NBR 12313: 2000 Combustion system control and safety for u se of combustible gases in iow and high temperature processes Source: Project NBR 12313: 2000 ABNT / CB09 Brazilian Brazilian Committee Committee on Fue! CE09: 401.01 Commission Combustion System Study and Safety for Use of Fuel Fu el Gases Gases NBR 12313 Combustion Control system and safety for fuel gas utilization in Iow temperature process Descriptors: Gas. Safety This standard cancels and replaces the NBR 13226: 1994 This standard supersedes NBR 12313: 1992 Vaiid from 31.10,2000 Preface ABNT Brazilian Association Association of Technical Technical Standards is the National Standardization Standardization Forum. Brazilian Standards, whose content is the responsibility of the Committees Brazilian (ABNT/CB) and Sectorial Standardization Bodies (ABNT/ONS), are prepared by Study Committees (CE), formed by representatives of the sectors involved, involved, their part: pa rt: producers, consumers consumers and neutral entities (universities, (universities, laboratories and others). The Brazilian Standard Project, developed under the ABNT/CB and ABNT/ONS circulate for public consultation between members of the ABNT and other interested parties, parties, This standard contains Annexes A, B and C, for information only.
1 Goal 1.1 This standard sets out the minimum requirements requirements for combustion combustion systems, with regard to security for the starting conditions, operation and equipment stop using gas. The following conditions, as a function of the temperatures on the inner surfaces of the working chamber and/or process are considered:
below or equal to 750oC (1023 K), where the normal working temperature is insufficient to promote the ignition of the fuel; above 750oC (1023 K), where the normal working temperature sufficient to romote ignition of fuel.
GRADES 1 This standard does not provide specifications for the manufacture of burners, equipment and Controls. 2 This Standard requires that all safety devices used in combustion systems installations installa tions are produced specifically for use with fuel gas and having performance certificate for the purpose in which it is used, issued by National or Internatio In ternational nal competent body. 3 The person responsible responsible for operation operation and maintenance maintenance or consumer consumer equipment equipment fuel gas is required required to maintain this equipment operating with all safety devices in perfect condition. 1.2 This standard considers considers the the following gases: a) natura! gas; b) retired manufactured manufactured gas; c) refinery gas; d) !iquefied petroleum gas (LPG); e) mixing LPG / air: defined as a gas gas from liquefied petroleum petroleum gas mixes mixes with atmospheric atmospheric air and set pressure. NOTE: The control and security for the production of the mixture LPG / air must comply with the guidelines of the supplier of the gas.
1.3 This standard apficase the use of gas equipment installed in commercial commercial or industriai establishments. establishments. 1.4 This standard applies bere bere to duocombustiveis duocombustiveis equipment with the characteristics characteristics described described in 1.1,1.2 and 1.3, when operating with gas. 1.5 This standard does not provide guidance for the constructi construction on and installation installati on of means that the relief of internai pressure in case of explosion equipment, resulting for example from incomplete combustion, fault protection device, or the presence of flammable fuels generated by the process, between others.
The design and installation of such panels and / or parts designed to enable the explosion of relief in accordance with the applicale rules, to be considered by the equipment manufacturer (example: ovens, stoves, boilers, etc.), and the responsive responsive and the operation or maintenance of these. 1.6 equipment operating cyclic cyclic or sporadically at high temperature must must meet the requirements for low temperature equipment. 1.7 This standard applies here to burner whose whose flame is partiaily or compietely confined. 1.8 In this standard are given in Annexes A, B and C the following typical diagrams and fiowcharts: fiowcharts: a.1)typical flowchart gas combustion System for low-temperature equipment with a single
burner; a.2)typicalblockdiagramofthegascombustionSystemstartingsequenceforlowtemperature equipmentwithasingleburner; b.1)typicalflowchartgascombustionSystemforhightemperatureequipmentwithmultiple bumersoffsetbyproofsealingSystem(bypass); b.2)typicalblockdiagramofthegascombustionSystemstartingsequenceforhigh-temperature equipmentwithmultipleburners; b.3)blockdiagramforadeviationproofsealingSystem(bypass)withrestrictionorifice; b.4)methodsfordeterminingtherestrictionorificearea,offsetbysealingproofsystems(bypass);
c) typical flowchart for using alternate gaseous fuel in the same pipe.
2 Defini Defini tions For the purposes of this document, document, aplicamse the following settings: 2.1 doubie lock and unloading: safety lock System System consists of three valves, two automatic lock installed in series in the gas line and a t hird automatic discharge valve valve installed between them with free outiet to the atmosphere. atmosphere. 2.2 Safety lock: gas flow interruption fuel by closing the shut-off valves, accompanied accompanied by the interruption of ignition source. source. 2.3 combustion chamber: chamber: Part of the equipment in which the main combustion combustion takes place. 2.4 the process chamber: Part of the equipment containing containing the product to be processed. 2.5 calls departure: Flame set the correct flow of starting, the main burner or separate pilot. 2.6 calls main: Flame, other than the flame of departure, established the main burner. 2.7 commissioning: set of procedures, tests, adjustments and adjustments of the combustion System, necessary for the placement of equipment in operation.
2.8 high control / low: Demand Control that under the action of the process controller allows the flow of fuel to be burned occurs only in two positions: maximum flow (high flame) and minimum flow (low flame). 2.9 on / off control: demand control which, under the action of the process controller allows operation with a single flow of fuel to be burned. The burner remains on or off. 2.10 Modulating control: demand control which, under the action of the process controller allows the flow of fuel to be burned is variable between the maximum and minimum flow rates. 2.11 flame protection control: Security Control responsible for security lock the drive in the absence of flame. 2.12 Disarm: Maintaining security lock condition of a combustion system, a result of which new game can not take place without manual intervention. 2.13 high temperature equipment: Equipment operating continuously at temperatures above 750 oC (1023 K) in the walls of the combustion chamber and / or process. 2.14 low temperature equipment: Equipment operating in less than or equal to 750 oC temperature (1023 K) in the walls of the combustion chamber and / or process. 2.15
establishment of starting calls: starting flame proven training and supervised on a burner.
