibility of the oxygen pressure becoming high enough to rupture the steel cylinder in case the temperature rises, an oxygen cylinder is equipped with a safety nut that allows the oxygen to drain slowly in the event the temperature increases the gas pressure beyond the safety load of the cylinder.An oxygen cylinder has an inside diameter of 21.6 cm, wall thickness 0.650 mm  and length  127.5 cm. In order to protect cylinder valve from getting damaged, a removable steel cap is screwed on the cylinder at all times When the cylinder is not in use.


You should never use bottled oxygen as compressed air. Never put oil or grease on oxygen guages, regulators or screw threads as pure oxygen reacts with the oil and can cause an explosion or spontaneous combustion. Keep this bottle very secure. If it drops and breaks the tap it becomes a live rocket due to the pressure. The video show how it dangerous the oxygen bottle can be.











Acetylene Cylinders

A acetylene cylinder is maroon in color and and all valves a screwed left handed. It can be easily recognised as the nuts have a cut or grove on them to show they are left hand threaded. This is also a solid draw steel cylinder with a pressure of  225psi. This is very low pressure compared to the oxygen cylinder.


The acetylene cylinder is filled with a porous type material that acts like a sponge. The sponge is filled with acetone. When the acetylene is compressed into the cylinder it is dissolved in the acetone. Never use the cylinder lying down orelse if there is a liquid draw into the hoses there can be explosions. Safe working pressure in the lines are up to 15psi. The video shows an acetylene factory explosion,







Safety With The Cylinders


Cylinders must be prevented from sharp impact with one another or with the ground.  Acetylene cylinders must always be kept upright.  A cap must be fitted on the cylinder while it is not in use.  Cylinders should not be exposed to welding flame, direct sun­ light, water, etc.  Cylinders should be well fastened at their places so that they do not fall.It should be stored in a well protected, well ventilated, dry location, well away from highly combustible materials such as oil or excelsior. One should not smoke at the place where gas cylinders have been stored. Cylinders containing acetylene and oxygen should be stored separately or quite far apart from each other.

• Do not use a cylinder as an electrical ground connection.
• Do not fasten cylinders to a work table or to structures where they could become part of an electrical circuit.
• Do not strike an arc on a cylinder.
• Do not use a flame or boiling water to thaw a frozen valve. Valves or cylinders may contain fusible plugs which can melt at temperatures below the boiling point of water.

• Mark or label them as "Empty cylinder" and store empty cylinders away from full cylinders.
• Return empties to the supplier.
• Remove regulators when not in use and store these away from grease and oil. Put protective caps on the fittings when in storage.
• Keep cylinders and fittings from becoming contaminated with oil, grease or dust.
• Do not use a cylinder that is not identified or if the label is not legible. The colours of industrial gas cylinders are not standardized.
• Remove the regulator and replace the valve protection cap before moving a cylinder.Move cylinders with appropriate trolleys. Use proper lifting cradles.Do not lift a cylinder by the valve cap..Do not drag, slide, or drop cylinders. If an acetylene tank has accidentally been left on its side, set it upright for at least one hour before it is used.Do not try to refill a cylinder or mix gases in a cylinder.

Pressure Guages

The pressure regulator has 2 gauges. One is the contents pressure and the other one is the working pressure you want to choose by turning the knob. Oxygen and acetylene use different gauges. Oxygen is right hand thread and acetylene is left hand thread. Therse are precision instruments and should be used very carefully. It should not be dropped.


Use the correct pressure regulator for a gas. For example, never use acetylene pressure regulator with any other gas. A pressure regulator shall be used, only, at pressures for which it is intended. Handle pressure regulators carefully. Cylinder valves should be opened slowly to avoid straining the mechanism of pressure regulators. Do not move the cylinder by holding the pressure regulator. For repairs, calibrations or adjustments purposes the pressure regulators should be sent to the supplier. Do cracking to take dust and dirt out of the valves and threads before connecting pressure regulator to the gas cylinder.
 Connections on regulators shall be inspected before use to detect faulty seats which may cause leakage of gas when the regulators are attached to the cylinder valves. Never use oil, grease or lubricant of any kind on regulator connections. Video Shows regulator safety and how it burn out when safety precautions are not taken.











Welding Hoses

These hoses are made of reinforced rubber and are color coded. Oxygen are normally black, green or blue. Acetylene hoses are maroon or red.  And also the fitting acetylene is left hand thread nd oxygen is right so you don't mixup when connecting up the hoses.


Hoses should always be checked for cracks burns and other damages. Never repair the hoses. It is a gud exercise to always change the hoses if damages. Always protect hose from being trampled on or run over. Avoid tangle and kinks. Never leave the hose so that it can be tripped over.Protect the hose from flying sparks, hot slag, hot workpiece and open flame. If dirt goes into hose, blow through (with oxygen, not acetylene) before coupling to torch or regulator. Store hose on a reel (an automobile wheel will do) when not in use. Never allow the hose to come into contact with oil or grease; they deteriorate the rubber and constitute a hazard with oxygen.






