Flash Back Arrester

8/12/2019 Flash Back Arrester

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FLASHBACKFLASHBACK

ARRESTERARRESTER

A PresentationA Presentation

Pramod KulkarniPramod Kulkarni


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installed on the Gas Welding or Cuttinginstalled on the Gas Welding or Cuttingorch.orch.

It is also known as SAFETY SEAL It is also known as SAFETY SEAL

OF THE FLAME UPSTREAMOF THE FLAME UPSTREAM

which prevents the UNINTENTIONALwhich prevents the UNINTENTIONALBACKFLOW of gases in the pipeBACKFLOW of gases in the pipe


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A "Flashback" is the combustion of a flammable mixtureA "Flashback" is the combustion of a flammable mixture

within the equipments used for handling of flammable gaseswithin the equipments used for handling of flammable gasesviz. Pipelines, Gas Regulators, Gas Mixing Devices, Cylinders,viz. Pipelines, Gas Regulators, Gas Mixing Devices, Cylinders,etc.etc.

Backfire / Flashback is defined as a Retrogression of theBackfire / Flashback is defined as a Retrogression of the,,

mixer i.e. at the tip of the torch or the hoses back into themixer i.e. at the tip of the torch or the hoses back into thesystemsystem

A "Flashback" is a root cause of backfire, which normallyA "Flashback" is a root cause of backfire, which normallya ears in a mixin device.a ears in a mixin device.


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A Flash ro a ation throu h an un burnt as atA Flash ro a ation throu h an un burnt as at

a rate that is above the speed of sound is calleda rate that is above the speed of sound is calledDetonation. It has a power to Explode Pipelines,Detonation. It has a power to Explode Pipelines,,, -- ..

It is prevented by maintaining proper distanceIt is prevented by maintaining proper distance

Arrestor, often termed as the RunArrestor, often termed as the Run--Up.Up.

At least at two locations, Flashback Arrestors areAt least at two locations, Flashback Arrestors are

to be installed, viz. Endto be installed, viz. End--ofof--line & Inline & In--line for aline for aindividual gas line to reduce the possibility ofindividual gas line to reduce the possibility of

..


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The backfire occurs due to excessive heat and theThe backfire occurs due to excessive heat and thepresence of fuel and oxidizer in the mixing device.presence of fuel and oxidizer in the mixing device.

enough to cause a "Flashback" inside the mixing device.enough to cause a "Flashback" inside the mixing device.

The backfire can be considered as a very tiny or a microThe backfire can be considered as a very tiny or a microvers on or cause o an exp os on.vers on or cause o an exp os on.

In event of a backflow, the residual mixture is consumedIn event of a backflow, the residual mixture is consumedby the flame point in such a rapid speed that it mightby the flame point in such a rapid speed that it might

create a condition of velocity of a shock wave, which iscreate a condition of velocity of a shock wave, which isthe probable cause of eruption of a "Flashback".the probable cause of eruption of a "Flashback".


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Gases in Cylinders (Pressure Imbalance )Gases in Cylinders (Pressure Imbalance )

. .

Failure to purge the Gas Systems.Failure to purge the Gas Systems. Improper pressure setting of Gases.Improper pressure setting of Gases.

Clo ed or Blocked Ti of Weldin orClo ed or Blocked Ti of Weldin orCutting TorchCutting Torch

..


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..

back to the source, wherein the valve seat ofback to the source, wherein the valve seat ofthe Non Return Valve is fit enough to seal athe Non Return Valve is fit enough to seal apressure differential and it is sufficient aspressure differential and it is sufficient as

essential.essential.

However a Non Return Valve will not stop aHowever a Non Return Valve will not stop a

F as ac ecause it oes not contain a veryF as ac ecause it oes not contain a verybasic element, which holds back the Flashesbasic element, which holds back the Flashes

. .


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when one cylinder gets empty, thuswhen one cylinder gets empty, thus

systemsystem

This condition results into the extremelyThis condition results into the extremely

angerous s ua on s ua on w en ueangerous s ua on s ua on w en ueand oxygen gases get mixed in the hosesand oxygen gases get mixed in the hoses


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the tip of the torch and the flame getsthe tip of the torch and the flame gets

This can happen at very High Gas ExitThis can happen at very High Gas Exit

This can also happen when the tip of theThis can also happen when the tip of theorc s oo c ose o e wor p ece oorc s oo c ose o e wor p ece o

which is at a very high temperaturewhich is at a very high temperature

he flame may get rehe flame may get re--ignitedignitedautomatically or through the ignition agentautomatically or through the ignition agent


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Another points responsible to developAnother points responsible to develop

enough to bring the hydrocarbon/air mixture to the

auto ignition temperature, rapid combustion will

start. Heat transfer from the hot surface dependson gas velocity and turbulence, explaining why

sw r , ype urners o en seems more s a e an

more linear types.