2.16
test switch position: Device which shows the position of a movable element by an electrical contact.
2.17 Interlock: Interconnection of security and control components necessary to monitor the state of a required condition. 2.18 period starting flame establishment of: Period between the end of the ignition period and the activation of the main safety lock system. 2.19 period of establishment of the main draws: Period between the activation of the main automatic locking system and the pilot in terruption. 2.20 period of ignition starting calls: Period between the activation of the ignition source and the evidence of the match flame. 2.21
pilot: secondary burner used to ignite the main burner.
2.22 alternate pilot: Pilot who is erased at the end of the main burner ignition period and is again lit before the main burner shutdown due to the control request. 2.23 continuous pilot: Pilot is lit before the lighting of the main flame and is extinguished simultaneously with her, flame supervision independent of the main burner. 2.24 pilot interrupted: Pilot is lit before the lighting of the main flame and is deleted at the end of the period of establishment this. 2.25 thermal power: Amount of energy per unit of time, which can be supplied by the burner equipment, under the conditions for which it was designed. 2.26
pre-purge: Purge the foregoing attempt to burner ignition, starting from a condition of standstill.
2.27 2.27 protection against high pressure gas: protection medium which promotes tripping of the combustion system, when there is an elevation of the gas pressure above a predetermined value for the safe operation of the equipment. 2.28 protection against low pressure gas: protection medium which promotes tripping of the combustion system, reduction occurs when the gas pressure beiow a predetermined value for the safe operation of the equipment. 2.29 purge: introducing an airflow into the combustion chamber, the working chamber and the chimney in order to completely eliminate any remaining fuel mixture. 2.30 burner: Component responsible for the maintenance of a stable flame, where a secure and controlled combustion is generated. 2.31 duocombustivel burner: Burner design which allows operating with gas or other fuel, but not both simultaneously 2.32
combined burner: Burner whose design allows to operate with gas and/or other fuel simultaneously.
2.33
burner with forced air supply: burner in which the combustion air is supplied under pressure.
2.34 induced burner with air supply: burner in which the combustion air is introduced by the depression created in the combustion chamber. 2.35 burner with natural air supply: burner which does not require introduction of air by mechanical means, removing the combustion air directly from the atmosphere through diffusion or carrier. 2.36 pulse burner control system: System multiple burners where it is controlled by the amount and l or period of operation of the burner, buming in two fixed thermal inputs, i.e., through high 1 low control; or on off control. 2.37 pressure regulator: valve designed to maintain a constant downstream pressure regardless of flow variations and pressure or upstream. 2.38 flame sensor: Component of a flame detection system that monitors the presence or absence of the flame. 2.39
starting sequence: Sequence of steps to ensure the early safe operation of a combustion system.
2.40
simulation calls: A condition in which the sensor misnamed detects the presence of the flame.
2.41 automatic system: one that meets the full cycle of events for the operation of a combustion system, without operator intervention 2.42 safety locking system: automatic shut-off valves system, controlled by the control and safety circuit that enables or not the gas flow to t he burner. 2.43 combustion system: set consisting of burner, combustion air supply system, gas supply system, detection system calls and operational control system of the burner. 2.44 Leak proof system: A system that aliows the identification otthe occurrence of gas ieaks through the safety interlock system.
2.45 deviation for sealing verification System (bypass): automatic procedure used in equipment with multiple burners to verify the occurrence of gas leakage through the automatic shut-off valves or manual for each burner. 2.46
flame detection System: Set composed of flame sensor, Signal ampiifier and relay calls.
2.47
tightness test: Procedure to verify the occurrence of gas leaks in the piping and / or components.
NOTE: Specific care regarding the maximum allowable pressure of the components must be observed. 2.48 mechanicai draft: draft type where the displacement of the combustion products is done through mechanical device, usually extractors. 2.49 natural draft: draft type where the displacement of the combustion products is done by natural convection. 2.50
torch lighting: flame source, burning off the combustion chamber.
2.51 automatic locking valve: automatic normally closed valve installed in the gas feed line, designed to allow or disallow gas flow in response to an eiectrical Signal. 2.52 relief valve: autooperada valve, normally closed, designed to allow the flow of gas when the pressure to amount to overcome a preadjusted value. 2.53 manual shut-off valve of the burner: manually operated valve in the gas supply line of the burner, which is downstream of all valves and accessories installed as close as possible to the burner body. 2.54 automatic discharge valve: automatic valve normally open, installed between the automatic shutoff valves in the gas line, with exit to the atmosphere. 2.55 automatic locking valve for overpressure: lock operated by gas pressure valve with manual reset, installed upstream of the throttle with the downstream pressure sensing this and adjusted to block the passage of gas in case of pressure elevation. 2.56 main valve Manual lock: manually operated valve, installed in the gas supply line upstream of all other components, for the purpose of full opening orfull closure ofthe gas supply. 2.57
check valve: the valve that prevents reverse flow.
2.58 normally closed valve: valve, when not activated, or rernains returns to the interrupted passage position. 2.59
normally open valve: Valve that when not activated, rernains or returns to the free passage position.
2.60 starting flow: limited gas flow, which is accepted by a pilot orthe main burner during the establishment period ofthe match flame. 2.61 Verification safe departure: Checking for premature flame or a flame simulation condition, in order to block the Start sequence. 2.62
calls display: Opening intended and appropriate flame view.
2.63 load.
volume of working chamber: All the space used in a device, to transfer heat to the process or the
2.64 control zone: given space inside the machine, which operates under the same parameters (eg temperature, pressure).
