Flare System: Types, Segregation, Tips, Purge System and More (2023)

Table of contents:

  • 1. Types of Flare
  • 2. Segregation of Flares
  • 3. Flare Knock-Out Drum
  • 4. Flare KOD Liquid Removal
  • 5. Flare KOD sizing depends on two aspects
  • 6. Liquid Seal Drum
  • 7. Purge reduction seals
  • 8. Flare Purge system
  • 9. Flare stack
  • 10. Flare Structure
  • 11. Flare Tip
  • 12. Ringlemann Chart
  • 13. Pilot burner
  • 14. Pilot Ignition
  • 15. Other Accessories

Flaring is defined as a process of controlled burning of exhaust gases which generates heat and noise. Flaring is a common practice in oil/gas exploration, production and processing operations. A flare system consists of a flare stack and pipes that feed gas to the stack. The type and amount of gas or liquids in the flare stack governs the sizing & brightness of the flare.

There are many function & reason for flaring, few reasons for flaring are:

  1. During well production testing after drilling is completed
  2. For safety and during emergencies and maintenance
  3. For managing gas during compression and processing
  4. Flaring at well sites to recover oil

1. Types of Flare

  1. Elevated Flare
  2. Ground Flare
    • Enclosed Flare
    • Open Flare

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Elevated Flare

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Enclosed Flare

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Open Flare

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(Video) Introduction to Flare & Relief System Design, Eng. Wael Bakr

Typical Flare System with Elevated Flare

2. Segregation of Flares

  1. Service
    • Acid gas flare
    • Cold dry flare
    • Warm wet flare
  1. Pressure
    • Atmospheric
    • Low pressure
    • High pressure

3. Flare Knock-Out Drum

    1. Objective
      • Separate bulk liquid from gas
      • Limit liquid droplet size entrained with gas to the flare
      • Provide adequate residence time for liquid
    2. Sizing basis
      • Based on API 521
      • Separation of liquid droplet size of 300-600 microns considering the design case for the flare
      • 20-30 minutes of liquid hold-up time based on a relief case that results in maximum liquid
      • No internals to facilitate separation
      • Many orientations / options possible, horizontal KODs most preferred

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Typical Inlet/Outlet for Flare KO Drum

    1. Flare Knock-Out Drum Elevation
      • KO drum elevation decides pipe rack elevation based on 1:500 slope of main flare header
    • KO drum elevation determined by pump NPSH requirement
    • To reduce pipe rack elevation options are
    • Reduce KOD elevation (option 1)
      • Use vertical can pump
      • Locate pump within pit
      • Locate KO drum within pit
    • Use intermediate KO drums (option 2)

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Flare KO Drum elevation arrangement (Option 1)

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Flare KO Drum elevation arrangement (Option 2)

4. Flare KOD Liquid Removal

Remove liquid from flare KOD after relief to avoid overfill during future relief event

  1. Options
    • Draining to evaporation pond or closed drain drums
    • Liquid removal by flare KOD pumps
    • Heater to be installed in KOD where freezing, pour point issues exist
    • Rate of liquid removal to consider frequency and amount of liquid release
    • High level in flare KOD to be considered for plant shutdown
  2. Sizing of Flare KOD

    Flare System: Types, Segregation, Tips, Purge System and More (9)

    Flare KO Drum

    (Video) Safety Lore No 3 flare systems

    • LLLL shall be sufficiently high to avoid any sludge deposition impacting LT nozzle (150 mm in above figure not correct, consider 300 mm minimum for services which are not clean).
    • LLLL shall be minimum 700-300 in case flare drum electrical heaters need to be installed.
    • LLLL Level at which pump trips.
    • LLL Level at which both pumps stops
    • HLL Level at which first pump starts
    • HHLL Level at which second pump starts
    • HHHLL Level at which entire plant goes into pressurized trip.