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rkrkSparks are used to ignite pilot burners andSparks are used to ignite pilot burners and

..

Occasionally small sparks (staticOccasionally small sparks (static

combustion, but the extra energy in acombustion, but the extra energy in a..

Undesired sparks, such as those resultingUndesired sparks, such as those resulting

or fans, can initiate combustion andor fans, can initiate combustion and. .


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DustDust

while welding or cutting and this dustwhile welding or cutting and this dust

blockage resulting a loud sound putt andblockage resulting a loud sound putt and-- --

results in the flame to fold back into theresults in the flame to fold back into the


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Functioning of FlashbackFunctioning of FlashbackArresterArrester

Flashback arrestor is a simple devise, whichFlashback arrestor is a simple devise, whichquenches the flame using the following methodsquenches the flame using the following methods

than the minimum flame velocity of the fuelthan the minimum flame velocity of the fuel

gas )gas )

pipepipec) By placing a flame arrestor at the end of thec) By placing a flame arrestor at the end of the

flammable mixture pipe feeding a flare orflammable mixture pipe feeding a flare orburner, flame can be prevented from movingburner, flame can be prevented from moving

velocity.velocity.


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Functioning of FlashbackFunctioning of FlashbackArresterArrester

d B assin a otentiall flammable mixtured B assin a otentiall flammable mixture

through a water chamber or some sort of heatthrough a water chamber or some sort of heatsink. This dissipates the heat and quenchessink. This dissipates the heat and quenches

e as ac .e as ac .

e)e) By blocking the fuel gas path, with a suitableBy blocking the fuel gas path, with a suitable

thermal fuse lu casin the flashback to diethermal fuse lu casin the flashback to die

out.out.

f)f) By blocking the flow of fuel gas in the oppositeBy blocking the flow of fuel gas in the opposite

direction by acting like a non return valve.direction by acting like a non return valve.


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have TWO FUNCTIONS :have TWO FUNCTIONS :..

flame arresterflame arrester

in check valvein check valve

metal filter. The gas can flow inmetal filter. The gas can flow insmoothly but the flame is extinguished )smoothly but the flame is extinguished )


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It is alwa s advisable toIt is alwa s advisable to

install a flash backinstall a flash backarrestor on ue ne asarrestor on ue ne as


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can cut off the supply of Oxygen in casecan cut off the supply of Oxygen in case

This is important as additional Oxygen canThis is important as additional Oxygen can


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Flashback Arrester is installed on the torch or aFlashback Arrester is installed on the torch or aline, it creates a PRESSURE DROP causing theline, it creates a PRESSURE DROP causing thereduction in FLOW CAPACITY.reduction in FLOW CAPACITY.

Ensure the Flow Demand of the system as perEnsure the Flow Demand of the system as perits design and then install appropriate Flashbackits design and then install appropriate Flashback

Arrester w ic wi meet t e require F owArrester w ic wi meet t e require F owDemand of the systemDemand of the system


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he reasons for usin a rotective device such as ahe reasons for usin a rotective device such as a

Flash Back Arrestor on a fuel gas line or even on aFlash Back Arrestor on a fuel gas line or even on acylinder are :cylinder are :

1.1. Safety of Human Life and PropertySafety of Human Life and Property

2.2. Flashback occurs under various conditions.Flashback occurs under various conditions.3.3. he flashback occurs inside the pipeline or vessels.he flashback occurs inside the pipeline or vessels.

4.4. The flame moves through a vessel or pipe.The flame moves through a vessel or pipe.

.. pipe or vessels, and if the pipe is long enough thepipe or vessels, and if the pipe is long enough thevelocity can increase to detonation levels, which arevelocity can increase to detonation levels, which are


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Flashback ArrestersFlashback ArrestersClassificationClassification

method of INTERRUPTIONmethod of INTERRUPTION

Active Methods ( Require maintenance ofActive Methods ( Require maintenance of

Velocity )Velocity )

as no moving parts or instruments areas no moving parts or instruments areinvolvedinvolved


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1.1. Venture T e Venture T e

Venture flashback arrestors simply create a restrictionVenture flashback arrestors simply create a restriction

the gas velocity is faster than the flame speed,the gas velocity is faster than the flame speed,preventing progression of a flashback upstreampreventing progression of a flashback upstream

Flashbacks in the direction of flow can still ha en.Flashbacks in the direction of flow can still ha en. Even a partly closed valve can create a high velocityEven a partly closed valve can create a high velocity

for flashback preventionfor flashback prevention If gas flow stops, the venture is no longer effective, soIf gas flow stops, the venture is no longer effective, so

methods to measure flow and add make up gasmethods to measure flow and add make up gasnitro en for instance are often included.nitro en for instance are often included.


