Frequently Asked Questions (FAQ)

The information on this page is intended to answer the most frequently asked questions about Zeeco, the industries we serve, and the products, services, and support we provide. Simply click on any question listed below to reveal the answer.

Can’t find the question or answer you’re looking for? Enter your question into the FAQ Inquiry form listed on this page.

For immediate needs and inquiries, speak directly with a combustion expert by calling +1 918 258 8551 or emailing


What is Zeeco?

Headquartered in Broken Arrow, Oklahoma, USA, Zeeco, Inc. is the global leader in advanced combustion and environmental systems for the refining, gas processing, production, petrochemical, LNG, power, pharmaceutical, marine and offshore, and biogas industries. For more than 40 years, Zeeco has engineered and manufactured ultra-low NOx burners, gas and liquid flaring systems, thermal oxidizers, equipment rentals, and parts and service. Zeeco also offers an array of vapor control products, including vapor recovery units (VRUs), vapor combustion units (VCUs), and flare gas recovery systems (FGRs). With thousands of installations worldwide, Zeeco has successfully executed more than 35,000 projects in more than 100 countries and offers aftermarket products and services for Zeeco equipment and other manufacturers. Zeeco also operates the world’s largest industrial-scale test facility and the first of its kind to be ISO-certified.

As a privately held company, combustion and environmental solutions are Zeeco’s focus, ensuring a high standard of excellence in our people, products, and processes. Our management team is comprised of the world’s leading combustion experts and our global experience provides innovative solutions and seamless project execution. Zeeco has more than 1,000 employees, 20 global locations, and six manufacturing facilities around the world to ensure we are always available for our customers.

What is combustion?

Simply put, combustion is the process of burning something. A combustion reaction occurs when suitable levels of fuel mix with oxygen for a duration long enough to burn, at a temperature high enough to sustain a chemical reaction.

Do combustion systems go against green initiatives?

No; in fact, combustion systems function to decrease the harmful impact of human activity on the environment. Zeeco’s equipment ensures that companies around the world comply with the most stringent environmental and safety regulations by increasing efficiency and decreasing output of carbon monoxide (CO) and other volatile organic compounds (VOCs), such as nitrogen oxides (NOx), sulfur oxides (SOx), and more.

How do I contact Zeeco?

To contact Zeeco’s Headquarters:
22151 East 91st Street, Broken Arrow, Oklahoma USA 74014
Phone: +1 918 258 8551 
Fax: +1 918 251 5519 

Click here to find contact information for any one of our 20+ locations worldwide.

Process Burners

What is a process burner and what are the components of a process burner?

A process burner is a device designed to inject, mix, and combust fuel with an oxidizer in a controlled manner within a process furnace. The two main components are the fuel injection and the combustion air injection.

What is a process burner used for?

Process burners operate in heaters and furnaces of refineries, petrochemical plants, and chemical process facilities to provide the necessary heat for a process while meeting emissions, flame dimensions, and performance criteria.

What methods can be used to reduce NOx emissions from process burner systems?

Several methods can be introduced individually, or in combination with one another, to reduce NOx emissions from process burner systems. Some examples are:

  • Staged air
  • Staged fuel
  • Internal flue gas recirculation
  • External flue gas recirculation
  • Lean premix combustion
  • Steam / Inert injection


What is a process burner pilot or igniter?

A process burner pilot – also known as a process burner igniter – is the component of a process burner used for the ignition of the combustion process. A pilot provides a stable source of combustion to the main burner from a separate fuel manifold.

What is a gas tip in a process burner?

A gas tip in a process burner is the orifice that meters the amount of fuel introduced to the furnace and controls where the fuel gas is mixed with an oxidizer and/or flue gas for combustion.

What is a burner tile?

A burner tile is the main orifice that meters the amount of combustion air introduced for combustion. In some process burner designs, the tile acts as the stability device to maintain a stable combustion reaction.

Should my pilot shield be glowing?

Yes. The pilot flame should stabilize internal to the pilot shield causing the shield to glow. The presence of a glowing pilot shield is an indication that the pilot is properly operating. Pilot shields are a consumable item and must be checked and replaced to maintain safe operation.

My pilot won’t light. What should I check?

