Today we’ll define the units which are the most commonly used in the Imperial System around the fire protection industry.
Note that sometimes, the unit in the Imperial System and the Metric System is the same. This is the case, for example, for the rotational speed of a pump, expressed in rounds per minute.
For most generic measurements,
For fire pumps,
For water supplies,
For sprinkler systems,
For fire alarm systems,
For gas protection systems,
For smoke control and performance-based designs,
To end with a little history.
Where does the difference between US gallon and Imperial gallon come from?
Before the 19th century, the definition of the gallon was depending on the country where the measurement was made and what was measured.
In the 19th century, two definitions became popular: the wine gallon defined as 231 cubic inches and the beer gallon defined as 282 cubic inches. This last value was further redefined as 277.42 cubic inches and was based on the volume of 10 pounds of water at 62 degrees Fahrenheit. This unit measurement was adopted by Great Britain in 1824.
But at that time, the US was using the wine gallons which had been defined as the volume of a cylinder with a diameter of 7 inches and a length of 6 inches. It never changed since then.
The difference in the units is coming from the fact that British preferred drinking beer while American preferred drinking wine.
For Franck Orset, I’m Jeff Kelm, this is MeyerFire University