The History of Steam


If you look up steam on the internet, you get a host of links – and most of these show old steam locomotives!! But steam is a lot more than the old world engines of the Industrial revolution. Steam today is an integral and essential part of modern technology. You cannot even begin to imagine the uses of steam in our modern world.

Steam timeline

Almost two thousand years ago, Hero (actually Heron) of Alexandria invented the first steam turbine, called the aeolipile, a hollow sphere supported on two brackets on the lid of a basin of boiling water. One bracket was hollow and conducted steam.

The steam escaped from two bent pipes on the top, therefore creating a force that made it spin around. The movement of the ball was used to make puppets dance. Hero’s aeolipile illustrated the scientific principle of Sir Isaac Newton’s third law of motion which states that for every action there is an equal and opposite reaction.

1660: Sir Isaac Newton proposes that a jet of steam could be used to power a carriage, an idea now considered to be a precursor to development of the jet engine.

1698: Denis Papin develops the first piston that is moved by the pressure of steam rather than atmospheric pressure.

1698: Thomas Savery patents "the Miner's Friend," a machine that pumps water from coal mines. It becomes the first practical machine powered by steam.

1712: Thomas Newcomen, in collaboration with Thomas Savery, builds the first practical steam engine to use a piston and cylinder, bringing the steam engine out of the lab. It drives a pump in a mine and produces about 5.5 horsepower.

1765: Scottish inventor James Watt patents the new steam engine design with a separate condenser. Watt's design used about 75% less fuel than a similar Newcomen engine. His improvements to the steam engine were fundamental to the changes wrought by the Industrial Revolution.

Watt Steam Engine in its most basic form showing the improvement of the separate condenser not found on the Newcomen steam engine.

As the steam engines developed, so did the boilers which produce steam for them. The steam engines were first used for pumping water, and then for running steamboats and steam locomotives.

Refer to Boilogy for evolution of boilers.


Steam facts – Believe it or not

Did you know that one kg of water at 100°C and at atmospheric pressure occupies 1/1,000ths of one cubic meter? When that kg of water is converted to steam under the same condition, it occupies 1.66 cubic metres. That's almost 1600 times in volume. Can you imagine that sudden release of energy?

Do you know that jet fighters -- jet fighter aircraft on aircraft carriers -- are launched by steam-powered catapults? Did you know that these jets weigh approximately 30 tons when fully fueled and armed? When the catapult is released, the same jet travels from zero kilometers per hour to 350 kilometers per hour in two seconds!! There is no medium which can generate that much thrust this fast.

Some other interesting uses of steam:

Steam is the force that drives turbines for electricity in power plants. The fuel has since changed from coal to Nuclear, but steam is still the motive force that drives the turbines.

Water is dropped on forest fires from aircrafts. It converts to steam and that is what extinguishes the fire.

In explosive areas, steam-operated fire extinguishers are used.


Pic: Jet being catapulted off an aircraft carrier

Steam – here and now

Steam is now used in a number of areas. Soft drink bottles are sterilized using steam and steam is used for cooking chocolate and to keep chocolate soft for moulding.

Food, paper, textile, chemical plants, power, heating, transport..... all these industries use steam. In fact, there are very few industries that don't use steam at all. And in the industries that do use steam, usually one third of the total energy bill is for steam generation!!

 


Hospitals use steam for sterilisation


F&B products like jams, ketchup and fruit-sauces are cooked in steam jackets by direct injection or jacket heating

 


Steam is used to sterilize and boil milk for making milk powder and cheese


Vegetable oil plants use steam for sterilization

 

In fact, there are very few engineering industries which do not use steam.
Some places where steam is not used is the engineering industry, forges...can anybody think of any other??

So, let us first understand steam. What is it? How do we use it? And why is it better than other forms of fluids for transporting heat?

What is steam?

Water exists in three forms. As a solid, when we call it ice; as a liquid, when we call it water, or as a gas when we call it steam. We will focus largely on the liquid and gas phases, and on the change from one phase to the other.

Steam is an invisible gas generated by adding heat energy to water in a boiler. Enough energy must be added to raise the temperature of the water to the boiling pint. Then additional energy - without any further increase in temperature - changes the water to steam. This additional energy which is required to make boiling water change to steam is called the heat of vaporization or latent heat. This heat is not lost but stored in the steam ready to be released to heat air, cook tomatoes, press pants or dry a roll of paper. The quantity is different for every pressure/ temperature combination, as shown in the steam tables.

What is the difference between water and steam?

The condensation of steam is an exothermic process.
• We can attain higher temperatures with steam.
• Steam absorbs a lot of energy. Steam at 100°C is a lot hotter than water at 100°C. This is because steam has a higher energy holding capacity/ unit mass.

