## What is Relative and Absolute Vibration?

Before we continue the discussion about relative and absolute vibrations, we need to straighten out this matter first. Relative and absolute vibration is not included in one of the vibration classifications (read the following article to find out the classification of vibrations). Relative and absolute vibration is only a method of viewpoint, for measuring vibration.

Relative Vibration

As the name implies, relative is a measuring technique that refers to a certain point that is not silent. Then relative vibration is a measurement of vibration (either displacement, speed, or acceleration) measured relative to the position of the vibration sensor.

We take for example in measuring the engine shaft vibration according to the picture above. The shaft vibration measuring instrument in the form of an eddy current sensor is installed very close to the engine bearing position. So that when a vibration arises on the engine shaft, the sensor will read the vibration whose value is relative to the position of the transducer.

If there is a simultaneous vibration between the shaft and the engine bearing, the vibration sensor will read zero. When this happens, the condition of the installation of the engine foundation against the basic foundation must be considered.

Vice versa, if there is vibration on the engine shaft due to bearing failure, for example, the transducer sensor will read high vibration value relative to the sensor position. In other words, if relative vibration occurs then it is estimated that damage occurs on the engine bearing.

There are two ways to use eddy current sensors, first is using one sensor. If this is used, the sensor is placed just above the center of the bearing. Whereas the second method is to use two sensors that are paired at +45° and -45° from the vertical line of the shaft (according to the image below).

Eddy current sensors require a conversion process so that the reading of the sensor output voltage can be changed to a displacement value. If you want to know the velocity value, you need an integration process from the displacement value, and double integration if you want to know the relative acceleration value of vibration.

Absolute Vibration

Absolute is a measuring technique that refers to a stationary point in free space. Then absolute vibration is a measurement of vibration (either displacement, speed, or acceleration) measured against a stationary point in free space.

Generally absolute vibration measurements only use speed transducers or accelerator. The speed transducer sensor is equipped with a coil as a reference point, while the acceleration transducer uses a mass.

Absolute vibration on a machine shaft cannot be measured directly. A real-time measurement method and calculation is needed.

Measuring the absolute vibration of a machine shaft as shown above, it is necessary to measure the relative displacement of the shaft using the same eddy current sensor as in the measurement of relative vibration. It is also necessary to measure absolute vibration on the bearing using an accelerometer sensor or speed sensor, which is set to have the same axis as the position of the eddy current sensor.

The absolute vibration value of the shaft is obtained by calculating the difference between the relative vibration of the shaft, and the absolute vibration of the bearing. The calculated absolute vibration value of the shaft can be in the form of 0-peak displacement, or also peak-peak displacement as shown in the graph below.

As for calculating vibration speed, an integration process of absolute displacement values ​​is needed. While the value of vibration acceleration is obtained by double integration.

References:

## Classification of Boiler

Boilers are a tool for creating steam. The existence of boilers has been important since its development in the range of the 18th and 19th centuries. Boilers also took an important role in the era of the Industrial Revolution and encouraged various other important discoveries. In subsequent developments many studies have succeeded in bringing out a variety of new boiler designs.

To classify a boiler, we can only do it by looking at it from various points of view. These various perspectives depend on the design of the three constituent components of the boiler, the elements of water, steam, and combustion chamber. For more details, let’s discuss one by one.

Classification of boiler based on the relative position of steam with the combustion chamber

1. Fire-tube boiler

Fire-tube boilers are the simplest type of boiler. This boiler allows it to be applied from low to medium steam requirements. This is possible because the design is not complicated than a water-tube boiler.

As the name implies, fire-tube boilers deliver hot gas from the combustion to the pipes which are covered by water. Hot gas from the combustion of fuel in the combustion chamber (furnace) is passed to these special pipes before being discharged into the atmosphere.

Fire-tube boilers have a very simple design that only requires less space. In fact, many of these boiler designs allow it to be moved to one place to another. However, fire-tube boilers have limited steam production which is only a maximum of 9000 kg/hour with a maximum pressure of 17 bar.

Fire-tube boilers themselves can still be classified into several types:

• Haystack Boiler
• This boiler is the simplest design boiler. Only composed of a giant stove carrying a large pan. This pan-shaped boiler was once inspired by a cooking pot. Whether in the century, how many boilers have started to be developed, but nowadays boilers that are only capable of working at a maximum pressure of 5 psi are rarely encountered. However, the Haystack boiler became the forerunner to the development of a variety of new boiler designs until the discovery of a modern fire-pipe boiler design.

(Credit: Science Museum Group)

• Center-flue Boiler
In the next development, boiler began to be designed more complex. The boiler center-flue is the beginning of the birth of a fire-tube boiler, because the combustion gas is flowed into the water tank through a large pipe before being discharged into the outside air. The flue gas pipe only has one direction away from the furnace.

This boiler is popular after being used as the first locomotive engine. This boiler is quite good at the side of the exhaust gas flow because of the use of the chimney. However, it is not very efficient if it is used to burn too much fuel such as wood or coal.

•

• Return-flue Boiler
Boiler return-flue is a further development of the center-flue type. If the center-flue uses one exhaust gas pipeline, then the exhaust gas pipe in the return-flue boiler is made to have a U-shaped backflow. The purpose of this design is to further improve boiler efficiency. Boilers that developed in the early 19th century were used as locomotive machines to replace boiler center-flue that were not very efficient.

(Credit: Wikipedia: Flued Boiler)

• Huber Boiler
The Huber boiler became the first fire-tube boiler to be more complex than several types of boilers before. This boiler has not used one large pipe as a return channel for exhaust gas, but has used several small pipes or tubes in order to maximize heat transfer from the flue gas to the water in the tank. The shape of the exhaust gas channel after exiting the combustion chamber also has a better design. The design makes gas distribution to be maximized to all pipelines.

• Cornish boiler
Another development of a fire-tube boiler design is the Cornish Boiler. This boiler is a horizontal boiler with a natural draft system, so it requires a high chimney shape to ensure adequate oxygen supply.

This boiler is made from a large water tank with the combustion chamber right in the middle. Flanked by a brick building, such that the flow of combustion gases coming out of the combustion chamber in the middle of the tank will flow back along the outer edge of the tank. Next the brick building will direct the exhaust gas to traverse a passageway under the tank, before finally passing through the chimney and out into the atmosphere.

For more details, let’s look at the picture on the side, top and front of this Cornish boiler.

• Butterley Boiler

Butterley boilers are the development of the Cornish boiler, which initially aimed to accommodate the needs of boilers in the northern United States which are rich in coal with lower calorific value than the southern mainland. This boiler is similar to the Cornish boiler design but by removing the exhaust gas lines under the water tank.