5. Flare KOD sizing depends on two aspects

  • Liquid Hold up requirement during a major liquid or two phase release.
  • Sufficient distance shall be available between inlet device bottom and HHHLL. It is possible to have manually initiated depressurization even after HHHLLL. Any possible liquid shall be accommodated above HHHLL.
  • Distance between HLL and HHHLL shall be designed to accommodate maximum liquid release scenario(?). Some standards this distance is between HHLL and HHHLL.
  • Residence time required for drop of liquid particles of 300-600 micron size.
  • Liquid particles separate
    • When the residence time of the vapor or gas is equal to or greater then the time required to travel the available vertical height at the dropout velocity of the liquid particles and
    • When the gas velocity is sufficiently low to permit the liquid dropout to fall. This vertical height is usually taken as the distance from the maximum liquid level.
    • Flare System: Types, Segregation, Tips, Purge System and More (10)

      Flare System: Types, Segregation, Tips, Purge System and More (11)

6. Liquid Seal Drum

  1. Objective
    • Prevent flashback from flare tip back to flare headers
    • Avoid air ingress into flare system during sudden temperature changes leading to condensation and maintain positive system pressure
  2. Use
    • Used in flare gas recovery systems
    • Staged flaring between enclosed flare and full size emergency flare
  3. Design specifications
    • Water as liquid sealing fluid not recommended for extremely cold releases; water-glycol mixtures of sufficient concentration used instead

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Liquid Seal Drum

7. Purge reduction seals

  1. Objective
    • Prevent air infiltration into flare system at low flow rates
    • Reduce amount of continuous purge gas injection into flare stack
  2. Design options
    • Buoyancy seal (molecular / density seal)
    • Velocity seal (fluidic seal)

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Purge Reduction Seal

8. Flare Purge system

  1. Objective
    • Prevent air infiltration into flare system at low flow rates
    • Prevent vacuum formation in flare headers and system following steaming or large relief event
  2. Design specification
    • Continuous purge rate with velocity in stack
      • 1-5 fps : without molecular seal
      • 01 : with molecular seal
      • 02-0.04: with velocity seal
    • Approximate purge flow rate can be calculated using section of API 521.

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Flare P&ID

9. Flare stack

    1. Objective
      • Combustion of relief gases at elevation to minimize radiation exposure to personnel/ equipment/ structure
      • Ensure adequate dispersion of un-burnt hydrocarbons and toxic components

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Flare protection

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  1. Design considerations
    • Radiation: Limit radiation, either continuous and peak, on off-site properties and persons, equipment, buildings and personnel on the installation. Applicable to impacted area, restricted area and equipment lay-out.
    • Flammable gas: Avoid ignition of a flammable gas cloud released from a cold vent or in case of flare flame out.
    • Toxic hazards: (Mainly for H2S and SO2, but not limited to) limit the risk of a toxic gas cloud to reach off-site population, provide means of alarm and adequate protection to personnel present in the restricted area.
    • Noise: Limit both continuous and peak noise
    • Stack height is determined by HSE group based on permissible radiation level as per project philosophy or API 521.
    • Taller stack will result in smaller sterile zone.
    • Locate process plant upwind of flare.

10. Flare Structure

  • Self supported flare stack
  • Guy wired supported flare stack
  • Derrick supported flare stack
  • More than one flare may be supported on the same structure

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Flare Stack Support

11. Flare Tip

  • Produce desired destruction/combustion efficiency of maximum specified relief gas
  • Establish and maintain proper ignition
    • Pilot gas /Pilot burners/ Ignition system
  • Ensure stable combustion
    • Windshield
    • Retention rings
  • Result in smokeless operation at normal continuous flows or at100% flows
    • Steam
    • Air (high pressure or low pressure)
    • High pressure water
    • No external medium, maintain high pressure at tip by staging

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Flare Tip

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Flare tip

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Flare Tip: Velocity Seal (top view)

