4 Characteristic Of High Pressure Boilers

In this article, I will share the characteristics of high-pressure boilers and some of their unique features that one can use to identify them.


What you need to know is that high-pressure boilers are different from the low pressure boilers.


And that is why we have several characteristics that can be used to identify such kinds of boilers.


Nowadays people tend to make use of high-pressure boilers because of its high evaporative capacity (of about 250Kg/cm2 steam pressure) that can be obtained at a temperature of about 5500C.


With the design of high pressure boilers, fuel of lower grades can be used and still generate the required amount of steam with its right conditions.


This means that high-pressure boilers are amazing when it comes to saving enough resources because costly pieces of equipment are not needed.


With high-pressure boilers, the higher efficiency of the boiler can even be achieved by the use of low-grade fuels.


And this is possible because of its design, the type of firing method used and so many other factors that you are going to know as you continue reading this article.


These are the characteristics of high-pressure boilers;

1. High-pressure boilers are water-tube types.

This is one of the first characteristics and features of high-pressure boilers you should know about.


There are two types of boilers according to the flow of water and combustion gasses in the boiler system namely; water-tube boilers and fire-tube boilers.


If you want to learn more about these types of boilers then you should read the article below.


You might like this: Boilers: Components, Types & Working Principle


In water-tube boilers, it’s possible to achieve generation of steam under high pressure compared to fire-tube boilers.


This is possible because the water in the boiler shell is passed through tubes of small diameters as the combustion gasses are passed on over the tubes to allow heat transfer.


When this happens, the water in the tubes is sufficiently heated by the flue gasses and steam generation happens easily and faster because the size of the tubes is smaller.


The high pressure will be achieved because the steam generated is still enclosed in a really tight space within the tubes.


The decreased volume of the tubes and expansion of the steam as it’s continuously heated by the flue gasses increases its pressure exponentially and that is why a pressure of about 250Kg/cm2 can be achieved under a very low temperature.


This is the kind of characteristic of water-tube boilers that makes them preferable when it comes to areas of application where high pressure steam is needed.


Also, with the use of the tubes in the water-tube boilers the pressure loss is significantly reduced.


Which is very different from fire-tube boiler where a large amount of steam generated is accumulated in the steam space and after that it’s conveyed through the steam distribution lines.


This shift of movement from the steam space to the distribution lines decreases the pressure of the steam.


In water-tube boilers, there isn’t a big drop of pressure since the steam is still conveyed via the same types of tubes that the water was heated into.


Also, with the tubes in use, there is no change in space that can allow the pressure of the steam to significantly drop.


With the use of the tubes in high-pressure boilers, it’s easier to have control over the quality of steam produced.


The quality of steam can easily controlled by changing the amount of heat supplied because the volume of water heated per the space of the tube is very little.


The change can take effect immediately which is very different from fire-tube boilers where a large volume of water is supposed to be heated.


The control of the quality of steam in fire-tube boiler is going to take a while compared to fire tube boiler.


You might like this: Advantages And Disadvantages Of Water Tube Boilers


2. High-pressure boilers use pulverized coal firing.

This is another characteristic you can use to identify high-pressure boilers easily.


When we talk about pulverized coal firing, high heat temperatures can be achieved easily without a hassle.


You might like this: Advantages Of Using Pulverized Coal


The heat temperatures provided by the use of pulverized coal is higher thus achieving high steam pressure becomes easier.


With the pulverized coal firing, the heat produced can be controlled easily compared to the other types of firing thus giving more control to the amount of steam generated at a certain time.


The pulverized coal firing produces a flame that is under high pressure because it’s ejected from the burner thus making it easier to heat the water tubes effectively.


The reach of the heat energy across the water-tubes can be increased by adjusting the flame length by using adjustable tools thus ensuring that every tube that carries water is effectively heated.


With the use of pulverized coal firing, extreme temperatures are produced from the furnace and a measure is needed to prevent accidents.


Water walls are used to regulate the temperature of the furnace.


And this is one of the investment people who choose to use high pressure boilers have to allocate a budget for.


As you know, with the improve design of the furnace and type of fuel used, the operational costs also increases.


You might like this: Disadvantages Of Using Pulverized Coal


3. High-pressure boilers make use of pumps to circulate water in the boiler system.

The water in the tubes has to be circulated by the use of pumps to help in the movement of steam and water.


The heat energy is not enough to keep the water circulating in the system of the boiler.