• Lancashire boiler
The Cornish boiler also has another fire-tube boiler design derivative called the Lancashire Boiler. If the Cornish boiler has only one combustion chamber and at the same time one large fire pipe in the middle of a water tank, then the Lancashire boiler has two combustion chambers that are simultaneously two fire-pipes in the middle of a water tank. The boiler developed by William Fairbairn in 1844 tried to adjust the Cornish boiler design when using coal fuel in the Lancashire area on the English plain, which tends to be difficult to burn in small boilers.

• Locomotive Boiler
The Locomotive Boiler becomes the first complex fire-tube boiler. Even this boiler is still often encountered today. Boilers that are named according to their use as a train driving machine are designed to produce superheater steam. The water vapor will be directly used as a piston drive on a steam engine that is designed to blend into the Locomotive boiler system.

This boiler has also been designed to have a lot of medium sized fire pipes that are smaller than fire pipes in the Center-Flue and Return-Flue Boilers, so that it will increase the transfer of heat energy from the combustion gas to the water.

An important component of the Locomotive Boiler is the presence of a superheater steam valve that is inside a section called the dome. This one-way valve will only open by superheater steam when it reaches a certain pressure. Furthermore, the superheater steam will enter into a steam piston driving medium.

• Scotch Marine Boiler
The Scotch Marine boiler is the most popular fire-tube boiler design used even today. This boiler was originally made to meet the needs of steam in marine engines. Even the legendary Titanic ship uses a total of 29 Scotch Marine boilers.

Scotch Marine boilers have high efficiency. This is obtained because the design of the fire pipe in the water tank is very much. Hot gas from the combustion process comes out of the combustion chamber in the middle of the water tank, towards the fire pipes which are next to the combustion chamber with the opposite direction of flow. Then the exhaust gas flows back to the fire pipes on the upper side with the direction of the direction of the direction of combustion in the combustion chamber. In short, the flow of combustion gases inside the fire pipes seemed to form the letter S.

• Vertical Fire-tube Boiler
Fire-tube boilers that are vertically areanged, known as vertical fire-tube boilers. This type of boiler has design advantages and the manufacturing process is not too complicated. The combustion chamber is under a water tank, with pipes for exhaust gas lines arranged vertically in the water tank.

• Horizontal Tubular Return Boiler

The Horizontal Return Tubular Boiler is similar to other fire-tube boilers that we have discussed. Has a flat arrangement of fire pipes. What is slightly different is the design of the placement of a combustion chamber that is not in a water tank, but is under the tank. The fire pipes in the tank will only be passed by hot exhaust gas from the combustion of fuel in the combustion chamber.

This fire-tube boiler is unpopular and has not been used by many since its appearance in the Ironclad warship era in the mid-19th century. One thing that made it unpopular was the design of the fire pipe that was connected directly to the combustion chamber so that over-heat was often occured on the pipe.

• Immersion Fired Boiler
This last fire-tube boiler has one characteristic that is not haved by other fire-tube boilers. The boiler developed by the Sellers Manufacturing manufacturer is designed so that each fire pipe in the water tank functions as a combustion chamber as well as a hot exhaust gas from the combustion process. So that this boiler has a lot of burners (burners) with an amount equal to the number of existing fire pipes. With an automatic boiler design that is only suitable for using liquid or gas fuels, it is claimed to have a relatively low temperature voltage. This boiler is still marketed to date by the manufacturer Sellers Manufacturing as the owner of the patent design.

2. Water-Tube Boiler
Water-tube boilers have a reverse design with fire-tube boilers. This boiler circulates water through the pipelines with a heat source coming from the furnace. A water tank commonly called a steam drum is one of the characteristics of a water-tube boiler. Steam drum serves as a water tank that is maintained at a certain level to ensure there is always circulating water to the water pipes. Besides that, the steam drum is also to separate steam from water-steam mixture inside the drum. Wet steam coming out of the steam drum will be heated further to produce superheated steam.

The popular water-tube boiler design is using the water pipes as the combustion chamber wall (wall tube). The water from the steam drum drops through a downcomer pipe to a header pipe connected to all the lower ends of the wall-tube pipe. The other wall-tube end that is at the top of the combustion chamber is directly connected to the steam drum. In this part of the wall tube, the phase changes from water to water vapor. This water-tube system produces a closed-loop circulation between the steam drum-downcomer-wall tube-and returns to the steam drum. From the steam drum, only saturated steam will come out.

Even water-tube boilers have slightly more complex designs than fire-tube boilers, but water-tube boilers tend to be able to produce higher quality steam (more superheated). Therefore, water-tube boilers are more suitable to be applied in large industries that are more demanding of high quality steam such as steam power plants.

Based on different designs, water-pipe boilers can be classified as follows:

• John Blakey Boiler (1766)

This boiler designed by John Blakey became the forerunner of the water tube boiler. This boiler is composed of a vertical funace with several connected pipes inside, which are made tilted to form a certain angle. The two ends of the pipe are connected to a smaller pipe.

This boiler was patented by John Blakey in 1766, but not too popular at the time.

• James Rumsey Boiler (1788)

The first functional water-tube boiler was created by a mechanical engineer from the United States, James Rumsey. He is known to patent several water-tube boiler designs, making James Rumsey touted as the inventor of the water-tube boiler. One of the most famous designs is a steam-powered boat.

The boat, which was then made to cross the Potomac River, was equipped with a water-tube boiler. The water tube in the boiler are twisted horizontally, inside a large enough furnace. The steam produced is used to drive a steam piston.

The steam piston, using a single shaft, is connected to another piston underneath it. The second piston serves as a water pump, with water from the river as the media where the boat operates.

The piston shaft, also connected to a large pendulum. The pendulum is connected to an injector pump and an air pump on the condenser.

Steam that enters the steam piston will lift the shaft, so that the water piston also lifted, and sucks the water of the river into the piston cylinder. When the piston reaches the top dead centre, a knob on the shaft will touch a stick mechanism, so the control valve will change its position.

When the control valve changes its position, the steam inside the cylinder will be pushed out and enter the condenser. The water piston will also be pushed down, so the water comes out of the cylinder, passing through the nozzle on the back of the ship, thus creating a force for the ship.

When the shaft position down, the injector pump pushes the river water into the boiler, while the air pump pushes the water inside the condenser to exit.

• Julius Griffith Boiler (1821)

This boiler has a fairly simple design, but has a significant impact on the development of the next water-tube boiler design.

This boiler was designed by Julius Griffith in 1821, which is composed of several horizontal pipes in several levels and placed inside the heat source. The horizontal pipes are connected to the twin vertical pipes on either side. At the very end, there is a last horizontal pipe as a gathering place for steam produced, which then comes out of the boiler. This top horizontal pipeline design will next to be the forerunner of the design of the steam drum in modern water-tube boilers.

