The Physics of Greeley’s

The October issue of Hixson’s From Experience newsletter looked at the use of Greeley’s Formula for estimating pipe leak losses.  As you read the issue, you may recognize the similarities between Greeley’s Formula and the established valve formula for calculating valve flow (Q) using the Valve Flow Coefficient (Cv), Specific Gravity (SG) and Pressure (P).

For example, Cv uses pressure to calculate flow using the following formula:

Where,
Q = Flow, GPM
SG = Specific Gravity of the Fluid
ΔP = Pressure drop, psi

Greeley’s Formula, however, replaces the Cv with an empirically derived coefficient based on the nature of each kind of leak, using an estimated leak cross-sectional area and the pressure of the fluid in the pipe to calculate the flow rate.

Since the pressure through a leak is dropping to atmospheric pressure, the ΔP in the above formula can be substituted for just the pressure in the pipe. Applying this and solving for Q results in:

To read more about Greeley’s Formula, read the October issue of From Experience.

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