Tank Oil / Water Interface Calculator
Uses bottom pressure, fluid densities, sensor elevation, and radar level to estimate the oil-water interface.
Inputs
ft
inches
Measure this for each tank. Enter the centerline elevation of the pressure sensing port above the inside bottom of the tank (for example 8, 9, 11, or 14 inches).
psi
Gauge pressure at the pressure sensing port.
SG
Example: 1.04 = density 4% greater than fresh water.
SG
ft
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Calculated Data
Pressure port elevation0.67 ft
All-water equivalent level16.77 ft
Oil-water interface from tank bottom12.65 ft
Water depth in tank12.65 ft
Oil layer thickness5.35 ft
Oil fraction of liquid column29.7%
Hydrostatic pressure check7.250 psi
Calculation valid.
Tank Profile
Tank top: 20.00′
Tank bottom: 0.00′
0′
1′
2′
3′
4′
5′
6′
7′
8′
9′
10′
11′
12′
13′
14′
15′
16′
17′
18′
19′
20′
WATER / BRINE
DEPTH 12.65′
DEPTH 12.65′
OIL
THICKNESS 5.35′
THICKNESS 5.35′
RADAR 18.00′
OIL/WATER 12.65′
PRESSURE EQ. 16.77′
PORT 8.0 in / 0.67′
Graphic Representation
Water / Brine
Oil
Radar Level
18.00 ft
actual liquid level
Pressure Equivalent
16.77 ft
assuming all water
Interface
12.65 ft
above tank bottom
Oil Layer
5.35 ft
estimated thickness
Note: Screenshots of the displayed tank details and calculated results may be captured and shared by text message, email, or other communication methods.
Calculation basis
Fresh water creates approximately 0.433 psi per vertical foot.
All-water equivalent level:
Interface solution:
where
Fresh water creates approximately 0.433 psi per vertical foot.
All-water equivalent level:
Leq = zs + P / (0.433 × SGw)Interface solution:
I = [P/0.433 + SGwzs − SGoL] / (SGw − SGo)where
I is interface elevation, zs is sensor elevation, and L is radar liquid level.