Check pilot fuel gas composition, local to the pilot. Fuel piping may have been purged with inert prior to commissioning. High levels of inert can prevent proper pilot operation. Please note that attempting to purge a fuel gas line through the pilot orifice may take a considerable amount of time, as the orifice size is typically nominal (1/16'' diameter).

Check pilot fuel gas pressure, local to the pilot. Typically, operating pressure is from 7 to 12 psig (0.5 to 0.85 kg/cm2).

Check to see if the electronic components are wired, energized, and grounded properly.

Confirm the pilot configuration matches the supplied drawing.

What is CFD and how is it used?

CFD stands for Computational Fluid Dynamics. CFD is used to mathematically simulate real-world conditions for many industries. Zeeco typically focuses on the use of CFD for combustion-related simulation.


What is a flare pilot?

A pilot is a critical component of a flare system that ensures proper ignition of waste gas streams. Without a pilot, toxic gases could potentially vent to the atmosphere.

Can a flare pilot operate under extreme wind and rain conditions, such as a hurricane?

Yes. Temperature, inert flare purge, flame impingement, environmental conditions, and weather events are just a few of the various extremes that flare pilots are vulnerable to. The ZEECO HSLF flare pilot is proven to withstand hurricane-force winds of 170 mph (274 km/h) and rainfall amounts of 51.7 in/h (131.2 cm/h) at Zeeco's Combustion Research and Test Facility.

What is the EPA’s Petroleum Refinery Sector Rule (RSR)?

On December 1, 2015, the U.S. EPA declared a new rule for petroleum refineries following a lengthy Risk and Technology Review (RTR) process required by the 1990 Clean Air Act Amendment, referred to as Petroleum Refinery Sector Rule (RSR) (USEPA, 2015a). The rule imposes new requirements for monitoring flares, among other requirements, at most refineries in the U.S. The method specified in the Refinery Sector Rule for monitoring flare performance is a surrogate method with a more stringent definition of the surrogate parameter, i.e., changing Net Heating Value of the Vent Gas (NHVvg) to Net Heating Value of the Combustion Zone (NHVcz).

According to the EPA, successful implementation of the Petroleum Refinery Sector Rule (RSR) will reduce 5,200 tons of hazardous air pollutants (HAPs), and 50,000 tons of volatile organic compounds (VOCs) per year.

When is my facility required to be compliant with the EPA’s Petroleum Refinery Sector Rule (RSR)?

By January 30, 2019, all US refineries must be compliant with the EPA’s Refinery Sector Rule.

How can I ensure my facility is compliant with the EPA’s Petroleum Refinery Sector Rule?

A method that will comply with the EPA’s newest regulations and optimize flare performance requires a long-term, simplified, and accurate solution. Contact Zeeco to find out how the implementation of new technology utilized in Zeeco’s FlareGuardian™ flare monitoring system can generate real-time continuous monitoring to meet this demand and satisfy compliance with ease.

Should I use fuel gas or nitrogen to purge my flare system?

Both gasses are acceptable and compatible with Zeeco flares. Local environmental requirements and availability of nitrogen or fuel gas at site usually help determine the specific purge medium.

What is the difference between a gas (buoyancy) seal and a velocity seal?

Zeeco uses gas and velocity seals to keep air from flowing back into the flare header and to reduce the amount of required purge gas.

Gas (buoyancy) seals are separate, larger drums that utilize the difference between the buoyancy of air and the buoyancy of purge gas to seal the flare stack from air.

Velocity seals increase the velocity of purge gas within the seal so that air is pushed out and prevented from entering the system below the seal.

Compared to a gas seal, a velocity seal is less complex, requires less maintenance, and has a lesser impact on the stack design; however, a gas seal offers a greater reduction in purge gas requirements than a velocity seal.

What is the purpose of a liquid seal drum?

A liquid seal drum is used to create a water seal barrier between the flare stack and the upstream flare header. They can also be used to provide back pressure for staging systems, flare systems, and upstream equipment.

When should I use a liquid seal drum?

Zeeco recommends using a liquid seal drum when there is a possibility of oxygen in the gas stream or excessive flame propagation; or when the purge gas may not be reliable or adequate.

Can I increase the life expectancy of my flare tip by using a higher temperature metal or alloy than 310ss?

