Working of Boiler – Explanation, Parts ...

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What is a Boiler ?

The boiler is commonly defined as a closed vessel into which water is heated to the point it is converted into steam at the imperative pressure. The main function of the boiler is either to produce hot water or steam. The Hot water boiler heats water for the domestic or commercial purpose of heating and hot water supply, whereas Steam boilers generate steam to power turbines for power generation and other various industrial heating applications.

To understand the steam generation effects using a boiler, try thinking about the steam powering a turbine. When steam is made to flow through the turbine blades, the force turns the blades and accelerates the turbine.

Also, Steam has an enormous amount of energy as it consists of the energy given for raising the temperature of the water along with the latent heat of vaporization. So, it makes the turbine quite efficient and based on the fuel used to boil the water, very energy-efficient too. The Boilers work under pressure to heat any liquid types for external use by the combustion of fossil fuels or energy from the sun.

Parts and Accessories of a Boiler

The boiler parts are classified into two divisions, these are:

Boiler Mounting

They are the essential parts that define the boiler&#;s performance. The main components of boiler mounting include:

• Pressure Gauge: The gauge type is used to measure the pressure inside the boiler, fitted at the boiler&#;s front.

• Water Level Indicator: This is used to check the inside water level of a boiler, fitted in the front of the boiler having a glass tube and three cocks and 

• Stop Valve: We can control the flow of steam from the boiler to the steam pipe using this.

• Safety Valve: The valve is fitted on the drum, which is used to prevent the boiler explosion due to high pressure, which blows off when the inside pressure exceeds the limit. There are always two of them present to ensure no explosion takes place in the boiler.

• Blow Off Cock: It is used to blow off water and mud, and is used to empty the boiler. It is generally fitted at the bottom of the drum

• Grate: It is the space in the furnace used for fuel-burning

• Feed Check Valve: The valve is used as a Non-Return Valve, and is fitted on the drum slightly below the normal water level. It is useful to regulate the water supply.

These boiler accessories are responsible for boiler efficiency. The main components of the boiler include:

• Super Heater: The heater is used to superheat the steam before it is passed in the turbine as saturated steam that causes corrosion

• Feed Pump:  This is to pump the water into the continuous boiler working. The Steam or electricity or turbine is used for the feed pump running

• Air Preheater: It is also used to increase the boiler&#;s efficiency by preheating the air

• Economizer: This component is used to increase the boiler&#;s efficiency as the flue gasses from the boiler is prepared to flow through the economizer before releasing it into the atmosphere

Working Principle of a Boiler

It is simple to understand how the boiler works. To understand it, let us have a look at it.

The boiler is a closed vessel, where the water is stored. Hot gasses are formed by burning fuel in the furnace. These glasses are made to come in contact with the water vessel, the point where the heat transfer takes place between the steam and water. Thus, the boiler&#;s basic principle is to convert water into steam with heat energy. There are various types of boilers available to use for different purposes.

Efficiency of Boiler

It is defined as the total percentage of heat exported by the outlet steam to the total supplied fuel.

Boiler Efficiency (%) = (Heat Exported by Outlet Steam) / (Heat Supplied by the Fuel) * 100

Classification of Boiler

Boiler&#;s classification is based on the following criteria:

According to the Relative Passage of Hot Gasses and Water

• Fire-Tube Boiler: This is the one where the hot combustion gasses are surrounded by the water

• Water-Tube Boiler: In this, the water flows via the tubes, surrounded by hot combustion gasses

According to the Arrangement of Water Circulation

• Forced Circulation: The is the circulation that happens by pumping the water present inside the boiler

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• Natural Circulation: This circulation happens because of the density difference 

According to the Usage

• Locomotive: Used in the railway engines

• Marine Boiler: Used in ships

• Stationary Boiler: Used for power plants

• Portable Boiler: These are used temporarily in sites and are movable

According to the Boiler&#;s Position

• Inclined

• Horizontal

According to the Pressure Generated by the Steam

• Medium Pressure Boiler: The maximum pressure is of 20-80 bars and is used to generate power

• Sub-Critical Boiler: If the boiler produces steam at a pressure less than the critical pressure it is called sub-critical

• Low-Pressure Boiler: The maximum pressure is of 15-20 bar and is used for the purpose of heating

• High-Pressure Boiler: This boiler has a maximum pressure of more than 80 bars

• Supercritical Boiler: These are used to produce steam at a pressure greater than the critical pressure

According to Charge in the Furnace

• Pulverized fuel

• Supercharged fuel

Steam boiler is kind of boiler where the water is heated inside tubes and the hot gasses surround them.

A steam boiler is a power generation device, used for generating steam by applying the heat energy to water. The pressure range of earlier boilers ranges from low pressure to medium pressure (7 kPa to kPa/ 1psi to 290 psi). The present boilers are more useful because it works with high pressure than old ones. This boiler is very used whenever a steam source is necessary, and the size, type mainly depends on the type of application like mobile steam engines which includes handy engines, steam locomotives, and road vehicles. These vehicles include a mini boiler that can be worked with steam power. Generally, power stations or stationary steam engines have a separate large steam generating capacity.

