This European Standard covers: fuel pipework downstream of and including the manual isolating valve; burners, burner system and ignition device; safety related control system prote
General
The safety goals of this European Standard shall include:
choice of materials such that the construction and operation of the system are not detrimentally affected
In particular, all the components of the fuel pipework shall be capable of withstanding the mechanical, chemical and thermal loads to which they can be subjected during normal operation;
reliable and correct time for ignition of the fuel/air-mixture at the burner(s);
prevention of unintentional release of unburned fuels;
shut-off fuel-supply in case of relevant fault;
protection of pipeline by precluding the propagation of flame in reverse flow;
prevent firing when the exhaust of combustion products is not ensured;
prevent firing when the process conditions are not in the safe state
Electrical circuits shall be designed in accordance with subclause 5.7 of EN 60204-1:2006
The combustion and fuel handling for IThE shall comply with the safety requirements and/or protective measures of Clause 5
Machinery must adhere to the safety standards and protective measures outlined in this clause Furthermore, the design of the machine should align with the principles of EN ISO 12100, addressing relevant but less significant hazards not covered by this document.
NOTE For guidance in connection with risk reduction by design, see clause 4 of EN ISO 12100-2:2003, and for safeguarding measures see clause 5 of EN ISO 12100-2:2003.
Gaseous fuels
Gas pipework
The pipework design shall take into account the composition and properties (e.g specific gravity) of the fuel gas and the need for venting, purging and cleaning
The pipework material shall comply with the relevant standards
Steel pipes should comply with EN 10208-1, EN 10208-2, EN 13480-2:2002 (Table A.3), or EN 10255, while copper pipes must adhere to EN 1057 standards It is important to note that copper soldering connections are not suitable for gas-carrying components where temperatures may exceed certain limits.
Threaded pipe fittings shall comply with EN 10241 or EN 10242
Metal is the primary choice for pipes and components; however, alternative materials may be used when they can meet the same safety standards The specific materials and service conditions will be detailed in the usage instructions.
Oscillations which may cause damage to pipework, components, safety systems shall be prevented (by firm anchoring and/or, use of flexible couplings)
Gas pipework connections shall be metallic and shall be of the threaded, compression, flanged, or welded types Threaded connections shall be used only for the following pressure/diameter combinations:
pressures up to 100 mbar, and diameters up to DN 80;
pressures up to 2 bar, and diameters up to DN 50;
pressures up to 5 bar, and diameters up to DN 25;
pressures up to 10 bar, and diameters up to DN 15
For other combinations of pressures and diameters connections shall be by means of welded flanges or welded joints The number of connections shall be kept to a minimum
Equipment with threaded connections must adhere to ISO 228-1 or ISO 7-1 standards For ISO 228-1 threads, a ring gasket is required to ensure tightness Sealants for ISO 7-1 threads must comply with EN 751, Part 1 or Part 2 Hemp should not be used in threaded connections unless it is reinforced with an appropriate sealant.
Other threaded connections shall only be used providing they ensure tight connections and are suitably identified
The design of pipework shall be such as to avoid tensile loading of the joints
Compression fittings shall comply with EN ISO 8434-1 or EN ISO 19879 They shall only be used for pressures up to 5 bar and diameters up to 42 mm
Any pipe passing through an unventilated space shall not have a connection except welded joints
Flanges shall comply with ISO 7005, Parts 1 and 2 as appropriate
Arc welding shall comply with EN ISO 5817, quality Level C
Any unconnected pipework shall be plugged, capped or blank flanged by means of metallic parts
The formation of galvanic cells shall be avoided by suitable choice of materials
Flexible tubing shall comply with the general requirements of 5.2.1.1, together with the following:
shall be as short as possible;
shall be suitable for the maximum and minimum working temperatures;
shall be suitable for a pressure 1,5 times the working operating pressure (with a minimum of 150 mbar), at the maximum and minimum working temperatures;
shall have a directly accessible, upstream shut-off valve;
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shall be mounted in such a way as to avoid distortion, whiplash and damage;
shall have end fittings as integral parts of the tubing;
shall be constructed from suitable material both metallic and/or non metallic selected for the application duty and not be easily damaged
Couplings for removable equipment shall ensure a gastight connection with the equipment connected and disconnected
The pipework shall be identified as gas pipework
NOTE Identification of gas pipework is dealt with by national regulations
The gas pipework shall be tight and shall be designed to withstand the internal pressure
The external leakage rate must not create a hazardous situation involving flammable or toxic substances under the expected conditions of equipment installation Additionally, the instruction manual should outline the frequency of testing required to assess external leakage.
An external leak rate of approximately 1 dm³(n)/h is typically considered safe for ventilated industrial installations, as it does not pose a dangerous condition However, the actual leak rate can vary based on several factors, including the volume of the system, the number of connections, the type of test gas used, and the number of valves and components involved.
The external leak rate test method must consider factors such as volume, number of connections, test gas, number of valves, component parts, and temperature Testing methods should include spray bubble leak identification and/or pressure decay tests.
To mitigate hazards from condensates, equipment must include drainage means at the lowest points for effective removal Suitable condensate drains should be installed when handling moist gases, ensuring they are easily accessible for inspection Flammable condensates must be collected safely, such as by piping them into a container Additionally, valves in condensate drains should be securely plugged, capped, or blank flanged with metallic components.
Means shall be provided to facilitate purging of the gas system during commissioning and maintenance to prevent the build up of flammable substances
5.2.1.10 Blow-off and breather pipes or conduits
Blow-off or breather pipes must be installed on regulators, relief valves, or vent valves to ensure safe gas venting from the system to a designated discharge area.
In case breathers or blow-off pipes are gathered, the cross section of the collector shall be suitable to evacuate simultaneously total flow rates of the exhaust sources
5.2.1.11 Pressure relief devices and flame arrestors on pipework
For equipment designed for situations in which flash-backs can occur, flame arrestors and/or pressure relief devices shall be fitted
Pressure relief devices must be engineered to activate at pressures lower than the pipework's design pressure Additionally, their placement should ensure that the discharge flow does not pose a risk to equipment, personnel, or third parties.
A flash-back at least shall trigger an alarm The required measures after a flash-back shall be described in the instruction for use
To prevent damage to gas pipework, components, and safety systems, it is essential to design the gas pipework to minimize gas velocities and pressure fluctuations This can be achieved by ensuring proper pipe sizing and incorporating pressure regulators.
5.2.1.13 Equipment supplied with different fuel gases
When a burner is designed to operate with multiple gaseous fuels, it is essential to implement measures that guarantee the supply pipework of the inactive gas is securely isolated.