Generally, no. Flare tips most often fail because of distortion and cracking due to differential heating and cooling, not pure oxidation, or strength loss at temperature – attributes of some higher alloys.

What inlet flare gas pressure is required for a high-pressure flare system?

The required flare gas pressure for high pressure systems will depend on the application.

Gas production or processing applications typically require 50 to 80 psig (3.44738 to 5.51581 bar). In this case, Zeeco recommends a Varijet flare.

Petrochemical applications typically require 20 to 25 psig (1.37895 to 1.72369 bar). In this case, Zeeco recommends using a multipoint ground flare.

Which type of pilot ignition system is better or more reliable – Flame Front Generator or High Energy Ignition?

Both systems are very reliable; however, you may favor the advantages of one system over the other, depending on your preference.

The Flame Front Generator (FFG) is easier to access for maintenance, as all operating components are at grade, and it has the option of a manual ignitor at grade; however, it requires regular maintenance to ensure smooth operation.

The High Energy Ignition (HEI) is easier to operate and requires a less complex piping arrangement; however, components must be replaced over time, requiring a shutdown of the flare or retractable system.

What methods are available for smokeless assist?

There are many methods for smokeless assist; however, the four main smokeless assist options are air, steam, gas/fuel, and pressure.

Does my flare tip need continuous steam or air injection?

Yes, because assist medium injection components are near the flame, some minimum continuous flow of steam, air, or other assist media is typically required to protect the equipment from high temperatures.

Incinerators/Thermal Oxidizers

What is the difference between a thermal oxidizer, vapor combustor and enclosed flare?

Typically, a thermal oxidizer (TO) will be designed for continuous flows that do not change suddenly. It will typically take several hours to heat up the TO to its operating temperature. A TO will have a more finely tuned control system that controls both the incoming utility fuel gas (for keeping the vessel hot), waste gas (sometimes), and combustion/quench air. As such, it is recommended to follow NFPA 86 for safety standards. The unit is controlled on operating temperature and residence time to obtain VOC destruction efficiencies up to 99.9999%.

A vapor combustor unit (VCU) is typically designed for loading terminals or tank batteries with batch processes. A VCU can preheat within minutes to a determined temperature. Generally, a VCU has rudimentary controls for the combustion air and utility gas for preheat/enrichment. Streams are usually laden with oxygen and therefore the VCU will have anti-flashback tips in the design. The VCU is usually controlled by chamber temperature and can meet VOC destruction efficiencies up to 99.9%.

An enclosed ground flare (EGF) is a safety relief device that primarily is designed to combust rich/flammable waste gases with the intent to reduce noise and eliminate flame visibility. Combustion air is usually not controlled but drawn in through natural draft. An EGF usually does not control the temperature inside the unit and will achieve a minimum VOC destruction efficiency of 98%.

Vapor Control

Are there different types of Vapor Recovery Units (VRUs)?

Yes, there are two completely different pieces of engineered equipment for different applications that are both referred to as Vapor Recovery Units.

What is the difference between a mechanical and a carbon bed or adsorption type vapor recovery unit (VRU)?

A mechanical VRU is a compression package that is often used to recover tank vapors- gas formed when liquid in a storage tank is heated by outdoor temperatures and collects in a space at the top of the tank. Tank vapor is routed to a mechanical VRU, where it is then compressed and sent to a pipeline that delivers the gas to another part of the facility or to a sales pipeline.

A carbon bed or adsorption type VRU is essentially a large filtration system. These are used to handle vapors that are offset during liquid loading of trucks, railcars, marine vessels, or tanks. Vapor is routed to the VRU, where it passes through a bed of activated carbon that adsorbs hydrocarbons and allows clean air to exit the system. When the carbon bed reaches its maximum capacity, a vacuum pump can then extract the hydrocarbon vapor, send it to an absorber tower, and return the vapor back to a liquid state, so it can be put back into the tanks.

I work at a truck loading facility. On average, how much gas can I recover with a carbon bed vapor recovery unit (VRU)?

On average, a typical carbon bed VRU can recover 1 gallon of gasoline for every 1000 gallons of gasoline loaded onto a truck.

What is Flare Gas Recovery?