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On line On Flashback Arresters :On line On Flashback Arresters :

1.1. Most commonly usedMost commonly used2.2. Mec anica ame arrestors are i e wit metaMec anica ame arrestors are i e wit meta

or ceramic, which absorbs heat from aor ceramic, which absorbs heat from a

flashback uenchin it to a tem erature belowflashback uenchin it to a tem erature belowwhat is needed for ignition. This stops thewhat is needed for ignition. This stops theflame.flame.

.. flow rate, if a flame travels to the face of theflow rate, if a flame travels to the face of thearrestor, it can become stable at that point.arrestor, it can become stable at that point.


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enough, ignition temperature can be reachedenough, ignition temperature can be reachedon the upstream side of the arrestor and theon the upstream side of the arrestor and theflashback can proceed.flashback can proceed.

( For this reason, a temperature switch is( For this reason, a temperature switch isoften installed on theflame side of eachoften installed on theflame side of each

arrestor a ng an act ve e ement .arrestor a ng an act ve e ement .


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--

DryDry

etet

Each type has its own advantages andEach type has its own advantages anddisadvantages. Most oxydisadvantages. Most oxy--fuel flashbackfuel flashbackarrestors are the dry type.arrestors are the dry type.


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combination of methods to stop flashbackcombination of methods to stop flashback

workshops, home or portable oxyworkshops, home or portable oxy--fuel kitsfuel kits

orientationorientation

Often small and light enough to beOften small and light enough to be


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Flame Trap : To cool the flame front. They are designedFlame Trap : To cool the flame front. They are designedto a ow ree ow o gas t roug t em ut to ta e t eto a ow ree ow o gas t roug t em ut to ta e t e

heat out of the flame front to get it below the ignitionheat out of the flame front to get it below the ignitiontemperature of the burning gas mixture.temperature of the burning gas mixture.

It is a device wherein the sealing is done by a sinteredIt is a device wherein the sealing is done by a sintered

metal or any other means other than employing a liquidmetal or any other means other than employing a liquid. .

The most common types are:The most common types are:

Sintered metal or ceramic.Sintered metal or ceramic. Layers of mesh.Layers of mesh. Ceramic beads.Ceramic beads.


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em eratureem erature--tri ered valves to sto the as flowtri ered valves to sto the as flow

completely.completely.

It relies on extracting heat from the flashback to stop itIt relies on extracting heat from the flashback to stop it

Most arrestors have a temperatureMost arrestors have a temperature--controlled valve thatcontrolled valve that

will cut off the gas flow when the unit reaches aroundwill cut off the gas flow when the unit reaches around ,,

The unit cools (if the unit is automatic) orThe unit cools (if the unit is automatic) or

he reset button is pressed (if the unit is manual).he reset button is pressed (if the unit is manual).

A check valve that closes due to the back pressure.A check valve that closes due to the back pressure.


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widely used in major applications at majorwidely used in major applications at majorinstallations because of the inherentinstallations because of the inherentdesign advantage.design advantage.

Leaka e roblems are minimized due toLeaka e roblems are minimized due toabsence of wet media.absence of wet media.

No reaction with source gas.No reaction with source gas.

Easy to install, handle & maintainEasy to install, handle & maintain


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following the principle of a siphon where thefollowing the principle of a siphon where theliquid stops the entering deflagration and / orliquid stops the entering deflagration and / ordetonation and extinguishes the flame.detonation and extinguishes the flame.

On smaller units having a pressure release valveOn smaller units having a pressure release valveto prevent the unit from bursting under a severeto prevent the unit from bursting under a severeflashback, the fluid level should be monitored toflashback, the fluid level should be monitored to

that the liquid could splash or overflow into thethat the liquid could splash or overflow into the..


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bubbling the gas through a nonbubbling the gas through a non--flammable andflammable andideally nonideally non--gasgas--absorbing liquidabsorbing liquid

It is a device wherein the sealing is done by helpIt is a device wherein the sealing is done by help

of wet media, normally water used as media.of wet media, normally water used as media. Sometimes a specialized nonSometimes a specialized non--flammable oil inflammable oil in

industrial uses is employed for the sealing .industrial uses is employed for the sealing .

hey stop the flame by preventing it fromhey stop the flame by preventing it fromreaching the submerged intake.reaching the submerged intake.


