Flash Back and Flame Arrestors

8/2/2019 Flash Back and Flame Arrestors

1/8

LASH BACK AND FLAME ARRESTORS

A flash back arrestor is a safety device that shuts off gas flow in event of flash back. Flashback is the combustion of a flame mixture that ca

ccur within your gas management system. This can travel back through the line of your gas management system to you gas source if a flas

ack arrestors is not in line. A flash back arrestor shuts off gas flow and extinguishes the flame before it can reach your gas source. Several

actors can cause flash back, including failing to purge line properly, using improper pressure, leaks in your gas management system and

mproper system operation. We recommend using a flash back arrestor on your fuel line as well as the oxygen line.

Classification of Flash Back Arrestors

roadly the Interruption Methods can classify the Flashback Arrestors into two types:

Many methods to stop flashbacks have been devised. "Active" methods require maintenance of certain parameters, such as liquid level or g

elocity. "Passive" methods require only routine inspection and typically have no moving parts or instrument requirements.

Venture type flashback Arrestors (active)

Venture flashback arrestors simply create a restriction in the hydrocarbon/air mixture delivery pipe so that the gas velocity is faster than the

ame speed, preventing progression of a flashback upstream. Flashbacks in the direction of flow can still happen. Even a partly closed valv

an create a high velocity for flashback prevention, but a venture shape creates much lower pressure drop. If gas flow stops, the venture is nonger effective, so methods to measure flow and add makeup gas (nitrogen, for instance) are often included.

Online flame arrestors (passive) (most commonly used)

Mechanical flame arrestors are filled with metal or ceramic, which absorbs heat from a flashback, quenching it to a temperature below wh

eeded for ignition. This stops the flame. With a low enough hydrocarbon/air mixture flow rate, if a flame travels to the face of the arres

an become stable at that point. Heating of the arrestor body and internals results. Once the arrestor temperatures increase enough, ign

emperature can be reached on the upstream side of the arrestor and the flashback can proceed. For this reason, a temperature switch is

nstalled on the flame side of each arrestor (adding an "active" element).

Causes of a Flash Back

Hot refractory

f the refractory lining a burner or furnace is hot enough to bring the hydrocarbon/air mixture to the auto ignition temperature, rapid combu

will start. Heat transfer from the hot surface depends on gas velocity and turbulence, explaining why "swirl, type burners o ften seems

table than more linear types.

lame

lames from pilot burners are the typical means of initiating combustion of a hydrocarbon/air mixture. Nozzle mix burners (where the

mixes with the combustion air within the furnace) have zones that are too lean or too rich for combustion, so the pilot flame must be positi

o heat a volume of well mixed gas. Large pilot flames can overcome poor positioning of the pilot tip.

parks

parks are used to ignite pilot burners and also main burners in some cases. Occasionally small sparks (static electricity) are capab

nitiating combustion, but the extra energy in a large spark helps insure light off. Undesired sparks, such as those resulting from debris mo

hrough steel ducting or fans, can initiate combustion and require careful design to avoid.

Dust -

Dust or very fine debris are generated while welding or cutting and this dust when in contact with the nozzle causes a blockage resulting a
http://www.iigas.com/fba.htm#fbahttp://www.iigas.com/fba.htm#fbahttp://www.iigas.com/fba.htm#fba


2/8

ound puut and the flame due to the pressurization results in the flame to fold back into the nozz le.

Why should one use Flashback Arrestors?

he reason for using a protective device such as a Flash Back Arrestor on a fuel gas line or even on a cylinder are

1) Safety of property and human lives

2) The flashback occurs under various conditions.

3) The flashback occurs inside the pipeline or vessels.

4) The flame moves through a vessel or pipe.

5) The flame velocity increases as it moves through these pipe or vessels, and if the pipe is long enough the velocity can increa

detonation levels, which are supersonic

Where should a Flashback Arrestor be placed?

he flashback arrestor should be placed at the closest point to the flame, if due to un-avoidable circumstances the Arrestor can not be

laces close to the cutting nozzle or the flame then it should be placed of the main pipe line, and also on the fuel gas bank, vessel, cylinder.

How does a flashback Arrestor works?

lashback arrestor is a simple devise, which quenches the flame using the following methods

a) By reducing the velocity of the flame, reducing the flame velocity even lower than the minimum flame velocity of the fuel gas

b) Stops the flame propagation into or through a pipe. By placing a flame arrestor at the end of the flammable mixture pipe feed

flare or burner, flame can be prevented from moving into the pipe regardless of the mixture velocity.

c) By passing a potentially flammable mixture through a water chamber or some sort of heat sink. This dissipates the heat and quen

the flashback.

d) By blocking the fuel gas path, with a suitable thermal fuse plug, casing the flashback to die out.

e) By blocking the flow of fuel gas in the opposite direction by acting like a non return valve.