Flare Gas Recovery (FGR) is the process of recovering waste gases that would normally be flared, so they can be processed and used as fuel gas elsewhere in the facility.

If I have H2S in my gas stream, can I still use flare gas recovery?

Yes. A flare gas recovery system can compress gas containing H2S to a high pressure (typically 100 to 120 psig or 6.89476 to 8.27371 bar) and route it to an amine system that will remove all H2S from the gas stream. Once all H2S is removed, the remaining gas can be sent back to the facility and used as fuel.

What is a vapor combustor?

A vapor combustor unit (VCU) is typically designed for loading terminals or tank batteries with batch processes. A VCU can preheat within minutes to a determined temperature. Generally, a VCU has rudimentary controls for the combustion air and utility gas for preheat/enrichment. Streams are usually laden with oxygen and therefore the VCU will have anti-flashback tips in the design. The VCU is usually controlled by chamber and can meet VOC destruction efficiencies up to 99.9%.

How do I decide if I should use a vapor combustor unit (VCU) or a vapor recovery unit (VRU)?

It depends how high your flow rates are, the cost of the equipment, and how often your facility is operating. For example, marine loading facilities have higher flow rates, require larger, more expensive vapor recovery equipment, and experience a lot of downtime between shipments. Therefore, a marine loading facility will often use a vapor combustor unit because the cost of capital equipment is much lower than a large chemical VRU and the facility is less likely to recoup their costs by recovering vapor.

What do I do if my vapor recovery unit (VRU) needs maintenance?

Zeeco can deliver a temporary or rental vapor combustor unit (VCU) for your facility to use while your VRU is offline. See our Combustion Rentals section or call +19188937795 to find the right combustion rental for your application.


How long do I have to wait for Zeeco’s Aftermarket team to respond to an inquiry request?

Zeeco offers 24/7 response and our inventory of key components ensures the fastest delivery to your facility.

Where can I get spare parts for combustion equipment?

Our Aftermarket and Rapid Response teams will support all critical spare parts requests. Our team can also custom engineer and fabricate a solution for our competitor’s equipment to ensure reliable operation.

If I have another manufacturer’s equipment, can Zeeco provide spare parts?

Yes. We will replace Zeeco parts, or other OEM parts, in-kind or better.

Will I receive service/support after the sale?

Yes. Zeeco’s Aftermarket support team consists of technicians and service engineers strategically located across the globe to support all your equipment needs after the sale. Zeeco can even provide service and support for our competitor’s equipment.

Flare Rentals

What is a flame arrester?

A flame arrester is a passive device that is used to prevent a flashback from propagating further upstream in the flare header.

If I use a flame arrester, do I still need to send purge gas to the flare?

Essentially, a flame arrester only protects what is upstream of it and therefore does not protect the flare. For this reason, it is still recommended to use purge gas to ensure that oxygen will not ingress in through the flare tip.

Can I use a continuous sparking device instead of a pilot?

No. In the United States, according to EPA 40 CFR 60.18, "flares shall be operated with a flame present at all times” and, "the presence of a flare pilot flame shall be monitored using a thermocouple or any other equivalent device to detect the presence of a flame."

What are the standardized flare sizes and capacities of Zeeco’s rental fleet?

There are no standard flare sizes or capacities in Zeeco’s rental fleet. Essentially, we can add to or modify equipment within our fleet to meet any capacity you may need.

How large can a trailer mounted flare be before it needs guy wire support?

Zeeco’s trailer-mounted flares reach a maximum size of 60 ft (18.29 m) in height and 60 in (152.4 cm) in diameter. For larger rental flares, Zeeco provides skid-mounted/guy wire supported systems.

How do I determine which rental solution is right for me?

If you provide values to work with, Zeeco can advise on what options are available and work with you to find the optimal solution to meet your needs.

What information do I need to provide to size a flare?

To size a flare, we will need to know your available pressure, flare gas composition, and flow rate for each stream.

Do I need to design my flare for 100% smokeless capacity?

Typically, emergency and/or fire cases are not required to be smokeless for the entire capacity. Normally, the smokeless capacity will be sized for events that are not catastrophic (i.e. continuous, routine events, or portion of the overall capacity = 20 % max flow). This helps optimize design and lower costs.