By-passes shall not be fitted in parallel with any item of safety equipment
This requirement shall not apply to valve proving systems (EN 1643) nor to system leak tightness checks on automatic shut-off valves
5.2.1.15 Isolation of required safety devices
Safety devices such as pressure switches and relief valves must remain connected to the equipment they protect during burner start-up and operation If isolating valves are necessary and installed between these safety devices and the main lines, they must be securely locked in the open position during operation using appropriate methods, such as a manual lock It is essential that operation cannot occur unless the isolation valves are fully open.
Required safety devices
A manually operated isolation valve shall be fitted upstream of the first control device in the gas circuit
Manual isolation valves shall be so designed or positioned as to prevent inadvertent operation but shall be easily accessible and capable of rapid operation when required
Only manual isolating valves that comply with EN 331 should be installed when technically feasible For valves not covered by EN 331, it is essential to meet the safety requirements outlined in EN 331 at an equivalent standard.
They shall be so designed that the "OPEN" and "CLOSED" positions are readily distinguishable (e.g a 90° turn valve if applicable and available)
To ensure optimal equipment operation, it is crucial to prevent particle ingress from both the pipework and gas This can be achieved by installing a suitable filter or strainer immediately downstream of the first manual isolating valve of the IThE Additional filters or strainers may also be necessary, particularly upstream of the automatic shut-off valve Furthermore, the positioning of the filter and/or strainer should facilitate easy periodic servicing.
In the event of the installation of a by-pass to the filter and/or the strainer, an identical filtering device shall be installed on the by-pass line
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Filter and/or the strainer shall be checked at intervals specified in the instruction handbook
Automatic shut-off valves shall be in accordance with the following subclauses of EN 161:2007:
for leak tightness: subclauses 7.2 and 7.3,
for the closing function: subclause 7.9,
for the closing force: subclause 7.10,
for the closing time: subclause 7.12
for the sealing force: subclause 7.13
The automatic shut-off valve shall endure the intended cyclings in the IThE
Valves construction and materials shall be suitable for the used gas composition
Automatic shut-off valve shall be capable of withstanding back pressure and differential pressure under all process circumstances
For low cycling applications designed for continuous operation exceeding one year, it is essential to implement a redundant safety shut-off system This system should be at least as effective as the flow sheet illustrated in Figure C.5 and must facilitate testing of the valve closure effectiveness at least annually.
For high cycling applications exceeding 10,000 cycles per year, it is essential to utilize valves specifically designed for increased cycle durability The instruction manual must outline the necessity of verifying valve functionality, detail the procedures to follow, and specify the intervals for these checks.
The gas supply to the burner shall be under the control of two class A automatic shut-off valves of EN 161 in series in the gas pipework
For natural draught burner with a controlled capacities below 70 kW there shall be at least two class B valves of EN 161
A thermo-electric flame supervision device that meets EN 125 standards is suitable for natural draught burners operating in open air with capacities under 70 kW, as well as for those in combustion chambers with capacities below 2.5 kW.
Automatic shut-off valves must remain closed or cut off fuel to the burner when any safety limit is reached, considering the following conditions.
minimum and maximum gas flow;
minimum and maximum gas pressure;
minimum and maximum air flow;
minimum and maximum air pressure;
failure of power supply and/or other utilities (e.g compressed air, steam);
failure of heat transfer fluid;
maximum operation temperature of IThE;
minimum and maximum combustion chamber pressure;
failure of system leak tightness check and/or valve proving system;
incorrect air/gas ratio as referred in 5.2.3.3
In these cases the automatic shut-off valves shall be de-energised by a protective system
This function shall meet the requirements of the protective system according to 5.7.2 and 5.7.3
Certain processes and machine conditions may pose risks if the burner continues to operate, but these specific conditions are not addressed by this standard.
It shall only be possible to manually reset the lock-out (see 3.48) of a closed automatic shut-off valve.
For typical examples of piping and components see informative Annex C
Each burner or group of burners must have a gas supply controlled by two class A automatic shut-off valves, compliant with EN 161, installed in series within the gas pipework.
For natural draught burner with a controlled capacities below 70 kW there shall be at least two class B valves of EN 161
A thermo-electric flame supervision device that meets EN 125 standards is suitable for natural draught burners operating in open air with capacities under 70 kW, as well as for those in combustion chambers with capacities below 2.5 kW.
In multiple burner installations, each individual burner shut-off valve is regarded as an automatic shut-off valve, provided it meets or exceeds the same class specifications For typical piping examples, refer to informative Annex C.
The automatic shut-off valve(s) must remain closed or cut off fuel supply to the entire IThE or independent zone upon reaching any safety limit It is essential to consider the following conditions:
minimum and maximum gas flow;
minimum and maximum gas pressure;
minimum and maximum air flow;
minimum and maximum air pressure;
failure of power supply and/or other utilities (e.g compressed air, steam);
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failure of heat transfer fluid;
maximum operation temperature of IThE;
minimum and maximum combustion chamber pressure;
failure of system tightness check and/or valve proving system;
incorrect air/gas ratio as referred in 5.2.3.3
In these cases the relevant automatic shut-off valves shall be de-energised by a protective system
This function shall meet the requirements of the protective system according to 5.7.2 and 5.7.3
NOTE In addition there may be processes and/or machine conditions that cause a risk if the burner continues to fire However these conditions are not covered by this standard
It shall only be possible to manually reset the lock-out (see 3.48) of a closed automatic shut-off valve
In the event of flame failure or a process control shut-down, two automatic shut-off valves connected in series will close, unless a single individual burner shut-off valve is deemed sufficient in specific cases.
in case of high temperature equipment;
in case of low temperature equipment providing the following conditions complied with:
A system leak tightness test is performed at each startup of the IThE or during specific test periods for the burner group, ensuring that the automatic shut-off valves for individual burners are closed This test is required to be conducted at least once a week.
The gas leakage dilution from a single valve, operating at full burner capacity, remains below 25% of the Lower Flammable Limit (LFL) This is accomplished through the introduction of fresh air or flue gas, taking into account all operational modes, including maximum power, partial load of the heating system, and fluctuations in the LFL due to changes in furnace temperature.
For typical examples of piping and components see informative Annex C
Automatic shut-off valves with capacities exceeding 1,200 kW must include a valve proving system This system should either adhere to EN 1643 standards or provide an equivalent level of safety.
Combustion air and pre-purging the combustion chamber and flue passages
The pipework to be designed shall take into account the properties of combustion air
All manual control devices (registers, valves, etc.) for the air shall be set in their pre-determined positions and protected against inadvertent movement
The combustion air intake must be strategically positioned to avoid the infiltration of exhaust gases, unless the design specifically allows for this to reduce nitrogen oxides (NOx) emissions.
