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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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Protect Your Boiler from Freeze Damage this Winter

When winter comes along, freeze protection should be a major consideration for any boiler owner or renter. Protecting your boiler from freeze damage is simple: enclose, insulate, and/or heat trace. If you continue operations as usual and allow your boiler to be exposed to near or below freezing temperatures, you will have a high probability of costly damage and system failures.

Below are a few reminders on the proper steps to take when it comes time to protect your temporary or permanent boiler system from the cold climate.

  - Enclose both the front and rear of the boiler, or build a full temporary enclosure, and utilize an external heating source.
  - Install the proper heat tracing (steam or electronic) and insulation to all of your main lines and piping components, regardless of if the
    boiler is in operation or not. This includes the following lines:
          - Sensing lines
          - Auxiliary low-water cut-off
          - Water column
          - Level control blowdown
          - Main and continuous blowdown, depending on length of piping runs
  - During non-operation times, drain and fill all sensing lines with a 50/50 water/glycol solution, making sure to re-connect each line.
  - When an extended downtime is expected, completely drain the boiler and all stagnant water lines.

In addition to the recommendations above, use sound engineering calls when it comes to deciding the correct freeze protection measures. And if you happen to have damage this winter, we have your back with a rental boiler to get you by during the repairs!

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Never Forget 9-11

Two Rental Boilers & One Feedwater Van at Ground Zero After 9-11
We will always remember those who risked their lives and those who lost their lives on this tragic day in history.

We are grateful today and always.

2018 9 11 Remembrance

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