Types of Boiler

Fire Tube Boiler

As it indicated from the name, the fire tube boiler consists of numbers of tubes through which hot gasses are passed. These hot gas tubes are immersed into water, in a closed vessel. Actually in fire tube boiler one closed vessel or shell contains water, through which hot tubes are passed. These fire tubes or hot gas tubes heated up the water and convert the water into steam and the steam remains in same vessel. As the water and steam both are in same vessel a fire tube boiler cannot produce steam at very high pressure. Generally it can produce maximum 17.5 kg/cm2 and with a capacity of 9 Metric Ton of steam per hour.

Water Tube Boiler

The heating surfaces of the boiler consist of a group of tubes, some of which are exposed directly to the flame and others are exposed to the flow of hot gases resulting from the combustion of the fuel. Piping groups are provided with Baffles, which create multiple paths for the hot gases flowing to increase the efficiency of heating surfaces. Thus, the heat is transferred to the water in the boiler through thin-section pipes compared to the thickness of the flame-tube boiler wall. Thus, the working pressure can be increased more than what is available in flame tube boilers.

Five common problems with steam boilers:

Wet steam (priming):

causes:

Incorrect kettle hull.

The high water level inside the kettle.

 Improper combustion rate.

High percentage of dissolved solids in boiler water.

High alkalinity.

Treatment

Maintain low levels of salt in the water.

Effective filtration of the water used in the boiler.

Remove sediment from time to time.

Blocked or accumulated scales:

causes:

The use of poor water causes severe damage to the boiler system. Minerals such as calcium and others build up in kettle and pipes as crusty deposits. These deposits can either slow down or block the passage of steam through the system.

Treatment

Use treated water to prevent mineral build-up in the water.

Hear noises while the boiler is running, such as whistling or knocking:

causes:

It could indicate that there is air in the system, the water pressure is too low, or the formation of a crusty layer of lime on the boiler heat exchange.

Treatment

Using the right pressure for gas and gas piping is important and should be checked along with proper flame, air intake and exhaust.

Loss of prassure:

causes:

 Steam leaks (you may not be able to see some of them), pressure loss can also mean problems with the return system such as steam traps, check valves, or feed pumps.

Treatment

Continuous checking and periodic maintenance of the boiler system.

Problems related to pressure due to water feeding during operation:

causes:

When boiler tanks contain an intermittent type water supply. Even though the new water is heated before entering the tank, it is still colder than the water already in the kettle. The temperature variation reduces the production of steam until the new water temperature rises. The decrease in steam production can cause the pressure in the boiler to be temporarily reduced.

Treatment

 A continuous water feeding system is the perfect solution to treat this problem.

Use of steam boilers in industry:

Equipping industrial facilities with a steam boiler system is one of the safest and most efficient ways to meet their requirements for producing the steam required for their manufacture.

Here are seven industries that benefit most from the steam boiler system:

• Hospitals and health care centers.
• Fermentation and distillation.
• Food and beverage industries.
• Commercial laundries.
• Textile industry.
• Pharmaceutical industries.
• Extraction of essential oils.

Methods of storing steam boilers:

It is preferable to inspect, wash and dry the boiler before the storage process. Steam boilers are stored in one of two ways, dry or wet.

Dry storage:

• Use when the kettle has been stored for 3 months or more.
• Cool the water to just before boiling at room temperature but be careful not to drop below 83ºC
• Wash and inspect the kettle to determine if it needs any necessary repairs before storing.
• Clean and dry all wet areas of the boiler.
• Trays of moisture-absorbing chemicals such as quicklime or silica gel are distributed in the boiler cylinder, and the kettle is sealed, preventing any moisture from entering.
•  In areas with high humidity, an oil treatment may be necessary.

Wet storage:

• It is used when storing the boiler for a short time, and includes the method of wet storage, forcing the air out of the boiler, by filling it completely with specially treated water.
• Cooling of water to below atmospheric boiling point but not lower than 83ºc.
•  Wash the kettle and inspect it to determine if any repairs are needed.
•  Clean and dry all wet areas of the boiler.
•  The clean, empty kettle should then be filled to the top with chemically treated water to reduce corrosion during prep.
•  Keep the water pressure higher than the atmosphere.
•  Add caustic soda and sulfites until the water level reaches 450 ppm.
•  Close drains and vents.
•  The kettle can now be filled with clean service water, provided it is treated with hydrazine and volatile alkalis.

We, Arabtec Boiler Company, specialize in the field of steam boilers, steam networks, maintenance, water treatment, with the help of a group of professional engineers and the finest local products with international specifications. We provide practical solutions for all industrial purposes.

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