The ventilation of IThE shall be such as to allow an adequate supply of process air and combustion air to reach the burner(s) under all conditions
Ensuring an adequate air supply to the IThE is crucial for optimal performance For many applications, it is advisable to install an air inlet filter equipped with filter monitoring to guarantee the reliable operation of the system.
The combustion air system shall be designed in a manner that prevents the back-flow of furnace atmosphere through combustion equipment
The air circuit shall be designed so as to avoid oscillations that may lead to material defects
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5.2.3.2 Pre-purging of the combustion chamber
Before initiating a start-up or re-start after a lock-out, it is essential to ensure that no combustible mixture exists in the combustion or processing chamber, as well as in connected spaces and the flue products evacuation circuit, including heat exchangers and dust extractors This safety condition must be met through a pre-purging period conducted immediately before ignition or within a timeframe specified in the instruction handbook.
The pre-purge duration must be sufficient to maintain the concentration of combustible products in the combustion chamber, connected spaces, and flue duct below 25% of the Lower Flammable Limit (LFL) of the fuel gas, assuming these areas are initially filled with flammable gases.
For effective operation, it is generally sufficient to achieve five complete air changes in the combustion chamber, connected spaces, and flue duct The pre-purge air flow rate should be at least 25% of the maximum combustion air flow rate In cases of natural draught, specific conditions to meet these requirements should be outlined in the instruction handbook.
Inert or non-flammable gases should replace air when necessary for specific equipment or processes Additionally, alternative methods can be employed to ensure that the combustion chamber and associated areas remain free of flammable gases, as long as they achieve an equivalent level of safety.
The pre-purge time and purge procedure and or methodology shall be specified in the instruction handbook
The system for ensuring correct pre-purge time and the airflow shall meet the requirements of a protective system according to 5.7.2 and 5.7.3
Pre-purge should be omitted in specific situations: a) when free oxygen poses a risk, such as in flammable atmospheres or when it could damage equipment like graphite crucibles or affect product quality; in these cases, additional measures must be implemented to prevent gas leakage across automatic shut-off valves by utilizing two class A valves of EN 161 along with a valve proving system; b) if the combustion chamber temperature exceeds 750 °C, as classified for high-temperature equipment; c) during the recycling of a burner after shutdown for control purposes, pre-purging is unnecessary in various scenarios.
where the burner is fitted with an independently supervised permanent or alternating pilot;
The burner is equipped with two class A valves compliant with EN 161, which close simultaneously and include a valve proving system; however, this system is not necessary for pulse-fired burners.
with pulse fired burners if the burner shut-off valve is certified by the supplier to be suitable for the increased number of cycles typical of pulse firing;
in multiple burner systems when one or more burners remain alight provided that not more than one burner is extinguished due to flame failure;
When the combustion chamber reaches temperatures exceeding 750 °C, it is classified as high-temperature equipment, and any flammable mixture from the burners will ignite immediately Additionally, if one burner in a group of radiant tube burners experiences a flame failure, only one restart is allowed before a lock-out occurs.
each burner has an automatic burner control system; and
The burner and exhaust system are engineered to handle the maximum pressure increase that can occur during ignition, ensuring safety when the ignitable fuel-air mixture within the exhaust system is below 25% of the Lower Flammable Limit (LFL).
the gas supply to each radiant tube burner is equipped with automatic shut-off valve class A of
To ensure safe ignition and stable combustion at each burner, the air mass flow rate must be proportionate to the gas mass flow rate This ratio may vary under different operational conditions.
The design of air/gas ratio control must take into account the specific process conditions and the characteristics of the fuel and combustion air Any defects or malfunctions in the system can lead to an increase in excess air or trigger a lockout if the air/gas ratio creates an unsafe environment.
Pneumatic gas/air ratio controls shall comply with EN 12067-1 or EN 12078 if applicable
Electronic gas/air ratio controls shall comply with EN 12067-2 if applicable
To maintain their reliability, air/gas ratio controllers must operate within the specified conditions of temperature, pressure, and flow rate as outlined in the instruction handbook, which also includes essential maintenance guidelines.
When utilizing alternative methods or technologies for ratio control, it is essential to implement additional protective measures based on the properties of combustion air and fuel gas This is particularly important in scenarios involving frequency control of the combustion air blower, preheated combustion air, or a variable Wobbe index of the gas The air/gas ratio control function must comply with the protective system requirements outlined in sections 5.7.2 and 5.7.3.
NOTE The combination of any ratio control (pneumatic or other) in combination with a flame supervision system that detects all possible incorrect ratios is generally considered to be sufficient protection.
Supply of pre-mixed fuel gas/air
To ensure safety, the volume of the mixture pipework should be minimized, and the system must be designed to maintain a sufficiently high mixture flow velocity to prevent upstream flame propagation Alternatively, it should be equipped with flame traps, arrestors, or pressure relief devices.
The system will be equipped with a sensor that triggers a lock-out if the flow velocity drops below a specified threshold or if a temperature sensor detects a flash-back.
These devices are not required for burners where the manufacturer can demonstrate that flash-back cannot occur in any circumstances (e.g pilot burners with their own mixing devices)
5.2.4.2 Air and gas supply to the mixture circuit
To ensure safety and efficiency, it is crucial to prevent the presence of a fuel gas/air mixture in the pipework supplying fuel gas or air to the mixing device This can occur due to reverse flow, ingress, or internal leakage, and must be effectively managed.
To ensure safety, when using a non-return valve that is not flashback resistant, it is essential to install a high gas pressure switch downstream This switch will automatically shut off the fuel gas flow to the equipment through the designated automatic shut-off valves in case of a flame flashback.
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A flash-back shall trigger an alarm The required measures after a flash-back shall be described in the instruction for use.
Burners
All burners shall be suitable for the working conditions and shall provide operating safety for:
the fuels used (type, pressure, etc.);
the operating conditions (pressure, temperature, atmosphere, etc.);
the nominal input rate and range of regulation (maximum and minimum capacity);
ease of visual monitoring (sight glasses, sight holes, etc.)
Radiant tubes burner system shall be suitable and allow safe operation
Radiant tube burner systems shall be designed in accordance with the requirements for a protective system in accordance with 5.7.2 and 5.7.3
be constructed of suitable materials for the thermal input rate, temperature and furnace atmosphere;
minimise the probability of combustion products having contact with the furnace atmosphere;
shall be equipped with an automatic burner control system according to 5.2.6 At temperatures above
750 °C no automatic burner control system is needed if a safe ignition of the air/gas mixture can take place The temperature limit of 750 °C shall be detected at the coldest point;
If additional burners are needed for IThE processes exceeding 750 °C and an automatic burner control system is unnecessary, they must be isolated from the fuel supply using automatic shut-off valves These valves should be controlled according to the protective system requirements outlined in sections 5.7.2 and 5.7.3, ensuring that fuel flow is only permitted when the ignition point temperature within the radiant tube exceeds 750 °C.