This is another unique feature of high-pressure boiler you should keep in mind.


When it comes to circulation of water in the boiler system there are of two types namely; natural circulation and forced circulation.


Natural circulation of water in the boiler system mainly depends on the difference of water and steam density to establish a flow of water and steam across the boiler.


The forced circulation on the other hand, mainly relies on the use of pumps to move water in the boiler system.


Pumps are used to maintain the continuous flow of water in the tubes thus ensuring that every volume of water lost through steam is immediately replaced.


What you need to know is that most high pressure boilers use forced circulation but the sub-critical boilers may use natural circulation.


The use of forced circulation in high-pressure boilers makes it easier to achieve the needed steam pressure.


Let’s say it’s like an added advantage because of the following points I am going to share here.


With the use of pumps in high pressure boilers it ensures that a positive circulation is always maintained in the boiler system.

There will be no point at any space of the tubes in the boiler that will lack water thus steam generation will always be high so will the pressure.


With the use of the pumps, the water will always flow fast within the tubes occupying any empty spaces left after steam generation.


This will end up increasing the evaporative capacity of the boiler because the steam generation will keep on going as the pump will keep on pumping the water in the boiler system.


You have to keep in mind as the water is being circulated by the pumps within the tubes of the boiler the flue gasses are still passing over the tubes thus increasing heat transfer.


The movement of water in the tube under pressure and the heat transfer that goes on keeps on increasing the evaporative capacity of the boiler.


This ensures that the steam is always produced under high pressure.


The continuous supply of water in the tubes of the boiler system by the use of a pump, ensures the fewer drums of water for the boiler are needed.


As long as the water is being continuously in the few drums available, the steam generation is going to keep on happening smoothly.


This eliminates the need to have a massive boiler unit and saves the cost that could have been used to purchase more boiler drums.


The downside is that the pumps will have to be always kept in shape by lubrication and maintenance.


You might like this: 8 Main Areas To Focus On When Maintaining A Boiler


Failure of the pumps decreases the operation capacity of the high-pressure boilers.


4. High-pressure boilers have improved methods of heating.

The unique features of high-pressure boilers I have shared in the above section of this article are nothing if the method of heating is not effective.


High-pressure boilers have improved methods of heating so that to increase the quantity and quality of steam generated.


Without measures to improve the method of heating in high-pressure boilers, there is no way a steam of high pressure would be generated.


The higher the heat transfer, the higher the pressure of the steam generated and its improved quality and quantity.


To save heat energy lost through evaporation (change of water into steam in the tubes) a higher critical pressure of steam is maintained.


This pressure can be achieved by the use of the pumps I talked about in the above section of this article.


The pumps ensure that the steam produced is always under high pressure when circulating within the tubes of the boiler thus reducing the heat lost through evaporation (by the steam).


Another method of improved heating that is done in high-pressure boilers is by heating the boiler water with a mixture of superheated steam.


This suggests that the steam that is already generated and passed through a superheater is passed again in water-tubes with the mixture of the boiler water to be heated.


The mixture of water and the superheated steam, also considering that the boiler water is initially heated before being supplied into the tubes, ensures that a high coefficient of heat transfer is achieved easily.


You might like this: Advantages Of Using Superheated Steam and 4 Reasons Why Boiler Feed Water Needs To Be Heated


With this improved method of heating a high-pressure steam is generated effectively.


Another method to improve heating in high-pressure boilers, there is the use of high-velocity water inside the tubes which increases the gas (flue gasses) velocity above sonic velocity; this increases the overall coefficient of heat transfer.


The high velocity of the water in the tubes can be achieved by using powerful pumps and the velocity of the combustion gasses can be improved by using an effective burner and also by the aid of a pump to pressurize the gasses as they move over the tubes.


With these improved methods of heating; the high pressure of the steam is easily achievable.




What I have shared in this article is just an elaboration of the features that high pressure boilers have compared to the low-pressure boilers.


What you need to understand is that it’s advantageous to use high-pressure boilers because of how effective they can be but you should also consider their cost.


Operating and maintaining high-pressure boilers isn’t a joke because of how many things you have to keep in check.


But that is the cost of wanting an improved steam pressure for your processes.


If you don’t need a very high steam pressure for your application it’s not necessary you use high-pressure boilers.


You should consider using fire-tube boilers, they can still get the job done.


Thanks for reading, I hope you have learnt something from this piece of information I have shared.


See you in my next piece of article.


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