Flame Arrester

Flame Arrester Dimensions

Flame Arrester Explosion Group

Flame arresters are categorized and specified based on their ability to handle different types of flammable gases and vapors, which are grouped according to their explosion risk. These groups are known as explosion groups, and they play a critical role in the selection and design of flame arresters to ensure safe operation within specific environments. The explosion group classification helps in determining the appropriate flame arrester design that can effectively quench and arrest a flame from a specific type of flammable substance.

Explosion Group Reference Data

① Based on ISO 16852 Explosion group IIA1
② The Maximum Experimental Safe Gap (MESG) is defined as the largest gap between two adjoining sections of the internal chambers in a testing apparatus. This gap prevents the ignition of an external gas mixture when the internal gas mixture is ignited under specific conditions, across a joint length of 25 mm for any concentration of the tested gas or vapor in air. The MESG is a crucial characteristic of the specific gas mixture being tested, as outlined in the standard EN 1127-1:2011.

Selection of Explosion Group IIA (D) (*Substances in the explosion group I)

Selection of Explosion Group IIB1-IIB (C)

Selection of Explosion Group IIC (B)

Flame Arresters Requirements

#3 Corrosion Resistance 

• Salt Spray Corrosion Resistance:

  The salt spray corrosion test should be conducted using the method specified in Test 3, and the flame arrester core should not show obvious corrosion damage. After the test, the flame arrester’s explosion-proof functionality should be tested as specified in Test 6 and should be able to prevent fire. Flame arresters with a stainless steel core are exempt from this requirement.

• Sulfur Dioxide Corrosion Resistance:

  The salt spray corrosion test should be conducted using the method specified in Test 4, and the flame arrester core should not show obvious corrosion damage. After the test, the flame arrester’s explosion-proof functionality should be tested as specified in Test 6 and should be able to prevent fire. Flame arresters with a stainless steel core are exempt from this requirement.

#4 Strength

The strength test of the flame arrester casing should be conducted according to the method specified in Test 5, and the casing should not exhibit any leaks, cracks, or permanent deformation.

#5 Explosion-Proof Performance

Perform 13 times explosion-proof tests according to the method specified in Test 6, within no more than 3 days, and the flame arrester should be able to prevent fire each time.

#6  Burn Resistance

Conduct the burn resistance test according to the method specified in Test 7, and the flame arrester should withstand 1 hour of burning without any backfiring occurring during the test.

#7 Connection Type

The connection type of the flame arrester should be a flanged connection, complying with GB/T 9112, or other specific standards that the customer requires. The explosion-proof joint surface gap on the connected parts of the flame arrester casing should meet the requirements of GB 3836.2, or other specific standards that the customer requires.

#8 Pressure Loss and Vent Capacity

The fluid pressure loss of the flame arrester should not exceed the specifications listed in Table 1. The Vent Capacity Should not less than data inTable 2.

Flame Arrester Valve Testing Standard

Test Conditions

Unless otherwise specified, the tests outlined in this chapter should be conducted under normal atmospheric conditions, which are defined as follows:

a) Ambient temperature: 15°C to 35°C;

b) Relative humidity: 45% to 75%;

Test 6: Explosion Suppression Test

Test 7: Burn Resistance Test

Test 8: Pressure Loss and Vent Capacity Test

1. Test Device

The pressure loss and ventilation capacity test uses a fan to provide the air source, as shown in Figure 3. The inner diameter d of the test pipe should match the nominal diameter of the flame arrester, and the inner wall surface should be smooth and even. All connections in the system must be free from leaks.

Figure 3. Pressure Loss and Vent Capacity Test Device

2. Inlet Specifications:

The inlet end must have no obstructions within a distance of 1.5d from the center of the test pipe (inner diameter $d$).

3. Pressure Measurement:

Drill four evenly distributed pressure measurement holes with diameters ranging from ø2 mm to ø3 mm around the circumference of the same cross-section of the test pipe, perpendicular to the pipe wall. The surrounding area of these holes should be smooth and free of burrs. Weld short pipes to the outer wall at the static pressure holes for easier connection; the inner diameter of these short pipes should be at least twice the diameter of the measurement holes. Connect each of the four static pressure holes individually to a pressure measurement device. The arithmetic mean of the four static pressure readings will be the average static pressure at that cross-section.