When designing radiant tubes, it is crucial to consider the temperature difference between the ignition point inside the tube and the surrounding chamber, as the tube's internal temperature can be significantly lower.
The start-up of the fuel supply and burner(s) is permitted only after verifying that the air and fuel gas proving devices, such as airflow and gas pressure checks, are functioning correctly Additionally, all relevant interlocks, including the positions of the burner(s), valve(s), and flue damper(s), must be confirmed to be in the proper position.
The energy released during the burner start-up must be controlled to ensure that the maximum pressure increase from ignition does not harm the IThE, as outlined in Table 3.
The start fuel flow rate shall be controlled by a protective system according to 5.7.2 and 5.7.3
Burners ignited manually with a lighting torch and having an input rate exceeding 70 kW must include a mechanism to limit the start-up gas.
The ignition process shall be initiated immediately or within a time to be specified in the instruction handbook after the conclusion of the pre-purging stage
During the ignition process of the main burner, which is initiated by a pilot burner, the gas supply to the main burner must be turned off for safety during pre-purge and ignition The automatic shut-off valve(s) for the main burner will only activate once the pilot burner flame has been confirmed.
When using oxygen-enriched air or pure oxygen as the oxidizing agent in gas combustion, known as oxy/fuel firing, it is essential to implement specific ignition procedures and times These systems necessitate careful design considerations to maintain equivalent safety levels.
The safety time and total closing time shall not vary by more than 20 % when the electrical supply voltage is varied between 85 % and 110 % of the nominal value
5.2.5.3.4.2 Maximum safety times for natural draught burners
The safety time and total closing time for natural draught burners shall not exceed the values given in Tables 1 and 2
Table 1 — Maximum safety times for natural draught burners operating in open air
Burner input rate Safety time Total closing time kW s s
1) Thermoelectric flame supervision device (EN 125) up to and including 70 60 45
2) Flame supervision device other than thermoelectric (EN 298) up to and including 70 10 10 above 70 up to and including 360 10 3 above 360 * a 5 3
* a Ignition at a rate of 33 % of the burner input rating with a maximum of 350 kW
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Table 2 — Maximum safety times for natural draught burners operating in combustion chamber
Burner input rate Safety time Total closing time kW s s
1) Thermoelectric flame supervision device (EN 125) up to and including 2,5 60 45
2) Flame supervision device other than thermoelectric (EN 298) up to and including 70 10 10 above 70 up to and including 360 10 3 above 360 * a 5 3
* a Ignition at a rate of 33 % of the burner input rating with a maximum of 350 kW
5.2.5.3.4.3 Maximum safety times for forced and induced draught burners
The maximum start gas rate and the corresponding safety time for forced and induced draught burners shall not exceed the values given in Table 3
The total closing time shall not exceed 3 s
Burner start-up shall be achieved in accordance with one of the following methods:
direct ignition of the main burner at full rate (see Table 3, Column 2); or
direct ignition of the main burner at reduced rate e.g by using slow opening valve; (see Table 3, Column 3); or
The main burner can be directly ignited at a reduced rate using a bypass gas supply to a separate inlet or through a two-step safety valve, as detailed in Table 3, Column 4.
ignition of the main burner by means of an independent pilot burner; (see Table 3, Column 5)
For methods of burner start-up see Annex D
Higher starting gas rates than those listed in Table 3 can be attained after the safety period, provided it is demonstrated that the total energy released in the combustion chamber during this time does not exceed the energy calculated by multiplying the maximum starting gas heat input by the safety time specified in Table 3.
Table 3 — Maximum safety times for forced and induced draught burners
Direct main burner ignition at full rate
Direct main burner ignition at reduced rate
Direct main burner ignition at reduced rate
Main burner ignition with independent pilot burner with slow opening valves withby-pass start gas supply
Second safety time tS 2 kW s s kW s s s
≤ 360 not allowed except as described below
3 with slow opening valves or ts * Qs < 150 (max ts = 3 s)
> 360 not allowed not allowed QST = 120 kW or ts * Qs < 100 (max ts = 3 s)
5 (QST ≤ 70KW) QST = 180 kW or ts * Qs < 150 (max ts = 3 s)
QF max = maximum main burner input rate in kilowatts
QST =start input rate in kilowatts
Qs = maximum start input rate expressed as a percentage of QF max (Qs = QST / QF max ) tS = safety time in seconds
In special cases of equipment construction or when necessary for process reasons, the ignition safety times may differ from those specified in Table 3, provided that the safety of the IThE is not compromised However, in such instances, the ignition safety times must not exceed the established maximum values.
/( v s v s P B Q t < × × 2) where t s is the safety time in s;
B v is the combustion chamber full load (MW/m 3 ), with a minimum of 0,015 MW/m 3 ;
Q s is themaximum start gas heat input expressed as a percentage of Q F max : (0 < Q S < 100);
P v is theallowable combustion chamber pressure (mbar) minus combustion chamber back pressure during ignition (mbar)
Burners with a nominal input greater than 120 kW are ignited directly at full capacity, while those exceeding 360 kW are ignited directly at a reduced rate using slow-opening valves.
2) This formula is typical for natural gas, LPG and comparable fuels (e.g not for fuels containing high amounts of hydrogen) firing with cold combustion air with 21 % Oxygen content
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`,,```,,,,````-`-`,,`,,`,`,,` - the combustion chamber/process chamber, flue ways and pipework shall be designed to take account of the maximum pressure rise
The total closing time and safety time must not exceed 10 seconds For long cross-ignited burners, a safety time extension of 1.5 seconds per meter of burner length is permissible, up to a maximum of 10 seconds, as long as the flame is monitored at the burner end opposite the ignition source and safe ignition is consistently achieved.
5.2.5.3.5.1 Flame failure on start-up
In the event that flame failure occurs during the safety time, the burner shall go to lock-out (see 3.48)
Recycling is permissible as long as equipment safety is maintained, with a maximum of two re-cycles allowed The control of these re-cycles must adhere to the protective system requirements outlined in sections 5.7.2 and 5.7.3 If a flame signal is not detected after the re-cycles, the malfunctioning burner will enter a lock-out state (refer to section 3.48) The specific conditions, time intervals between re-cycles, and the total number of re-cycles must be detailed in the instruction handbook.
