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Oil Gas Separator Sizing Calculator

Per API 12J with Souders-Brown Methodology

Size oil gas separators instantly with our free API 12J calculator. Design 2-phase & 3-phase vessels using proven Souders-Brown methodology with retention time analysis. No signup required - start sizing now!

Gas-Liquid Separator Sizing Calculator
Size 2-phase and 3-phase production separators using Souders-Brown equation for gas capacity and retention time for liquid capacity per API 12J and GPSA. Includes pressure-corrected K-factors, Stokes law droplet settling, vessel thickness per ASME VIII, and nozzle sizing per API RP 14E.

Flow Rates & Conditions

Gas flow at standard conditions (60°F, 14.7 psia)
Oil/condensate flow rate
same
Produced water (same units as oil)
psig
°F

Fluid Properties

lb/ft³
At operating conditions
cP
At operating temperature
lb/ft³
At operating conditions
cP
At operating temperature
lb/ft³
Typically 62.4 lb/ft³
μm
100-200 microns typical

Design Parameters

Affects K-factor for gas capacity
-
3-5 typical for horizontal
min
API 12J: 1-3 min for oil
-
1.15-1.25 for flow variations
in
4-6" for mesh pads

Calculated Sizing Outputs

Vessel Dimensions:
Diameter (ID), Seam-to-Seam Length (L_ss), Effective Length (L_eff), L/D Ratio.
Gas Capacity:
Gas Velocity (Vg), Terminal Velocity (Vt), K-Factor, Souders-Brown Limit.
Liquid Capacity:
Retention Time, Liquid Level Height, Surge Volume, Slenderness Ratio.

Design Formulas

Souders-Brown Equation (API 12J):

Vmax = K × √[(ρL - ρG) / ρG]

Maximum allowable gas velocity for droplet separation

Stokes Law (Droplet Settling):

Vd = g × dp² × (ρL - ρG) / (18 × μG)

Liquid Retention Volume:

Vreq = QL × tr × Fs

Shell Thickness (ASME VIII UG-27):

t = P×R / (S×E - 0.6×P) + CA

K-factor Selection:
K-factors vary by vessel orientation, mist eliminator type, and operating pressure. Values are automatically selected per GPSA and API 12J.

Typical Retention Times:
• Oil phase: 1-3 min (2-phase), 3-5 min (3-phase)
• Water phase: 3-5 min minimum

Design Guidelines

Separator Selection:
• Horizontal: High liquid rates, foam control, L/D = 3-5
• Vertical: High GOR (>10,000 scf/bbl), small footprint, L/D = 2-4

Mist Eliminator Selection:
• Wire Mesh: 10-100 μm removal, ΔP = 0.5-1 psi
• Vane Pack: 5-50 μm removal, ΔP = 1-2 psi, compact
• None: Design for 500+ μm droplet, conservative

Standard Diameters (API 12J):
12", 16", 20", 24", 30", 36", 42", 48", 60", 72", 84", 96"...

Frequently Asked Questions

How do you size an oil gas separator?

Oil gas separator sizing uses the Souders-Brown equation for diameter (based on droplet settling velocity) and retention time requirements for length. Per API 12J: diameter controls gas-liquid separation, length controls liquid residence time.

What is separator sizing calculator used for?

Separator sizing calculators determine vessel dimensions (diameter and length) for 2-phase and 3-phase oil-gas-water separators using API 12J standards, Souders-Brown methodology, and retention time analysis.

What retention time is required for oil separation?

Per API 12J: oil gravities above 35°API need 1 minute; 20-30°API need 1-2 minutes; 10-20°API need 2-4 minutes. Three-phase oil-water separation typically requires 3-30 minutes depending on fluid properties.

What is the difference between horizontal and vertical separators?

Horizontal separators provide longer residence time for better liquid separation and handle higher liquid rates. Vertical separators require less plot space and handle higher gas-to-liquid ratios more efficiently.

How to calculate separator diameter using Souders Brown equation?

Souders-Brown equation: Vg = K√[(ρL-ρG)/ρG], where Vg is gas velocity, K is design factor (0.1-0.35), ρL and ρG are liquid and gas densities. Diameter = √(4Q/(π×Vg)) where Q is gas flow rate.