• Joseph Eve Boiler (1825)

The first sectional water-tube boiler with well-defined circulation was designed by Joseph Eve in 1825. This boiler composed of several vertical pipes with curve variations in the center of the pipe, two larger horizontal pipes as a water reservoir and a steam reservoir, as well as two large external vertical pipes as a circulating pipe between the steam reservoir on the upper side and the water reservoir on the lower side. These two vertical pipes have a function to ensure good natural circulation of water and steam inside the boiler system between the water pipes, reservoirs and external pipes.

• Goldsworthy Gurney Boiler (1826)

The Gurney water-tube boiler design was patented in 1825, first made in 1826, and tested in 1827 by Simon Goodrich.

This boiler is composed of several U shaped pipes laid with one side in the top position. Each end of the U pipe is interconnected with a horizontal pipe with a larger diameter, both top and bottom. Then these two horizontal pipes are connected with vertical pipes to ensure the occurrence of water-steam circulation. There is also a long and large diameter cylindrical tube, vertically standing connected to the upper and lower horizontal pipes. This cylindrical pipe serve as a water reservoir and water vapor.

• Stephen Wilcox Boiler (1856)

This Wilcox design boiler became the first water-tube boiler to use inclined pipe design. These tilted pipes connect the water spaces on the front and back, with the steam room at the top.

This boiler design later developed into Babcock & Wilcox boiler design, and dominated the water-tube boiler market in the late 19th to early 20th centuries.

• Spiral Water-Tube Boiler

If the fire-tube boiler develops along with the train development, the water-tube boiler design was developed in tandem with car technology.

The birth of car technology in 1770 created by Nicolas-Joseph Cugnot, encouraged the development of cars in the 1800s that still use steam engines. Most of the car’s engines use spiral water tube boilers with different designs. Since then, spiral water tube boilers have developed into various uses.

Spiral water tube boiler designs include Climax Boilers, Lune Valley Boilers, Monotube Boilers, The Baker Boiler, Ofeldt Boilers, and many others.

• D-Type Boiler
The first water-tube boiler type that we will discuss is called the D-type because the shape of the boiler is similar to the letter D. This boiler is equipped with two tanks namely the steam drum on the upper side and the mud drum (water tank) on the lower side. These two tanks are connected to many water pipes which are partially arranged vertically, and some are arranged in the shape of the letter D. In the middle of the D-shaped pipes has a functions as a combustion chamber.

• Type-A Boiler
Still because the design is similar to the form of one of the Latin letters, the A-type boiler is named so indeed because its design is similar to the letter A. This boiler has one steam drum but with two water tanks below. The purpose of using these two water tanks is to further extend the life of the boiler because the water pipe will be longer than the D-type design. This boiler has a slimmer design than a D-type boiler, however an A-type boiler cannot produce higher energy-containing steam than the D-type for the same dimensions.

(Credit: Wikipedia: Package Boiler)

• O-Type Boiler
The O-type boiler is the last type of water-tube boiler whose design is similar to one of the letters. This O-shaped boiler has a symmetrical shape with the position of the above steam drum and water tank below. Both are connected with symmetrical water pipes so that in the middle become boiler combustion chambers. This O-type boiler is claimed to be able to produce water vapor faster than the D-type. The low maintenance requirements are also another advantage of this boiler.

• Babcock & Wilcox Boiler
As the name implies, the Babcock & Wilcox boiler was developed by a firm with the same name as the boiler. This boiler design was developed and patented in the mid-nineteenth century. This boiler has only one tank, the steam drum positioned at the top of the boiler. The steam drum is partly filled with water and the other part contains wet water vapor. The typical design of this boiler is water pipes that are designed to be tilted to form a 15 ° angle. This slope serves to ensure the occurrence of natural circulation of water-water vapor in the boiler. On top of the water pipes there is also a further hot steam pipe which functions to further heat water vapor that has been sufficiently hot and escaped from the steam drum to be further heated to achieve superheated quality. For the flow of combustion gases in the boiler is made tortuous so as to maximize absorption of heat from the flue gas to the water fluid.

(Credit: Mech4Study)

• Stirling Boiler
The Stirling boiler is one of the predecessors of the water-tube boiler. These boilers were popularly used in the early 1900s, and are very difficult to find at this time. This boiler has the characteristics of using two kinds of water tanks, steam drum at the top with an amount that is always more than the second tank, the water tank at the bottom of the boiler. Characteristics of the design make the Stirling Boiler can be classified based on the number of water tanks, there are three tanks with two steam drums and one water tank, four tanks with three steam drums and one water tank, and five tanks in the form of three steam drums at the top and two water tanks at the bottom of the boiler. The more number of tanks, the higher ability to produce steam. However, this boiler is old-fashioned and is no longer used because it has relatively lower efficiency values ​​than modern boilers.

Boiler Stirling Tiga Tanki
(Credit: Wikipedia: Stirling Boiler)

Boiler Stirling Empat Tanki

Boiler Stirling Lima Tanki

• Yarrow Boiler
The Yarrow boiler is an important type of high pressure water-tube boiler. They were developed by Yarrow & Co. (London), and is widely used on ships, especially warships.
Yarrow boiler design has the characteristics of a boiler with three water tanks: two tubes of straight water are arranged in a row of triangles with a single furnace between the two. A single steam drum is installed at the top between them, with a smaller water drum at the base of each bank. Circulation, both up and down, occurs in this same bank tube. Yarrow’s specialty is the use of straight tubes and also the circulation in both directions that occur entirely in the tube bank, and does not use external energy or we are familiar with natural circulation.

Because of the characteristics of the three drums, Yarrow boilers have greater water capacity. Therefore, this type is commonly used in boiler applications for old warships. Its compact size makes it attractive for use in power generation units that can be transported during World War II. In order to be transported in its time, boilers and auxiliary equipment (fuel oil heaters, pump units, fans etc.), turbines and condensers are installed in their own carriages to be carried through the railroad tracks.

•

• Thornycroft boiler
This boiler was designed by the ship manufacturer John I. Thornycroft & Company. The special design of this boiler is to use just one steam drum on the upper side, with three downcomers so that it is arranged similar to the M formation boiler. However, due to the design of several pipes that have sharp bending, it risks leaking quickly not only because of the possibility of thermal stress, but also because of its own difficulties when needing to be cleaned. Because of these weaknesses, this boiler is not as popular as Yarrow Boiler.

• Tube-Walled Boilers

In the early days of its development, water-tube boilers were not as fast developed as fire-pipe boilers. This is because water-tube boilers require more complex design calculations and manufacturing techniques. But the main advantages of fire-tube boilers that have almost no maximum capacity limit, making the development in the next period, only need to wait for the birth of modern welding and materials technologies.

After electricity was discovered, then the construction of steam power plants began intensively in the early 20th century, the Stirling Boiler type still dominated. To meet this need, numbers of Stirling Boilers are built at once in parallel so they can produce more steam.

Why isn’t the Stirling Boiler made larger, and bigger, so it can produce more steam?