In pulse firing burners, a flame failure in one burner will trigger a safety shut-down rather than a lock-out However, if there are three consecutive flame failures, a lock-out will occur The total number of burners affected by this rule must adhere to the limits set in section 5.2.5.3.1 (refer to 3.48), and the specific number of burners will be detailed in the instruction handbook.
In the event of flame failure during operation the burner shall go to lock-out (see 3.48)
In specific situations, a safety shut-down is permissible as long as equipment safety remains intact Only one re-cycle is allowed, with conditions outlined in the instruction handbook If a flame signal is not detected at the end of this re-cycle, the malfunctioning burner will enter a lock-out state (refer to section 3.48).
The IThE shall be designed such that a recycle of a single burner system requires a complete recycle including pre-purge
In any combustion system, the turndown ratio shall be such that the burner(s) is/are fully stable at all firing conditions
Automatic burner control systems
The main flame and pilot burner flame must be monitored by an automatic burner control system, with exceptions allowed only when equipment safety is ensured, as outlined in sections 5.2.6.2 and 5.2.6.3.
Automatic burner control systems must adhere to EN 298 or EN 125 standards, where applicable If process requirements necessitate, the system's characteristics may deviate from the specifications outlined in EN 298.
EN 125 providing the levels of safety and reliability are not reduced
In systems where the pilot burner operates concurrently with the main burner, it is essential to install separate flame detection devices for both the pilot and main flames The main flame detector must be positioned to ensure it does not detect the pilot flame under any circumstances If the pilot burner reliably ignites the main flame, monitoring the pilot flame alone is adequate, provided that the flow rate of the pilot burner is regulated by a protective system in accordance with sections 5.7.2 and 5.7.3, such as a minimum gas pressure switch.
In systems where both the pilot burner and the main burner have individual flame detection devices, it is crucial that the ignition flame does not affect the response of the main flame sensor.
For systems where the pilot flame is extinguished during main burner operation a single flame detector device may suffice
Where fitted, flame sensors shall be unresponsive to unintended radiation
Where a burner is required to fire continuously for periods in excess of 24 h, the automatic burner control system shall be designed for permanent operation
The detection of an unexpected flame or a malfunction in the automatic burner control or protective system will lead to a lock-out, as outlined in sections 5.7.2, 5.7.3, and 3.48.
Where manual checking of the automatic burner control system is carried out, the instruction handbook shall specify the procedures to be followed in the event of a malfunction
Low temperature equipment fitted with a single burner shall be equipped with an automatic burner control system in accordance with 5.2.6.1
For low temperature multiple burner equipment, each burner shall be equipped with an automatic burner control system
Only one burner must have a continuous automatic burner control system, as long as the burners maintain stable combustion across their regulation range, share the same air/gas ratio control system, and are positioned close enough for quick and smooth re-ignition by the adjacent burner if one goes out This requirement does not apply to burners using "on/off" control systems.
Flame supervision is essential during the start-up phase when the processing chamber wall temperature is below 750 °C, and it can be conducted either through an automatic burner control system or by the operator.
Any automatic burner control system shall comply with the requirements of 5.2.6.1
Automatic burner control systems should only be replaced by operator supervision if the operator can promptly implement corrective actions during the heat-up phase The procedure for supervision must be detailed in the instruction manual.
In the event of flame failure, if the design and construction of the IThE ensure that the processing chamber walls' temperature drops below 750 °C within one hour, an acoustic and visual alarm must be installed Additionally, the instructions for use should outline the necessary actions to take following a flash-back.
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For automatic switchover systems, the switching point must be set at a temperature of no less than 750 °C This functionality should be developed in compliance with the protective system requirements outlined in sections 5.7.2 and 5.7.3.
NOTE For radiant tube burner systems additional information is given in 5.2.5.2
5.2.6.4 Automatic burner control systems for burners operating in the open air
Burners with a heat input exceeding 70 kW must be equipped with an automatic burner control system that adheres to EN 298 or EN 125 standards, where technically feasible.
Where the burner heat input rating is 70 kW or less, the flame may be supervised by the operator, provided that the flame is visible from his workplace
If the flame cannot be observed continuously from the workplace, an automatic burner control system complying, if technically applicable, with EN 298 or EN 125 shall be provided
In installations with multiple burners, an automatic burner control system is unnecessary if the burners are configured to ensure that the flame from an active burner can reliably ignite another burner in case of flame extinction However, at least one burner must have a spark restoration system or a supervised permanent pilot, which is designed to ensure that any failure in the permanent pilot or spark restoration system results in the safety shutdown of all burners.
For production operations, the flame supervision function must be integrated into a control system that is not a standard automatic burner control, provided it can initiate an automatic shut-down This device should be designed to trigger an alarm during a safety shut-down, and the necessary procedures following a flash-back must be outlined in the user instructions.
In cases where process requirements dictate, such as when load damage occurs due to lock-out, and for single burner capacities under 100 kW, the lock-out function in a multiple burner system can be substituted with an acoustic and visual alarm This replacement is permissible provided that the operator can respond within a specified timeframe outlined in the user instructions.
Liquid fuels
Liquid fuel pipework
The pipework design shall take into account the composition and properties of the liquid fuel and the need for venting, purging and cleaning
The pipework material shall comply with the relevant standards
NOTE For steel pipes e.g EN 10208-1 and EN 10208-2, EN 10216-1, EN 10217-1 or EN 10220 as appropriate and for copper pipes with EN 1057 allowing connections according to 5.3.1.2
Metal is the primary choice for pipes and components; however, alternative materials may be used when they can meet the same safety standards The specific materials and service conditions will be detailed in the usage instructions.
Oscillations which could cause damage to the pipework, components, safety systems shall be prevented (e.g by firm anchoring, use of flexible coupling)
Where excessive pressure can occur in the pipework due to thermal expansion of the liquid fuel, means of pressure relief shall be provided
Liquid fuel pipework connections must utilize threaded, compression, flanged, or welded types For removable equipment, couplings must guarantee a liquid-tight connection during both connection and disconnection Threaded connections are restricted to specific combinations only.
Threaded connections are essential for applications involving high pressures and temperatures, as they are specifically engineered to function safely under these conditions The manual will provide detailed ratings for both pressure and temperature to ensure proper usage.
Compression connections shall be used comply to EN ISO 8434-1, ISO 8434-2, ISO 8434-3, EN ISO 8434-4 and EN ISO 19879 only for the following combinations:
For other combinations of pressures and diameters connections shall be by means of welded flanges or welded joints The number of connections shall be kept to a minimum
Equipment with threaded connections must adhere to ISO 228-1 or ISO 7-1 standards, as applicable For parallel threads, it is essential to ensure a proper seal to prevent leaks.