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  • Based on velocity of gas exit from tip, flare tips are considered as sonic and subsonic (pipe flare) type. This is the term used by process designer for high pressure flares and low pressure flares.
  • General stack pressure drops are as given below.
    • Sonic flare – 2 to 4 bar
    • Subsonic flare – 0.2-0.5 bar
  • Open Pipe flare tips: These are used for combustion of gases that do not produce smoke, gases with a low heating value, or for installations where smokeless combustion of heavy hydrocarbons is not required. These flare tips are one of the lower capital cost options for safe disposal of waste gases. In general these kind of flares have tips with very low pressure drop.
    • Open pipe flare tips with steam injection: Steam injection is provided reduce the smoke formation.
    • Open pipe flare tip with high pressure gas injection: This will increase the turbulence at flare tip and reduce the smoke formation. Fuel gas can be generally used as assist gas. Fuel gas injection can be either continuous or initiated manually based on monitoring of flare tip.
  • Air assisted flare tip: When smokeless flaring is desired and neither steam nor assist gas is available, blowers can be used to inject combustion air directly into the waste gas stream as it exits the flare tip. Combustion efficiency of flared gas is increased by installing air blower which will reduce smoke formation.
  • Multiple nozzle type flares: They are used where high flare gas pressures are available (1 barg and up) and where it is preferred to have some smokeless burning capability and also lower radiation levels. These kinds of flares are used for HP flare application. They have good combustion efficiency and less chances of smoke formation.
  • Coanda flare tip: The Coanda effect is a gas-adhesion principle that dramatically enhances the combustion process, resulting in maximum destruction of waste gases. Coanda Effect occurs when gas is passed over and adheres to a carefully profiled, curved surface, creating a near vacuum that pulls in substantial amounts of air. The air turbulently mixes with the gas flow, resulting in high-efficiency combustion.

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Multi Nozzle Flare

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Flare System: Types, Segregation, Tips, Purge System and More (24)

Coanda Flare

12. Ringlemann Chart

  • A series of charts, numbered 0 to 5, that simulate various smoke densities by presenting different percentages of black.
  • Ringelmann No. 0 is clear smoke
  • Ringelmann No. 5 is 100 percent black.
  • Ringelmann No. 1 is equivalent to 20 percent black

Flare System: Types, Segregation, Tips, Purge System and More (25)

Ringleman Chart

13. Pilot Burner

  1. Objective
    • Provide flame for reliable ignition of main flare gas at all times
  2. Design specifications
      • Pilot system to comply with API 537
    Minimum number of pilotsFlare burner outer diameter, DN
    1 (2 for toxic gas)Up to 200
    2>200 to 600
    3>600 to 1050
    4>1050 to 1500
    To be agreed with purchaser>1500
    • Pilots designed to remain lit and capable of being relit at wind speeds up to 160 km/h under dry conditions

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Pilot gas line

14. Pilot Ignition

    1. High Energy Ignition (HEI)
      • Electrode capable of high energy or high voltage discharge near pilot tip
      • Does not require propagation of a flame front as in FFG system
      • Does not require compressed air, self aspirating pilots
      • Simple and easy to use and automate, require little training or maintenance. Re-ignition takes few seconds
      • Shutdown of flare system required for maintenance
      • Back up FFG ignition (when using HEI) may be considered for
        • Very tall flares that are difficult to access
        • Flare systems that can be off line only once in more than 3-5 years
        • Offshore platforms in corrosive and salt environments

Flare System: Types, Segregation, Tips, Purge System and More (27)

Electrical Ignition Panel

  1. Flame Front Generator (FFG)
    • Ignition line from panel to flare pilot filled with flammable fuel gas- air mixture and spark introduced. Mixtures ignited and flame front travels through piping to ignite pilot at flare tip
    • FFG panel located at grade
    • Panel operated manually or automated to reignite of pilot flame out detection. Re-ignition can take several minutes
    • Moisture accumulation can lead to corrosion, flame extinguishment Ignition lines to be heat traced

Flare System: Types, Segregation, Tips, Purge System and More (28)

FFG Panel

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15. Other Accessories

  • Flow measurement
    • Monitoring relief devices leaks during normal operation
    • Assess flaring of gases due to pressure control operations
    • Note relief flows for assessing flare system adequacy checks and potential for flare gas recovery
    • Non-intrusive ultrasonic flow meters with wide range and no pressure drop is preferred
  • Smokeless flaring : medium control
    • Proper steam or air control is required
      • By measuring gas being flared and adjusting steam rate / blower capacity
      • Detection smoke using infra-red analyzers
  • Aircraft Warning Lights
    • Required when flare heights exceed 61m or when site is close to airport
    • Type and number based on regulations


What are the types of flare? ›

There are three basic types of flare, namely the handheld flare, the parachute or rocket flare and the smoke canister. The handheld flare is, as the name suggests, held by the user and burns fast and bright for approximately 60 seconds.

