Frequently asked Questions
Flame Arresters
Fundamentals
A Flame Arrester is a safety
device
Device
A device is a pipe component that influences the media flow by opening, closing, or partially shutting off the flow channel or by dividing or mixing the media flow.
. The purpose of a Flame Arrester is to allow the flow of gases, liquids, etc.
but to prevent the transmission of a flame and
explosion
Explosion
Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously.
.
Flame Arresters Flame Arresters A flame arrester, deflagration arrester, or flame trap is a device or form of construction that will allow free passage of a gas or gaseous mixture but will interrupt or prevent the passage of flame. (or ‘flame arrestors’) are designed to allow the flow of gases, liquids, etc., while preventing flame transmission. PROTEGO® Flame Arresters consist of individual FLAMEFILTER® (flame arrester discs), spacers, and a casing. The FLAMEFILTER® is made of wound, corrugated metal strips.
The principle of flame
quenching
Quenching
Cooling of a fluid by mixing it with another fluid of a lower temperature.
in small gaps is applied in both PROTEGO® end-of-line flame arresters and PROTEGO® in-line flame arresters. When a mixture ignites in a gap between two walls, the flame spreads towards the non-combusted mixture. The expansion of the combusted mixture pre-compresses the non-combusted mixture and accelerates the flame.
The flame is extinguished through heat dissipation in the boundary layer “s”, transferring it to the large surface of the gap length compared to the gap width “D”, and by cooling the
product
Product
Includes equipment, protective systems, devices, components and combinations of these.
below its
ignition temperature
Ignition temperature
Lowest temperature (of a hot surface) at which ignition of a flammable gas or vapor in a mixture with air or air/inert gas occurs under specified test conditions.
. The gap width and gap length of the flame arrester disc determine its extinguishing capability.
The narrower and longer the gap, the greater the extinguishing effectiveness. Conversely, the wider and shorter the gap, the lower the pressure loss. Experiments help determine the optimum balance between these conditions.
The operator is responsible for regular maintenance Maintenance Combination of all technical and administrative actions, including supervision actions, intended to maintain or restore a unit in working order. of the device. Fault-free functioning requires regular testing and maintenance work. The necessary intervals depend on the properties (e.g., condensation, sublimation, polymerization, consistency) of the products in the plant or the mixtures flowing through the devices, as well as the mechanical stress they undergo.
If the personnel lack experience in operating the device, the operator must ensure the following measures:
- Regular checks after startup
- Determination of future maintenance intervals
Documentation of the defined maintenance in the operational specifications
Key points to consider in determining maintenance intervals:
- An annual inspection is generally sufficient for "clean" products and normal mechanical loads.
- Impurities, potential polymer formations or other deposits, condensate collection, or high mechanical loads may necessitate significantly shorter maintenance intervals. Initial maintenance after 3 months at the latest is recommended.
- The service life of wearing parts such as seals and diaphragms depends on environmental influences, process materials, and mechanical stress. Only the operator can determine the required maintenance intervals.
- Deposits in the devices and dirt contamination of the FLAMEFILTER® disks lead to increased pressure loss or reduced flow rate.
Replace the PROTEGO® Flame Arrester Unit after any registered burning or flashback Flashback Phenomenon occurring in a flammable mixture of air and gas when the local velocity of the combustible mixture becomes less than the flame velocity, causing the flame to travel back to the point of mixture. . Check all other parts of the device for damage.
For versions with temperature sensor Temperature sensor Temperature sensor for monitoring the temperature. (-T, -TB), also observe the following:
- After a registered burning, check the temperature sensor for damage and replace if necessary.
- If the temperature has exceeded the operating temperature Operating temperature Temperature reached when the equipment is operating under design conditions. of the sensor, replace the measuring insert.
A Flame Arrester is not a valve. The purpose of a flame arrester is to allow the flow of gases, liquids, etc. but to prevent the transmission of a flame. The purpose of a valve is to prevent the tank from being damaged during pressure and vacuum Vacuum Vacuum is the pressure in an enclosed space that is lower than the ambient pressure. scenarios. Closed vessels or tanks filled with liquid products must have an opening through which the accumulated pressure can be released so that the vessel Vessel Container or structural envelope in which materials are processed, treated or stored. does not explode. Along the same lines, a vacuum must be compensated for when the tank or vessel is drained so that it does not implode.
