One day, way way back in history, there was a day when mankind decided to start measuring, recording, weighing, and dividing things. Whatever day that was, it was probably the very next day that someone else proposed a different unit of measure. We still haven’t sorted it all out. Length, distance, mass, pressure, temperature, volume, each of them multiple different standards depending on the country, or even industry, you’re in.
When it comes to the boiler room, though, everyone needs to be on the same page. Boilers need constant attention, and part of that means accurate measurement of operating conditions and parameters to operate efficiently and safely.
Let’s start with the most basic one you’ll probably encounter: Temperature.
Converting Celsius (C) to Fahrenheit (F).
C = (F-32) x 5/9
F = (C x 9/5) + 32
Next, when you’re dealing with pressure, it depends if you are looking at boiler pressure, or gas train pressure.
Boiler pressure is most often measured in psig (pounds per square inch), but sometimes is measured in bar, which is much more common in other parts of the world.
Bar = psi x 14.5038
psi = bar X 0.069
Gas pressure is often also measured in psig, but on lower pressure applications, the unit of inches of water-column is used. Other units less commonly used include mbar, kPa, or old school ounces per square inch.
PSI = Inches of water column X 0.0360912
Inches water column = PSI X 27.7
When you want to talk about boiler operations, you’re going to use units and measurements that relate to the amount of energy required to make a certain amount of steam. In our industry, you’ll often hear about boiler horsepower (BHP). One boiler horsepower is the amount of energy required to produce 34.5 pounds of steam in one hour at a pressure of 0 psig and a temperature of 212°F.
In the boiler industry, boiler capability is also talked about in terms of the number of British Thermal Units per hour. One British Thermal Unit is the amount of energy required to raise the temperature of one pound of water by 1°F at a pressure of 0 psig. So if you wanted to do that by one degree per hour, you’d need one BTU per hour.
In the boiler world, though, we’re talking about a lot more energy. So here’s how they relate:
BHP = BTU/hr x 33,475
While we’re talking about BTUs, let’s take a second to talk about another way they are used. While BTUs/time is a measurement of power, the BTU in the boiler world is also used to measure the energy content of specific types of fuel. In other words, natural gas, propane, and fuel oil can each deliver a specific amount of heat per a given quantity, and BTUs indicate how much usable heat each can provide.
If you know how much heat your boiler needs to keep operating at rate, then you know how much energy you’re going to need to extract from the fuel you’re pumping in every minute. This is where it’s helpful to be able to compare BTUs to CFH, or Cubic Feet Per Hour. That’s the literal amount of fuel (propane, natural gas, fuel oil) that goes into your burners every hour.
By comparing the flow rate of the fuel in CFH, and the heat you’re supposed to be getting in BTUs, compared to the amount of steam you’re actually getting, you can calculate how efficiently your boiler is operating.
Here’s what you need to know to do that:
1 cubic foot of propane contains the potential to generate 2,516 BTUs.
1 cubic foot of natural gas contains the potential to generate just over 1000 BTUs.
1 cubic foot of #2 heating oil, which is about 7 ½ gallons, contains the potential to generate over a million BTUs.
So to determine the Cubic Feet Per Hour, you simply divide the BTUs per hour of heat you need by the number of BTUs per Cubic Foot your fuel source can provide. As an example, if you’re using natural gas with a nice, even BTU of 1,000, and you need 10000 BTUs per hour, you’re going to have to have a flow rate of 10 cubic feet per hour.
If you’d like to know more about helpful formulas used in the boiler industry, check out our Formulas and Measurements blog. If you’d like to know even more, consider taking an online or in-person class at WARE’s Boiler University. Of course, we’re always here to help you with whatever you need, whether that’s some boiler expertise, boiler parts, service and maintenance, or a new or rental boiler. However we can help, just let us know.