Steam Boiler

The steam boiler is a high-pressure tank that heats water through combustion to produce steam used in various industries. In the following, specifications, working pressure, brands, and how to select steam boilers are presented.

Steam Boiler Selecting Guide

The steam boiler is one of the essential heating factors in steam manufacturing used in industries and some air conditioning systems. Steam boilers can be divided into water tubes and fire tubes primarily based on their sketch, regardless of their capacity, size, and working temperature. Fire-tube steam boilers come in two types: wet back and dry back.

In dry back boilers, the end of tubes in passes two and three are connected to a network. Due to the temperature difference between the past two (1000℃) and past three (250℃), the network may experience thermal stress and start leaking. Dry boilers require insulation and maintenance on fire-resistant materials, separating passes two and three in short periods, which increases maintenance costs. Therefore, considering the significance of heat transfer surfaces and the use of the back shell of the boiler for heat exchange, wet-back boilers are more common.

Steam Boiler components

The main components of a boiler are:

1. Burner: The burner is the part of the boiler that combines fuel (usually gas or oil) with air and ignites it in the combustion chamber. This action produces heat and thermal energy, which is used to convert water into steam.
   
   
2. Combustion chamber: The combustion chamber is the place where fuel and air mix and the ignition takes place. The energy from combustion provides the heat needed to convert water into steam.
   
   
3. Heat exchanger: The heat exchanger or the pipes used in steam boilers are used to transfer heat from the hot gases resulting from combustion to the water inside the pipes. This process turns water into steam, which produces energy in the form of steam. The heat exchanger acts as a medium that allows the heat produced by the burner to be transferred to the water. This process turns water into steam, which produces thermal energy. To exchange heat between hot gas and water, a system of tubes or bent pipes is created. Hot gas (usually from burner combustion) passes through the tubes and transfers its heat to the tube wall. In other words, the heat of the gas is transferred to the water inside the pipes through the pipe wall, but the gas and water themselves do not come into contact with each other.
   
   
4. Thermostat: In the steam boiler, the thermostat is used to control the temperature of the produced steam and maintain the desired temperature. The main function of the thermostat in these systems is to control the temperature of the environment or the working fluid (such as water or steam). When the temperature reaches the value set by the user is reached, the thermostat sends a signal to the corresponding control device to stop or start the heat production process (for example, the combustion of the burner in the boiler). This control is optimized by the thermostat, which means that the thermostat, by detecting the desired temperature when the heat No more is needed, automatically reduces the heat production process. Usually, 2 or 3 thermostats are used to ensure the performance and safety of steam boilers.
   
   
5. Check valve: A check valve is a type of control valve that is used to limit the flow of fluid in a specific direction in a pipeline or system. This valve also acts as a safety unit and prevents reverse fluid flow. A backflow valve automatically causes fluid to flow in a specific direction, usually the direction of normal flow, and prevents reverse flow. This feature contributes to the safety of the system because preventing reverse flow can prevent potential hazards such as equipment failure, reducing system efficiency, or causing problems in processes. These valves are used in various cases, including in water, gas, oil, industrial processes, and heating and cooling systems. The importance of using backflow preventer valves in controlling fluid flow and preventing reverse flow problems in systems is very important.
   
   
6. Safety valve: Safety valves play an important role in pressure control and boiler safety. Sometimes, due to the existence of many problems, the pressure gauges in the boiler cannot measure the internal pressure of the boiler correctly. For this reason, the pressure inside the boiler increases suddenly. In these cases, these valves operate automatically. If the pressure inside the boiler rises to a level that threatens safety, the safety valves open and release the pressure in a controlled manner. This action reduces the pressure in the boiler and maintains the safety of the system. As mentioned in the case of boiler thermostats, in the case of boiler safety valves, in order to maintain 100% safety in the operation of the boiler, more than one safety valve is always installed on the boilers.
   
   
7. Pressure gauge: Pressure gauges are responsible for measuring the steam pressure in the system. If the steam pressure inside the boiler exceeds the virtual limit that has been determined, the pressure switch sends the information resulting from the pressure increase to the control circuit. The control circuit also compares the information it receives from the pressure gauges with the limit set by the operator. If this pressure is higher than the limit, it sends an order to shut down all the components of the boiler.
   
