We are all aware of the 3 basic forms of matter: solid, liquid, and gas. In the most basic sense, steam is the gaseous form of water. Typically we associate the words “boil” and “freeze” with water as we make ice to keep our drinks cold and boil water for tea or other making pasta. However, every substance has a boiling point and freezing point. Steam is the form of water that exists beyond the boiling point.

Speaking of boiling point, if we were to ask what the boiling point of water is, most people would respond that it is 212° F (or 100° C), which is correct, but only at atmospheric pressure. If we held water at a lower pressure, the boiling point would be lower, and likewise if we held water at a higher pressure, the boiler point would be higher. So when we are discussing boiling points and temperatures, it is important that we know at what pressure (and what elevation above sea level) we are operating.

Steam is the product of boiling water and requires an input of energy to create a phase change from liquid to gas. The amount of energy required is referred to as latent heat. The word “latent” is a derivative of the latin word “latere” which means hidden. The reason for this name is because the energy only produces a phase change and does not increase the substance’s temperature. In contrast, sensible heat is the term that refers to the energy required to raise the temperature of a substance.

Let’s look at an everyday example. You fill a pot of water from the sink to make macaroni and cheese and the tap water is about 60° F. You place the pot, with water, on the stove to add the required heat to bring the water to a boil. The first thing that happens is that the flame (or electronic coil) adds energy to the water, which results in the water gradually increasing in temperature. The water does not immediately begin to boil. This is adding sensible heat.

However, if you were to keep a thermometer in the water, you would notice that at 212°F (as long as you are at sea level) the water would be boiling but would never achieve a higher temperature. Even though the flame is still lit and energy is still being added to the water, the temperature does not change. This is latent heat, which is being added to cause the phase change and not a temperature change. The water, unless contained and pressurized, will never reach a temperature above 212 °F.

A steam boiler system at the most basic level can be considered as a loop. Ideally, there would be no water lost from the loop but that is highly dependent on the exact application. Because of this self-contained setup, steam is a very efficient energy carrier, it’s easy to produce and control, and it’s a safe option for many uses.

In the loop, there are the following major components:

• The feedwater system that collects, preheats, and pre-treats the water to prepare it for being introduced into the boiler.
• The steam boiler with a burner, which acts as a large heat exchanger to capture the heat from combustion and transfer it into the water inside the boiler. Pressurized steam is created at the desired pressure/temperature from the steam boiler.
• The steam delivery piping carries the pressurized steam from the steam boiler to where it is required for use. The pipework utilizes many smaller components such as stop valves, control valves, steam traps, and other fittings to properly control the steam.
• The point of use varies based on the intended use but typically the steam is used in some sort of heat exchanger and is condensed which releases the stored latent energy and transfers it into the product, substance, or environment to be heated. The condensed steam is then collected and returned to the feedwater system to again be prepared for reentry into the boiler.

The importance of steam in the boiler room cannot be understated as it is the lifeblood of many facilities in operation today. Since steam is the gaseous form of water, is intrinsically safe (not a chemical hazard) and is a very efficient and cost effective energy carrier, no matter what it’s needed for. Steam is relied upon to safely provide the energy source for many institutions, facilities, production lines, hospitalities, and industries.

Even outside of individual uses, steam is an important industry. A study by the ACEEE revealed that 42% of fossil fuel consumption in the chemical production industry and 23% in the petroleum refining industry is devoted to steam production.

Since steam can play such a key role in daily operations, there are a few things to consider when looking at steam boiler systems. Important considerations include:

• Heat Load Required: Typically measured in Btu/hr
• Steam Type: Saturated vs superheated
• Steam Pressure Required: For saturated steam, steam pressure and steam temperature are directly related. If you know one, you can look at a steam table to get the other, typically just steam pressure is specified.
• Steam Temperature Required: This is only applicable with superheated steam, which is the process of pushing the steam past the saturation curve, allowing the steam temperature to increase without simultaneously increasing the pressure.
• Steam Usage: The expected usage of the steam is vital to know as this is the largest contributor to determining the required size of the boiler.

• Condensate Return: The expected amount of condensate being returned is vital to know, as the system will look a little different if there is no condensate being returned, and the boiler will be fed by 100% make-up water from a water source.

As we noted above, steam is an important commodity for many industries and facilities. Steam boilers have a high impact on capital expenditure for procurement and installation. Because of this, redundancy is often limited in permanent boiler rooms. Steam boiler maintenance is often postponed or neglected which results in a potential unscheduled downtime.

When looking into rental boilers to keep up steam production, there’s a few things you’ll want to look for. Make sure you know what type of steam is required in your system, what pressure and temperature of steam is required, and what flow is required. That way, you’ll get a rental that fits in seamlessly with your system.