The main reason was the use of fire bricks as the boiler wall. Fire brick walls would certainly be troublesome if you have to be arranged too high, as well as widened, following the boiler design if you want to be enlarged. Beside that, this large-sized wall must be able to isolate the heat energy of the combustion chamber, to ensure maximum heat absorption in the boiler.

Gradually, new innovations were born to replace fire brick walls. The advancement of pipeline material and welding technology are also driving the advancement of boiler wall technology.

Tube and tile boiler walls, became the initial innovation of the boiler wall design revolution. Found in the 1920s, this boiler wall combines a 6 inch diameter pipe with 2.5 inch thick tiles or 4.5 inch thick fire brick. Tube and tiles are arranged alternately, and the outer side of the wall is insulated to maintain boiler efficiency.

The existence of the tube in the boiler wall, has a function to cool the wall so that the thickness of the fire bricks can be reduced from the previous thickness which can reach 22 inches. Since that time, the boiler design continue to grow in both size and capacity.

In the late 1920s and early 1930s, the appearance of the flat studded tube and the loose tube wall constructed boilers. This design was able to increase the absorption of boiler heat. So in those days, boilers that used those two designs were able to receive the highest heat generated from coal combustion.

Large changes in the water-tube boiler wall design occurred in the late of 1950s and early 1960s. Since then, and are still used today, water-tube boiler walls made from long steel tube which arranged in a row and welded each other with certain widths of steel membrane bar between every tube.

This design is much easier to fabricate because making every wall panels can be done at the workshop. Then the wall panels can be much easier to assemble when build the boiler. The process of building boilers has become much more practical, time-saving, and certainly effective in cost.

Not only that, the main advantage of this boiler wall-tube design makes the water-tube boilers could be built even larger and bigger. Known this day, huge water-tube boilers are capable to produce superheated steam of more than 4,000 tons per hour. That’s the same as more than a thousand kilograms of steam produced by this boiler, every second.

Again, in every second!

• Once-Through Boiler

Once-through boiler is a concept of water tube boiler that does not occur a non-vaporizing water circulation. That is, each water molecule only passes through the boiler pipes once. This concept greatly increases boiler efficiency because it is no longer requires a steam drum as a water and steam separator, so there is no need for additional boiler circulation pumps.

This boiler concept is actually not new. The boiler design was once patented in 1824. But the first commercial application of this boiler could only be done in 1923, by a Czechoslovakia inventor, Mark Benson. At that time, Benson only could build 1.3 kg per second boiler capacity. The boilers built to fulfill orders from English Electric Co.. The boiler was originally designed to operate at critical steam pressures. However, due to the frequently damage of the pipeline, boiler operating pressure was then forced to be lowered.

The once-through boiler continues to grow until now. Supercritical and ultra-supercritical boilers have used this concept. So even though this boiler is used in power plants with a capacity of 1000 MW, the efficiency can reach 46%.

Classification of boilers based on water circulation method

In water-tube boilers, the circulation of water in boiler pipes is important to pay attention. In addition to good boiler water circulation, it will increase boiler efficiency, water circulation is also important to maintain boiler durability. This is because the water in the boiler also as a cooling medium, delaying the water circulation, resulting high thermal stress on the pipe. Of course this is very avoided.

Against this background, there are known two types of boilers based on the way of water circulation. Here are both:

1. Natural Circulation Boiler
Boilers with natural water circulation do not use external energy to circulate water in boiler pipes. The water in this boiler is naturally circulated due to the pressure difference between low temperature water and high temperature. Naturally high temperature water will have a relatively lower density. Therefore, the water is getting hotter and the phase changes to steam, the more it will be pushed upwards. Because of this process, the water in the boiler pipes will be circulated.

Boilers with natural circulation include Babcock & Wilcox boilers, Lancashire, Cochran boilers, locomotive boilers, and so on.

Perbedaan Boiler Sirkulasi Natural dan Paksa
(Credit: Wikipedia: Forced Circulation Boiler)

2. Forced Circulation Boiler
Boilers with forced circulation, use additional pumps to help the circulation of water in the boiler. This type of boiler does not need to wait for water phase differentiation to be able to circulate water. With the help of external energy for the process of water circulation, the process of generating steam will not be limited by the size of the boiler. When compared, forced circulation boilers can produce twenty times more steam than natural circulation boilers that have the same volume size.

Examples of forced circulation boilers include Benson boilers, La Mont boilers, Velox boilers, and so on.

Classification of boilers based on their working pressure

In accordance with technology advancements, the quality of boiler steam also continues to improve. The boiler designers believe that the higher steam pressure can be achieved, the boiler efficiency will be higher to. So the following are the classification of boilers based on the steam pressure produced:

1. Low-pressure boiler: This boiler produces 15-20 bar of steam.
2. Medium-pressure boiler: This boiler produces steam from 20 to 80 bars.
3. High-pressure boiler: This boiler produces steam pressure above 80 bar.
4. Sub-critical boiler: The critical point of a boiler is a condition where boiler steam reaches a temperature of 560 ° C at a pressure of 221 bar. If a boiler works below these conditions, the boiler is called a subcritical boiler. Typically subcritical boilers are designed to work at 160 bar and steam temperature of 540 ° C.
5. Supercritical boiler: If a boiler works above its critical point, the boiler is called a supercritical boiler. Supercritical boilers have better fuel efficiency than subcritical boilers. Supercritical boilers have a design efficiency value of around 45%. While subcritical boilers can only reach 38%.

This is due to the impossibility of forming bubbles in the supercritical boiler cycle. As a result of the work pressure and temperature above the critical point, the water will not experiencing the nucleate boiling phase (the transition phase from liquid to vapor) and immediately changes the phase immediately to steam. One characteristic of supercritical boilers is that they do not use steam drum components which to separate water from wet steam at sub-critical boiler.

6. Ultra Supercritical boiler:
The working point of the boiler which is high above the critical point, the boiler will be more efficient. To achieve this, more sophisticated and expensive boiler pipe material technology is needed. The last few decades have made possible the manufacture of the material in question, so that at present the boiler design has been able to reach the point of work very far above its critical point. The boiler that we know as the Ultra Supercritical (abbreviated as USC) has an operational point of around 260 bar and a temperature of 700 ° C. This modern boiler has a theoretical efficiency value of up to 50%.

Classification of boilers based on their energy sources

In accordance with technological advances as well, now there are so many sources of energy that can be used as a source of boiler heat. Boilers developed at the beginning of its history only used fossil fuels, now there are several boiler technologies that can use renewable energy.

The following are among them:

1. Coal-Fired Boiler
Coal is the most commonly used fuel in large capacity boilers, including in Indonesia. The price is cheap, abundant (especially in coal-producing countries including Indonesia), high heat values, a number of reasons for the use of coal as boiler fuel to date.