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stopping flashbacks from reaching the manifoldsstopping flashbacks from reaching the manifoldsor regulators or tanks.or regulators or tanks.

They have the disadvantages of only working inThey have the disadvantages of only working in

one orientation and tend to be much larger thanone orientation and tend to be much larger thandry type arrestors.dry type arrestors.

The liquid level needs to be constantly checkedThe liquid level needs to be constantly checked

Above disadvantage makes them suitableAbove disadvantage makes them suitablemainly for large or fixed installations.mainly for large or fixed installations.


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1919thth Century Models of Dry and Wet FlashbackCentury Models of Dry and Wet Flashback

ArrestersArresters


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with the help of Check Valve andwith the help of Check Valve andExtin uishin the flame after the BackExtin uishin the flame after the Backflash with Flashback Arrester, it canflash with Flashback Arrester, it can

further CUT OFF Gas Supply which can befurther CUT OFF Gas Supply which can bereset y t e operatorreset y t e operator

It is essential to find out the cause ofIt is essential to find out the cause ofback fire and set it right before resettingback fire and set it right before resetting

e as upp ye as upp y


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Prevention of Gas Supply from thePrevention of Gas Supply from the

If this function is activated, then the FBAIf this function is activated, then the FBAcannot be Re set but requires replacementcannot be Re set but requires replacement


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event of back fire:event of back fire:

the gas supply after the back firethe gas supply after the back fire

ame rrester ext ngu s es t e ameame rrester ext ngu s es t e ame

NRV restricts the Reverse FlowNRV restricts the Reverse Flow

Temperature sensing cut off device cuts ofTemperature sensing cut off device cuts ofthe heat su lthe heat su l


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depends upon advantages & disadvantagesdepends upon advantages & disadvantagesof each s otof each s ot

Regulator or outlet is the Far Greater FlowRegulator or outlet is the Far Greater FlowRate of Gas than the Rate achieved byRate of Gas than the Rate achieved by

installing it on the Torchinstalling it on the Torch


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FBA is that it cannot prevent the HOSEFBA is that it cannot prevent the HOSEEXPLOSION which can be avoided by TorchEXPLOSION which can be avoided by Torchmounted FBAmounted FBA

Maximum safety is therefore achieved byMaximum safety is therefore achieved byinstalling FBAs both on Torch as well asinstalling FBAs both on Torch as well as

Regu ator. T s s poss e un ess gRegu ator. T s s poss e un ess gflows are neededflows are needed


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Where High Flow Rates are necessary,Where High Flow Rates are necessary,s a ways a v sa e o ns a es a ways a v sa e o ns a e

Check Valves on the Torch andCheck Valves on the Torch andFlashback Arrester on the RegulatorsFlashback Arrester on the Regulators


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A defective Flashback Arrestor should beA defective Flashback Arrestor should beimm i l r m v f rm .imm i l r m v f rm .

A Flashback Arrestor should be servicedA Flashback Arrestor should be serviced

eriodicall to et a more troubleeriodicall to et a more trouble--free life of it.free life of it.All connections and joints should be checkedAll connections and joints should be checked

periodically from time to time. Leakyperiodically from time to time. Leaky

connections and joints will lead toconnections and joints will lead tomalfunctioning of a Flashback Arrestor.malfunctioning of a Flashback Arrestor.


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Gas should flow from the Outlet of a FlashbackGas should flow from the Outlet of a Flashback

Arrestor. If the gas flow path is blocked thereArrestor. If the gas flow path is blocked therewill be a dro in deliver ressure.will be a dro in deliver ressure.

Defect should be rectified in accordance withDefect should be rectified in accordance withe manu ac urer s sugges onse manu ac urer s sugges ons

,,

all Filters in a Flashback Arrestor should beall Filters in a Flashback Arrestor should becleaned from time to time.cleaned from time to time.


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It is advisable to follow the following proceduresIt is advisable to follow the following proceduresduring a Shutdown, whether planned orduring a Shutdown, whether planned orunp anne .unp anne .

Close the Gas cylinder valve that supply the gasClose the Gas cylinder valve that supply the gas

installed.installed.

Drain the residual as in the Flashback ArrestorDrain the residual as in the Flashback Arrestor

any equipment, device, instrument or fixtureany equipment, device, instrument or fixtureconnected any where in the line.connected any where in the line.


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Disconnect the Flashback Arrestor.Disconnect the Flashback Arrestor.

