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Boiler Basics 101: Superheat vs. Saturated Steam

Playing off our last topic, some might argue that there is another boiler type, or classification, to consider. In today’s article, we will discuss the difference between saturated and superheated steam boilers, and the applications that they are most commonly used for.

Let’s begin by talking about the science behind these two types of steam. Simply put, when water is heated to its boiling point, it will begin to vaporize and saturated steam is produced. Superheated steam occurs when the water is continually heated to temperatures beyond the boiling point, without any increase in pressure. Also known as dry steam, superheated steam has a much lower density and produces zero condensate.

As with the other types of boilers previously discussed, saturated and superheated steam boilers each have their own unique advantages and disadvantages and are better geared for certain applications over others. Saturated steam has a high density and is an excellent heating source. Commonly utilized in food processing, sterilization, district heating, and pulp & paper processing, saturated steam has the following advantages: 

  • - Produces fast and even heating due to latent heat transfer
  • - The temperature can quickly be established through the control of pressure
  • - Has a high heat transfer coefficient, which requires a smaller heat transfer surface and in turn, allows for reduced initial
  •   equipment costs

Superheated steam is not typically utilized in heat transfer applications. However, due to its dry composition and ability to cool while remaining in the same physical state, it can be extremely versatile and is most commonly utilized in refineries, for generating electricity, and for powering turbines.

Superheated steam is ideal for powering turbines for the following reasons:

  • - The dry steam allows for steam-driven equipment to function effectively and efficiently (while condensate from wet steam
  •   would negatively affect performance of the equipment)
  • - Improves thermal efficiency and work capabilities of turbines
  • - Contains zero condensate, minimizing the risk of corrosion and erosion damage

With a low heat transfer coefficient that is equivalent to that of air, superheated steam has more energy and can work harder than saturated steam, but the heat content is less useful. In addition, boilers that are built to produce superheated steam require more expensive components on the boiler system, in comparison to a saturated steam boiler. Therefore, it is extremely important to do your homework ahead of time to determine which type of steam is best suited for your particular application.

Did you know that Nationwide Boiler maintains a fleet of both saturated and superheated steam boilers for rent and for sale? In fact, we own the World’s Largest 125,000 lb/hr saturated steam mobile boiler, and the World’s Largest 110,000 lb/hr superheated steam mobile boiler!  Visit our website at nationwideboiler.com to learn more.

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Boiler Basics 101: Types of Boilers

When we think about boilers, there are a two types that typically come to mind; firetube, or scotch marine, and watertube boilers. These types of boilers can be classified as hot water, steam, high pressure, and low pressure. In today’s blog post we will be answering the question: what are the basic differences between the different types of boilers?

Although their final function is the same, the main difference between a firetube and watertube boiler is the construction and design of each system. In a firetube boiler, water inside a vessel is surrounded by tubes that contain combustion gases. In other words, the ‘fire’ is inside the tubes, making it a ‘firetube’. Watertube boilers are essentially the opposite in design. Combustion gases surround a series of tubes that contain water, coining the name, watertube.

By definition, high pressure boilers are built to a maximum allowable working pressure (MAWP) above 15 psig, while low pressure boilers are designed for operation at 15 psig or below. Low pressure boilers are most commonly utilized in heating applications and require less maintenance than that of a high pressure unit. Furthermore, firetube boilers can be built for both low and high pressure applications, while watertube boilers are typically built for high pressure needs.

Some may think that firetube and watertube boilers are in the same category as hot water and steam boilers. However, steam and hot water boilers are actually a classification, and can be considered a subcategory to firetube & watertube boilers.

Hot water and steam boilers operate in a very similar manner, but hot water boilers don’t actually produce steam. In reality, a hot water boiler is just a fuel fired hot water heater, in which heat is added to increase the temperature to a level below the boiling point. Hot water boilers are not as powerful as steam boilers, which is why they are more commonly used in heating applications providing hot water at 120 – 220F.

Steam boilers heat water to levels that are above boiling point, in order to produce steam. They are much more powerful and are utilized in more industrial and heavy-commercial applications. Steam boilers can be designed to produce either saturated or superheated steam, which we will discuss further on in a future post.  

Be it a firetube, watertube, hot water, or steam boiler, they are all effective and efficient in their own unique ways. To learn in more detail about the differences between boiler types, visit the section on our website, “What Boiler Is Best For You”.
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Boiler Basics 101: Basic Anatomy of a Boiler

Boilers are designed to produce steam to accomplish a multitude of tasks; from powering a plant to sterilizing hospital equipment. In simple terms, a boiler is a closed container in which water is heated to its boiling point to produce usable steam. In order to produce steam, there are two key items that must be involved: water and heat.

A boiler is comprised of two seperate systems: the steam-water system (waterside), and the fuel-air-flue system (fireside). As you might have guessed, water is first introduced into the waterside of the boiler. Alternatively, the fireside of the boiler provides heat, produced through the combustion of fuel (commonly natural gas or fuel oil, but can be another source) and air, which is controlled by the burner.  The heat that is created within the fireside is transferred to the waterside to produce steam.

To complete a boiler system, additional elements are required. This typically includes the following major components:

  •    - Burner: a mechanical device that supplies the required fuel and air for proper combustion.
  •    - Controls: the BMS (burner management system) protects the equipment and personnel from safety issues.
         The CCS (combustion control system) controls the air and fuel for proper combustion.
  •    - Fan: supplies air for the combustion to take place.
  •    - Water Softener: pre-treats the boiler feedwater for removal of hardness, which would otherwise cause detrimental scale
         inside the boiler system.
  •    - Deaerator / Feedwater System: removes oxygen and gases from boiler feedwater supply (which will also damage boiler
         internals), and feeds it to the boiler system via high pressure feedwater pumps.

All of these elements come together to create a robust steam supply system that is utilized in an abundance of processes throughout many different industries. Boilers truly are a work of art, with many pieces working as one system to make something extremely powerful and impactful, which is why we at Nationwide Boiler are so passionate about what we do.

Stay tuned for the next article in ur Boiler Basics 101 series to learn more about common types of boiler systems.  

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Boiler Basics 101: What is Steam?

To kick-off our ‘Boiler Basics 101’ series, we are starting at the very beginning. The extremely useful resource, produced by the commercial and industrial boilers that we rent, sell, service and maintain… that resource is steam.

Our business, and the boiler industry as a whole, revolves around steam. We provide boilers and related equipment for both temporary and permanent applications; equipment that works together to produce the valuable resource of steam, utilized in an abundance of processes across many different industries. So, what exactly is steam and what is it used for?

Let’s start with the chemical composition of steam. Water can exist in three physical states; solid, liquid, and vapor. These physical states, in more common terms, are referred to as ice, water, and steam. When water is heated at atmospheric pressure, its temperature rises until it reaches the highest temperature at which water can exist at this pressure. This temperature, 212F or 100C, is the saturation temperature, or boiling point. As water boils and temperature continues to increase, water particles begin to form small bubbles that rise to the surface and vaporize. This is how steam is formed.

Traditionally, steam was associated with locomotives and the Industrial Revolution. However, now steam is an integral part of modern-day technology. Not only is it an excellent source of energy and heat, but it is also sterile, which makes it ideal for use in the food, pharmaceutical, and health industries. Many other industries also utilize steam for processing, petroleum refining, utility and power, and manufacturing.

Steam has become an invaluable part of our world.  Without it, many of the advances and technologies in today’s time would not be as effective or efficient as they are now.

Stay tuned for the next article in our Boiler Basics 101 series to learn about the basic anatomy of a boiler system.

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