Gas welding

Welding is an important industrial tool to join cuts. Gas welding is an important welding process which is actually a fusion welding process. Here heat is developed by the combustion of oxygen or air with a fuel like acetylene, hydrogen butane etc. The commonly used combination is oxygen-acetylene which can reach up to 3000 degree Celsius temperature and is most preferred for welding metals and metal alloys. Oxygen is filled in a steel cylinder at a pressure of 150 kg per square cm. Colour code used for oxygen cylinder is black. Acetylene is also filled in a cylinder at a pressure of 16 kg per square cm. Here acetylene is dissolved in a cylinder containing porous silicate filler. For directing the flow, a welding torch is used. This torch also helps to mix up the gases and control the volume of the gases. Here flame is produced by ignition technique. Pressure regulators are also required here to regulate the cylinder gas pressure. Green colour hose is used for oxygen gas and red colour hose for acetylene. For the protection of eyes from heat, ultraviolet rays and infrared rays, goggles are used while gloves are used to protect hands from heat and the metal splashes. To clean the surfaces of joints before and after welding, a wire brush is used.

Reciprocating engines

Aircraft engines, marine engines, automotive engines and stationary engines are examples of reciprocating engines. Engine can be designed on the basis of the otto cycle where fuel is mixed with air before compression. In otto engine, combustion takes place with no excess air. In diesel engines, fuel is injected near the end of the compression and combustion takes place with much excess air. Spark ignition is employed in otto engines where volatile fuels are used. Low volatile fuels are used for its operation in diesel engines where ignition is by compression. Depending upon the number of piston strokes required for the complete combustion cycle, there exist two varieties in the engine- two stroke and four stroke. In two stroke engines, piston uncovers exhaust ports in the cylinder wall near the end of the expansion stoke and permits the exhaust gases to flow out. The various events that occur in four stroke engine are stroke, exhaust, suction and compression. According to the arrangement of cylinders with each other and the crankshaft, there exist three types of engines. They are three-cylinder in-line engine, five-cylinder in-line engine and V-type engines. V-type engine has two banks of in-line cylinders connected to a single crankshaft.