Gas welding equipment | Basic Of Gas Welding
Oxy Acetylene Welding Principle of Operation:
When acetylene is mixed with oxygen in correct proportions in the welding torch and ignited, the flame resulting at the tip of the torch is sufficiently hot to melt and join the parent metal. The oxyacetylene flame reaches a temperature of about 3200°C and thus can melt all commercial metals which, during welding, actually flow together to form a complete bond.
A filler metal rod is generally added to the molten metal pool to build up the seam slightly for greater strength. Oxyacetylene welding does not require the components to be forced together under pressure until the weld forms and solidifies.
Gas welding equipment:
The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source (usually cylinders), two pressure regulators and two flexible hoses (one of each for each cylinder), and a torch. The cylinders are often carried in a special wheeled trolley.
1. Oxygen Cylinder:
Oxygen cylinder is usually painted in black colour. In this cylinder, oxygen is stored under a pressure of 1550 N/m2. The common cylinder is 1.8 m3, 3.5 m3, 7 m3, etc.,
2. Acetylene Cylinder:
Acetylene cylinder is usually painted in maroon colour. In this cylinder, acetylene is stored under a pressure of 175 N/m2. The common cylinder is 1.6 m3, 2.8 m3, 8.4 m3, etc.,
The regulator is used to control pressure from the tanks by reducing pressure and regulating flow rate.
4. Gas hoses:
The hose is usually a double-hose design, meaning that there are two hoses joined together. The oxygen hose is green and the fuel hose is red. The type of gas the hose will be carrying is important because the connections will have different threads for different types of gas. Fuel gases (red) will use left-hand threads and a groove cut into the nut, while the oxygen (green) will use right-hand threads. This is a safety precaution to prevent hoses from being hooked up the wrong way.
5. Non-return valve:
Between the regulator and hose, and ideally between hose and torch on both oxygen and fuel lines, a flashback arrestor and/or non-return valve should be installed to prevent flame or Oxygen-fuel mixture being pushed back into either cylinder and damaging the equipment or making a cylinder explodes.
6. Check valve:
A check valve lets gas flow in one direction only. A check valve is usually a chamber containing a ball that is pressed against one end by a spring: gas flow one way pushes the ball out of the way, and no flow or flow the other way lets the spring push the ball into the inlet, blocking it.
The torch is the part that the welder holds and manipulates to make the weld. It has a connection and valve for the fuel gas and a connection and valve for the oxygen, a handle for the welder to grasp, a mixing chamber (set at an angle) where the fuel gas and oxygen mix, with a tip where the flame forms. The top torch is a welding torch and the bottom is a cutting torch
a) Welding torch:
A welding torch head is used to weld metals. It can be identified by having only one or two pipes running to the nozzle and no oxygen-blast trigger and two valve knobs at the bottom of the handle letting the operator adjust the oxygen flow and fuel flow.
b) Cutting torch:
A cutting torch head is used to cut metal. It is similar to a welding torch, but can be identified by having three pipes that go to a 90 degree nozzle and by the oxygen-blast trigger. Only iron and steel can be cut using this method.
8. Other Accessories:
a) Filler rod / Welding rod: Filler rod is a metal which is used in gas welding to supply additional metal to make the joint.
b) Flux is used in oxy-acetylene gas welding to prevent oxidation and also to remove impurities. The flux may be either in powder or liquid form.
9. Safety devices:
b) Leather goggles
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