Inline vs End-of-Line Flame Arresters: Which Is Better for Your Facility?

Industries that handle flammable gases or vapors, like oil and gas, chemical manufacturing, or biogas processing, rely on flame arresters to prevent explosions and keep people, equipment, and facilities safe. Not all flame arresters work the same way. The two main types, inline and end-of-line flame arresters, are each designed for specific uses and locations within a system.

Choosing between them can be the difference between safe operation and catastrophic failure. In this guide, we’ll explore the key differences, working principles, advantages, and ideal applications of inline and end-of-line flame arresters to help you make the best choice for your facility.

1. What Is a Flame Arrester?

A flame arrester is a safety device that lets gases or vapors move through a pipeline or vent, but stops flames from spreading by putting out the flame front. It acts as a passive explosion protection device and is used in systems that handle flammable gases, vapors, or liquids.

The core component of a flame arrester is the flame element, often a tightly wound stainless-steel crimped ribbon or mesh, which absorbs heat from a flame and cools the gases below their ignition temperature, extinguishing the flame.

Main Functions

▪ Stop flame propagation: Prevent an external flame from entering process equipment or a tank.

▪ Allow normal flow: Enable gases to vent or flow without obstruction under normal conditions.

▪ Protect equipment: Safeguard tanks, pipelines, and process systems from explosion damage.

6200 In-Line Deflagration Flame Arrester

2.Understanding the Two Main Types

Flame arresters are generally divided into inline and end-of-line types, depending on where they are installed in the process system.

For engineers who need a broader understanding of how these two arrester types interact with tank venting, pressure relief, and explosion-prevention hardware, you may also refer to the Comprehensive Tank Venting & Flame Control Guide, which explains how flame arresters fit into a complete protection architecture.

Type	Installation Location	Main Purpose	Typical Use
Inline Flame Arrester	Within a pipeline	Stops flame traveling in either direction	Between tanks, reactors, or process lines
End-of-Line Flame Arrester	At the outlet of a vent or tank	Stops external flame from entering	On storage tank vents or exhaust lines

3. Inline Flame Arrester Overview

An inline flame arrester, sometimes called a detonation or deflagration arrester, is placed inside a pipeline, usually between where flammable vapors start and where an ignition source might be. Its main job is to stop flames from moving through the piping system in both directions.

Working Principle

If a flame moves through a pipeline, the flame arrester’s element takes in the heat and spreads it into the metal around it. This cools down the flame and stops it from burning any further. Inline arresters are designed to handle different kinds of flame fronts, such as:

-Deflagration (subsonic flame front)

-Detonation (supersonic flame front)

Applications

▪ Fuel vapor return lines

▪ Biogas systems

▪ Chemical processing lines

▪ Vapor recovery units

Advantages

▪ Provides bidirectional protection

▪ Suitable for continuous gas flow

▪ Can handle higher pressure and temperature

Limitations

▪ Higher pressure drop

▪ Requires regular maintenance

▪ More expensive

4. End-of-Line Flame Arrester Overview

An end-of-line flame arrester is installed at the end of a vent, exhaust, or tank breathing line. It blocks outside flames or flashbacks from getting into the tank, but still lets gases escape safely.

Working Principle

If a flame or spark happens outside the vent, such as from lightning or welding nearby, the flame arrester’s element puts out the flame before it can enter the tank. During normal use, it lets vapor out freely to relieve pressure.

Applications

▪ Storage tank vents

▪ Gasoline or ethanol tanks

▪ Biogas digesters

▪ Vapor recovery vents

Advantages

▪ Low pressure drop and simple design

▪ Cost-effective and easy to install

▪ Requires minimal maintenance

Limitations

▪ Protection in one direction only

▪ Not for continuous flow systems

TYPE

APPLICATIONS

ADVANTAGES

LIMITATIONS

Inline Flame Arrester

-Fuel vapor return lines

-Biogas systems

-lChemical processing lines

-Vapor recovery units

√Provides bidirectional protection

√Suitable for continuous gas flow

√Can handle higher pressure and temperature

✘Higher pressure drop

✘Requires regular maintenance

✘More expensive

End-of-Line Flame Arreste

-Storage tank vents

-Gasoline or ethanol tanks

-Biogas digesters

-Vapor recovery vents

√Low pressure drop and simple design

√Cost-effective and easy to install

√Requires minimal maintenance

✘Protection in one direction only

✘Not for continuous flow systems

5. Key Differences Summary

Aspect	Inline Flame Arrester	End-of-Line Flame Arrester
Location	Installed within a pipeline	Installed at the end of a vent or outlet
Protection Direction	Both directions	From external flame only
Flow Type	Continuous or bidirectional flow	Venting or intermittent flow
Flame Type Protection	Deflagration and detonation	Deflagration only
Maintenance	More complex	Easier
Cost	Higher	Lower
Applications	Process pipelines, vapor return lines	Tank vents, exhaust outlets
Pressure Drop	Higher	Minimal
Installation Complexity	Requires engineering design	Simple to install

6. Choosing the Right Arrester

Choosing between inline and end-of-line flame arresters depends on a few important engineering and operational factors. Here are the main things to consider.