Flame Arresters are subdivided into different types according to the combustion process (
endurance burning
Endurance burning
Stabilized burning for an unlimited time.
,
deflagration
Deflagration
Explosion propagating at subsonic velocity (EN 1127-1:1997).
,
detonation
Detonation
Explosion propagating at supersonic velocity and characterized by a shock wave (EN 1127-1: 1997).
, and the various sub-groups).
Deflagration Flame Arresters
Deflagration flame arrester
Flame arrester designed to prevent the transmission of a deflagration. It can be an end-of-line flame arrester or an in-line flame arrester.
are safety devices that are used in systems handling explosive mixtures to protect process
equipment
Equipment
Machines, appliances, fixed or mobile devices, control parts and accessories, and warning and prevention systems, whether separate or combined, intended for the generation, transfer, storage, measurement, control, and conversion of energy, and for the processing of materials, which have their own potential source of ignition and may cause an explosion.
from deflagrations. They reliably suppress the effect of a deflagration in the pipelines near potential
ignition source
Ignition source
Any source with enough energy to initiate combustion.
, extinguish the flame, and protect systems that cannot withstand the pressure of an explosion.
Detonation flame arresters are safety devices that are used in pipe systems where detonations can occur. They reliably suppress the effect of a detonation, extinguish the flame, and protect non-explosion-proof components and vessels.
Deflagration is an explosion that propagates at subsonic velocity. Depending on the geometric shape of the combustion area, a distinction is made between atmospheric deflagration, pre-volume deflagration, and in-line deflagration.
Atmospheric deflagration is an explosion that occurs in open air without a noticeable increase in pressure.
Pre-volume deflagration is an explosion in a confined space (such as within a vessel) initiated by an internal ignition source.
In-line deflagration is an accelerated explosion within a pipe that moves along the axis of the pipe at the flame propagation speed below the speed of sound.
Detonation is an explosion propagating at supersonic velocity and is characterized by a shock wave.
End-of-line Flame Arresters can be short-time or endurance burning proof according to their type approval.
Stabilized burning
Stabilized burning
Steady burning of a flame stabilized at, or close to the flame arrester element.
refers to the even, steady burning of a flame that is stabilized at or near the flame arrester element. A distinction is made between short-time burning (stabilized burning for a specific period) and endurance burning (stabilized burning for an unlimited period).
Flame arresters are used in a wide variety of applications across the upstream and downstream oil and gas sectors, as well as in the petroleum, chemical, pharmaceutical, and bio-energy industries. They are essential when processing and storing flammable liquids. The purpose of a Flame Arrester is to allow the flow of gases, liquids, etc. but to prevent the transmission of a flame.
An atmospheric deflagration-proof Valve is a highly developed combined Pressure/Vacuum Relief Valve designed
for high flow capacities with an integrated Flame Arrester Unit. It is primarily used for
flame transmission-proof
Flame transmission-proof
Characteristic of a device to avoid flashback.
in-breathing and out-breathing on tanks, containers, and process equipment. This Valve offers reliable protection against
overpressure
Overpressure
Overpressure refers to an increase in pressure in a system or vessel above the normal operating pressure.
and vacuum, prevents the in-breathing of air, reduces product losses, and safeguards against atmospheric deflagration.
Selection
Flame Arresters are selected based on the combustion process (deflagration, detonation, endurance burning) and the installation site (in-line or end-of-line). The effectiveness of Flame Arresters must be tested and approved.
The following criteria should be considered when selecting the correct Flame Arrester:
- Operating conditions as pressure and temperature
- Explosion group of the flowing mixture
- Approvals in accordance with ATEX, USCG, CSA, GOST-R, GL, IMO, etc.
- Concentric, excentric, or 90-degree design
- Nominal diameter and type of connection
- Heating jacket or custom supplied electrical heat tracing
- Critical substances
- Uni-directional or bi-directional
Based on this initial selection, additional details such as materials, coatings, etc. can be requested or defined in the data sheet.
Either Deflagration Flame Arresters or Detonation Flame Arresters are required depending on installation and operating conditions. Depending on the mode of operation, resistance against stabilized burning (short burning, endurance burning) may be necessary.
Flame Arresters are subdivided into different types according to the combustion process (endurance burning, deflagration, detonation, and the various sub-groups) and by type of installation (in-line, end-of-line, in equipment).
Flame Arresters are made of steel, stainless steel, or Hastelloy.