3. General cond itio ns 3.1 Gas sup ply 3.1.1 Design and assembly of the internal gas distribution piping shall be carried out in such a way that: No fluctuation of internal di stribution pressure occurs; The maximum permissible pressure drop between the gas inlet and each point of consumption is 20%, regardless of the flow variation; Means are provided to facilitate purging of the gas during commissioning and maintenance; No diversions are installed (by-pass) in parallel with any safety equipment;
3.1.2 Pipes to and including the safety interlock system shall be mounted in a position not vulnerable to the possibility of damage from unforeseen events in their surroundings; 3.1.3 Where it is necessary to use part of a pipeline for more than one fu el within the other’s line, for example by the physical separation of the networks. See attachment C; 3.1.4 Any piping in the gas distribution network which is not connected at the point of consumption and which is under load, must be plugged, capped or have blind flange mounted downstream of the manual locking va lve 3.1.5 The piping shall be visually identified as being a gas pipe; 3.1.6 In cases where condensates can create hazards, means should be provided at the lowest points so that drain any condensate. When wet gases are used, suitable condensate drains to the gas should be installed. Any condensate drain must be in a position where it can be easily vented. Flammable condensates must be collected b y appropriate means. Condensate drain valves must be plugged, capped or blind flanges installed.
3.1.1 Filters 3.1.1.1 A filter shall be installed, immediately downstream of the main manual b locking valve of the equipment, to protect the other components of the gas supply line from deposits and erosion due to particulates. 3.1.1.2 Filters must have filter elements with holes up to 20 microns. 3.1.1.3 It is essential that the pipes are thoroughly cleaned prior to the installation of the components of any combustion system, as well as during and after any modification or maintenance service.
3.1.2 Pipes 3.1.2.1 General It is essential that the pipes are thoroughly cleaned prior to the installation of the components of any combustion system, as well as during and after any modification or maintenance service.
3.1.2.2 Flow rate The piping of the combustion system shall be designed so that the gas velocity does not exceed 45 m/s.
3.1.2.3 Disch arge pipes 3.1.2.3.1
The discharge pipes from the safety system shall have their discharge ends positioned in an external and
ventilated environment. The point of discharge must be located outside the buildings, and positioned so as to guarantee the non-return of gas coming from this point in to the interior of this building: a) b) NOTE -
For gases lighter than air, the building openings (eg: windows) cannot be above the point of discharge; for gases heavier than air, building openings (eg: windows) may not be below point of discharge. The point of discharge should be turned to the external environment and constructed in such a way as to prevent the entry of water and bodies strangers inside.
3.1.2.3.2
The diameter of the discharge pipe shall be at least equal to the diameter of the outlet nozzle of the
element discharge controller. For long discharge pipes or with excessive number of bends, it is necessary to increase in diameter to compensate for load losses. 3.1.2.3.3
For pressure regulators that have an internal relief valve or vent, installed indoors, It is necessary to
install discharge pipes. The same applies to regulators without internal relief valves, but with a vent, when the discharge orifice has a diameter greater than 3 mm. This requirement does not apply to pressure regulators having a second diaphragm, which ensures that no gas leakage into the rupture in the service diaphragm. 3.1.2.3.4
The discharge pipe of a pressure regulating valve shall be independent of the other pipes o f discharge.
3.1.2.3.5
The discharge pipes of the automatic discharge and relief valves may be interconnected, provided that
the cross-sectional area of the collecting discharge pipe is greater than or equal to the sum of the cross-sectional area of the two largest discharge pipes to be connected to it.
3.1.3 Gas press ure Installers of a combustion system shall anticipate the gas pressure ranges reported by the manufacturers and / or designers of the control system.
3.1.4 Manu al lo cki ng valves 3.1.4.1
Manual override valves to be used in gas lines shall meet the following basic requirements:
Course for opening or closing it should b e 90 °;
they must have mechanical limiters of course;
the drive lever cannot be mounted in such a way as to enable an ambiguous indication of its position of operation;
3.1.4.2
be easily opened or closed, even after long periods of no n-operation. A manually operated main valve shall be installed as close as possible to the equipment in a position safe
and easily accessible. In addition, in equipment with multiple burners, each burner shall be fitted with of a manual override valve. 3.1.4.3
Manual valves shall be so installed that, when subjected to moving from their operating position, due to
the force of gravity or vibrations, these forces act in the direction of their closure.
3.1.5 Cont rol of the gas suppl y 3.1.5.1 Check valves 3.1.5.1.1
When the burner running on gas for food with compressed air and / or oxygen, it must be installed. In
the feed line of each burner or group of burners a check valve in the gas line, and another line of compressed air and / or oxygen.
3.1.5.2 Pressur e Regu lators 3.1.5.2.1
A properly specified pressure regulator shall be fitted to control a supply pressure make the gas to the
equipment burner. When the pressure variations do not reach the pilot to cause operational problems, a unique regulator must be installed. NOTE
- A pressure regulator for a combustion plant must meet the following characteristics: - the pressure of a pressure regulator shall not vary by more than 10% of the set pressure, irrespective of the flow, and or pressure variation to its upstream; - the pressure on the outlet pressure, provided it does not flow; - be of the self-operated or operated type, the working fluid b eing the gas itself.
3.1.6.1.1 The discharge pipe of a pressure regulating valve shall be independent of the other pipes of discharge maximum flow rate of gas without pipes extending the pressure counting the impulse lines of pressure regulators shall not exceed 20 m/s, despite those prescribed in 3.1.2.2.