How many types of flares are there? ›

Flare types

Flares are classified into two common types: elevated and ground flares. Elevated flares are the most widely used flare type in CPI sites. In elevated flares, the gases are combusted using flare headers that are located at a considerable height above the ground.

What is a flare tip? ›

Flare tips are used to burn off gases given off in chemical plants, refineries and LNG plants in an environmentally-friendly way. Since the eighties BUTTING has been producing flare tips ready for installation according to customer's requirements for the energy and environmental technology.

What is a flaring system? ›

• A Flare System is an arrangement of piping and specialised equipment that. collects hydrocarbon releases from relief valves, blowdown valves, pressure. control valves and manual vents and disposes of them by combustion at a. remote and safe location.

What are the two types of flaring? ›

Two types of flaring tools are used to make flares on tubing: the impact type and the rolling type.

What are flares called? ›

A flare, also sometimes called a fusée, fusee, or bengala in some Latin-speaking countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, or defensive countermeasures in civilian and military applications.

What is flare used for? ›

What are flares? Flares are important safety devices used in refineries and petrochemical facilities. They safely burn excess hydrocarbon gases which cannot be recovered or recycled.

What is the range of a flare? ›

Handheld flares

Flares like this are typically visible up to about 5km (3 miles) away for anything from 30 seconds to several minutes. Since smoke doesn't generate light, smoke flares are useful only in daylight.

What is the life span of 3 types of flares? ›

Flares have a life span of 3 years and must be replaced before they expire. The expiry date is printed on the flare.
Flare typeAt nightDuring the day
Red hand flare5 to 10 nautical milesAre red in colour and can be used during the day
1 more row
6 Jun 2022

What is purging in flare? ›

Flare purge gas means gas introduced between a flare header's water seal and the flare tip to prevent oxygen infiltration (backflow) into the flare tip. For a flare with no water seal, the function of flare purge gas is performed by flare sweep gas.

What is a flare device? ›

Flares are an effective device for signaling distress and showing your position - they're highly visible on the water and from the air. This article will tell you about the different types of flares, and how to store, use and dispose of them.

What is a dual tip flare? ›

Dual HP/LP flare can be used for both high and low flow and pressure ranges. The perk of having both HP and LP tips tied in together is sharing pilot burners, hence reducing the total number of pilot without affecting the tips performance. This dual flare tips are also integrated with one windshield.

What is the first step in flaring? ›

Flaring Steps

Step 1: Cut your copper or aluminum using a tube cutter to ensure a clean cut - hacksaws and other cutting tools can make for an uneven cut or burrs, which will compromise the flare. Step 2: Use a deburring tool or abrasive cloth to remove any burrs and debris in and around the pipe end.

What is co2 flaring? ›

Flaring is the process of burning excess natural gas at the production well using a dedicated flare to ignite the methane and other components in the gas, which can result in both methane and carbon dioxide emissions (CO2). Venting is the direct release of natural gas into the atmosphere, typically in small amounts.

How is flaring done? ›

The typical flare used in the oil and gas industry is composed of a boom or stack which collects the unwanted gases to be flared. At its tip is an air-assist mechanism which combines free air with the generated gases being burned to improve combustion efficiency.

What is single flare and double flare? ›

Single-flared plugs have a groove in the plug to hold the o-ring in place. A double flared plug has a flared end on both sides of the cylindrical piece of jewelry. This piercing requires the hole to be big enough for the flare to fit through, which is usually larger than your gauge size.

What is difference between flare and stack? ›

Difference Between a Vent Stack and a Flare Stack

The difference is that a flare stack is continuously lit on fire with a pilot flare whereas a vent stack is not. Now, that we are clear about the functions of the vent and flare stacks, as well as how they are different, learn about a few mandatory standards.