4. Collector Specifications:

The collector can be either arc-shaped or hammer-shaped, with the dimensions and shape shown in Figure 4. The inner wall surface must be smooth, with a surface roughness $Ra$ value not exceeding 3.2 µm.

Figure 4. The Dimensions of Collector

5. Flow Straighteners:

The dimensions of the inlet and outlet flow straighteners are shown in Figure 5. The thickness of the baffles in the flow straighteners should be$\delta =0.012d\sim 0.015d$, and the spacing between the baffles in the outlet flow straightener should be $b=0.08d\sim 0.75d$.

Figure 5. Dimensions of Inlet Flow Straighteners and Outlet Flow Straighteners

6. Pressure Measurement Devices:

Use U-shaped manometers with uniform inner diameters, typically 6 mm to 10 mm, and length depending on the pressure being measured.

7. Preparation for Testing:

Clean the flame arrester core before installing it in the flame arrester for testing. The test medium should enter from the inlet end of the flame arrester.

8. Test Conditions:

The absolute pressure of the air used as the test medium should be 0.1 MPa, with a temperature of 20°C, a relative humidity of 50%, and a density of 1.2 kg/m³. If the air conditions deviate, convert them to this state.

9. Measurement of Air State:

Measure the air state near the inlet using a pressure gauge, thermometer, and dry-wet bulb thermometer.

10. Conducting the Test:

Start the motor to run the fan, and adjust the valve to regulate the flow rate. Once the liquid level in the manometer stabilizes, record the readings (Δℎ2,Δℎ3Δh2​,Δh3​) once per minute, three times in total, and take the average value. Calculate the pressure loss using formula (1), and ensure the results meet the requirements of Table 1. Pressure Loss of Flame Arrester.

Where:

• $$\delta p\text{is the pressure loss in Pascals (Pa);}$$
• Δh2 ​is the pressure difference between segments a and a1 in Pascals (Pa);
• Δh3 ​is the pressure difference between segments a and a2 in Pascals (Pa).

11. Calculating Ventilation Capacity:

Record the stable reading of the manometer at point e (Δh1​) once per minute, three times in total, and take the average value. Calculate the ventilation capacity using formula (2), ensuring the results meet the requirements of Table 2. Vent Capacity of Flame Arrester.

Where:

• $$Q\text{is the ventilation capacity in cubic meters per second (m³/s)};$$
• F is the cross-sectional area of the test pipe in square meters (m²);
• ∅ is the collector coefficient (0.98 for conical, 0.99 for arc-shaped);
• Δh1 ​is the vacuum at point e in Pascals (Pa);
• ρ is the density of the ambient air in kilograms per cubic meter (kg/m³).

Flame Arrestor Element Material

Flame arrestors element are typically constructed from stainless steel due to its high melting point, excellent thermal conductivity, corrosion resistance, and structural stability under high temperatures. Stainless steel ensures that the flame arrestor can withstand intense conditions without deforming. In contrast, materials such as aluminum or copper, though lightweight, are prone to deformation and even failure under strong flashback pressures, compromising their effectiveness in arresting flames.

The interaction between the flame arrestor element and the flame is pivotal. Greater contact area facilitates more efficient heat exchange, enhancing the fire retardance capability of the arrestor. Optimizing the dimensions of the triangular units and the channels within the arrestor is essential:

• Smaller triangular units and longer channels increase the cooling efficiency, effectively quenching the flame.
• Adjusting the height h of the triangular units influences the length l of the channels. A smaller h may reduce the channel length, potentially increasing gas flow resistance, while too short a length l may diminish the flame arrestor’s capability to quench flames.