3.1.6 Protection against high pressure and low gas pressure 3.1.6.1 Protect ion against high gas press ure The components of the combustion system are designed to withstand maximum Internal distribution of gas supply, a quantity of main manual locking valve. When it is not A system consisting of an automatic overpressure locking valve with Manual, installed upstream of pressure regulator with downstream pressure sensor and adjusted in A blockage of the passage of gas in case of pressure rise. A partial safety valve must be installed downstream of the pressure regulator and adjusted with an intermediate pressure between a blocking and operating pressure. 3.1.6.1.1 High pressure gas protection must be installed under all circumstances, except when all conditions the following are met: - the pressure loss through the gas p ressure regulator is less than 30% of the minimum outlet pressure (Δp <0.3 Ps); - failure of the throttle does not result in an unsafe starting flow; - the power of the equipment is less than 500 000 kcal/h (580 kW) and the gas supply pressure does not exceed 100 mbar (10 kPa). 3.1.6.1.2 The protection against high pressure of the gas must disarm the system, and new starting must occur from the beginning of the sequence. 3.1.6.1.3 In cases where the pilot gas supply is through an independent regulator and in case of failure of this regulator, the values required in paragraph a) of 4.1.3.4.2 can be exceeded, it is necessary to use protection against high gas pressure exclusive to the pilot. Said protection must be operative from the beginning of the period lighting. 3.1.6.1.4 Between the gas piping and the high-pressure gas sensor, the use of a shut-off valve is forbidden. 3.1.6.1.5 It is not permissible to delay the action of the high pressure sensor after energizing of the automatic locking valves. 3.1.6.1.6 The high pressure sensor shall be installed downstream of the pressure regulator and upstream of the control system and should be adjusted to a value of at most 20% above the maximum possible pressure to occur in conditions. 3.1.6.1.7 During commissioning it shall be checked whether the burner operates safely up to the set pressure of the high pressure sensor
3.1.6.2 Protection agains t low gas pressure 3.1.6.2.1 The installation of protection against low gas pressure immediately downstream of the pressure. 3.1.6.2.2 The protection against low gas pressure shall disarm the system when it occurs. 3.1.6.2.3 If a compressor or other similar equipment is used to raise the gas pressure, a low gas pressure must be installed upstream of it, in order to shut it down, in the event of a reduction of pressure, and prevent automatic restart if the pressure is restored. Authorization to use a compressor and the shear pressure value should be decided by the gas supplier and depend on the l ocal requirements of distribution. 3.1.6.2.4 The use of a locking valve is prohibited between the gas piping and the low gas pressure sensor. 3.1.6.2.5 The low pressure sensor shall be set to a value of not more than 20% below the minimum pressure possible under normal operating conditions. 3.1.6.2.6 During commissioning it shall be checked whether the burner operates safely up to the set pressure of the low pressure sensor.
3.1.7 Air / gas mix tures 3.1.7.1
The use of a combustion system using the distribution of air/gas mixtures within the flammability limit
should be avoided, but when essential the following precautions must be taken: a) The pipe leading the mixture should be as short as possible; b) Devices should be installed to protect the mixer, or blender, flame back (eg: flame arresters and explosion relief devices); NOTE
- For mixer protection systems, specific standards on the subject must be consulted.
c) Mixer or mixing machine must stop and have its gas supply interrupted, under pressure condition abnormal gas inlet, or obstruction in the air intake, and require manual reset to be reset in operation.
3.1.7.2
When distributing air/gas mixtures outside the flammability limit, means shall be provided to control and
prevent the mixer or mixing machine from producing a mixture with an inconsistent and flammable Wobbe number.
3.2 Combust ion air supply 3.2.1 The conditions of ambient ventilation, the equipment and the construction in which it is situated must be such that allow adequate supply of combustion air to the burner under al l operating conditions. 3.2.2 Failure to supply combustion air for burners with forced or interrupting the operation and causing a safety lock or trip. 3.2.3 Installation of a forced or induced air pressure gauge is recommended. 3.2.4 Evidence of airflow can be made by monitoring its static pressure if it can be demonstrated this provides reliable proof of airflow during purging, ignition and operation. 3.2.5 Where the evidence required in 3.2.4 is doubtful, the airflow must be checked by means of the differential pressure, in order to meet the requirement of 4.1.2.2a). - The connection points of a p ressure monitoring system shall be so positioned that when the air or draft are closed, the resulting static pressure difference does not translate into an apparent airflow signal. NOTE
3.2.6 In addition to 3.2.4 and 3.2.5, the fan magnet auxiliary contact must be used to verify its correct position during burner operation. Failure of this interlock shall cause disassembly. Exception is made for fans that use single-phase motors fed directly from the mains. 3.2.7 Combustion fans should not be installed where temperatures combustion conditions. 3.2.8 Air intakes of combustion fans and air intakes of injectors and burners shall be protected against clogging or restrictions. - Attention must be given to the installation of filters for the combustion air due to the process requirement, the burner or when the air intake is located in an environment with excess particulate matter. NOTE
3.2.9 Means shall be provided to securely secure any adjustments made to combustion or drainage. The design shall provide that, in the event of failure of the fastening device, due to the force of gravity or vibrations, these forces act in such a way that the adjustments are changed to a position. 3.2.10 Where a change in combustion chamber pressure leads to a risk condition, such security lock. 3.2.11 When there is an air-generating station that feeds more than one combustion chamber, this shall, in addition to providing evidence of the airflow of the generation system, specifically provide evidence of air flow in each chamber served.
3.2.12 Special attention should be given to the requirements necessary for the operation of complex systems, such as: a) b) c) d)
Draw systems with multiple fans; Multiple burner installations; Electrostatic precipitators; Other devices that may be possible sources of ignition in the exhaust gases.
3.2.13 Air intake from combustion fans should not be carried out in areas where of combustible gases (vapors).
3.3 Electricit y supply 4.1.2 Any electrical installation that feeds an electrical circuit or component must comply with the requirements of standards specific. 4.1.3 The supply of electricity to the components of a combustion system (flame controllers, automatic shut-off valves, ignition transformers, auxiliary elements, etc.) shall be supplied by means of a suitable voltage stabilizer and sized to meet The load required, or the equipment should go to safety locking and/or tripping if the voltage variation exceeds the allowable limits of the system components. 4.1.4 The interruption and/or restoration of the electricity supply at any time cannot safety or disarmament. 4.1.5 A properly identified wiring diagram of the electrical installation must be kept inside the panel. If this is impractical, this diagram should be available near the installation. 4.1.6 If it is necessary to use a timer relay, it should preferably have a fixed or variable switching time with sealing after adjustment. The predetermined times should not suffer a variation greater than 20%, depending on the variation of the supply voltage within its acceptable range of 85% to 110% of the rated value. 4.1.7 In systems where the control panel of the equipment is installed in a control room, or away from the control the installation of the burners, an emergency device must be installed near the burners to enable the system shutdown when necessary.
4.2 Equipment and auxili ary inform ation 4.2.2 General It is essential that all equipment manufacturers or designers make sure that users are provided with information regarding the equipment provided or designed.