Welding Torch and Tips

The welding torch is where the 2 gases are mixed to get the working gas. There are 2 control valves one for the oxygen gas which is black or blue and the other one for acetylene which is red or maroon in colour. These valves are there to control how much of each gas you want to make your working flame.  The mixing chamber 
has the threading fitting in which the tips are fitted.


The tip and all fittings should be tight so that there is no gas leaks. Always leave the torch on the holder and turn it off when not in use.

Welding tips are made of pure copper and shaped inside to give an ideal welding flame. There are diggerent sizes of tips for different applications and heats. For general gas welding we used a 8mm tip and to make the flame a bit hotter we went for a 10mm. The tip cleaner is used to clean the tip when it gets noisy or the flame seems to be a bit out.


Gas torches and tips should be stored in clean boxes to avoid gas holes from becoming burred and choked with dirt. Never use a gas torch as a lever or hammer. A spanner and not a plier should be employed for changing tips. Screw tips only tight enough for a gastight Joint. All blow pipes and other apparatus shall be periodically dismantled and cleaned internally, preferably by the supplier. Gas holes must be clean, smooth and of correct size.During working, if the tip becomes overheated it may be cooled by plunging the torch into water; close the acetylene valve but leave a little oxygen flowing. Never hang a torch with its hose on regulators or cylinder valves. The video shows how to set up your plant properly.







Flashback Arrestors

A flashback arrestor is a device in the welding plant that prevents the flame burning back to the gas cylinders and causing explosions ad fires. This is a safety device and all welding plants should have it fitted. The arrestors are fitted to the regulators and are able to be reseted after a flash back occurs.


Flashbacks are caused by:

• wrong gas sequence during start up
• insufficient purging of gases before use
• blocked,worn,undersized or overheated tips
• hoses run over a vehicle during welding
• incorrect gas pressures
• blocked or kinked hoses
• flame held too close to working surfaces
• inappropriate use of the welding equipment

Flashbacks happen very quickly so before you could turn the system off the flashback arrestor shuts the gases from flowing ans saves you and your system from damage. It is a must to be in every welding plant and is part of the health and safety rule for gas welding. The Videos below show a good understanding about flashbacks and how the flashback arrestors work.

Welding Flames

Neutral Flame


A neutral flame is used for most weldings. It has roughly equal amounts of oxygen and acetylene. It can be recognized by a light blue inner flame cone with a darker blue outer flame. The neutral flame takes its name from the fact that it produces very little or no chemical reaction in the molten metal. In fact, the neutral flame actually acts as a gas shield to protect the weld pool from chemical reactions with the atmosphere. This flame is used to weld Mild steel, stainless steel, copper and aluminum. 


Carburising Flame


The carburising flame has excess acetylene and are used for specific processes. This can be done by reducing the oxygen. It contains three distinct levels of color: a very light blue cone at the nozzle, surrounded by an envelope or feather of darker blue; both of those are surrounded by an outer envelope of even darker blue.It is used for welding high-carbon steel and other metals that do not readily absorb carbon.  It is also used for hard facing materials as stellilte and silver bronze. If used for normal welding it will leave a lot of caron on the weld resulting in a poor weld.


Oxidising Flame


Oxidising flame has excess oxygen.The flame is shorter and bluer than both the neutral and carburizing flames, and the inner cone is more pointed. The excess oxygen from this flame will combine with the metal and form oxides, which are brittle and weaken the weld and the metal. Because of its oxidizing properties it is seldom used to weld steel, but is sometimes used for copper-based and zinc-based metals, as well as cast iron and manganese. A slightly oxidizing flame is used in braze-welding and bronze-surfacing while a more strongly oxidizing flame is used in fusion welding certain brasses and bronzes.


The video shows different flames types.






References



http://en.wikipedia.org/wiki/Oxy-fuel_welding_and_cutting
http://www.welding-technology-machines.info/gas-welding-processes-and-equipments/oxygen-gas-cylinder.htm
http://www.airproducts.com/nr/rdonlyres/9d325c49-7c62-41e5-aa0b-8411db4d84f8/0/safetygram13.pdf
http://www.ccohs.ca/oshanswers/safety_haz/welding/storage.html
http://www.hse.gov.uk/pubns/indg297.pdf
http://www.commerce.wa.gov.au/worksafe/PDF/Guidance_notes/WSguidnote_flashback.pdf
http://www.weldreality.com/gasdata.ht

http://en.wikipedia.org/wiki/Oxy-fuel_welding_and_cutting#Types_of_flame