A Flame Arrester is installed at he the opening of an enclosure or to the connecting pipework of a system of enclosures.
To determine if Flame Arresters affect flow rates, flow capacity charts should be consulted for each specific
device type. These charts illustrate the pressure drop at different flow rates.
Valves
Selecting the correct pressure vacuum relief valve Vacuum relief valve A vacuum relief valve is used to ventilate a part of the system and protects it from impermissible underpressure. (PVRV) is critical to ensuring the safe operation of your system.
Follow these guidelines to choose the appropriate valve:
Function: Determine the need for a pressure relief valve Pressure-relief valve Valve designed to open and relieve excess pressure and to reclose and prevent the further flow of fluid after normal conditions have been restored. , a vacuum relief valve, or a combined pressure/vacuum relief valve Pressure/vacuum relief valve Pressure/vacuum relief valve is an umbrella term that includes pressure or vacuum relief valve as well as pressure and vacuum relief valve. with a pipe-away connection if required.
Design: Choose between a combined end-of-line valve or separate pressure and vacuum relief valves, with either a vertical or horizontal connection.
Adjusted Set Pressure: This is the standard maximum allowable tank pressure Tank pressure Tank pressure is the pressure within a tank. minus 10% overpressure. The set pressure Set pressure Set pressure is the gauge pressure at the device inlet at which the relief device is set to start opening under service conditions. determines the choice of materials for the valve pallet Valve pallet Valve pallet is the generic term for the assembly that rests on the valve seat. .
Type of Seal Seal A seal prevents or limits unwanted transfer of product from one container to another. Seal is used as superordinate term for all types of sealing elements. : Select the appropriate seal type based on the pressure level. Options include an air cushion seal or a metal seal for an extremely tight seal.
Special Operating Conditions: Consider specific requirements such as handling viscous and adhesive substances, frost-protected operation, or use with polymerizing products.
Nominal Diameter: The nominal diameter is typically determined by the flow rate needed to prevent unacceptable over-pressure and under-pressure. Certified flow rate diagrams are available to aid in selection. For correct sizing, consider the operating conditions, pressure loss in the pipelines, including other installed devices, and any possible backpressure.
Sizing Considerations: The valve size should ensure that allowable pressures are not exceeded when releasing the required flow rate.
By carefully evaluating these factors, you can select a pressure vacuum relief valve that ensures optimal performance and safety for your system.
Pressure and Vacuum Relief Valves feature weight-loaded or
spring
Spring
A spring is a spiral of wire which returns to its original shape after it is pressed or pulled.
-loaded valve pallets. When excess pressure builds up in the tank, the pressure valve pallet, which is guided in the
housing
Housing
A housing is a solid shell, which surrounds a content, either protecting the content from external influences, or protecting the environment from the content.
, lifts and releases the flow into the atmosphere until the pressure falls below the set level. The Valve then re-seats.
The vacuum side of the Valve remains tightly sealed by the additional overpressure load. When there is a vacuum in the tank, the atmospheric pressure lifts the vacuum disc, allowing the tank to be vented.
PROTEGO® end-of-line Valves are mainly used for storage tanks, vessels, or ventilation lines. In pipes, PROTEGO® in-line Valves serve as backflow preventers, overflow valves, and occasionally as control valves.
PROTEGO® Pressure/Vacuum Relief Valves are used as in-breathing and out-breathing valves, pressure relief valves, conservation valves, and for simple control and venting of tanks and equipment when unacceptable vacuum or pressure levels are exceeded. These valves are suitable for low pressure ranges where classic safety valves cannot be used due to their limited performance characteristics. PROTEGO® Valves are available as pressure relief valves, vacuum relief valves, or as combined pressure/vacuum relief valves.
Closed vessels or tanks filled with liquid products must have openings through which accumulated pressure can be released to prevent the vessel from exploding. Similarly, a vacuum must be compensated when the tank or vessel is drained to prevent it from imploding. Unallowable overpressure or underpressure can occur during loading and unloading, steam cleaning processes, or blanketing due to thermal effects.
For free exchange with the atmosphere or connected pipe systems that are uncontrolled and unmonitored, Pressure/Vacuum Relief Valves are used. These openings allow for safe pressure and vacuum relief, ensuring the integrity of the vessel or tank.
