Enclosed Ground Flare
Smokeless, Low-Noise Flaring with Enclosed Ground Flares
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Ground-level combustion with no visible flame and minimal site impact
CRA designs and builds enclosed ground flares for upstream oil and gas, gas gathering stations and process plants. The gas burns at grade inside a refractory-lined enclosure, so the flame stays out of sight and the noise and radiant heat at the fence stay low. Each flare is engineered for the site's own gas and flow range, and CRA has built the largest enclosed ground flare in India.
Destruction Efficiency
>98%
Visible Flame
Zero
Design
CFD-validated
Standard
API 537
What is an Enclosed Ground Flare?
An enclosed ground flare burns waste and relief gas at grade inside a refractory-lined chamber. The chamber hides the flame and holds in most of the heat and noise, which is why operators choose it for sites near communities and for any location where a visible flame is not acceptable.
How it works
Gas reaches the flare from the site's relief or waste gas header, normally through a knockout drum that removes liquids before the gas reaches the burners.
The gas is divided between groups of burners at the base of the enclosure. More burner groups come into service as the flow rises, which keeps combustion clean from small routine flows up to full relief.
Combustion air enters through dampers at the base of the enclosure, by natural draft or with air blowers, and mixes with the gas at the burners.
The flame burns inside the refractory-lined enclosure, where it cannot be seen from outside. The lining keeps the combustion zone hot enough for destruction efficiency above 98% and shields the surroundings from radiant heat.
Pilots and flame detection keep the flare ready to light. The burner management system supervises the burners through routine flaring, upsets and emergency relief.
Key Benefits
Combustion inside the enclosure is smokeless, with destruction efficiency above 98%.
The enclosure hides the flame and dampens combustion noise, which suits sites close to homes and other sensitive neighbours.
Staged burners keep combustion stable from small routine flows up to full emergency relief.
Each flare is designed around the site's own gas, flow range and limits, with CFD used to check the combustion design.
Designed to meet API 537, EPA 40 CFR 60.18, EU IED, and other international environmental standards.
Projects That Push Boundaries
LSTK delivery of three enclosed ground flares replacing atmospheric venting with enclosed combustion.
Single enclosed flare for HP and LP associated gas, designed to meet the site's radiation, noise and emission limits.
Low-flame, low-noise operation inside active plant boundaries, designed to API 521/537.
Single-package BMS, burner and enclosed flare engineered for a highly variable pyrolysis vapour stream.
Advanced combustion design maintaining stable operation on near-limit hydrocarbon concentrations.
The CRA Edge
Over 30 years in gas handling and flare engineering.
End-to-end design, R&D, and manufacturing under one roof for speed and quality.
ISO 9001 certified; designs aligned with ASME, API and CE
CFD and simulation-driven design with precise in-house fabrication.
Applications
Built to help you specify.
Sizing tools, decision guides, and technical references. Use them before, during, and after your evaluation.
Frequently Asked Questions
When should I choose an enclosed ground flare over an open elevated flare?
Choose an enclosed ground flare when noise, flame visibility and ground-level radiation must be kept to a minimum, which is typical near residential areas, sensitive environments and sites with strict community-impact requirements. Combustion takes place inside a refractory-lined enclosure, so there is no visible flame and the noise is dampened. It also suits sites where a steady or moderately variable flow allows compact sizing and a ground-level installation is preferred. An open elevated flare remains the right choice for very high-flow emergency relief where elevation is needed for heat dispersion. CRA is a major oil and gas enclosed ground flare manufacturer and built the largest enclosed ground flare in India.
What noise and visibility levels can an enclosed ground flare achieve?
An enclosed ground flare is designed for the noise limit at the site boundary and shows no visible flame in normal operation. The refractory-lined chamber contains the flame, and the exhaust leaves through the top of the enclosure without a visible glow. Staged burners lower the intensity of each burner, the lining absorbs radiant heat and dampens combustion noise, and acoustic treatment on the air inlets can reduce intake noise further. CRA carries out dispersion and radiation studies to set the enclosure height and layout against the site limits.
What destruction efficiency does an enclosed ground flare deliver?
An enclosed ground flare from CRA is designed for destruction efficiency above 98% on hydrocarbons, VOCs and most waste gas streams, in line with API 537 and EPA 40 CFR 60.18. The enclosure helps because it holds the combustion temperature steady and shields the flame from wind. The chamber is sized for the residence time needed for full oxidation, and the staged burners stay stable across the turndown range. Where a permit calls for a higher destruction efficiency, a thermal oxidiser is usually the better choice, and CRA builds both.
Which regulations and standards apply to enclosed ground flares?
Enclosed ground flares are designed to API 537 for flare design, EPA 40 CFR 60.18 for general control device requirements and the EU Industrial Emissions Directive (IED) for European installations, with local environmental and noise regulations adding site-specific limits. The design basis covers pilot flame monitoring with assured ignition, net heating value above the regulatory minimum at the combustion zone, provision for continuous emissions monitoring of CO, NOx and SO₂ where the permit requires it, and the noise limit at the property boundary. CRA is ISO 9001 certified through TÜV NORD, and its enclosed flare designs are aligned with API, ASME and CE practice.
How much space does an enclosed ground flare need?
The footprint of an enclosed ground flare depends on the design flow, and the approach piping, concrete pad and foundations add to it. Smaller units are supplied pre-fabricated and skid-mounted, which cuts site work to positioning, piping and electrical connection. Larger units are shipped in sections and erected on site. CRA sizes the enclosure, burners and air inlets for the gas flow and composition, and checks the layout against the site's radiation and dispersion requirements.