4.2.3 Minim um inf ormatio n to be provi ded Manufacturers or designers shall provide all relevant information, including: a) b) c) d) e) f) g) h) i) j)
Name and address of the manufacturer; Complete description of the equipment supplied, including the serial number; Refractory details, if a pplicable; Appropriate electrical diagrams, including logic sequence; Requirements for installation; Type of fuel, thermal power and pressures for which the combustion system is designed; Voltage, number of phases and frequency of electrical components; Size and type of gas inlet connections of the combustion system; Instructions for reversing fuel, for burners designed to operate wi th more than one type of fuel; Clear and simple instructions on stopping, starting, operating, emergency conditions of the combustion system and routine checks.
4.2.4 Nameplates Each component shall be marked in a durable and easily visible manner, with all the information ch aracterization.
4.2.5 Commis sion ing data 4.2.5.1 The manufacturer, installer, designer and / or gas supply company shall provide sufficient information for the correct commissioning of the equipment. 4.2.5.2 The manufacturer, installer or gas supply company shall keep records of the equipment commissioned by its technicians.
4.2.6 Flame dis play It is necessary to provide means for the visual observation of the flame, in order to allow the evaluation of its stability, under all operating conditions.
4.2.7 Explos ion-Proof Devic es Consideration should be given to the need to install explosion-relief devices on gas-consuming equipment.
4.2.8 Equipment involving the use of flammable solvents When the process involves the use o f flammable solvents, additional precautions are required under this Standard. It is advisable to consult specific standards or codes.
4. Specific conditions 4.1 System Requirements 4.1.1 General The requirements of combustion equipment of any system dependent on the operation method, and in particular, the degree of automation required, 80 the security system of the combustion system must be designed and instailed so that in the event of a single failure of any electrical component, electronic or mechanical system should be taken automatically to a safe condition. Some requirements must be met: a) relays and contactors should be de-energized to perform safety lock, disarm, or other security condition; b) a single failure of any component linked to the security locking system can not keep him always energized; c) air flow interlock must be checked in position "naoar" before starting the fan; d) flame detection system should block the starting sequence if it is detected the presence offlame or sensor faiiure (flame simulation) before the start of the ignition sequence; e) the operation buttons, keys, or other devices, incorrectly or out of sequence, can n ot undermine system security; f) where they are used connectors quick coupling type (electronic, electrical or mechanical), their construction must differ as to prevent improper connections, 4.1.2 Pre-purge 4.1.2.1 No attempt ignition can occur without prior security procedures are followed to ensure that no combustible mixture is present in the combustion chamber and or work. This can be achieved by a suitable period of pre-purge. 4.1.2.1.1 Special considerations should be given to the dead space ventilation in working chambers, ducts, etc, before the pre-purge. 4.1.2.1.2 Any auxiliary equipment that might be a source of ignition within the combustion chambers and or work must be disabled during pre-purge. 4.1.2.1.3 It is necessary to interlock the operation of vital components to the effectiveness of purging within the starting sequence (for example fans, switches, switches for confirmation of open air damper, doors, drawing records, etc). 4.1.2.1.4 Where chimneys are equipped with valve for dispensing the adjustment, care should be taken to ensure that your misfit can not result in the closure of the chimney during the purge, i gnition or burner operation. Examples of precautions: a) the vaive for drawing scale adjustment such that when it is in the fully closed position, at least a third of the cross sectional area of the chimney remains open; b) put together a travei stop in the valve for drawing adjustment to prevent its complete closure; c) automatically controlling the valve to adjust the drawing, so that it opens to the proper positions for purging, ignition and burner operation. Such positions should be substantiated and electrically interlocked to the starting sequence and burner operation.
4.1.2.1.5 Specific considerations shouid be taken with respect to pre-purge in cases of processes using controlled atmospheres. 4.1.2.2 In the System with forced or induced air supply shouid be noted:
a) pre-purge shouid be made, preferably with the maximum combustion air flow can not be made at a lower flow rate at 25% of maximum flow of combustion air; b) pre-purge time shouid be such as to ensure that the concentration of any fuel in any pari of the combustion chamber and chi mney, is below 25% of the fuel gas lower flammable limit; it is calculated assuming the combustion chamber and chimney are initially 100% filled with flammable gases. Generally pre-purge shouid provide at least five changes of the internal volume of air contained in the combustion chamber and / or work, ducts and outlet chimneys of the combustion products as well as in peripherai Systems as, for example, air preheater combustion and others; NOTES
1 For equipment with thermal input below 100 000 kcal/h, where the five exchanges parameter of the internal volume of air could harm the process or product, a fewer number of transactions will be accepted, provided it can be demonstrated by the designer this need, and in this case the minimum time necessary pre-purge is 30 s. 2 This paragraph does not apply to Systems that are served by collective chimney, where, in addition to this requirement, must be analyzed the specific conditions of each case.
c)
d) e)
regardless of the number of installed burners, the equipment must be purged, usandose all burners, unless it can be demonstrated that a more effective purging is obtained usandose fewer burners with a higher air flow burner; any hood or fan shouid be operating, and all records correctly positioned to ensure the effectiveness of pre-purge; in case of disconnection of all the burners, devese perform a pre-purge as specified in paragraphs a, b, c and d above, except when used pulse burner System (for normal work regime).
4.1.2.3 In the System with natural air supp ly shouid be noted:
a) any attempt to ignition and / or re-ignition must be preceded by a controlled fixed time automatically and interlocked to the c ontrol System and flame protection with enough time to vent any residual fuel mixture, which may be present in the equipment; b) all equipment doors must remain open until all burners are ready to be connected. If the efficiency of drainage is reduced by the fact that the doors have been opened, they must be kept in a position such as to ensure the effectiveness of the purging until its completion, and then, if possible, opened before start ignition by the ignition of the burners. 4.1.2.4 In the following cases the pre-purge may be omitted (both during the match and after blocking):
a) under which the presence offree oxygen can be dangerous (eg flammable atmospheres) or their presence could affect the equipment or product quality; b) In these cases, additional precautions must be taken to prevent leakage of gas through blockade of blo automatic valves, through the use of two Class 1 or A valve in series with a sealing proof System. c) when it is proved that the combustion chamber is a temperature higher than 750 oC (as defined for high temperature equipment).