Threaded connections must be utilized as long as they guarantee secure fittings and are properly labeled Additionally, the pipework design should be structured to prevent tensile stress on the joints.
Sealants used shall comply with EN 751, Part 1 or Part 2, as appropriate
Hemp shall not be used in threaded connections unless re-inforced with a suitable sealant
Solder with a melting point below 450 °C and adhesives shall not be used
Any pipe passing through an unventilated space shall not have a connection except welded joints
Flanges shall comply with ISO 7005, Parts 1, 2 and 3, as appropriate
Arc welding shall comply with EN ISO 5817, quality level C
Special requirements for liquefied petroleum gas in the liquid phase shall be considered
Any unconnected live pipework shall be plugged, capped or blank flanged by means of metallic parts
Flexible tubing shall comply with the general requirements of 5.3.1.1, together with the following:
shall be as short as possible;
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shall be suitable for the maximum and minimum operating temperatures;
shall be suitable for a pressure 1,5 times the maximum operating pressure (with a minimum of 1 bar), at the maximum and minimum operating temperatures;
shall have a directly accessible, upstream manual shut-off valve;
shall be mounted in such a way as to avoid distortion, whiplash and damage;
shall have end fittings as integral parts of the tubing;
shall be constructed from suitable material both metallic and/or non metallic selected for the application duty and not be easily damaged
The pipework shall be identified with respect to the liquid fuel being carried
The liquid fuel pipework shall be leak tested for tightness and ability to withstand the internal pressure
After assembly, the liquid fuel circuit must undergo a pressure test to ensure tightness, with the test pressure set at a minimum of 1.5 times the maximum working pressure at any point.
Effective leak tightness testing methods include visible leak detection and pressure decay monitoring The instruction handbook (refer to section 7.3) outlines the specific methods and testing frequency required.
In addition to the pressure test on the pipework, all the pressure relief valves shall be tested to ensure their operation at the correct pressure
The external leakage rate must not create a hazardous situation involving flammable or toxic substances under the expected conditions of equipment installation The instruction handbook will specify the frequency of testing required to assess external leakage.
To ensure the liquid fuel pipe maintains the necessary temperature, it must be heated and insulated Additionally, safeguards are essential to prevent the temperature and pressure of the fuel from exceeding the maximum design limits.
The trace heating system must encompass all necessary equipment, including regulating and shut-off mechanisms For effective vapor or liquid heating, it is essential to incorporate appropriate condensate outlets and shut-off valves.
By-passes must not be installed alongside any automatic shut-off valve unless the by-pass serves as a standby system that includes an automatic shut-off valve of the same classification as the one being bypassed.
Means shall be provided to purge gases safely from the liquid fuel system The venting of the purge gases shall take into account, in particular:
avoidance of recirculation into the combustion chamber;
avoidance of introduction into drains and pits;
specific gravity of the gas
5.3.1.10 Equipment supplied with different liquid fuels
When a burner is designed to operate with multiple liquid fuels, it is essential to implement measures that guarantee the supply line of the inactive fuel is securely isolated, such as through physical blocking or disconnection.
Required safety devices
A manually operated isolation valve must be installed upstream of the initial control device in the liquid fuel circuit These valves should be designed or positioned to avoid accidental operation while remaining easily accessible for quick activation when necessary.
They shall be so designed that the "OPEN" and "CLOSED" positions are readily distinguishable (e.g a 90° turn valve if applicable and available)
To ensure optimal equipment operation, it is crucial to prevent particle ingress from both the pipework and liquid fuel This can be achieved by installing a suitable filter or strainer immediately downstream of the first manual isolating valve of the IThE Additional filters or strainers should also be placed upstream of the automatic shut-off valve Furthermore, the positioning of these filters and strainers must allow for easy periodic servicing.
In the event of the installation of a by-pass to the filter and/or the strainer, an identical filtering device shall be installed on the by-pass line
Filter and/or the strainer shall be checked at intervals specified in the instruction handbook
The liquid fuel distribution circuit shall be under the control of automatic shut-off valves Automatic shut-off valves shall comply with EN 264
In the event of damage, failure of the electricity supply or actuating fluid, the automatic shut-off valves shall shut off the fuel supply to the burner(s)
Automatic shut-off valve shall be capable of withstanding backpressure and differential pressure under all process circumstances
For low cycling applications designed for continuous operation exceeding one year, it is essential to implement a redundant safety shut-off system This system must facilitate annual testing to ensure the effective closure of the valves.
For high cycling applications exceeding 10,000 cycles per year, such as pulse firing, it is essential to utilize valves specifically designed for increased cycle durability Regular inspections of these valves should be conducted at intervals outlined in the instruction manual.
For liquid fuels with an initial boiling point below 200 °C or a viscosity under 6 mm²/s at 20 °C, and when the burner input rating exceeds 1,200 kW, it is essential to install two automatic shut-off valves in series.
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A single shut-off valve managing over 1,200 kW must include a proof of closure device to trigger an alarm The instructions for use should outline the necessary actions following a flash-back in case of a failure to close If proof of closure cannot be achieved, it is essential to install two automatic shut-off valves in series.
Where the automatic shut-off valves are closed and lock-out (see 3.48) has occurred, they shall be only manual reset
Automatic shut-off valves must remain closed or cut off fuel to the burner when any safety limit is reached, considering the following conditions.
minimum and maximum liquid fuel flow;
minimum and maximum liquid fuel pressure;
liquid fuel temperature outside a safe operating range;
minimum and maximum air flow;
atomizing fluid pressure outside a safe operating range;
failure of power supply and/or other utilities (e.g compressed air, steam);
failure of heat transfer fluid;
maximum operation temperature of IThE;
In these cases the automatic shut-off valves shall be de-energised by a protective system according to 5.7.2 and 5.7.3
NOTE There may be processes and/or machine conditions that can cause a risk if the burner continues to fire However these conditions are not covered by this standard
Where required, the fuel circuit shall be fitted with calibrated pressure relief valves
A liquid fuel pressure regulator shall be incorporated where this is necessary for control of the flow rate
5.3.2.6 Pressure regulation of auxiliary fluids
For auxiliary fluids (compressed air, steam, ), automatically operated pressure regulators shall be installed where this is necessary for control of the burner system
5.3.2.7 Combustion air, liquid fuel, atomizing and control fluid flow and pressure detectors
Equipment equipped with forced or induced draught burners must include devices to ensure sufficient air flow during pre-purge, ignition, and operational phases Any failure in air flow during these critical stages will trigger a safety shut-down, and if there is no operator supervision, it will result in a lock-out.
