Two-phase separator

General Introduction

In case the processed gas flow is so insignificant that it is ignored, the separator is used for two liquid phases separating and it is called liquid/liquid separator. It surely is two-phase separator but the design and structure are basically the same with Three-phase separator, only gas outlet is canceled or combined with light-phase outlet.


Two-phase separator is also called gas-liquid separator. As its name suggests, it is used for separating gas and liquid in wet gas stream, or more generally the gas/liquid stream, when the complex liquid phase components are not required to be separated from each other. Since the stream conditions and required efficiency may vary widely, the Two-phase separator can be designed in many models and with different performances. For instance, a gas/liquid separator upstream of a gas compressor would need to be very efficient, whereas in other cases only bulk separation of the gas and liquid phases is required.

Gas/Liquid Two-phase separator is often used as a buffer/surge/accumulator tank/vessel. Different names show different parts of processed stream behavior and the application emphasis.

Sometimes the key structure or component may also be indicated on separator names, such as vane pack separator and coalesce separator.

Two Phase Separator Advantages:

1.Skid mounted for easy transportation;

2.Dual safety device: rupture disc and spring safety valve;
3.Equipped with automatic control system and integrated blocking manifold system for easy operation;
4.High automation and high measurement accuracy;
5.Clear curves of temperature, pressure and velocity;
6.Continuous operation from beginning to end;

7.ASME certified and meets international standards.

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How Does A Two-Phase Separator Work?

A two-phase separator, commonly used in oil and gas fields, works based on the principle of gravity separation to separate a mixture of gas and liquid into their respective phases. Here's how it typically operates:

Inlet: The mixture of gas and liquid enters the separator through an inlet pipe or manifold. This mixture may also contain solid particles, which may need to be separated out in some cases.

Primary Separation: Inside the separator, the mixture encounters a large vessel or chamber with a relatively low velocity. This allows gravity to act on the mixture, causing the gas to rise to the top while the liquid settles at the bottom due to differences in density. The separation efficiency is enhanced by various internal components, such as baffles, plates, or mesh pads, which help to increase the surface area and promote coalescence of the liquid droplets.

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Secondary Separation: After the initial separation, there may still be some mixing of gas and liquid phases. To further improve separation efficiency, some separators include secondary separation stages. These stages often involve additional chambers or internals designed to allow further settling and separation of the remaining gas and liquid phases.

Outlet: Once the separation process is complete, the separated gas and liquid phases are drawn out of the separator through separate outlets. The gas phase typically exits from the top of the separator, while the liquid phase is collected from the bottom. In some cases, there may be multiple outlets for different liquid phases or for specific purposes such as draining off water.

Overall, the efficiency of a two-phase separator depends on various factors including the design of the internals, the flow rates and characteristics of the incoming mixture, and the operating conditions such as temperature and pressure.

Vertical KO Drum

Two-phase separator is also often called knockout drum, KO Drum in short. The “knockout” suggests the free liquid droplets “knocked out” from continuous phase which carry them. For example, a low-pressure free-water KO Drum is so called because it`s designed to separate the free water from wet gas.

Vertical KO Drum is often used for bulk separation of gas and liquid. It has very low pressure drop and takes relatively small ground area to install. It is insensitive to fouling and foaming service.

It is often used to handle fluid with high gas/liquid flow ratio. 

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Horizontal KO Drum

Horizontal KO Drum is often used for demisting of gas where a high liquid handling capacity is required. Comparing with Vertical KO Drum, it takes larger ground area and is relatively sensitive to fouling, but gives better water removal efficiency and larger liquid capacity.

For Horizontal KO Drum, mist extractor is often necessary. If the mist extractor (also called as demister mat, mist trap, condensate trap, etc.) is equipped and considered important enough in the KO drum, it will also be called a Demister or Demister Drum.

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  • Including vertical and horizontal gas-liquid two-phase separator
  • Adopt advanced control system
  • Durable internals

Code & Standards

  • ASME Section VII, DIV 1
  • NACE MR0175
  • API 12J
  • UL, Exp
  • PED
  • CE
  • API 6A, API 6D
  • ANSI B31.3 Class M (H2S)


  • Exploration well testing
  • Extended well testing
  • Clean-ups and flowback operations chemical plant

Product Photo


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