The use of coal as boiler fuel requires special treatment not carried out on other types of boilers. Characteristic of solid coal, the average size of your fist, requires a grinding process before it is burned in the boiler combustion chamber. Of course this is the main objective to facilitate the burning of the coal.

Not only that, the processing of coal boiler exhaust gas is also different from other boilers. This boiler exhaust gas contains ash, carbon dioxide, sulfur, to NOx. Some binding processes for these wastes also need to be considered. Like the use of Electrostatic Precipitator to bind ash, then use Flue-Gas Desulphurization to bind sulfur, to the use of staggered combustion technology to minimize the formation of NOx.

The complexity of coal boiler design, makes the economics of these boilers not as good as oil-fired boilers if used on a small scale. Therefore, coal boilers are more widely used for subcritical to ultra-supercritical production scales.

2. Oil-Fired Boiler
Oil-fired boilers are quite popular for small scale use only. This is due to a much simpler design than a coal-fired boiler. These boilers are generally fire-tube boiler, which only require the main component of the burner and the pipe network for the flow of fire (hot gas) which is made inside the water furnace.

These boilers generally use diesel fuel, or commonly known as High Speed ​​Diesel (HSD). The simple design makes this boiler very suitable for the production of low pressure steam with low steam production capacity.

3. Nuclear Boiler
As the name implies, nuclear boilers use nuclear technology as a source of heat energy. This boiler is very popular for use in nuclear power plants. In nuclear power boilers, the heat energy from the fission reaction inside a nuclear reactor is absorbed by the coolant material which can be gas, liquid, or even liquid metal, depending on the type of reactor. This cooling material then flows into the boiler and is used to heat water so that it changes phase to further steam. The steam that is produced is channeled into turbines to generate electricity in nuclear power plants.

The popular raw material for nuclear reactors is Uranium. Uranium is a type of heavy metal that is not very useful on Earth and is easily found in the oceans and rocks. There are two types of uranium with different isotopes that we know, namely uranium-238 (U-238) and uranium-235 (U-235). These two types of uranium have a major difference in their reactive age. U-238 has a longer reactive life than U-235, which also shows that U-235 is less radioactive than U-238.

One major risk of using a nuclear reactor is of course the radioactive hazard. Therefore, nuclear reactors are always made in a dome that serves to prevent radioactive reactor leakage. Generally the outside of a nuclear reactor is made in a dome shape with strong concrete material which not only serves to prevent radioactive leakage, but also to resist natural disturbances from the outside.

4. Solar Concentrated Powered Boiler
The boiler we will discuss next is very new technology. This boiler uses a very renewable source of energy from sunlight. Although sunlight is only available during the day, this boiler can operate 24 hours a day. Thanks to the special fluid called molten salt, that able to stored heat from the sunlight.

Solar concentrated boilers use main component of large number of mirrors, arranged around a heat-receiver tower. The mirrors are positioned in such a way that the reflection of the sunlight captured by each mirror is reflected centrally to the heat-receiver tower. Each mirror component is equipped with an automatic mechanism, so that it can move following the sun, so that the direction of the sunlight reflection always leads to the heat-receiver tower.

A mechanism is used to circulate the molten salt into a heat-receiver tower. It is estimated that the heat caught in this tower can reach 1500 times hotter than what we normally feel. The heat is absorbed by the molten salt and stored in a special thermal storage tank.

Then, through a heat exchanger, the water absorbs the heat from the molten salt so that the water boils and reaches the superheat temperature. In concentrated solar power plants, this steam is then used to rotate steam turbines and produce electricity.

Many power plants that have used this technology are built in Spain, the United States, South Africa, India, and a little in China.

5. Waste-to-Energy Boiler

Waste power boilers or also known as waste-to-energy boiler are the most environmentally friendly solution to two problems at once: garbage and fossil fuel crisis. Waste production that continues to increase every time becomes one of the energy sources that can be used as boiler fuel.

Waste-to-energy boilers are not much different from other biomass boilers. First, the waste is brought to the facility. Then, the waste is sorted to remove recyclable and hazardous materials. The waste is then stored until it is time for burning. A few plants use gasification process, but most combust the waste directly because it is more efficient. The waste can be added to the boiler continuously or in batches, depending on the design of the plant.

It is known that waste-to-energy boilers have a friendlier emission level than coal-fired boilers. This is due to the absence of sulfur pollutants as contained in coal.

Biggest Waste-to-Energy Power Plant will be built in Shenzhen, Cina

Waste-to-energy power plants have been used for more than two decades in Sweden. And now many have been built in China, the United States, and many other countries.

## Classification of Vibration

Classification of Vibration – In general, vibrations can be classified into several ways:

1. Free and Forced Vibration
Free Vibration. If a system is initialised with interference, so it vibrates by itself, then the vibration is called free vibration. No external force works on the system. The motion of back and forth of a pendulum is an example of free vibration.

Forced Vibration. If a system is subjected to an external force (more precisely the repetitive force), then the vibrations that arise on the system is known as forced vibrations. The vibrations that arise on a working diesel engine is one example of forced vibration.

If the frequency of an external force is exactly same as the vibration frequency of the system, a condition known as resonance occurs. Resonance is very dangerous. Damage from the structures of buildings, bridges, turbines, and airplane wings is often associated with the resonance of the vibrations.

2. Undamped and Dumped Vibration
If there is no energy lost or dissipated due to friction or other resistance during vibration, then the vibration is known as Undamped Vibration. Whereas, if a vibration experiences a gradual reduction of energy, it is called Damped Vibration. In various systems, the value of the damping is so small that it is often disregarded for most engineering purposes. But also vice versa, there are other systems that put damping system into important components, shock absorber in vehicles for example. Consideration of damping becomes extremely important in analyzing vibratory systems near resonance.
3. Linear and Nonlinear Vibration
If all the basic components of a vibration system the spring, mass, and damper behave linearly, the resulting vibration is known as Linear Vibration. However, if one or more of these basic components behaves nonlinearly, then the vibration is called Nonlinear Vibration. Differential equations are made to describe the behavior of linear and nonlinear vibration systems. If the vibrations are linear, the superposition principle applies, and the mathematical analysis technique is well developed. For nonlinear vibrations, the superposition principle becomes invalid, and the analytics technique becomes more difficult. Since all vibration systems tend to behave nonlinearly as oscillation amplitude increases, knowledge of nonlinear vibrations is more developed in handling practical vibration systems.
4. Deterministic and Random Vibration
If the value or magnitude of the excitation (force or movement) acting on the vibration system is known at any given time, the excitation is called deterministic, and the resulting vibration is known as Deterministic Vibration.

