Thermit Welding Process | Laser Beam Welding Process


Welding the parts by using liquid Thermit steel around the portion to be welded is called Thermit welding. this is a type of fusion welding process. In this process, neither arc is produced to heat parts nor flames are used. high temperature is being obtained by the usage of the exothermic reaction. Welding principle is the heat of the Thermit reaction used for welding in plastic state and mechanical pressure is applied for the joint.


It depends on the chemical reaction between iron oxide and aluminium. The reaction in thermit welding is that the reaction takes place about 30sec only and the heat liberation temperature is about 2800°C. It is twice the melting temperature of steel.


Thermit is a mixture of aluminium and iron Oxide in the ratio of 1:3. This is placed in a furnace and it is ignited. On heating the chemical reaction takes place. Due to this, liquid and slag are formed which are used for welding.


The Thermit welding process is classified into two types.

1. Pressure welding process

During the pressure welding process, the following steps are adopted.

· The parts to be welded are butted and enclosed in a mould. The mould can be easily removed after the welding of metals.

· The heated iron stag is poured to the mould.

· Then the aluminium oxide is poured on the parts to be welded.

· This will create the heating of parts and then the pressure is applied on the workpiece to join.


2. Non-pressure welding

In this process, the following steps are adopted.

· The parts to be welded are lined up in parallel and a groove is taken in the parts.

· The wax pattern is formed in and around the welding parts.

· Then sand is rammed around he wax pattern and mould is completed with gate, runner and riser around the joint area.

· Then the mould is heated and wax is melted, it will give a space between the joint.

· Finally, the heated iron slag and aluminium are poured into the mould after solidification of liquid metal. Thus, the joint is made.


The word laser sands for light Amplification by the stimulated emission of radiation.


Light energy is converted into heat energy. Here, the light energy is produced from the laser source like ruby rod in the form of monochromatic light.



Electrical discharge from the capacitors makes the flash tube converts the electrical energy into light flashes. Then ruby rod is exposed to the intense light flash. This helps the chromium atoms of the crystal excited and pumped to a high energy level beam. This high energy level is immediately reduced to intermediate and drop to original state with the evolution of red fluorescent light.

This laser light is intense and can be readily focused without loss of intensity. The laser light is focused by the focusing lens to the work piece in the form of coherent monochromatic light.


The light energy is impacted to the work piece. This light energy gets converted into heat energy. This heat energy is sufficient to melt the materials to be welded. The various laser forms that are generally used are Liquid laser, Gas laser, Ruby laser, Semi-conductor laser.

Mechanical Energy Storage Systems | Pumped Storage Hydro Plants | Compressed Air Energy Storage Systems (CAES)

Mechanical Energy Storage Methods in Renewable Energy Plant

There are three methods is to be used for storing the energy and they are:

1. Pumped Storage

2. Compressed Air Storage

3. Flywheel Storage

1. Pumped Storage method in Renewable Plants

01 - Renewable Energy Storage Methods - Pumped Hydro Storage system

Pumped storage is the most successful, economical and widely used energy-storage technology presently available to electrical utilities for load levelling (peak shaving). It could also be used for storing electrical energy produced from solar and wind energy. Electrical power in excess of immediate demand is used to pump water from a supply (lake, river or reservoir) at a lower level to a reservoir at a higher level. During peak demand period when the demand exceeds the normal generating capacity, water is allowed to flow backwards through a hydraulic turbine, which drives an electric generator and produces power to meet additional demand.

In most pumped storage plants, the turbine generator system is reversible and can serve to pump water as well. In the pumping mode, the generator works as motor and draws electrical power from the electrical network. The turbine then operates as a pump driven by the motor. Start up of the turbine-generator or reversal from motor-pump to turbine-generator requires only a few minutes. The overall energy recovery efficiency of pumped storage, that is, the recovered electrical energy as a percentage of electrical energy used to pump water, is about 70 per cent.

01 - Pumped energy storage plants- pumped energy hydropower plants

There are relatively few suitable sites where there is water supply at a lower level and a reservoir can be constructed at a higher level. However, the use of natural or excavated underground caverns as lower reservoirs, now being developed, should greatly increase the number of possible sites.

2. Compressed Air Storage method in Renewable Energy plant

In a compressed-air storage system, excess electrical energy is used to compress air, which is stored in a reservoir to be used later in the combustor of a gas turbine to generate electric power. In a gas turbine, roughly 60% of the power output is consumed in compressing air for combustion of the gas. Compressed air can also be used to produce mechanical output through an air turbine.

01 - Compressed Air Energy Storage Systems - CAES - power generation plants

Electric power in excess of immediate demand is supplied to the motor/ generator unit which drives the compressor. The compressed air at about 70 atm, is stored in a suitable reservoir. The air is heated during compassion and may have to be cooled prior to storage to prevent damage to the reservoir walls. When additional power is needed to meet the demand, the compressed air is released and heated in a combustor using gas or oil fuel. The hot compressed air is then expanded in a gas turbine connected to the motor/generator unit which now acts as generator. The overall recovery efficiency is 65 to 70 per cent. A clutch is used for coupling and decoupling the motor/generator unit with a compressor/turbine.

Compressed-air storage reservoirs would probably be too large and too expensive for above-the-surface construction; hence underground, reservoirs preferably the naturally existing ones, are being considered. Among the possibilities are natural caverns, deep aquifers, depleted gas or oil reservoirs mined-out rocks or salt caverns, and abandoned mines. A commercial installation is in operation near Bremen, Germany.