On intending for the reuse/restart of theOn intending for the reuse/restart of theapplication follow the FLASHBACKapplication follow the FLASHBACKARRESTOR INSTALLATION PROCEDUREARRESTOR INSTALLATION PROCEDURE

as advised by the Manufacturers Guide .as advised by the Manufacturers Guide .


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IS :11006IS :11006 --1984 covers information on1984 covers information on..

European Standard EN 730.European Standard EN 730.

European Standard DKSG91 / DKST 91.European Standard DKSG91 / DKST 91.

International Standard ISO 5175.International Standard ISO 5175.

British Standard BS 6158.British Standard BS 6158.

Some of the Indigenous ModelsSome of the Indigenous Models


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Model FBA - NRV

These Flash Back Arrestors come in two

basic design flanged and threaded.

The Normal Sizes are:

MediaMedia

Maximum WorkingMaximum Working

PressurePressure

ThreadThread

eded

(R(R

DNDN

11

55

DNDN

22

00

DNDN

22

55

DNDN

33

22

DNDN

44

00

Air / OxygenAir / Oxygen 40.0040.00 barbar

LPGLPG 10.0010.00 barbar

HydrogenHydrogen 16.0016.00 barbar

DNDN

33

22

DNDN

44

00

DNDN

55

00

DNDN

66

55

DNDN

88

00

Natural GasNatural Gas 10.0010.00 barbardd DNDN

1100

00

DNDN

1122

55

DNDN

1155

00

DNDN

2200

00

DNDN

2255

00



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Some of the Indigenous ModelsSome of the Indigenous ModelsModel FBA WT

The water and the disk, works like a flame

, .

Two Non return valves in series- one in the

incoming line and the other at the bottom of the

cu s o supp y n e even o any as

back in the down stream equipment. Further

relief valve provided at the top releases vapourand hot gases and prevent damage to the

equipment.Working Pressure:Working Pressure: Size:Size:

MediaMedia Maximum WorkingMaximum WorkingPressurePressure Inlet / OutletInlet / Outlet

AcetyleneAcetylene 1.51.5 barbar 1/4"1/4"

LPGLPG 55 barbar 1/2"1/2"

HydrogenHydrogen 55 barbar 3/4"3/4"

Natural GasNatural Gas 55 barbar 1"1"

S f th I di M d lS f th I di M d l


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Some of the Indi enous ModelsSome of the Indi enous ModelsModel FBAModel FBA -- HPHP

Hose Size (mm)Hose Size (mm) Thread Size BSPThread Size BSP

INLET / OUTLETINLET / OUTLET OUTLETOUTLET

5.05.0 1/41/4 LH/RHLH/RH

MediaMediaMax.Max.WorkingWorking

PressurePressure

6.06.0 1/41/4 LH/RHLH/RHAir OxygenAir Oxygen 20.0020.00 barbar

LPGLPG 5.005.00 barbar8.08.0 3/83/8 LH/RHLH/RH

9.09.0 3/83/8 LH/RHLH/RH

AcetyleneAcetylene 1.501.50 barbar

Natural GasNatural Gas 1.601.60 barbar

10.010.0 3/83/8 LH/RHLH/RH


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Model FBA PM

The Flash Back arrestors are designed for fitting on the Pipeline /

Manifold to prevent flash back and protect your precocious equipment

Return Valve, (3) Flame Block, (4) Flame Trap, (5) Temperature

Activated Flow cut off device.

WorkingWorking

PressurePressure:: Size:Size:

MediaMedia

MaximumMaximum

WorkingWorkingRHRH --

BB FOR AIR /FOR AIR /

SS

PP

OXYGEOXYGE

NNAcetyleneAcetylene 22.022.0 barbar

AIR/OXYGENAIR/OXYGEN 40.040.0 barbar

LPGLPG 5.05.0 barbar LHLH --

SS

PP

FOR FUELFOR FUEL

GASGASHydrogenHydrogen 5.05.0 barbar

Natural GasNatural Gas 5.05.0 barbar


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93 / E of EIGA ( European Industrial Gases93 / E of EIGA ( European Industrial GasesAssociation )Association )

World Wide Web ( Internet )World Wide Web ( Internet )

Document No.: FBADocument No.: FBA--0A1 Modification A of0A1 Modification A ofPaarth Industries, Vadodara, GujratPaarth Industries, Vadodara, Gujrat

IS :11006IS :11006 --1984 of B.I.S.1984 of B.I.S.

Gases & Instrumentation Magazine, Article byGases & Instrumentation Magazine, Article byDavid Pryor, Sept / Oct. 2008David Pryor, Sept / Oct. 2008

Flash Back Arrester

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