In some cases, excitation is nondeterministic or random; excitation values ​​at certain times can not be predicted. In this case, extensive excitation data may indicate some statistical regularity. Under these conditions it is possible to estimate averages such as the mean and mean square values of excitation. Examples of random excitation are wind speed, roughness of the road, and ground movement during an earthquake. If the excitation is random, the resulting vibration is called Random Vibration. In this case the vibration response of the system is also random; and that condition can only be explained through statistical calculations.

## How quantum computing works, explained in a simple way!

Quantum computing is bringing new standard that will change almost everything we know and believe about computer. Thanks to the superposition, a particular physical behavior, this new computation technology can solve problems that not even the conventional computer memory could solve today.

Now compare and remember that current computer works in bit. Your computer only knows how to “read” information in two states: zero or one (on or off). For this, we use voltages: we apply 3V on a wire = 1; we apply 0.5V in the same wire = 0. Everything done by computer is transcribed into this system by transistors, a small boxes that stored energy and release it when necessary.

Understanding transistors is important for comparison: when transistor has electricity stored we interpret 1, and 0 in otherwise. The use of transistors for the construction of logic gates depends upon their utility as fast switches. When the base-emitter diode is turned on enough to be driven into saturation, the collector voltage with respect to the emitter may be near zero and can be used to construct gates for the TTL logic family. For the AND logic, the transistors are in series and both transistors must be in the conducting state to drive the output high. For the OR logic, the transistors are in parallel and the output is driven high if either of the transistors is conducting.

Simplifying it a lot for the case in hand, these are the physical elements that carry out the calculations that we send through programs and apps. As you can imagine, this “mechanical” system show the speed of the computer to process information, which is linear to the number of bits it has. It surely depends on the hardware and by default has a technical limit.

The technical limit might seems like an exaggeration, making bigger computers and create multibits computer. But it’s not like that. The limit becomes evident when we think that not all the classic computers in the world are smart enough to solve optimization problems when the amount of data is too large. And at this moment in history, as a civilization, we generate immense amounts of data: climatic, population, geonomic, behavioral patterns, ect. We can not create useful versions or patterns of them because of the impossibility of a classic computer assimilating them all.

The difference that makes quantum technology special, and why it has such an immensely great potential, is that its ‘bit’ also works with the superposition of both states: on and off. This happens because the process does not depend on mechanical system at transistor, thanks to the rules of quantum physics. By applying ‘quantum logic’ to the computer world, problems are solved at full speed, parallel with multitude results for each variable.

Qubits

The bits of quantum computing are called ‘qubits’. Like a bit, a qubit represents a unit of quantum information, which is governed by the rules of quantum physics. Therefore the qubit can be 0 or 1, or something between them. In fact, it can be 1 and 0 in parallel. For its hardware part, the “container” effect of transistors and logic gates are replaced by more complicated processes: “isolate” the qubit as it occurs within the transistor.

The ways of making a quantum computer

Quantum computers can varying themselves depending on the way they manage to isolate and drive qubits, but we are always interested in creating the same thing as in the transistor: getting them to interact only when we want, and there are several systems to achieve it.

When its applied to the interior of a dilution refrigerator, the gold-colored coaxial cables send input and output signals from inside the refrigerator. There are superconducting circuits, for example. These are based on small circuits cooled to very low temperatures (-273 °C) so that the properties are ‘quantized’. Imagine, for example, it can circulate through the circuit at very low temperatures 1V or 2V, but not 1.5V. This allows the machine to know which is the 0 and the 1. This is the most successful technology for now.

The other one is using trapped ions for the computer. In this process, the quantum computer uses ions (atoms that have been removed or added one or more electrons) as qubits in a certain state and keeps them trapped in laser, then combine them according to the calculation to be performed. The 0 and 1 signal are identified with different distributions of the remaining electrons. The operations are done through lasers that modify the positions.

Finally, another well-known quantum computer system is the nuclear spins. The spins are a physical property of the elementary particles. It is enough to understand that the molecules are in a certain state and the operations are implemented changing their state to a new one with magnetic resonance.

How quantum computer works

So far, it might seem that the quantum computer does magic on its own. The fact is BIG NO. It is not magic, they are physical laws, just the same way like magnets of opposite charge stick together or gravity causes things to fall. With quantum computer, we noticed new norms of phenomena that we can take advantage of.

When atoms or molecules are not part of larger chemical structures, they have different “rules” from those we see in our everyday world. These rules are dictated as quantum physics and specifically known as quantum superposition.

Quantum computing is based on a phenomenon called wave-particle duality

We talk about a behavior that is observed in subatomic particles, like the electrons of the electric charge. This phenomenon is the behavior of a flow of electrons, which are particles. A wave consists of the propagation of a disturbance of some property, involving an energy transport without transporting the matter. For example, an easy wave to imagine is acoustics. A subatomic particle is smaller than the atom, as an electron is, but it has a specific mass and position.

Therefore, strange as it may seem, the particles can behave like waves and particle also. And, according to the quantum law, when this phenomenon occurs, the particle enters a superposition of states, in which they behave as if they were in both simultaneously or at an intermediate point between the two. While classical objects are in one state or another (but always a certain one), the state of a quantum system can be a superposition of several possible states. In this case, the analogy of the coin is usually used: if the two states of a coin were to be in face or in cross, then a quantum state would be an overlap of the two.

How the same phenomenon can have two different perceptions

Sometimes in the shade you see a circle, and sometimes a rectangle. What we can say with the shadows is that, depending on how you look at it, it has the properties of a circle or a rectangle. The case of wave-particle duality is very similar. Sometimes, light behaves like waves, for example when we make interference experiments, but other times it behaves like particles when we use lasers that send a photon per pulse.

The utility of the overlay

Quantum computing tries to use the superposition of states to be able to execute more than one computation at a time. As the electrons of the qubit can be 0 and 1 at the same time, we have “yes and no” of each assumption in parallel, which allows us to have much faster computers. Of course, it does not guarantee more speed for all the problems but in those that can take advantage of this parallelism.

Imagine a given program that takes two numbers and one additional bit and does the following: if the additional bit is in state 0 then the program adds the two numbers and gives you the result, and if the bit is in state 1 the program subtracts the numbers and gives you the result. If you wanted to get the addition and subtraction of two numbers, you would have to run the program twice: one with the additional bit at 0 and one with the bit at 1. On a quantum computer, since the qubit can be in an overlay of 0 and 1, the program runs the two instructions ‘in parallel’, and with running it once you can get a result that is the superposition of the addition and subtraction of the numbers .

However, using it is not so easy. Atoms and particles have their rules, and if we do not stick to them, we can not control them. For example, you can not even look while the computer computes. As strange as it may seem, another of the laws that govern the quantum world is that superpositions can not be observed or destroyed.

Quantum properties are very fragile and even degrade over time, so many resources have to be invested in keeping quantum computers isolated from the environment. Not only have a temperature of -273 ° C, but also to keep them in vacuum conditions where an external atom can not hit them, for example.