This function shall meet the requirements of the protective system according to 5.7.2 and 5.7.3
Before starting up, the air-proving device must be verified in a 'no flow' state, which can be achieved by halting the combustion air supply or interrupting the air signal to the device If the device does not prove the 'no flow' condition, start-up will be prohibited.
Air flow shall be monitored:
It has to be shown that any of these devices provide satisfactory and reliable proof of the flow for all operating conditions
Air pressure detectors shall comply with EN 1854
In all Low Temperature applications, it is crucial to install high and low fuel pressure detectors to maintain operation within preset pressure limits, ensuring proper flow and atomization Any deviation from these limits will trigger a safety shut-down or prevent start-up.
This function shall meet the requirements of a protective system according to 5.7.2 and 5.7.3
In low temperature applications, it is crucial to install high and low fuel temperature detectors to maintain operation within preset pressure limits, ensuring proper flow and atomization Any deviation from these limits will trigger a safety shut-down or prevent start-up altogether.
This function shall meet the requirements of a protective system according to 5.7.2 and 5.7.3
5.3.2.8 Individual manual shut-off valves for multiple burners
For multiple burners which are independently ignited, each individual burner shall be fitted with a manual shut- off valve
The manual shut-off valve(s), if installed, must not compromise the system's safety; for instance, it is essential to ensure that the atomizing fluid valve is confirmed to be open before introducing liquid fuel.
5.3.2.9 Automatic shut-off valves for multiple burners
Individual burners with automatic shut-off valves must adhere to EN 264 standards, where applicable, ensuring that their functionality does not compromise the safe operation of other burners.
Where 5.3.2.3 requires two automatic shut-off valves it is permissible for an individual burner to be shut down by a single automatic shut-off valve in the event of flame failure or for process reasons (e.g thermal input) providing it is a high temperature application
Flue gases shall be vented in a safe way
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IThE units featuring a closed combustion chamber or one with a minimum of three surrounding walls must include a flue system The design of the flue system's cross-sectional area should be based on the volume, pressure, and temperature of the flue gases, which consist of combustion products, excess air, and process emissions.
Combustion air and pre-purging the combustion chamber and the flue passages
The pipework to be designed shall take into account the properties of combustion air
All manual control devices (registers, valves, etc.) for the air shall be set in their pre-determined positions and protected against inadvertent movement
To ensure optimal performance and safety, the combustion air intake must be strategically positioned to avoid the infiltration of exhaust gases, unless specifically designed to mitigate nitrogen oxides (NOx) emissions.
The combustion air system shall be designed in a manner that prevents the back-flow of furnace atmosphere and/or flue gases through combustion equipment
The air circuit shall be designed so as to avoid oscillations that are potentially dangerous
The building and IThE must be designed to ensure a sufficient supply of process and combustion air to the burner(s)/IThE under all circumstances.
5.3.3.2 Pre-purging of the combustion chamber
Before starting up or restarting after a lock-out, it is essential to ensure that no combustible mixture exists in the combustion or processing chamber, as well as in connected spaces and the flue products evacuation circuit, including heat exchangers and dust extractors This safety condition must be met through a pre-purging period conducted immediately before ignition or within a timeframe specified in the instruction handbook.
The pre-purge duration must guarantee that the concentration of combustible products in the combustion chamber, processing chamber, and flue duct remains below 25% of the Lower Flammable Limit of the liquid fuel, assuming these areas are initially filled with flammable gases.
For effective operation, it is recommended to achieve five complete air changes in the combustion chamber, processing chamber, and flue duct Additionally, the airflow rate during the pre-purge phase should be no less than 25% of the maximum combustion air flow rate.
In the case of natural draught, the condition to achieve the above requirements shall be defined in the instruction handbook
Inert or non-flammable gases should replace air when necessary for specific equipment or processes Additionally, alternative methods can be employed to ensure that the combustion chamber and associated areas are free from flammable gases, as long as they maintain an equivalent level of safety.
The pre-purge time and purge procedure and or methodology shall be specified in the instruction handbook
The pre-purge time and the airflow requirement during a pre-purge shall be controlled by a protective system according to 5.7.2 and 5.7.3
Restart after a lock-out condition shall commence with a pre-purge (see 3.48)
Pre-purge should be omitted in specific situations: a) when free oxygen poses a hazard, such as in flammable atmospheres or when it could damage equipment like graphite crucibles or compromise product quality; in these cases, additional precautions, such as purging with inert gas, must be implemented to eliminate combustible residues in the combustion chamber b) Pre-purge is also unnecessary if the combustion chamber temperature exceeds 750 °C, which is the threshold for high-temperature equipment c) Lastly, when re-cycling a burner after a shutdown for control purposes, pre-purging is not required.
1) where the burner is fitted with an independently supervised permanent or alternating pilot; or
2) where the burner is fitted with two automatic shut-off valves complying with EN 264 closing simultaneously or one automatic shut-off valve equipped with a proof of closure device; or
3) with pulse fired burners if the burner shut-off valve is certified by the supplier to be suitable for the increased number of cycles typical of pulse firing; or
4) in multiple burner systems when one or more burners remain alight in the same zone, even in the case of flame failure of one single burner; or
5) when the combustion chamber is proved to be at a temperature above 750 °C (as defined for high temperature equipment) at any point where a flammable mixture coming from the burner(s) will ignite without delay;
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`,,```,,,,````-`-`,,`,,`,`,,` - d) where one burner of a group of radiant tube burners has locked-out, a maximum of one re-start shall be permitted before lock-out after a flame failure (see 3.48), if:
1) each burner has an automatic burner control system; and
2) the exhaust system dilutes the ignitable fuel-air-mixture inside the exhaust system below 25 % of the LFL or the radiant tube, the burner and the connection to the exhaust are designed for the maximum pressure increase that is possible during ignition; and
3) the liquid fuel supply to each radiant tube burner is equipped with an automatic shut-off valve complying with EN 264
The air mass flow rate must be proportionate to the liquid fuel mass flow to guarantee safe ignition and stable combustion at each burner across the operating range This ratio may vary under different operational conditions.
The air/fuel ratio control function shall meet the requirement of the protective system according to 5.7.2 and 5.7.3
NOTE The combination of any air/fuel ratio control (pneumatic or other) in combination with a flame supervision system that detects all possible incorrect ratios is sufficient.
Liquid fuel atomisation
Burners for liquid fuels shall be equipped where applicable with fuel atomizing systems to permit their correct combustion
To prevent contamination, it is essential to implement measures that stop liquid fuel from entering the atomizing fluid pipe and vice versa In cases where the atomizing fluid is a combustible gas, the applicable requirements outlined in subclauses of 5.2 must be adhered to.