   In general, depending on the type and capacity of the boiler, usually two or three pressure gauges are considered, including the following:

• Burner pressure gauge
• Burner flame pressure gauge
• Reliable pressure gauge

Types of steam boilers

There are two main and common types of boilers, known as water tube boilers and fire tube boilers. These two types have important differences in structure and function.

Water-tube Boilers

In water tube boilers, flow tubes are parallel and connected and consist of a large amount of tubes. These pipes are exposed to the gases from the furnace. The feed water flows through these pipes and is heated by the hot gases around them. These types of boilers are used for industrial and large applications due to their more specific design and ability to withstand higher pressure.

Fire-tube Boilers

In fire tube boilers, fuel such as oil, gas, or coal is ignited in a horizontal furnace, and the heat is transferred to the filler (tubes). Inside the tank, the water turns into steam, and the steam produced is collected in the boiler. This steam can be used to provide energy or generate electricity. These types of boilers are generally used in smaller applications and home use.

Comparison table of specifications of water tube boilers and fire tube boilers

Note that this specification is only a general comparison of fire tube and water tube boilers, and for more detailed information about your specific needs, refer to relevant sources and standards.

Steam Boiler classification based on the path of combustion gases

This classification is based on the number of paths that flue gases travel in the boiler.

• Single-pass boiler: In this type of boiler, the combustion gases go through the boiler once and then are transferred to the chimney. These types of boilers were often used in the first generation of coal-fired boilers and steam locomotives.
• Two-pass boiler: In two-pass boilers, the flue gases first travel through a boiler, then go back and pass through the boiler again, and finally are transferred to the chimney. These types of boilers are usually used to produce hot water.
• Return furnace boiler: In this type of boiler, the combustion gases first pass through the furnace twice, and then they are transferred to the pass pipes and move towards the chimney. These types of boilers are usually more efficient than double-pass boilers.
• Three-pass boiler: In three-pass boilers, flue gases pass through the boiler three times and are finally transferred to the chimney. These types of boilers are used to produce hot water and steam.
• Four-pass boiler: In four-pass boilers, flue gases pass through the boiler four times and are finally transferred to the chimney. These types of boilers are usually used in high tonnages and for steam production.

These categories indicate the differences in performance and application between different types of boilers and refer to the number of passes or paths that flue gases take.

Important points in choosing and ordering steam boilers

When choosing firetube boilers, in addition to the capacity and working pressure of the boiler, you should also pay attention to other important things such as the number of passes in the combustion chamber of the boiler, whether the boiler is wet back or dry back, and the type of fuel and burner. (Always note that the nominal capacity of the burner should be considered 20% more than the capacity of the boiler).

Also, The quality of peripheral equipment such as feed water pump, safety valve, discharge valve, pressure switches, level controls, one-way feed valve, main steam outlet valve, electrical panel, consumable electrode, and even the way of making and assembling other tubes are important factors to guarantee its stable performance. According to generally accepted international standards, in the construction of steel boilers, the body (shell), furnace or combustion chamber, and grids must be made of special alloy steels for the construction of tanks under heat and pressure according to DIN 17MN4 or ASMEA516/G70 and for the material Boiler pipes or tubes should be made of DIN ST 35.8 seamless refractory pipes with the ability to roll.

One of the most important points in the design and production of boilers is the conformity of all parts of construction, execution, parts, control, access, testing, etc., with documented and well-known standards, as well as the implementation plans for the construction and design of boilers from approved brands. It is international. In other words, only the use of high-quality alloy steels and those, as mentioned earlier, standard refractory tubes alone cannot guarantee the performance, efficiency, and useful life of the boiler. Still, it is necessary to build the boiler using approved plans and methods. Defined and accepted by international standards. This point is so important that the construction of a boiler without documented and approved plans cannot be justified in any way.

Another important point regarding the construction and production of standard boilers is the way to connect the fire tubes of the firetube boiler to the tube plates at the beginning and end of the boiler. This connection must necessarily be done by the expand (waltz) method, except for the resistant pipes inside the sub-furnace, which must be done according to the standard by the expand welding method and using special I.S.A.B. devices to weld the network for the hot water or steam boiler.

The effect of all corrugated furnaces and pipes in increasing the efficiency of the steam boilers

Nowadays, due to the importance of convection heat transfer in increasing the efficiency of steam and hot water boilers, the use of techniques that can increase heat transfer has increased. Based on complete studies on increasing heat transfer from the heat transfer method known as V.H.T.E. (Vortex Heat Transfer Enhancement) and as the name suggests, the basis of work in these methods is based on the creation of a vortex, one of the most popular methods. The application of the V.H.T.E. method is the use of China or Corrugated in Corrugated Furnaces and Corrugated (Spiral) Tubes of boilers, which, by producing more turbulence in the fluid flow, causes an increase in displacement heat transfer and, of course,, an increase in the efficiency of boilers.