The current idea is not that each person on the planet has its own ‘quantum laptop’ just because the required conditions are very restrictive, but there is a ‘limited’ amount of quantum computers in places where they have the right conditions of temperature, vacuum, etc. Not everyone can have a dilution refrigerator at home to keep the qubits cool, but you have to think bigger. Quantum computers are being designed with the idea of ​​solving problems that are currently too complex for classical computers.

One of the first and most promising areas to applicating the quantum computer will be chemistry. In a simple molecule of caffeine, the number of quantum states in molecules grows surprisingly fast, so fast that not all the conventional computing memory that scientists could build and contain it. Other future applications could be, for example: medicines and materials (complex molecular and chemical interactions could lead to the discovery of new medicines), logistics and supply chain (calculation of optimal trajectories along global systems), financial services (modeling of financial data and investments on a global scale), artificial intelligence (automatic learning when the data flow is very large), security (breaking cryptography, the Shor algorithm, for example, could do it).

Finally, discovering the real utility of quantum computing is going to require many hands to experience and the potential is still to be quantified. In other words, the exponential growth of this technology is still unimaginable and who knows how far it will take us? What’s certain is that the limit of computing is no longer the limit as it is being revolutionized once again, and we are lucky to contemplate it.

## Calculation of the Excess Air of Combustion Process

The amount of air needed to completely burn a certain amount of fuel can be calculated theoretically using the basic principles of stoichiometry (see following article). In other words, if every fuel molecule precisely contact with oxygen in the air and reacted, then the entire fuel must be burned, and there will not be a certain amount of excess air at the exhaust. But in reality, it is impossible. Fuel molecules can not 100% met directly with the oxygen. It takes some excess air to make sure all the fuel molecules can burn completely. This is what we know as excess air (read the following article).

What is the right amount of excess air for a burning process?

Determining the amount of excess air in the boiler burning process depends on several main factors such as fuel type, boiler design, burner design, and boiler load. Generally, coal fired boilers use excess air as much as 15% to 30%. For boilers with gas or petroleum as its fuel, requires less excess amount of water. Gas-fired boilers require excess air of 5% to 10%, while petroleum-fired boilers require excess air of 3% to 15%. This condition indicates that the gas and liquid phase fuels more easily mix and react with oxygen, compared to solid phase fuel.

How much the boiler load has a great impact on excess air. The design of the diagonal cross-section of the boiler’s combustion chamber should be able to bear the flow of gas flow when the boiler is in full load. The opposite condition occurs when the boiler load is lower, where the flow of gas decreases so that mixing the fuel with air becomes more difficult. Therefore, when the boiler is below full load, the amount of excess air required increases to ensure a complete combustion. In coal-fired boilers for example, at 50% load, takes two times excess air than when the load is 100%.

Although the excess air is important to ensure complete combustion, excess air has a negative impact on boiler efficiency. The higher amount of excess air will make the heat energy wasted following the exhaust gas. Therefore, in terms of efficiency, the amount of excess air should be kept as low as possible.

To keep the excess air stay at the optimum value, modern boilers equipped with sensors of amount of oxygen and carbon monoxide on the boiler exhaust side. Both of these parameters can be use to keep the excess air amount stay at the optimum level throughout the boiler operating time.

Excess Air Calculations

Let’s use the example of coal data at the previous article as follows:

Which the stoichiometric combustion reaction equation is as follows:

CH0,74O0,061N0,018S0,026 + 1,211(O2 + 3,762N2) → CO2 + 0,37H2O + 0,026SO2 + 4,565N2

Furthermore, if determined boiler using excess air of 15%, then the chemical reaction of combustion becomes as follows:

CH0,74O0,061N0,018S0,026 + 1,393(O2 + 3,762N2) → CO2 + 0,37H2O + 0,026SO2 + 5,24N2 + 0,212O2

From the above reaction we can calculate the percentage of excess oxygen in boiler flue gas:

O2 excess = $\dfrac {0,212}{1+0,37+0,26+5,24+0,212}\times 100\%$

O2 excess = 3,096%

While the air-fuel ratio corrected to:

AFR = $\dfrac {1,393\left( 32+3,762\times 28\right)}{12+1\times 0,74+16\times 0,061+14\times 0,018+32\times 0,026}$

AFR = 12,926

Free ebook: Combustion Air Requirements for Power Burner Appliances

## Stoichiometric Calculation of Coal Burning Process

Generally, coal is composed of several important chemical elements. They are carbon (C), hydrogen (H), sulfur (S), oxygen (O), and some other elements. These elements interconnect chemically to form new hydrocarbon compounds. The hydrocarbon chemical bonds stored energy. When the bond is cut off through the combustion process, the stored energy will be released into the environment. If we write into a chemical reaction, then coal combustion will look like the below:

Coal + O2 → Product + Heat Energy

The carbon burning process, produced the most heat energy for the entire process. Carbon burning also allows the formation of carbon monoxide if incomplete combustion occur. The content of hydrogen and sulfur in coal also contributes a small part of the heat energy when the combustion process takes place.

To facilitate our understanding, let us consider the following example calculations.

For example, a coal content analysis mention that the coal has the following composition:

• Carbon: 73%
• Hydrogen: 4.5%
• Oxygen: 5.9%
• Nitrogen: 1.5%
• Sulfur: 5%
• Water: 2.1%
• Ash: 8%

From the above data, we can determine the mol/100 gram value of each coal component, as well as we specify the mol/mol of carbon to be able to determine the chemical structure of the coal molecule.

So the chemical formula of coal molecule is:

CH0,74O0,061N0,018S0,026

With a slight rounding up the air composition, which is 79% nitrogen and 21% oxygen, so for one mole of oxygen, there are 3,762 nitrogen. With that data let us make a perfect burning stoichiometry reaction from the related coal.

CH0,74O0,061N0,018S0,026 + 1,211 (O2 + 3,762N2) → CO2 + 0,37H2O + 0,026SO2 + 4,565N2

From the equation of the perfect combustion above, then we can determine the air / fuel ratio, so we know how much air is needed to burn 1 kg of coal.

AFR = $\dfrac {1,211\left( 32+3,762\times 28\right)}{12+1\times 0,74+16\times 0,061+14\times 0,018+32\times 0,026}$

AFR = 11,237

## Air Molecular Weight Calculation

The molecular weight (molar mass) of a substance is the mass of one mole of the substance, which can be calculated based on the molar mass of the constituent atoms. Dry air is composed of two important chemical elements: 78% nitrogen and 21% oxygen, and about 1% are mixtures of carbon dioxide, neon, helium, methane, krypton, hydrogen, and xenon.