Key Factor	Inline flame arresters	End-of-line flame arresters
System Layout and Flow Direction	Protection within a piping system that transfers vapors or gases between units	Only protecting a tank vent or exhaust point
Type of Hazard (Deflagration vs. Detonation)	Deflagration or detonation	Only deflagration-slower flame propagation through a gas mixture
Operating Pressure and Temperature	Higher pressures and temperatures, often up to 300°C or more	Ambient or low-pressure systems
Maintenance and Accessibility	Installed within pipelines, require shut-downs or bypass lines for inspection and cleaning	Installed at open vent points
Cost and Budget Considerations	higher investment, but offer comprehensive protection for critical systems	More affordable, ideal for smaller tanks or vent systems

7. Compliance Standards

Flame arresters must meet international safety standards to ensure reliable performance under hazardous conditions. When choosing a model, verify that it complies with the following:

Common Standards

▪ ISO 16852: Flame arresters for general use

▪ API 2028: Flame arresters for tank vents in petroleum industries

▪ EN 12874: European standard for explosion prevention devices

▪ US Coast Guard / UL / FM Approvals: For marine or industrial use

▪ ATEX Certification: Required for use in explosive atmospheres (EU)

Performance Testing

Manufacturers test flame arresters in conditions that mimic explosions to make sure they can stop flames at certain pressures, temperatures, and gas types. Each product should have a model number, a flow direction arrow, and a certification mark on its nameplate.

8. Maintenance Best Practices

Regular maintenance helps flame arresters work well in an emergency. Skipping inspections can cause clogging, rust, or reduced performance.

Routine Maintenance Checklist

▪ Visual inspection: Check for dirt, corrosion, or blockages.

▪ Cleaning: Remove accumulated particles, oil, or debris.

▪ Element check: Inspect the flame element for damage or deformation.

▪ Gasket replacement: Ensure tight sealing to prevent leaks.

▪ Flow test: Verify there’s no excessive pressure drop.

Frequency

▪ End-of-line: Inspect every 6–12 months.

▪ Inline: Inspect every 3–6 months, depending on gas type and process conditions.

Warning Signs of Failure

▪ Increased pressure drop across the arrester

▪ Discoloration or corrosion of the flame element

▪ Abnormal noises or vibration in the system

▪ Visible damage after an ignition event

9. Installation Tips

Installing flame arresters correctly is just as important as choosing the right type. Here are some key tips:

▪ Inline Flame Arrester Installation：

1) Install as close as possible to the potential ignition source.

2) Follow the correct flow direction indicated by the arrow.

3) Use flanged or threaded connections rated for system pressure.

4) Avoid long pipe sections between the arrester and the ignition point.

5) Ensure easy access for removal and maintenance.

▪ End-of-Line Flame Arrester Installation：

1) Mount vertically on top of the vent or exhaust line.

2) Include a weather hood to prevent rain or debris entry.

3) Ensure unobstructed gas flow through the arrester.

4) Avoid placing too close to heat sources or open flames.

6500 In Line Unstable Detonation Flame Arrester

10. Case Studies: Comparing Performance in Real Applications

Scenario 1: Chemical Plant Vapor Line

A solvent recovery system operates with flammable vapor transfer between process vessels. Engineers installed inline detonation flame arresters at multiple points to isolate sections and prevent flame spread in case of ignition. The system operates safely even under pressure surges.

Scenario 2: Storage Tank Vent System

A petroleum storage tank requires atmospheric venting to relieve pressure buildup. Engineers installed end-of-line deflagration flame arresters on each vent. These units protect against external ignition from welding sparks or lightning strikes while allowing normal breathing.

Result:

Both systems met safety requirements. The inline model protected the inside of the system, while the end-of-line model guarded against outside threats. Using the right type in the right place improved both safety and cost-effectiveness.

11. Which Type Is Better?

There is no single answer for every situation. The best flame arrester depends on your process conditions. Here is a summary to help you decide:

If Your Facility Has...	Best Choice
Pipeline transferring flammable gases between units	Inline Flame Arrester
Storage tank or vessel with vent to atmosphere	End-of-Line Flame Arrester
Risk of detonation due to long pipelines	Inline Detonation Arrester
Simple venting under low pressure	End-of-Line Deflagration Arrester
Limited budget and space	End-of-Line
High hazard area with process interconnections	Inline

In most cases, facilities use both types together. End-of-line arresters are placed at vent points, and inline arresters are installed between process sections. This approach provides complete explosion protection.

12. Conclusion

Both inline and end-of-line flame arresters are essential components in explosion prevention systems.

▪ Inline flame arresters protect against internal flame propagation and are ideal for pipeline systems with continuous flow or multiple process connections.

▪ End-of-line flame arresters guard against external ignition sources at tank vents and are simple, cost-effective, and easy to maintain.

The right choice depends on your system layout, gas type, operating conditions, and safety standards. When in doubt, consult a qualified flame arrester manufacturer or safety engineer to ensure proper specification and compliance.

Final Takeaway

To achieve maximum protection:

▪ Conduct a hazard analysis to identify flame propagation risks.

▪ Choose the appropriate flame arrester type and rating.

▪ Follow installation and maintenance best practices.

▪ Always ensure certification compliance with international standards.

Investing in the right flame arrester is not just about meeting regulations. It helps save lives, protect assets, and keep your operations running smoothly. BASCO has focused on safety pressure relief products and solutions for over 20 years, with our own intellectual property and dozens of patents. If you have any questions or need help, please contact us anytime.