4.1.2.5 In the case of the burner stop clue to the process control action, pre-purge is not required to split when:
a) burner is installed with a continuous or alternate pilot supervised; b) systems with pulse burners since the automatic locking valve each burner is certified that is suitable to the high number of cycles required for the firing p ulses; c) when the burner is installed with two automatic Class 1 or A shut-off valves in series, simultaneously ciosing with a seating verification system; NOTE For pulse burners the sealing proof device is not required. d) systems with multiple burners, where one or more burners are lit in the same zone. 4.1.3 Ignition and establishment of starting calls 4.1.3.1 General 4.1.3.1.1 The ignition and starting flame establishment shouid occur shortly after pre-purge period. 4.1.3.1.2 For the burner firing of a smooth and reliable way, devese provide an adequate source of ignition and take special care with its positioning (see 4.1.3.5). 4.1.3.1.3 The ignition source must be triggered before or simultaneously with the gas supply. 4.1.3.1.4 The ignition and I or starting flame establishment must be done safely and au tomatically without the use of any hand torch. 4.1.3.2
Torches gas firing equipment to set as hi gh temperature
4.1.3.2.1 lighting torches are used for ignition of the match flame or main flame, when there is no automatic ignition. 4.1.3.2.2 should be provided displays and portholes for ignition, so that the burner available for easy access to your ignition, and starting flame and main can be clearly observed and should be guaranteed the saf ety of the operator. 4.1.3.2.3 For firing a burner with torch, three simultaneous operations are required, without displacement of the operator. They are: positioning of the torch on the burner, opening the manual shut-off valve and the burner flame of view. After firing the starting flame and main, the torch should be removed and can not b e used to stabilize any of them. NOTE
4.1.3.2.4 In the case of gas lighting torches, a manual shut-off valve, easily accessible, must be installed upstream of the supply hose. The hose should be as short as possible. 4.1.3.2.5 The gas igniting torches should be stable under all operating conditions and shall not be affected during the firing, pressure fluctuations, variations in the pressure of the combustion chamber, etc. 4.1.3.2.6 The flow of ignition gas torch must be limited to the amount necessary for a reliable i gnition and can not exceed the specified values for starting fire. 4.1.3.3 Ignition by electrical arcing 4.1.3.3.1 should be provided an adequate ground for the system. 4.1.3.3.2 All high voltage cables should be as short as possible, and all terminals and altatenséo cables must be protected to prevent the possibility of personal injury or system failures.
4.1.3.3.3 should be used, preferably with a single transformer secondary pole. Transformers that have more than one pole may be used, but the other poles are not used must be protected to prevent th e possibility of accidents. 4.1.3.3.4 The transformer should be mounted as close to the bu rner, but where is not subject to o verheating. 4.1.3.3.5 All ignition electrodes must be mounted and property insulated, so as to ensure that arcing does not occur outside the correct position to ignite the flame of departure. 4.1.3.3.6 The spark for ignition can not be energized before the prépurga period has been completed and should be isle-energized at the end of the ignition period of the match flame (see 4.1.3.4.3). 4.1.3.3.7 To set equipment as high temperature, and that does not have control and protection system flame should be possible to visually confirm the presence of spark ignition and starting gas flame and main, while the abrese manual shut-off valve of the burner. 4.1.3.3.8 If it is necessary to pass the altatensao of cable conduit, it must be unique. 4.1.3.4
starting Flame
4.1.3.4.1 The ignition of a burner must be carried out:
a) through a pilot with stable and correctly positioned flame, and the subsequent establishment of the main flame, or; b) b) through direct ignition of the main flame, set the correct flow for the flame of departure, and the subsequent establishment of the main fl ame itself, for burners with forced air supply and burners, to supply natural air with thermal energy released in the chamber combustion up to 100 000. Kcal/h (120 KW); c) by gas lighting torches to set equipment as high temperature (see 4.1.3.2.). 4.1.3.4.2 The energy released during the starting flame ignition period should be limited. The following criteria must be met to determine the starting flow:
a) for the flame established starting according to 4.1.3.4.1a) limit the starting flow to a maximum of 25% of the required gas flow to obtain a stoichiometric burning, with the air flow that is proven, it is supplied to the main burner during the ignition period of the starting flame; NOTE When applying the criteria defined in 4.1.3.4.2a) lead to low thermal power drivers, especially in the case of burners with high ratio of maximum power/minimum power, special considerations must be made to ensure adequate power and pilot ensure smooth ignition of all gas through-holes of the main burner. b) to set the starting flames according to 4.1.3.4.1b), the release of energy during its ignition must not exceed 100 000 kcal/h (120 kW). 4.1.3.4.3 The ignition time of departure calls can not exceed 7s. Admitese that this period be extended to 15s, only for burners with natural air supply, thermal power of less than 300 000 kcal/h (350 kW). 4.1.3.4.4 In the case of non-establishment of the starting flame should occur safety lock and/or automatic tripping. However, in certain cases (for example for automatic ignition cycles) the split is acceptable, provided that the safety equipment is not compromised. The conditions and split number can not exceed three for burners with power more than 300 000 kcal/h (350 kw) and must be specified in the instruction manual. lf there is no flame signal at the end of the split, the burner should go to disarm.
4.1.3.4.5 In systems with multiple burners starting flame from a burner should not interfere with the starting other burners. 4.1.3.5 Pilots (additional requirements) 4.1.3.5.1 In burners where the starting flame is established on a pilot burner, the chamapiloto must be erased or interrupted during operation of the main flame; otherwise, there must be a separate and reliable detection of the main flame. In cases where there is more than one unit power burner, below 300 000 kcal/h (350 kW) installed in a single combustion chamber, permitese the use of continuous pilot with p rotective flame without sensing separately from the main flame. NOTE
4.1.3.5.2 In the case of burners with natural air supply and thermal power of less than 300 000 kcal/h (350 kW), admitese continuous pilot burner without independent sensing the main flame, provided that they met the requirements 4.1 .2.3. 4.1.3.5.3 A pilot flame should be stable under all conditions of operation and must not be affected by the combustion air of the main burner, pressure fluctuations over the burner ignition, pressure fluctuations in the combustion chamber, etc. Note
stabilization by continuous sparking, among others, is not permitted.
