How to Check if a Horizontal Pipe Carrying Liquid is Full

In this post I want to share how to check if a horizontal pipe carrying liquid is full or partially full. We can use the following criteria to check:

• The pipe is full if: Q/d⁵ ≥ 10.2
• The pipe is partially full if: Q/d⁵ < 10.2

For partially full pipe, we need to do partially full flow analysis as follows.

x = ln (Q/d^2.5)

Then we calculate height of liquid in the pipe using the following equation:

H/D = 0.446 + 0.272x + 0.0397x² – 0.0153x³ – 0.003575x⁴

Equivalent diameter (D_e) is calculated by the following equation:

D_e/D = -0.01130 + 3.040 (H/D) – 3.461 (H/D)² + 4.108 (H/D)³ – 2.638 (H/D)⁴

Where:

D = pipe diameter, ft

D_e = equivalent diameter, ft

H = height of liquid in the pipe, ft

Q = flow rate, gpm

d = pipe diameter, in

q = flow rate, ft/s

u = velocity, ft/s

D_e is substituted for D in subsequent flow analysis.

I made a simple spreadsheet to check pipe carrying liquid is full or partially full, what the liquid height is, and pipe equivalent diameter. Please check and download if you find this useful.

Download: calculation of pipe carrying liquid is full or partially full.

Reference:

Branan, Carl, Rules of Thumbs for Chemical Engineers, 2005, Gulf Professional Publishing.