What is flaring process in HVAC? ›

The goal of the flaring process is to create a surface in the end of the tubing that exactly matches the preformed flare inside the flare nut. You want a smooth, round flare of sufficient size and length to completely match the inside surface of the flare nut.

What is example of flare? ›

A flare is a sudden burst of light. The flare of a lit match in the dark night is strangely beautiful. The flare of a flame in the dark is sudden and bright, and the flare of an idea or emotion is similarly intense.

What Colour are flares? ›

Handheld red flares

The hand-held red is a short range distress signal and is used during the day or at night when in sight of another vessel, a rescue helicopter or land.

What metal is used for flares? ›

Magnesium is the element that may use in flares and flashbulbs because it can burn with a bright, white light. It is an alkaline earth metal.

Why steam is used in flare? ›

Steam is used at the flare to aspirate air into the combustion zone, shape the flame of the flare, cool the tip of the flare and reduce noise. While steam can be fed to three parts of the flare (center steam, upper rim and inside tubes), they are typically regulated through a single control valve.

What is a closed flare system? ›

Enclosed Ground Flares

An Enclosed Ground Flare, also known as a thermal oxidizer or vapor combustor, is a combustion system that takes exhaust gases which are potentially toxic or flammable and converts them into less harmful vapors without using a stack.

What are the 5 distress signals? ›

The signals are internationally recognised and must only be used if you are in distress.
Distress signals
  • 'mayday, mayday, mayday' in emergencies only.
  • 'pan pan, pan pan, pan pan' for urgent messages that aren't emergencies.
  • SOS in Morse code (using marine radio or another signalling method).
6 Jun 2022

What are the 3 types of visual distress signals? ›

Visual distress signals include day signals that are visible in sunlight, night signals that are visible in the dark, and anytime signals that can be used both day and night. VDS are either pyrotechnic, which use smoke and flame, or non-pyrotechnic, which are non-combustible.

What are the 3 PyroTechnics on board the ship? ›

Different Types PyroTechnics Available Onboard Ships
  • Hand flare. A hand flare is a small cylindrical stick which when activated, produces an intense red smoke or light without an explosion. ...
  • Rocket parachute flare. ...
  • Buoyant smoke signals. ...
  • Line Throwing Appliances.
6 Jun 2019

Why do flares expire? ›

Flares never really expire:

They can go bad, they can rust or be damaged, but they don't really expire. (Highway flares — made of the same stuff as signal flares — have no expiration date.)

What do flare colors mean? ›

Color is one of the main distinctions in types of flares. White flares are for signaling in non-emergency circumstances -- say, for finishing a race -- and red flares are supposed to indicate an emergency. Red flares owe their distinctive color to the presence of strontium nitrate.

What do you mean by Purge? ›

Definition of purge

to rid of whatever is impure or undesirable; cleanse; purify. to rid, clear, or free (usually followed by of or from): to purge a political party of disloyal members. to clear of imputed guilt or ritual uncleanliness. to clear away or wipe out legally (an offense, accusation, etc.)

What is purge rate? ›

purge rate. Because of the wide explosive range of hydrogen/oxygen mixtures (hydrogen concentration from 4 to 75 vol. %), the probability of formation of flammable and explosive mixtures is higher when hydrogen-containing streams are discharged into the flare system than when hydrogen-free streams are discharged.

Why is purging necessary? ›

There are several main reasons for purging: Removing resident gases from a system before introduction of a new gas or gas mixture which may react. Removing impurities from a system delivering a pure gas or sensitive gas mixture. Removing dangerous or damaging gas from a system after use.

What is a pilot on a flare? ›

The pilot burner is essentially a robust premixed burner unit designed to provide a stable flame for igniting the waste gas exiting the flare tip and features three main components, the venturi or mixer, gas jet or orifice and the burner nozzle.

How many flares do I need? ›

Ensure you carry the required flares for your vessel and know how to use them. Many recreational vessels are required to carry two hand-held red distress flares and two hand-held orange smoke signal flares, of an approved type, when operating on coastal and enclosed waters.