Before further calculating the dry air molar mass, we must understand the notion of the mole. Mol is a unit of measurement for the number of substances, which denotes the number of representative particles equal to the number of atoms in 12 grams of carbon-12 atoms (12 C). The number of particles is expressed in Avogadro Numbers which is equivalent to 6.022140857 × 10 23 particles / mol. One thing to note is that one mole of nitrogen, has a size of the number of constituent atoms equal to one mole of oxygen, one mole of carbon dioxide, and one mole of other substances present in the world.

Now let’s calculate how much dry air molar mass goes through the table below:

The molar masses of each of the above air constituent components are calculated according to the standard data from the periodic table of chemical elements. Nitrogen for example, with the chemical formula N2, has an atomic molar mass of 14.007 g/mol. Then the molar mass of 2 nitrogen atoms (which make up N2) is 28.014 g/mol. The same calculation is also performed for other dry air constituent elements.

Furthermore, the molar mass of each constituent element is multiplied by the percentage value of the element content in the dry air. From this we get the elemental element molar value. After the elemental molar mass of the portion is summed, we obtain a molar mass for air of 28.9647 gram/mol.

## What is Water-tube Boiler?

What is Water-tube Boiler? – Water-tube boiler is a type of boiler with pipes containing circulated water, which is heated by a fire on the outer side of the pipe. The water-tube boiler has the opposite design with the fire-tube boiler. This boiler circulates water through the pipelines with the heat source coming from the furnace. These pipes, which become the water-vapor circulation pipes, are inside the combustion chamber blanket or the combustion hot gas duct. In modern water-tube boilers with large production loads, there are several parts of water pipes designed to be the walls of the boiler’s combustion chamber. The pipes are usually known by the term wall-tube.

A water tank, commonly called a steam drum, is one of the water-tube boiler character. Steam drums serve as a water tank to ensure there is always enough water circulated to the water pipes. Otherwise, steam drum also serves to separate the saturated steam with water. Saturated steam coming out of the steam drum will be heated further to become superheated steam.

Modern water-tube boiler, equipped with water pipes designed as the boiler walls (wall-tube). Water from the steam drum goes down through a pipe called downcomer to the header pipe (lower ring header) connected to all the lower ends of the wall-tube. The other end of the wall-tube at the top of the combustion chamber is directly connected to the steam drum. In the wall-tube, there is a phase change from water to steam. This water-pipe system produces a closed water circulation between the steam drum – downcomer – wall-tube and back to the steam drum. From steam drum only saturated steam will come out. In superheater boilers, the saturated steam will be heated further into superheated steam.

Even though the water-tube boiler has a slightly more complex design than a fire-tube boiler, this boilers tend to be more capable of producing higher steam quality, as well as a much larger capacity. Hence the water-tube boiler is more suitable to be applied to large industries, such as steam power plants, that demand more quantity, as well as high steam qualities.

## Working Principle of Hydraulic System

Working Principle of Hydraulic System – We are certainly familiar with the above heavy equipment. A lot of heavy work using this equipment. This equipment is designed to conquer heavy loads raised, or for the purpose of digging. The system used as a “fork” driver is a hydraulic system. Hydraulic system is a system that uses liquid fluid power to do a simple job. The hydraulic system is an application of the use of Pascal’s Law.

Hydraulic machine, supply pressurized hydraulic fluid to a hydraulic motor or hydraulic cylinder to perform certain work. Hydraulic motors produce a rotating motion that can be used to rotate heavy loads such as pulleys, chains, etc. Hydraulic cylinders produce back and forth motions that are widely applied to heavy equipment, water gates (at dams for example), or also for large valves. Hydraulic fluid is controlled by flow control valve and passed through hydraulic tube.

The hydraulic system can be simply explained through the picture above. The first image shows that by using a hydraulic system, it takes a smaller (F) force to be able to lift a larger load.

F2 = F1 • (A2/A1)

While the second picture explains the principle of using a hydraulic motor on a pulley. And it takes a smaller torque to be able to rotate pulleys with a larger load (large torque).

Tmotor = Tmotor • (Vmotor/Vpompa)

Hydraulic Circuit

A hydraulic system consists of hydraulic pumps, pipelines, control valves, hydraulic fluid tanks, filters, actuators (cylinders or hydraulic motors), and other devices as a complement.

The picture above illustrates a hydraulic system that works to drive hydraulic cylinder piston. The working fluid collected in the tank is pumped by a hydraulic pump so that it has specific pressures. Fluid flows to the solenoid valve, this valve regulates the movement of hydraulic cylinders. If the cylinder position lengthens (advance) then the solenoid valve will go to the left, so the fluid can push the piston forward. When the solenoid valve is directed to the right, the hydraulic cylinder will retract. At the time of movement in the cylinder, then there is some hydraulic fluid is wasted. This fluid returns to the tank through a special pipeline.

The system above is not much different from the hydraulic system that has a piston actuator. It’s just that here the actuator is a hydraulic motor for its use of torque (torque). The solenoid valve adjusts the direction of rotation of the hydraulic motor. Unlike the more complicated electric motors required to be able to rotate in both directions, hydraulic motors are easier to apply when needed to rotate in both directions.

## What is Fire-Tube Boiler?

What is Fire-Tube Boiler? – Do you remember what boiler mean? Boiler is a vessel that serves to heat water. In principle, a pan is also a boiler, but it’s not a boiler of this kind that we will discuss. Long ago, mechanical engineers created boilers by simply increasing the size of the ‘pan’. Then gradually they design the boiler with more complex again. One important principle is that larger surface contact between the heat source and the heated water, the more steam produced by the boiler in equal size. Then came the idea of ​​making pipelines in the gigantic ‘pan’, so the pipes flowed the fire – or at least the hot gases – through the amount of water housed by the giant ‘pan’. This is the forerunner of the fire-tube boiler. So the definition of a fire-tube boiler is one type of boiler that flows the heat of the combustion process into one or more pipes, which were inside a sealed container filled with water.

Fire-tube boiler is the simplest type of boiler. This boiler can be applied from low to medium water steam requirements. This is possible because the design is not complicated as the water-tube boiler. The size of the fire-pipe boiler is also relatively smaller, and allows it to be moved very easily. That advantages make this boiler is very popular when developed in conjunction with the steam engine. In the 19th century until the beginning of 20th century, fire-tube boilers were developed massively to meet the transportation needs of the time. Steam locomotive, naval ships, and early models of cars, became the most sophisticated models of fire-tube boiler transportation in that period.

As the name, the fire-tube boiler flows the hot gas to the water-coated tubes. Different pipeline designs from the various fire-tube boilers, are to maximize the heat absorption of the combustion gases. The water level inside the boiler tank, must be maintained to avoid overheating. On the other hand, this boiler is also equipped with a safety relief valve avoid the explosion from over pressure.

Many types of fire-tube boilers are also equipped with advanced steam heating systems to produce superheated steam. Nevertheless, the fire-tube boiler has limited steam production of only 2500 kg/h with a maximum pressure of 10 bars only.