The magic of steam

This series of articles will cover boilers and the most common type of steam system used in dry cleaning and laundry operations. Steam systems are designed to provide heat to finishing equipment, coils used to heat air and moisture, and heat for conditioning garments to facilitate wrinkle and spot removal.

 The essential parts of this system are as follows:

1. Boiler
2. Regulators
3. Steam piping
4. Equipment that uses steam
5. Steam traps
6. Return piping
7. Return Tank

Let’s begin with the essence of the steam system, which is WATER. As we all know, water can exist in three forms called states. The solid state is ice, the liquid state is water, and the gaseous state is steam. We will only be concentrating on water’s liquid and gaseous states. For our purposes, the most exciting and important qualities of water take place during the CHANGE OF STATE from liquid (water) to gas (steam) and then back again to water (condensate).

 We need to take a short course in energy measurement to understand these changes better. Let’s talk about the BTU. The BTU (British thermal unit) is a quantity of heat energy that will raise 1 pound of water 1 degree Fahrenheit. Water boils and turns to steam at 212 degrees F. (at sea level).

Let’s do a little arithmetic. Say you have a pot with a pound of water in it (a little over 15 oz.). It came out of the tap at 65 degrees F, and you want to boil it. You would subtract 65 from 212 and come up with 147 degrees difference. One would think that by adding 147 BTUs of heat energy to the water, you would turn that pound of water into steam. That would be correct except for a unique property of water called LATENT HEAT, and it’s that latent heat that makes steam systems so effective.

The heat energy added to raise the temperature of the pound of water from 65 F to 147 F is called SENSIBLE HEAT, and up to 212F, it works just fine, that indeed took 147 BTU’s worth of heat energy, and you’ve now reached 212F, the temperature at which the water changes state to steam. However, pushing that pound of water over that threshold and converting it into steam will require an addition of 976.57 more BTUs of heat energy. This 976.57 additional BTUs is the LATENT HEAT.

Over 6.4 times the amount of energy is required to change that pound of water at 212F to steam; the temperature of which is also 212F, then it took to heat that same pound of water from 65 to 212 F. Therein lies the “magic” of steam. Conversely, when that steam changes back into water, a process known as condensation (what boiler people call condensate), which we call return water, that 976.57 BTUs of latent heat energy is released to its surroundings. For example, heating the head of that legger your pressing pants on, or the fins of the coil used to heat the air during the drying cycle of your cleaning machine or, if you’re unlucky, providing you with an instant burn when you rest your elbow against a steam pipe. This latent heat effect allows heat energy to be stored in the form of steam and delivered to areas where it is needed via steam piping, releasing the heat energy to perform work by condensing back into the water. The water is then returned to the boiler return tank in the form of condensate.