4.1.3.5.4 Pilots must be constructed and assembled so as to be accessible to performing maintenance. 4.1.3.5.5 To equipment defined as high temperature, which are not installed flame protection control systems (see 4.1.4.3), the chamapiloto should be checked visually after its ignition, to ensure the establishment of a suitable flame with conditions to provide a smooth and reliable ignition of the main flame. 4.1.3.5.6 The pilot gas supply must be taken upstream of the security locking system of the main burner, with due regard to the requirements in 3.1.5.2.1. 4.1.3.5.7 The pilot supply system (air, gas, spark) must provide a means to set your settings to always provide the same lighting conditions. 4.1.3.5.8 The installation against high-pressure gas protection devices may be required to q ueimadorespiloto (see 3.1.6.1.3).
4.1.4 Detection Flame 4.1.4.1 A detection system and fire protection must be installed for each burner individually. 4.1.4.2 To set equipment as high temperature, a detection system and fire protection is not required, but must be installed for each individual burner, in the following cases: a) in which equipment, for process requirements, a part of the operation is performed at temperatures less than 750oC (1023 K) and the combustion chamber or process; b) equipment that provide more than one type of process and occasionally work at temperatures below 750oC (1023 K); c) in burners with multiple devices where one or more zones of control operate continuously or sporadically at temperatures less than 750 oC (1023 K), at least for all the burners of these areas; d) where there are technical or operational need.
4.1.4.3 To set equipment as high temperature, where a detection system and fire protection is n ot installed: a) the equipment must be under the constant supervision of a qualified operator during its startup, at least until the temperature of 750oC (1023 K); is reached; b) devese immediately stop the gas supply to any burner that has suffered loss of flame. In equipment with multiple burners, only the burner that suffered loss flame needs to be deleted. However, if there is any possibility that this may result in an unsafe condition, so all equipment should be paralyzed; c) design for special care to ensure that, i n equipment with multiple burners, if the loss of flame in one or more of them r esult in reducing the temperature beiow 750oC (1023 K), the equipment or p art thereof, are provided means that the operator is alerted and safe procedures are adopted; d) installations with multiple burners must be equipped with a leak proof system for manual shutoff valves for each burner; e) in case of fall of temperature below 750oC (1023 K), the system must provide a means of automatically generating an alarm signal that can be used for system lock, and providences or operator.
4.1.4.4 When the burner has a power output exceeding 100 000 kcal/h (120 kW) and operate continuously for a period exceeding 24h, shall be equipped with a fl ame detection system with continuous self-check failure (self checking) or burner should be turned off and performed the same split as in a period of less than 24h. 4.1.4.5 The flame detection system with continuous self-checking fault (self checking) must be actuated automatically every period of at least 1h, with the burner operating. 4.1.4.6 A flame detection system must be installed individually for each main burner or set of pilot and main burner, and the flame must monitor only this set. This system must be installed so as to cause the disruption of gas supply to this burner. A flame failure will cause the automatic tripping of the burner. 4.1.4.7 The detection system and fire protection must de tect the flame of departure, provided the pilot, onlyif it is in a position that allows a smooth and reliable lighting of the main flame. The location of the sensor must be such that in the event of reduction, slope or unstabie starting flame, which may damage the main fl ame lighting security, this calls starting not sensitize the sensor, causing the automatic tripping of the system. 4.1.4.8 The automatic flame detection should check for the presence of flame or false signal that simulates this, before attempting to burner ignition. The occurrence of this fact the automatic flame detection should cause the automatic tripping of the burner. 4.1.4.9 Any detection system and fire protection must respond to loss of calls within 4s. 4.1.4.10 Any detection device and flame protection using microprocessor or microcontrolier must have a program (software), constructed such that access to and modification thereof by the user i s impossible. 4.1.5 Establishment of the main flame 4.1.5.1 Only after the establishment and verification of the match flame, podese allow the lighting of the main flame.
4.1.5.2 After the establishment and verification of the match flame, there must be a period of establishment of the main flame for each burner. This p eriod should be limited to a maximum of 3s in the case of rapid opening valves. in the case of slow opening valve until one third o f the total opening time, provided that no more than 10s. At the end of this time must occur: a) for systems with interrupted pilot, the pilot flame should be extinguished and devese supervise only the main flame; ' b) for systems with continuous pilot, the presence of the main flame should be proven by its own flame detection system. it is essential that the main flame is stable without the presence of pilot flame. 4.1.5.3 If the main flame failure, the system should go to di sarm and 4.1.2 must be met. 4.1.5.4 in equipment with multiple burners, in case the occurrence of flame failure, the respective burner should go to automatic tripping (or tripping exclusively manual for equipment defined as high temperature). NOTE Special considerations must be made by the designer, in order to evaluate the need to bring the whole system to disarm in the event of flame failure in more than one burner. 4.1.5.5 Where one main burner is ignited by a pi lot, the thermal power of the main flame during its establishment period may not exceed 35% of the maximum thermal power of the burner. 4.1.5.6 Restrictions on the thermal power of the main flame in 4.1.5.5 do not apply to: a) systems where the starting flame is obtained through ignition of the main burner itself, in accordance with 4.1 .341 b); Note Podese allow the main burner ignition at the maximum thermal power, provided that the energy released during the ignition satisfies the requirements 4.1.3.4.1b) and 4.1.3.4.2b). b) in the case of multiple burners installed in a single combustion chamber and the unit po wer is less than or equal to 300 000 kcal/h (350 KW), the lighting of the main flame of each burner can be done at maximum power; c) in the case of burners with natural air supply and thermal power of less than 300 000 kcal/h (350. KW), admitese the main burner ignition at full power through single pilot provided that the lighting the flame remains fully within the combustion chamber, even when the device is at ro om temperature. 4.1.5.7 The burner design must ensure smooth ignition of all gas passage holes. 4.1.5.8 in systems with multiple burners, the main flame should preferably be lit separately and in order compatible with the equipment of the project. 4.1.5.9 is not allowed switching on a main flame through the cross firing wi th another major. However, Recognition is that some burners with multiple portachamas are designed to be lit by a single source of ignition and therefore should be treated as a simple burner. 4.1.5.10 The power delivered by the main flame during its establishment period, should be established separately by monitoring the air supply conditions and gas eg usandose pressure sensors and I or pro of of position, and this case without the possibility of manual intervention. 4.1.5.11 For systems equipped with mechanical connections (levers, rods) directly connecting the gas control valves and air, it is acceptable to prove the correct position of the valves during the period of establishment of the main flame. For example, in systems using prépurga air valve in the high heat position, podese prove the complete opening of the air control valve to drain through a test switch position without the possibility of manual intervention and, after the prépurga, another switch can check if the gas control valve is open correctly to control the power to be released by the main flame during its establishment period.