Pressure Vacuum Relief Valves (PVRV) come in several types, each designed for specific applications:
Pressure Relief Valves: These valves prevent vapor loss up to the adjusted set pressure Adjusted set pressure Adjusted set pressure is the pressure at which a valve opens on a test bench. and provide reliable protection against excess pressure.
Vacuum Relief Valves: These valves prevent the unallowable entrance of air up to the adjusted set pressure and offer reliable protection against vacuum formation.
Pressure/Vacuum Relief Valves: These valves perform both pressure relief and vacuum relief functions, ensuring comprehensive protection in varying conditions.
Emergency Pressure Relief Valves: When extremely high venting rates are required due to fire on the outside surface of the tank or malfunctions in special tank equipment, additional emergency pressure relief valves must be used to ensure safety and prevent catastrophic failure.
Diaphragm Diaphragm A diaphragm is a thin layer of material, which has a large surface area. Valves: PROTEGO® diaphragm valves are used for handling problematic products and low temperatures, offering specialized performance.
Pilot Operated Valves: These valves are advantageous for precise control responses and offer a tight seal up to the point at which the valve begins to open, making them ideal for applications requiring strict regulation.
High-Velocity Vents: High-velocity vent valves are specifically used on tanker ships and for special land-based applications to manage rapid pressure changes effectively.
To select the appropriate valve type, consider the following:
Function: Determine the need for a pressure relief valve, vacuum relief valve, or a combined pressure/vacuum relief valve, with a pipe-away connection if necessary.
Design: Choose between a combined end-of-line valve or separate pressure and vacuum relief valves, with either a perpendicular or horizontal connection.
Setting the pressure in a pressure relief valve correctly is vital to ensure the safe operation of your system. Here are the steps and considerations for setting the pressure:
Valve Size: Ensure that the valve size is adequate so that the allowable pressures are not exceeded while releasing the required flow rate. When determining the opening pressure of the valve, also consider pressure losses in connected pipes and other installed devices.
Set Pressure Determination: The set pressure of the valve should be calculated to safely release the expected volume flow. For valves that require 10% overpressure to reach full lift Lift Lift is the actual travel of the valve pallet from the main valve out of the closed position. , the set pressure should be 10% below the fully open pressure (e.g., maximum allowable tank pressure). It is important to consider the pressure drop within the piping system and any other installed devices to ensure accurate pressure settings.
Conventional Valve Considerations: Many conventional valves require 100% overpressure to reach full lift. In these cases, the set pressure might be just half of the maximum allowable tank pressure. This results in the valves opening earlier, potentially causing unnecessary product losses. For optimal safety and environmental protection, it's crucial to account for such factors when setting the pressure.
By carefully evaluating these elements, you can set the pressure in a pressure relief valve to ensure safe and efficient operation.
When extremely high venting rates are required due to a fire on the outside surface of the tank or malfunctions in special tank equipment (such as tank blanketing gas systems), additional emergency pressure relief valves must be used, especially if the tank roof is not designed to be frangible.
Tanks storing flammable and non-flammable liquids are designed and manufactured in accordance with different standards:
EN 14015, API 620, or API 650 are the most important standards worldwide. Depending on the standard, different maximum tank pressures are allowable where the discharge flow has to be achieved.
Calculation of the Out-breathing and In-breathing venting capacity in acc. with ISO 28300/API 2000:
The maximum required venting capacity is the total amount of pump capacity and thermal capacity due to weather related conditions. The calculation of the maximum required capacity from weather related conditions is based on ISO 28300 with regard to aboveground storage tanks with or without insulation.
Calculation of the Out-breathing and In-breathing venting capacity in acc. with TRGS 509:
To calculate the out-breathing and in-breathing capacity of storage tanks (e.g., tanks in acc. with DIN 4119 for aboveground, flat-bottom storage tanks, or DIN 6608 for underground or underground horizontal tanks), the calculation formulas of TRGS 509 (as of 1 January 2013, VdTÜV-Merkblatt Tankanlagen 967) are to be applied.
Calculation of Out-breathing and In-breathing venting capacity in acc. with API 2000, 5th Edition / ISO 28300
Annex A:
The out-breathing and in-breathing capacity of petroleum storage tanks can be calculated in acc. with ISO 28300 Annex A (approximately equivalent to API 2000 5th Edition) if specific boundary conditions are fulfilled (see ISO 28300).
Talk to a PROTEGO® engineer to request guidance for your vessel or terminal loading application