3/8


4/8

Model: FBA - NRV

We recommend using a flash back arrestor on your fuel line as well as the oxygen line

The Flash Back Arrestors are made to international standards and confirm to BS: 615, BIS: 11

DIN BN 730 ISO:5175 class 1

The Flash Back arrestors are designed for fitting on the Pipeline / Manifold to prevent flash ba

and protect your precocious equipment and lives.

Working Pressure:

MediaMaximum Working

Pressure

Air / Oxygen 40.00 bar

LPG 10.00 barHydrogen 16.00 bar

Natural Gas 10.00 bar

These Flash Back Arrestors come in two basic design flanged and threaded.

The Normal Sizes are:

Threaded(RH)

DN 15 DN 20 DN 25 DN 32 DN 40

FlangedDN 32 DN 40 DN 50 DN 65 DN 80

DN 100 DN 125 DN 150 DN 200 DN 250

N.B. OTHER THREAD FORMS AND CONNECTIONS ARE ALSO AVAILABLE ON REQUEST


5/8

Model: FBAWT

A flash back arrestor is a safety device that shuts off gas flow in even

flash back. Flashback is the combustion of a flame mixture that can occwithin your gas management system. This can travel back through the

of your gas management system to you gas source if a flash back arrestis not in line. A flash back arrestor shuts off gas flow and extinguishes

flame before it can reach your gas source. Several factors can cause flaback, including failing to purge line properly, using improper pressure,

leaks in your gas management system and improper system operation.

We recommend using a flash back arrestor on your fuel line as was the oxygen line.

The Flash Back Arrestors are made to international standards and con

to BIS: 11006

These Flash Back arrestors are a qualitative product.

The water and the disk works like a flame arrestors are quenches the fl

back and the two Non return valves in series, one in the incoming line

the other on the at the bottom of the FBA cuts off supply in the event oany flash back in the down stream equipment. Further relief valve

provided at the top releases vapour and hot gases and prevent damage t

he equipment.

Working Pressure: Size:


PressureInlet / Outlet

Acetylene 1.5 bar 1/4"

LPG 5 bar 1/2"

Hydrogen 5 bar 3/4"

Natural Gas 5 bar 1"

N.B. OTHER THREAD FORMS AND CONNECTIONS ARE ALSO AVAIABLE ON REQUEST


6/8

Model: FBA - HP

We recommend using a flash back arrestor on your fuel line as well as

oxygen line.

The Flash Back Arrestors are made to international standards and confirm to B

6158 (tested and approved at CMRI Dhanbad), BIS: 11006 DIN BN 730ISO:5175 class 1

The Flash Back arrestors are designed for fitting on the welding andcutting hose pipe to prevent flash back.

Normal Size:

Hose Size (mm) Thread Size BSP

INLET / OUTLET OUTLET

5.0 1/4 LH/RH

6.0 1/4 LH/RH

8.0 3/8 LH/RH

9.0 3/8 LH/RH

10.0 3/8 LH/RH

Working Pressure:


Pressure

Air / Oxygen 20.00 bar

LPG 5.00 bar

Acetylene 1.50 bar

Natural Gas 1.60 bar



7/8

Model: FBAPM

We recommend using a flash back arrestor on your fuel line as well as the oxygen lin

The Flash Back Arrestors are made to international standards and confirm to BS: 6158, BIS:11006 DIN BN 730 ISO:5175 class 1

The Flash Back arrestors are designed for fitting on the Pipeline / Manifold to prevent flash band protect your precocious equipment and lives. The safety elements are (1) Contaminate

Filter, (2) Non Return Valve, (3) Flame Block, (4) Flame Trap, (5) Temperature Activated F

cut off device.

Working Pressure:Size:

Media MaximumWorking Pressure

RH -BSP

FOR AIR /OXYGEN

Acetylene 22.0 bar

AIR/OXYGEN 40.0 bar

LPG 5.0 bar

LH -BSP

FOR FUELGAS

Hydrogen 5.0 bar

Natural Gas 5.0 bar


TOP OF THE

WOULD YOU LIKE MORE INFORMATION OR L
http://www.iigas.com/fba.htm#tophttp://www.iigas.com/fba.htm#top


8/8

Flash Back and Flame Arrestors

Documents

Transcript of Flash Back and Flame Arrestors