Research has shown that the heat transfer inside the furnace and all-corrugated or all-corrugated pipes have a very complex pattern, but in summary, according to the curve below, the displacement heat transfer in the furnace and all-corrugated pipes is almost five times the heat transfer In furnaces and pipes, it is smooth, in furnaces and pipes that are completely corrugated, due to many folds and, of course, the increase of their surface, the radiation heat transfer also increases, and the total increase of the heat transfer by the V.H.T. method E and radiation due to many folds in the oven Corrugated pipes greatly increase the efficiency of boilers and hot water.

Important points when buying and installing steam boilers

When buying and installing a steam boiler, you should pay attention to the following points:

• The ability to access various parts of the boiler and the presence of headhole-handhole-manhole valves in different parts for periodic services and even the possible replacement of defective tubes.
• Paying attention to the full dimensions of the steam boiler with accessories and their weight for entering the engine room and installing it at the inspection site.
• In engine rooms where steam boilers are used, water hardness devices or sediment removers and deaerators must be used in the way of boiler feed water. The maximum water hardness allowed for steam boilers is 20 P.P.M.

 Damatajhiz HVAC Group: The best prices and brands of construction equipment 

Buying a steam boiler

All thermal boilers are usually built according to the pressure boiler and pressure vessel regulations prepared by the American Society of Mechanical Engineers because their pressure is generally greater than 15 pascal. The selection of steam boilers is based on the combination of loads (load of steam-consuming processes and equipment, steam required for hot water production, pipe waste, and initial start-up).

In order to choose and buy a steam boiler easily, you must first determine the required capacity and working pressure. On the website of Damatajhiz HVAC Group, the technical information of dozens of models of steam boilers from reliable brands with original warranties has been presented in order for you, dear ones, to enjoy the good feeling of an optimal and smart purchase.

Steam Boiler price

You can check all types of steam boilers at the best price for the best choice on the specialized website of Damatajhiz HVAC Group. The price of steam boilers varies according to the variety of models, capacities, and brands available in the market; it should be noted that the prices presented on the Damatajhiz HVAC website are up-to-date, and the discounts desired by consumers are included in these prices. So that these prices also include a part of guaranteeing the best prices on the DamaTajhiz HVAC website.

Factors to increase the life of the boiler

Important factors to increase the life of the boiler are as follows:

• Boiler design and construction based on approved construction drawings and also according to accepted methods provided by international standards
• The use of alloy steels and standard refractory tubes, the sufficient heat level of the tubes, the number of passes of the boilers, and the waltzing of the tubes instead of welding to the tubes and plates.
• Choosing a burner with a calculated capacity suitable for boiler heating (maximum 20% more than the boiler capacity)
• Adjusting the burner flame (blue burning and direct longitudinal flow of the burner flame in steam boilers)
• If a diesel burner is used, the type and angle of fuel injection from the diesel burner nozzle are determined based on the diameter and length of the combustion chamber of the boiler and according to the suggestion of the boiler manufacturer.
• Accurate calculation and implementation of the chimney in terms of diameter and height of smoke suction according to the volume of combustion air
• Carrying out periodic inspections and services, especially in relation to how the burner ignites in the steel spa boiler, periodically checking the correct functioning of controls, safety valves, thermostats, etc.

Prepared and arranged by the Heating Equipment department of Damatajhiz HVAC Group

Dear user:

While thanking you for the trust you have in the technical opinions of DamaTajhiz HVAC sales experts, it should be noted that the determination and selection of the desired product brand based on history, brand strength, service, and product price is ultimately determined by the buyer. But in steam boilers, most of the users and buyers choose and buy best-selling brands such as Hararat Gostar due to their quality, price, and after-sales service.

If, after reading the above material, you have more questions about deciding on the type of steam boiler you need, you can ask your questions from the heating equipment and engine room sales experts after contacting DamaTajhiz HVAC by the extension numbers 107-108-121-122.

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1Atm.=1.013 Bar
Kw*860=K.cal
1Atm.=14.7 P.S.I
1HP(boiler)=9.809 Kw

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