Steam is a very efficient and easily controlled heat transfer medium. It is most often used for transporting controlled energy from a central location (the boiler) to any number of locations in the plant where it is used to heat air, water or process applications. It both transports energy and provides energy.

Steam at Work – how is the heat of steam utilized?

Heat flows from a higher temperature level to a lower temperature level in a process known as heat transfer. Starting in the combustion chamber of the boiler, heat flows through the boiler tubes to the water. When the higher pressure in the boiler pushes steam out, it heats the pipes of the distribution system. Heat flows from the steam through the walls of the pipes into the cooler surrounding air. This heat transfer changes some of the steam back into water (condenses). That's why distribution lines are usually insulated to minimize this wasteful and undesirable heat transfer.

When steam reaches the process areas like jacketed vessels and heat exchangers in the system, the story is different . Here the transfer of heat from the steam is desirable. Heat flows to the air in an air heater, to the water in a water heater or to food in a cooking kettle. Nothing should interfere with this heat transfer.

Why do we use steam?

There are many reasons why steam is one of the most widely used ways for conveying (transporting) heat energy.

It is economical because the raw material is water. Water is available freely and is relatively inexpensive. It is not toxic and is environmentally safe.

It is efficient as steam can hold five or six times as much potential energy as an equivalent mass of water. Therefore, in its gaseous form, it is a safe and efficient energy carrier.

Steam is an excellent carrier of potential heat energy. If we pressurize steam, it can carry higher temperatures. (Take a look at the steam tables) At higher temperatures, more heat energy is contained so its potential to do work is greater.

We find it is very easy to pressurize steam. So, in most boilers steam is generated at high pressures to give high steam temperatures.
Steam technology is so advanced, that boiler designs and plant processes use almost all the energy carried by steam. In fact, boilers are now using bagasse (sugarcane husk) and other agri wastes as fuels, thus making the steam boiler a natural choice for environmental reasons. Even "heat losses" in blowdown and condensate are now being utilised in the process.

Steam is easy to distribute Boilers generate steam under pressure and steam flows naturally in response to the pressure drop along the line.

Pressurized steam has a high heat content, so small bore pipework is required to distribute the steam at high pressure. The pressure is then reduced at the point of use, if necessary. Therefore if steam is used installation is easy and cheap. Its easier to maintain. Therefore it is the preffered choice to convey heat over distances.

Steam is easy to control As seen earlier, there is a direct relationship between the pressure and temperature of saturated steam, so it´s easy to see why controlling steam is very easy. The amount of energy input to the process is easy to control, simply by controlling the saturated steam pressure.

Modern controls are precise and react very fast to changes of pressure or temperature. We use Pressure Control Valves (PRVs) and Control Valves to control pressure. Also, we use two-port valves on steam, whereas liquid systems necessitate three-port valves. This reduces cost as well.

Heat transfer properties of steam are very high. Steam evenly surrounds the product to be heated or can be injected directly into the product being heated. It can fill any space at a uniform temperature and will supply heat by condensing at a constant temperature. Therefore the required heat transfer area is relatively small; resulting in a compact, easy to install and physically small plant.

Managing a modern steam plant is easy. Everyone is trying to reduce costs and increase the energy efficiency of steam operations. Now, more than ever, industrial energy users are looking to maximise energy efficiency and minimise production costs and overheads. Your per unit production costs can mean the difference between survival and failure in the marketplace. Some plants even hook-up their steam system to modern networked instrumentation and control systems to allow centralised control. If the user wishes, the components of the steam system can also operate independently (standalone).


Pic: A modern boiler house

Plant personnel starting from the boiler in-charge up, are made aware of costs. Planned maintenance and systematic checks aid quality and drastically cut downtime. Any leaks or blockages are automatically pinpointed and immediately brought to the attention of the utilities engineer. With proper maintenance schedules, plants last for many years (One of the oldest boilers seen by us is a water-tube boiler at a match lites factory. It is a 105 years old, and still working!)

In addition to this, when a steam system requires maintenance, the relevant part of the system is easy to isolate and can drain rapidly, meaning that repairs may be carried out quickly. Even if your steam plant is old, it is far cheaper to bring it up to date than replace it with an alternate method of energy distribution system.

Steam is sterile, and thus widely used in hospitals and in the food, pharmaceutical and health industries. It is also used for sterilisation purposes.

Steam is safe - it cannot cause sparks and presents no fire risk. It is therefore ideal for use in hazardous areas or explosive atmospheres. Steam is also used in fire-extinguishing systems.

 

 

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