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Balanced Draft Furnace


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#1 Mayank Joshi

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Posted 29 May 2014 - 01:51 PM

I want to know why there is a trip of furnace (balanced) on :

1) High Draft Pressure

2) Low Draft Pressure
 



#2 Mayank Joshi

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Posted 30 May 2014 - 10:24 PM

Plz give your views??



#3 Mainak Sarkar

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Posted 31 May 2014 - 06:12 AM

At high draft pressure the furnace may explode and in low draft pressure the furnace may get succumbed  due high out side pressure.



#4 SSWBoy

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Posted 31 May 2014 - 03:46 PM

High draft - Risk of flame lift off from burner and subsequent burner extinguishing ... and fuel gas still on

Low draft - Risk of operator opening a peep door and hot air rush out rather than in

 

From my point of view high/low draft doesn't really compromise the structural design of the furnace it is more of a safety issue as outlined above



#5 PKS

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Posted 01 June 2014 - 12:01 AM

Hello Members!!

 

Very High and Very low draft are injurious for the health of furnace as well as operationally hazardous.

 

High High Draft pressure:

 

1. Burner back fire.

2. May lead to the development of leaks in the furnace body.

3. May lead to the cracks in the refractory.

 

Low Low Draft pressure:

 

1. Burner may get off due to excessive air intake though primary and secondary air slots.

2. Excess air may lead to heat loss and in-turn more fuel consumption to maintain Coil outlet temperatures. Hence leading to decrease in Thermal efficiency.

3. Very low pressures again not good for furnace body.

4. May lead to the cracks in the refractory and refractory falling down.

 

There may be more operational hazards and ill-effects on furnace health and performance. I have listed few above.

 

Thanks

PKS



#6 Mainak Sarkar

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Posted 01 June 2014 - 12:44 PM

These are all effect of High and low draft pressure in furnace, but is there any requirement of providing Safety switch (Trip)? According to me Cracking of furnace or structural damage in case of low draft may be the reason for providing Trip.



#7 MJ94

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Posted 01 June 2014 - 08:31 PM

Hello Members!!

 

Very High and Very low draft are injurious for the health of furnace as well as operationally hazardous.

 

High High Draft pressure:

 

1. Burner back fire.

2. May lead to the development of leaks in the furnace body.

3. May lead to the cracks in the refractory.

 

Low Low Draft pressure:

 

1. Burner may get off due to excessive air intake though primary and secondary air slots.

2. Excess air may lead to heat loss and in-turn more fuel consumption to maintain Coil outlet temperatures. Hence leading to decrease in Thermal efficiency.

3. Very low pressures again not good for furnace body.

4. May lead to the cracks in the refractory and refractory falling down.

 

There may be more operational hazards and ill-effects on furnace health and performance. I have listed few above.

 

Thanks

PKS

In Hydrogen Reformer the Trip of Plant is :

+3mm Water Column - HIgh Draft 
-25 mm H20 Column - Low draft

Can Refractory break or be sucked at -25 mm H20 Column.??

From what I read burner Backfire reason looks convincing and at High Draft air may come out from peep holes also looks ok.
but is there any structural threats to the furnace at just +3 mm or -20 mm H20 Column.??

 



#8 PKS

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Posted 01 June 2014 - 11:12 PM

MJ94

 

These pressures seem to be low but the surface area of the inside of furnace is quite large. 

 

Pressure=Force/Area;

 

Force=Pressure x Area

 

So, larger the area, larger will be the force exerted. 

 

High drafts may lead to leakages from the furnace body by weakening of weld joints and there may not be structure failure.

 

Can Refractory break or be sucked at -25 mm H20 Column.?? ---> It depends on the age of the furnace. 

 

Thanks 

PKS



#9 Mayank Joshi

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Posted 02 June 2014 - 02:16 AM

 

 

1. Burner may get off due to excessive air intake though primary and secondary air slots.

2. Excess air may lead to heat loss and in-turn more fuel consumption to maintain Coil outlet temperatures. Hence leading to decrease in Thermal efficiency.

 

CAn u please explain these two points ?
on very low draft (-30mm) more air will be sucked in but fuel intake will also increase , I am assuming excessive air due to higher pressure  drop across the burner or air register .



#10 PKS

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Posted 02 June 2014 - 02:38 AM

Mayank

 

These events may happen depending upon the condition/situation of the burner, amount of excessive air sucked in, it may blow-off the burner.

 

If moderate excess air (moderately low pressure inside the furnace, but below normal draft pressure) is sucked, it may lead to loss in thermal efficiency of the furnace.

 

That's what these two points mean. 

 

The things mentioned above may not happen simultaneously. These are situations anticipated when a furnace draft pressure deviates from normal draft pressure. The after-effects depend on the cause of problem and degree of deviation / condition of furnace.

 

Hope it clarifies!!

 

Thanks

PKS






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