(4) When you put volumes of measurement together with units of time, you have different
measures of flow rates. Some of the more common flow rates we will discuss throughout the course are:
gallons per minute, barrels per hour, and cubic feet per second.
b. Conversion of Flow Rates. Often, when working in the petroleum field, we are required to take a
flow rate that is given in one unit of measurement and convert it to another in order to solve a specific
problem. For example, we may be given a flow rate of gallons per minute but may have to convert that
unit of measurement to barrels per hour to satisfy a specific scenario. Luckily, most flow rate
conversions we are required to make have already been figured out mathematically and placed into FM
10-67-1, Appendix M. All you have to do is take the correction unit from FM 10-67-1 and multiply it
by your answer to convert the flow rate. However, there may be some cases in which a specific flow
rate is not listed in that reference manual. Therefore, we need to discuss how to perform these
conversions so that you can understand how they were calculated.
(1) Let us take an example and solve it together. Problem: You re operating a hose line
system, and you have a meter in-line. You have received 500 gallons over the past two minutes, but
your supervisor needs to know how many cubic feet per second it equals. To solve, you follow this
(a) The first requirement in this example is to convert the time down to a minute of
measurement. Since we are dealing with two minutes, divide by two to convert to a by-minute unit of
measurement. Thus, 500 gallons over two minutes convert to 250 gallons per minute.
(b) Using FM 10-67-1, Appendix M, note that converting from gallons per minute to
cubic feet per second requires multiplying your answer by 0.002228. By multiplying this factor by the
250 gallons per minute, we can determine that a flow rate of 250 gallons per minute is equal to 0.557
(2) Where do the conversions come from? As was previously stated, it is important to
understand where these conversion factors in FM 10-67-1 come from, since not all possible flow rates
are listed in that reference.
(a) All units of measurement are convertible, as long as you know their characteristics.
For example, most people do not know offhand that 1 hour equals 3,600 seconds. But, everyone knows
that 1 hour equals 60 minutes and 1 minute equals 60 seconds. By multiplying these two conversions
together, we can quickly determine that 1 hour equals 3,600 seconds.
(b) Looking at the previous example, the flow rate gallons per minute had to be
converted to cubic feet per second. How was this conversion derived? One of the first things to
remember is that whenever we have measurement units in a numerator or denominator, the only way to
cancel those units is to put them on the other side of the fraction.
(c) Starting with the flow rate gallons per minute, we can write that flow rate as a
fraction, gallons over minutes. This flow rate must be converted to cubic feet per second, or cubic feet
over seconds. Breaking these fractions down, we see that we are required to convert gallons to cubic
feet for the volume measurement, and minutes to seconds for the time measurement.
(d) Gallons can be converted to cubic feet by determining the number of gallons in a
cubic foot. That number is 7.48. So, if you start with your fraction gallons over minutes and multiply