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HAWK21M
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Catalaytic Convertor

Sun May 21, 2006 7:05 pm

How prevalent are Catalaytic convertors used on present Commercial Aircraft in the ECS system.
Also What exactly is the Precious metal used as the catalyist
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
bri2k1
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RE: Catalaytic Convertor

Sun May 21, 2006 11:31 pm

In automobiles, catalytic converters use a two-step chemical process -- the famous redox (reduction, oxidation) reaction.

The most common catalyst in the first step is platinum mixed with rhodium. This first stage reduces nitrogen oxides (NO) to simple N2 and O2.

The second stage, also using platinum but usually mixed with palladium as the catalyst, oxidizes carbon monoxide (CO) to produce less-harmful CO2.

Caveat: I know nothing about the use of catalytic converters in aircraft. The gases present in automobile exhaust are functions of the fuel used and the temperatures at which it's burned. Airplanes, using different fuel and very different engines, probably don't use this system at all.
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litz
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RE: Catalaytic Convertor

Mon May 22, 2006 12:28 pm

Quoting Bri2k1 (Reply 1):
Caveat: I know nothing about the use of catalytic converters in aircraft. The gases present in automobile exhaust are functions of the fuel used and the temperatures at which it's burned. Airplanes, using different fuel and very different engines, probably don't use this system at all.

AFAIK, the exhaust of combustion in a jet engine pretty much just goes right out the back end as thrust ... putting any kind of catalytic converter on that exhaust would totally defeat the purpose of thrust, would it not?

If you ever get a close-up look at a modern jet engine, you can pretty much see right through the thing from front to back, on the LP (bypass) side. And from behind, you can see directly into the HP turbines, too, from the center core of the exhaust.

Speaking of modern jets ... other than Spirit of Delta, are there any newer jets (late 70s, early 80s design or newer) on display anywhere in the world? I guess some 747s, most likely ... but can you even see into a '47 engine from the ground?

Spirit is nice because the 767's engines are right down at "person-level", so it's easy to see into them. And yes, no catalytic converter, or any other kind of "filter" on that thing ...

The Dash-80 at the Smithsonian, I don't think would count, as the JT3D isn't a modern high-bypass engine ...

- litz
 
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HAWK21M
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RE: Catalaytic Convertor

Mon May 22, 2006 1:49 pm

This Catalaytic convertor in concern is used in the Bleed inlet Ducts upstream of the FSOV [Pack valve].Its used to reduce the content of Ozone in the Bleed air used for Air Conditioning prior to distribution in the Pax cabin.Has a life of approx 12,000 cycles for the B752.
Is it frequently installed on Current Aircraft.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
prebennorholm
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RE: Catalaytic Convertor

Fri May 26, 2006 8:32 am

Catalytic converters are not used on aircrafts, neither on turbine nor recip engines.

As stated by Bri2k1 catalytic converters mainly convert NO into N2 and O2, and CO into CO2. (They also convert any unburned HC into H2O and CO2, that's why they are called 3-way-converters).

Since NO and CO are both unstable and rather short-lived gasses, then they are relevant to convert when generated by street traffic, but much less relevant on aircrafts.

Turbine engines produce very small amounts of CO since the burning (unlike a gasoline recip engine) takes place in an environment with vastly excess oxygen.

That the same as diesel engines which also run in street traffic without catalytic converters. Special converters have been designed for diesel engines aimed more on converting HC (and NO), but they are not in widespread use. The main issue for cleaning diesel emission is particle filters, but that's an entirely different issue. They could have been very useful on the Convair 880. Big grin

NO is an issue around airports, and therefore great effort has been made to reduce NO emission from modern turbine engines. It's not an easy issue because a general rule of thumb is that the greater the compression ratio by the HP compressor, the more NO is generated, and the lower SFC, and visa versa. Meaning low NO emission = high fuel consumption. Anyway some clever tricks combined with for instance double annular combustion chambers do shift the numbers a little sidewards.
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HAWK21M
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RE: Catalaytic Convertor

Fri May 26, 2006 5:25 pm

Thanks for the details.

Quoting Prebennorholm (Reply 4):
Catalytic converters are not used on aircrafts, neither on turbine nor recip engines

The B752 has an option for Installation of These convertors in the Pack area,upstream of the FCSOV.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
kaddyuk
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RE: Catalaytic Convertor

Fri May 26, 2006 9:53 pm

Quoting Prebennorholm (Reply 4):
Catalytic converters are not used on aircrafts, neither on turbine nor recip engines.

Mel isnt asking about engine Catalytic Converters, as he said....

Quoting HAWK21M (Reply 3):
Its used to reduce the content of Ozone in the Bleed air used for Air Conditioning prior to distribution in the Pax cabin

I've never seen such item on the B747 Mel... It might be an option however...
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A/c train
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RE: Catalaytic Convertor

Fri May 26, 2006 11:28 pm

I think what mel is talking about is the ozone filter, usually found upstream of the pack valve, ive changed one on a 320 but never on a 757. 2 clamps and a couple of mount bolts. You need to take it out to change the pack valve on a 320.
 
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HAWK21M
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RE: Catalaytic Convertor

Sat May 27, 2006 12:08 am

Quoting A/c train (Reply 7):

Bingo.Thats the Item.
Whats the Precious metal on the B752 installed convertor.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
IFIXCF6
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RE: Catalaytic Convertor

Sat May 27, 2006 10:05 am

Hello Mel,
Looking in my books (generic, not A/C specific), one possible answer would be the catalyst palladium. I don't know of the B757, but I've changed them on B767's.
Mike
 
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HAWK21M
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RE: Catalaytic Convertor

Sat May 27, 2006 10:39 pm

Palladium
Interesting.

