Flare Knockout Drum Design

Learn More About Flare Knockout Drums

What is the Flare Knockout Drum?

A flare knockout drum is a vessel in the flare header that is designed to remove and accumulate the liquids that are condensed from the relief gases. It is the primary component in a pressure-relief arrangement in industries. It is also known as a vapour-liquid separator or knock-out pot and is available in vertical and horizontal configurations.

Flare Knockout Drumflare knock out drums

Flare Knockout Drum Sizing – The Parameters

The size and structure generally depend on the specifications required which is decided with the help of trial-and-error procedures. It is based on the settling theory which states that the liquid droplets will settle due to the force of gravity. The size is determined by the anticipated flow rate of liquid and vapour. Then, vessel diameter is calculated to ascertain the maximum allowable vapour velocity.

Flare Knockout Drum Design & Configuration

It needs to be precisely designed because the failure of the equipment may lead to economic loss, as well as safety and health risks. The structure of KO drums generally depends on the operating parameters and other plant conditions. Listed below are the design features:

  • Flare Knockout Drum SizingHorizontal Drums
    This is a preferred design when a large quantity of liquid is required to be stored. The standard length-to-diameter ratio of the horizontal drums ranges from 2 to 4, and it should be large enough to contain the liquids and allow them to settle. They are either designed to let vapours inside from one end and exit at the opposite top side or enter from the center and leave at each end of the vessel.
  • Vertical Drums
    They have vapour inlet nozzles placed radially, and the top of the drum’s vertical axis has the outlet nozzle. They are also available with a tangential spout. Here gravity causes the liquid to settle down at the bottom of the vessel, and the vapour travels upwards.
  • Tangential Knockout Drums
    These are vertical vessels with tangential nozzles. They are designed in a way to allow gases to enter and spin around a center tube that extends below the liquid inlet nozzle. The gases and liquids flow downwards, which causes droplets of liquid to fly off and gather on the sides of the drum and gather at the bottom. Once the vapours reach the bottom of the center tube, they change direction and flow upward and out of the nozzle.
  • Common Features
    All knockout drums include the vapour-liquid inlet line, the vapour area, and the liquid zone. They also have a liquid level gauge or an indicator, a control valve, a de-entrainment pad, and an intel distributor in some cases.

Functions of Flare Knockout Drums

Their roles and purposes are as follows:

  • The primary aim is to remove any water or oil from the relieved gases.
  • To knock out free liquid gas or water that enters a compressor when it is at the point of suction.
  • When it is at the fuel stack’s bottom, its function is to knock out the free liquid.
  • It also works to entrain crude oil into the furnace or the burner.

Choose Us for Vessel Fabrication Using Flare Knockout Drums

At Aspire Energy Resources Inc., we use our experience to come up with innovative ideas to help you with a project involving fabrication or repairs. We have a team of experts who are passionate about their work and strive to deliver the best results efficiently and effectively. For more information on flare knockout drums, please get in touch with us by calling 403-314-5422 or 1-800-993-9958. We will be happy to discuss your project and assist you with any questions you may have.

Request a Project Discussion: 403-314-5422 or

Contact Us Today
  • ABSA
  • ComplyWorks
  • COR
  • ISN