What is a 2 3 shift flare? ›

When the computer did not turn the “B” solenoid off cleanly, it would not exhaust its oil fast enough and the 2-3 shift valve would move gradually instead of moving crisply from one position to the other. This allowed the 2-4 band to come off momentarily before the 3-4 clutch applied, resulting in a 2-3 flare.

What is a sonic flare tip? ›

Sonic flares are a unique type of high pressure flare tip. A sonic flare uses the flare gas pressure to eliminate smoke, lower flame radiation and shorten the flame length. Sonic flares can reduce capital costs with lower stack heights and a smaller flare header size.

When should we use double flare vs single flare? ›

All brake lines need to be double flared, due to the high hydraulic pressure. If your brakes leak or the hoses crack, it could prove to be fatal. Single flared lines are suitable for low-pressure lines in other applications, but not your vehicle's brakes.

What are the effects of flaring? ›

Flaring releases air pollutants such as carbon monoxide, carbon dioxide, volatile organic compounds, sulphur dioxide, polycyclic aromatic hydrocarbons, and particulate matter in the form of soot.

Why does flaring happen? ›

When natural gas is brought to the surface but cannot easily be used, it is burned for disposal or “flared.” Flaring mainly happens when gas is produced as a byproduct of oil extraction. If there is no infrastructure to put this “associated gas” to productive use, it is simply burned off.

How can we reduce flaring? ›

Best practice for reducing flaring includes preventing waste gas from being generated, recovering waste gas to sell it and injecting waste gas into oil and gas reservoirs. If waste gas cannot be recovered to be sold or injected into gas or oil reservoirs, it may be able to be used for generating electricity.

Can you flare h2s? ›

Flaring is also used to burn gases that would otherwise present a safety problem. It is common to flare natural gas that contains hydrogen sulfide (i.e., sour gas), in order to convert the highly toxic hydrogen sulfide gas into less toxic compounds.

How much gas is flared? ›

Annually, 140 billion cubic meters (BCM) of natural gas is flared worldwide.

What is gas flaring PDF? ›

Gas flaring is the combustion of associated gas. produced with crude oil or from gas fields [3]. The option to release gas to the atmosphere by flaring. and venting is an essential practice in oil and gas produc- tion, primarily for safety reasons.

What is a female flare? ›

Flare fittings are suitable for use in the plumbing and heating industries for gas, oil, air and water. They are applicable with aluminum, brass, copper and steel tubing. Flare fittings can be disassembled and reassembled many times with no effect on the seal.

What is the difference between flare and flair? ›

Flair is only used as a noun referring to a natural ability, an inclination toward something, or an attractive or stylish quality. Meanwhile, flare can be used as both a noun and verb. As a noun, it refers to fire or light, something that bursts outward (such as anger), or something that widens.

What is the function of flare? ›

What are flares? Flares are important safety devices used in refineries and petrochemical facilities. They safely burn excess hydrocarbon gases which cannot be recovered or recycled.

What is flare size? ›

The most common flare fitting standards in use today are the 45° SAE flare, the 37° JIC flare, and the 37° AN flare. SAE 45° flare connections are commonly used in automotive applications as well as for refrigeration and air conditioning.

What is a double flare used for? ›

The double flare is used for installations that require repeated tightening/untightening. The fitting moves against the folded over section causing that to wear and not the already thinned outer pipe wall. There is no difference between the pressure rating of single and double flares.

What is flare pipe end? ›

A flare fitting has a tapered end that fits into a flared piece of tubing and is secured in place with a sleeve and flare fitting (threaded nut) to produce a pressure-resistant, leak-tight seal.

What is an example of flair? ›

Flair is always a noun. It's often used to refer to a natural talent or to stylishness, especially in a certain area. For example: Kelly has a real flair for playing guitar.

What does flair stand for? ›

Fluid-attenuated inversion recovery (FLAIR) is an MRI sequence with an inversion recovery set to null fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid (CSF) effects on the image, so as to bring out the periventricular hyperintense lesions, such as multiple sclerosis (MS) plaques.

What is flashback in flare? ›

Flashback usually occurs when the flame propagates towards the upstream fresh gases at a speed higher than the incoming flow speed. From: Stabilization and Dynamic of Premixed Swirling Flames, 2020.


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