Quoting IFIXCF6 (Reply 9):
I've changed them on B767's

What Frequency.12,000 cycles.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
VC-10
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RE: Catalaytic Convertor

Sun May 28, 2006 12:14 am

Airbus CC's are removed for workshop chk @ 20 000 FH

B747 CC's are inspected in situ every 3C or 22 500 FH
 
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HAWK21M
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RE: Catalaytic Convertor

Mon May 29, 2006 5:16 pm

Quoting VC-10 (Reply 11):
Airbus CC's are removed for workshop chk @ 20 000 FH

B747 CC's are inspected in situ every 3C or 22 500 FH

Is Flying Hrs the only Criteria or is Flight Cycles also Involved.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
VC-10
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RE: Catalaytic Convertor

Mon May 29, 2006 6:41 pm

IF FC had been a factor I would have mentioned it.

Think about it. How would the number of landings 'wear' out a CC?

It's the number of hrs air passes through a CC that will affect its condition.
 
Buzz
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RE: Catalaytic Convertor

Mon May 29, 2006 7:21 pm

Hi Hawk21M, Buzz here. About 20 years ago there was a time change item to replace DC-10 ozone converters, I forget what time interval was for replacing them.
I've removed the A320 converters to replace a pack valve, and I've forgotten where they live on a 757... never had to replace one there. I can't recall if the 737-300's have 'em either.
g'nite
 
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HAWK21M
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RE: Catalaytic Convertor

Mon May 29, 2006 9:59 pm

Just Checked with Alteon [Boeing].
As per their Email.

The B752 Catalytic Converter is Scheduled Maintenance Replaced after 12,000 Operational Hrs.
Its a Housing containing a Precious metal [Not specified] catalyst on a Ceramic Honeycomb substrate.The Substrate is held in the housing by a corrugated knitted wire mesh.

The Catalyatic Convertor decreases the level of Ozone through a catalytic reaction between the Ozone and the precious metal catalyst.

They state 12,000 operational hrs.Is that Flight hrs.What about Ground operational time.How would that be monitored when Packs are on.
Although one needs to be at a high Altitude to have Ozone.
Just a doubt.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
A342
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RE: Catalaytic Convertor

Mon May 29, 2006 11:46 pm

Quoting HAWK21M (Reply 15):
Although one needs to be at a high Altitude to have Ozone.

IIRC Ozone is also quite unstable. When using hot bleed air, most of it reacts back to O2 anyway. The filter is just to make sure absolutely nothing goes into the cabin.

But fliters could be an issue with the 787.
Exceptions confirm the rule.
 
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HAWK21M
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RE: Catalaytic Convertor

Tue May 30, 2006 11:13 pm

Quoting A342 (Reply 16):
The filter is just to make sure absolutely nothing goes into the cabin.

So how common is its use by Commercial Airlines.Considering its optional.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
VC-10
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RE: Catalaytic Convertor

Wed May 31, 2006 3:12 am

Quoting HAWK21M (Reply 15):
They state 12,000 operational hrs.Is that Flight hrs.What about Ground operational time.How would that be monitored when Packs are on.

You are a Licensed Engineer aren't you? Ground ops time doesn't count, just engine runs.
 
A342
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RE: Catalaytic Convertor

Wed May 31, 2006 3:42 am

Quoting HAWK21M (Reply 17):
So how common is its use by Commercial Airlines.Considering its optional.
regds
MEL

Sorry, I'm no expert here, I've just said what I've read in an article about cabin air (or was it in a book about Concorde ?). But I think on the Concorde, the filters weren't optional because it flew at very high altitudes where there's a lot more ozone than say at FL410.
Exceptions confirm the rule.
 
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HAWK21M
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RE: Catalaytic Convertor

Wed May 31, 2006 10:56 pm

Quoting VC-10 (Reply 18):
You are a Licensed Engineer aren't you? Ground ops time doesn't count, just engine runs

Easy VC...Its not a crime to Double check with others.And nor is it for an Engineer to ask questions from others.I dont think there is an Engineer that knows everything.
Maybe its the Language We use.

Many things done out here seem to be very different from those done in CAA/JAA/FAA regulatory covered Areas.eg a Definition of Snag/Incident or maybe Catergories of Licences.Out here A&C cannot touch Electricals,Instruments,Radio etc.

Quoting A342 (Reply 19):
But I think on the Concorde, the filters weren't optional because it flew at very high altitudes where there's a lot more ozone than say at FL410

Any Name of the book.
Thats very Educational.

Any link to a Manufacturer of these Convertors on Aircraft.

Thanks.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
A342
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RE: Catalaytic Convertor

Thu Jun 01, 2006 3:52 am

Quoting HAWK21M (Reply 20):
Any Name of the book.

I've read in the book again, the Ozone filter thing is not in it. I must have read it somewhere else.

The book is in German, but if you're interested:

Hans-Juergen Becker

CONCORDE: Geschichte - Technik - Triumph und Tragoedie
(History - Technology - Triumph and Tragedy)

ISBN: 3-613-02250-8
Exceptions confirm the rule.
 
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HAWK21M
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RE: Catalaytic Convertor

Fri Jun 02, 2006 6:45 pm

Quoting A342 (Reply 21):
The book is in German, but if you're interested:

Hans-Juergen Becker

Too bad not in English.Thanks Anyway.
regds
MEL
I may not win often, but I damn well never lose!!! ;)

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