Performance Considerations of Flame Arrester Mesh

Why Flame Arrester Required

Flame arresters are essential safety devices for the protection of storage tanks, vessels, and process equipment that handle flammable gases or vapors. They are particularly crucial in situations where there is a potential for fire or explosion. Here are the main reasons why flame arrestors are required.

a. Enhanced Safety for Venting Systems

• Vents are pivotal for the safe operation of storage tanks and vessels, providing necessary ventilation to accommodate both normal and emergency scenarios. Following the guidelines of API 2000/ISO 28300, vents facilitate the independent ventilation of vessels, thus ensuring safety under various operational conditions. Flame arresters are integrated into these systems to prevent flames from entering a vessel through the venting system, which could cause a catastrophic explosion or fire.

b. Performance and Efficiency

• YeeValve vents are designed with weight-loaded valve discs that achieve full valve lift once pressures exceed 10% above the set pressure. This design allows for rapid pressure relief, maximizing performance while minimizing product losses. Incorporating flame arresters into these systems enhances this efficiency by ensuring safety without compromising the venting function.

c. Durability and Reliability

• Constructed with corrosion-resistant materials such as standard valve seats, discs, and spindles, these vents are built to last. They also feature high-quality sealing technologies, including a metal foil and an air cushion, to minimize leak rates. This durability is particularly beneficial in explosive atmospheres where the integrity of the venting system is critical. The addition of flame arresters further ensures that these systems can reliably prevent the ignition of flammable mixtures, even under high set pressures.

d. Certified Safety

• The vents, particularly those equipped with flame arrester elements, undergo strict testing and certification to ensure they meet safety standards. As per the EC Directive 94/9/EC, these systems are not only tested for their ability to handle inflammable mixtures but are also certified as safety systems. This means they are recognized for their capability to stop flame propagation, thereby safeguarding the equipment and personnel from potential hazards.

e. Integrated Safety Solutions

• Integrating a flame arrester with the vent combines the benefits of both systems into a single, compact device. This integration not only simplifies the overall system design but also enhances the safety features by ensuring that any flames or sparks that could result from the venting of flammable gases are effectively contained and extinguished.

Where are Flame Arrestors Required

Flame arresters are vital safety devices used in various industries to prevent the propagation of flames and ensure safe operations. Their primary function is to stop flames from spreading through flammable gas or vapor mixtures, thereby mitigating the risk of explosions and fires. Here are some key areas where flame arresters are commonly used.

1. Storage Tanks – Diesel and Fuel Storage Tanks:

• Flame arresters are installed on vents of diesel and other fuel storage tanks to prevent external ignition sources from igniting the flammable vapors inside the tank.
• They are also used to prevent flames from propagating into the tank in case of an internal ignition.

2. Chemical Processing Plants – Reactor Vents and Relief Systems:

• Used to protect chemical reactors and relief systems by preventing external flames from igniting the volatile gases within the system.
• Ensure safe venting of gases during emergency relief scenarios.

3. Oil and Gas Industry

• Pipeline Protection:
  • Installed on pipelines transporting flammable gases or liquids to prevent the spread of flames along the pipeline.
  • Essential for offshore platforms and refineries where the risk of gas leaks and explosions is high.
• Storage and Transportation:
  • Flame arresters are used in storage tanks, tanker trucks, and railcars to prevent explosions during the storage and transportation of flammable liquids and gases.

4. Pharmaceutical Industry – Solvent Recovery Systems:

• Used in systems that recover flammable solvents to prevent the spread of flames through the piping and equipment.
• Protects the equipment and environment from potential fire hazards.

5. Waste Treatment Facilities

• Biogas Plants:
  • Installed on biogas digesters and storage tanks to prevent flames from entering the system, ensuring the safe handling of biogas.
  • Used to protect the entire biogas processing and storage infrastructure.
• Landfill Gas Systems:
  • Used in landfill gas extraction systems to prevent flames from traveling back into the landfill, which could cause fires or explosions.

6. Marine Applications – Marine Fuel Tanks:

• Installed on the vents of marine fuel tanks to prevent the ignition of flammable vapors, ensuring the safety of ships and offshore platforms.
• Essential for complying with marine safety regulations.

7. Power Generation – Generator Fuel Systems:

• Used in the fuel supply systems of power generators to prevent the ignition of flammable vapors and ensure continuous safe operation.
• Protects both the generator equipment and surrounding infrastructure.

8. Industrial Manufacturing – Paint and Coating Facilities:

• Used in facilities where flammable solvents and coatings are used to prevent fires and explosions.
• Essential for spray booths and drying ovens where solvent vapors can accumulate.