Burners
All burners shall be suitable for the working conditions and shall provide operating safety for:
the fuels used (type, pressure, etc.);
the operating conditions (pressure, temperature, atmosphere, etc.);
the nominal input rate and range of regulation (maximum and minimum capacity);
ease of visual monitoring (sight glasses, sight holes, etc.)
The start-up of fuel supply and burners is only allowed when the air and liquid fuel proving devices, such as airflow and fuel pressure indicators, have been verified for proper operating condition, and all relevant interlocks, including burner and valve positions as well as flue dampers, are confirmed to be correctly positioned.
The energy released during burner start-up must be controlled, ensuring that the maximum pressure increase from delayed ignition does not harm the IThE, as outlined in Table 4.
The start fuel flow rate shall be controlled by a protective system according to 5.7.2 and 5.7.3
The ignition process shall be initiated immediately or within the time to be specified in the instruction handbook after the conclusion of the pre-purging stage
During the ignition of the pilot burner, the liquid fuel supply to the main burner must be shut off to ensure safety The burner input rating should be designed to prevent hazardous pressure levels in the combustion and flue chambers Additionally, the automatic valves for the main burner should only open once the pilot burner flame has been confirmed.
Where air enriched with oxygen or oxygen alone is the oxidising agent for the combustion of a fuel,
(commonly called oxy/fuel firing), then the ignition procedures and times for such systems requires specific additional design attention to ensure the equivalent levels of safety
The safety ignition time and total closing time must not fluctuate by more than 20% when the electrical supply voltage is adjusted between 85% and 110% of the nominal value or the voltage range specified by the manufacturer.
The ignition and total closing times shall not exceed the values given in Table 4
Heat input Direct main burner ignition at full rate
Direct main burner ignition at reduced rate Q s reduced rate Q s by pilot burner
Q F max in kW t smax in sec t smax in sec
Q smax in % t smax in sec
Q s = start heat input expressed as a percentage of Q F max
Q s max = maximum start heat input expressed as a percentage of Q F max
Q F max = maximum heat input in kilowatts t s max = maximum safety time in seconds
NOTE For liquid fuels, the ignition safety time commences with the release of the fuel into the combustion chamber
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5.3.5.2.5.1 Flame failure on start-up
In the event of failure occurs during the safety time, the burner shall go to lock-out (see 3.48)
Recycling is permissible under specific conditions, ensuring that equipment safety remains intact The instruction handbook must outline the allowable time delay between recycling and limit the number of cycles to a maximum of two Additionally, recycling must be managed by a protective system as per sections 5.7.2 and 5.7.3 If a flame signal is not detected after these recycling attempts, the burner will enter a lock-out state, as detailed in section 3.48.
In pulse firing burners, if one burner fails to ignite, it will trigger a safety shut-down rather than a lock-out However, if there are three consecutive flame failures, a lock-out will occur (refer to section 3.48) The total number of burners affected by this provision is restricted to meet the requirements of section 5.3.5.3, and the specific number of burners will be detailed in the instruction handbook.
In the event of flame failure during operation the burner shall go to lock-out (see 3.48)
In specific situations, a safety shut-down may be permissible as long as equipment safety remains intact Only one re-cycle is allowed, with conditions outlined in the instruction handbook If a flame signal is not detected at the conclusion of this re-cycle, the malfunctioning burner will enter a lock-out state (refer to section 3.48).
A recycle on a single burner system requires a complete recycle including pre-purge
In any combustion system, the turndown ratio shall be such that the burner(s) is/are fully stable at all firing conditions
Permanent pilots must be provided with a consistent quality of clean fuel and equipped with automatic burner control systems These systems should control the ignited main burner, ensuring that the safety of the equipment remains uncompromised.
Automatic burner control systems
The main flame and pilot burner flame must be monitored by an automatic burner control system, with exceptions allowed only when equipment safety is ensured, as outlined in sections 5.3.6.2 and 5.3.6.3.
In systems where the pilot burner operates alongside the main burner, it is essential to install separate flame detection devices for both the pilot and main flames The main flame detector must be positioned to ensure it does not detect the pilot flame under any circumstances If the pilot burner reliably ignites the main flame, monitoring the pilot flame alone is adequate, provided that the pilot burner’s flow rate is regulated by a protective system in accordance with sections 5.7.2 and 5.7.3, such as a minimum gas pressure switch.
In systems where both the pilot burner and the main burner have individual flame detection devices, it is crucial that the ignition flame does not affect the response of the main flame sensor.
For systems where the pilot flame is extinguished during main burner operation a single flame detector device shall suffice
Where fitted, flame detector device shall be unresponsive to unintended radiation
Automatic burner control devices must adhere to EN 230 standards when applicable However, if process requirements necessitate deviations from these specifications, the system's characteristics may vary, provided that safety and reliability levels remain uncompromised.
Where a burner is required to fire continuously for periods in excess of 24 h, the automatic burner control system shall be designed for permanent operation
The detection of an unexpected flame or a malfunction in the automatic burner control or protective system will lead to a lock-out, as outlined in sections 5.7.2, 5.7.3, and 3.48.
Where manual checking of the automatic burner control system is carried out, the instruction handbook shall specify the procedures to be followed in the event of a malfunction developing
Low temperature equipment fitted with a single burner shall be equipped with an automatic burner control system in accordance with 5.3.6.1
For low temperature multiple burner equipment, each burner shall be equipped with an automatic burner control system
Only one burner can have an automatic control system that operates continuously, as long as the burners ensure stable combustion across the regulation range, share the same air/gas ratio control system, and are positioned closely enough for quick and smooth re-ignition by the adjacent burner if one goes out This guideline does not apply to burners managed by "on/off" systems.
Flame supervision is essential during the start-up phase when the processing chamber wall temperature is below 750 °C, and it can be conducted either through an automatic burner control system or by the operator.
All automatic burner control system shall comply with the requirements of 5.3.6.1
Automatic burner control systems should not be replaced by operator supervision unless the operator can promptly implement corrective actions during the heat-up phase The necessary level of supervision must be detailed in the instruction manual.
In the event of flame failure, if the design and construction of the IThE ensure that the processing chamber walls' temperature drops below 750 °C within one hour, an acoustic and visual alarm must be installed Additionally, the instructions for use should outline the necessary actions to take following a flash-back.
For automatic switchover systems, the switching point must be set at a temperature of no less than 750 °C This functionality should be developed in compliance with the protective system requirements outlined in sections 5.7.2 and 5.7.3.
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