4.1.5.12 The establishment of the main flame must be done in order to ensure smooth firing, avoiding delayed ignition occurs. 4.1.6 security lock system 4.1.6.1 General 4.1 .6.1.1 This section defines the requirements for automatic shut-off valves for all combustion systems covered by this standard. It is necessary that all the burners are under the control of two or more automatic shut-off valves. The type of automatic shut-off valve required in this section is defined by the requirements of its closing force. The automatic shut-off valves do not n ecessarily have to open automatically. For high temperature equipment with multiple burners, the individual automatic locking device of the burner may be regarded as one of the safety shut-off valves. 4.1.6.12 The body of the automatic shut-off valves and automatic discharge may not have axles, levers, steering wheels, etc. exposed to permit manual actuation of the valve, independent of the normal sequence of operation. 4.1.6.1.3 Each automatic shut-off valve should have a specific device failsafe to provide its clos ure, so that close when de—energized or when subjected to a failure of its operating fluid. They must have closing spring with sufficient force to ensure its tightness under operating conditions. 4.1.6.1.4 The security locking systems must be installed in a safe position and as close to the burner. 4.1.6.1.5 The condition of tightness 'of valves that make up the security locking system should be checked periodically. 4.1.6.1.6 The valves used in safety lock systems must be valves that have been developed for this specific application. This requirement must be satisfied through technical documentation, to prove that the valve in question was developed for the automatic locking application fuel gas combustion system. In addition, the manufacturer must provide a certificate attesting that their valves support a lifetime of proof test at least 250,000 operations without presenting any irregularity in their performance. 4.1.6.2 Automatic Shut-off valves of the main burner (normally closed) 4162.1 The gas supply for each main burner or group of burners must be under control of a safety interlock system. NOTE It is understood as a group of burners, the set of two or more burners installed in the same combustion chamber and close to each other. 4.1.6.22 The safety interlock system installed to a burner or group of burners must meet the requirements listed in Table 1, which considers the thermal power released by a burner or group of burners. 41.62.13 The security locking system should be de—energized when the machine is turned off. 4.1.6.2.4 The automatic locking system must stop the gas supply to the burner or group o f burners whenever, for example, one of the foll owing hazardous situations occur: gas pressure below or above the safe operating range of the burner; combustion air failure; ’ power outages; lack of flame; by performance of equipment safety interlocks (examples: high vapor pressure, low water, excess temperature); , circulation system failure of the process.
4.1.6.2.5 When the automatic locking system is pie—energized by a risk, new start can only take place by manual intervention. 4.1.6.2.6 For systems with multiple burners of different power given the same working chamber, all the burners should have the safety interlock system with the same configuration. Selecting this configuration should be done according to table 1, considerandose the highest power burner. 4.1.6.2.? Where two automatic shut—off vaives are used, one of them can be us ed for demand control. NOTE Additional care must be taken when using automatic shut-off valves, as demand for control valves in burners with forced or induced air sup ply (see 4.1.8.4). 4.1.6.28 The maximum gas flow speed through automatic shut-off valves must not exceed 30 ml 5. 4.1.6.3 Automatic Shut-off valves departure ftame (no rmaily closed) 4.1.6.3.1 independent thermal power starting flame, and even if it is less than 100 000 kcal I h (120 kW), the security locking system should meet the requirements of table 1. 4.1.6.4 Requirements for automatic shut-off vaives The automatic shut—off valves must meet the following requirements: a) Maximum closure time should be 1 sec; b) should be selected so as to open against all possible differential working pressures up to the pressure iimit to which they are classified; c) maintaining under a watertight closing differential pressure condition of at least one and a half times the working pressure to which has been classified; d) maintain a tight closure under all differential pressures in counter flow, as defined below: valves with nominal diameter up to 50 mm (2 ") including 150 mbar (1.5 kPa); Vaives with a nominal diameter of 50 mm (2 ") 100 mbar (1 kPa).
At tac hm ent A (Inf ormat ive) A.1
Low temperature equipment with single burner Typical gas flow system flowchart for low temperature single burner equipment
01 02 03
Main burner Flame protection control Flame sensor
11 12 13
Manual locking main valve Filter Pressure regulator
21 22 23
Pressure gauge Register for pressure gauge Low pressure switch
04 05
Ignition transformer Flexible tube
14 15
Automatic overpressure locking Relief valve
24 25
High pressure switch Pilot burner
06 07
Manual burner lock valve Manual air flow adjustment valve
16 17
Automatic shut-off valve Automatic discharge valve
26 27
Draw control damper Exhaust fan
08 09 10
Air flow control valve Servomotor Combustion air blower
18 19 20
Bubbler Leakproofness system Gas flow control valve
28 29 30
Differential pressure switch Manual pilot locking valve Manual gas flow control valve of the pilot
A.2 Typical block diagram of the starting sequence of the gas combustion system for low temperature with a single burner
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