X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 Jan 2012 12:34:50 -0500 Message-ID: X-Original-Return-Path: Received: from elasmtp-scoter.atl.sa.earthlink.net ([209.86.89.67] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTP id 5351969 for lml@lancaironline.net; Mon, 16 Jan 2012 08:44:42 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.67; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=sdu0ZzTsCk8mTEaAO/XaWnVy4c81zyFuVv20A6IdK09bhSiG5osgkrKNzMEEqtgF; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [72.73.82.72] (helo=[192.168.1.24]) by elasmtp-scoter.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1Rmmr0-0003Yq-Ok for lml@lancaironline.net; Mon, 16 Jan 2012 08:44:07 -0500 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: multipart/alternative; boundary=Apple-Mail-100-521895195 Subject: Re: [LML] Re: Ceramic exhaust coatings - careful y'all X-Original-Date: Mon, 16 Jan 2012 08:44:06 -0500 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1084) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9409891b604f6846616e1bc3fe395af97cc350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 72.73.82.72 --Apple-Mail-100-521895195 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii That data makes it pretty clear. I had a mechanical engineer/metallurgist friend who was a pilot at one = point. His comment on the equipment was "Airplanes barely work. = Helicopters don't work" I think this exhaust situation is an example = of "barely work". Those margins are really thin. So does this also mean that it is better to paint stainless black than = leave it shiny? Colyn On Jan 15, 2012, at 10:39 AM, Frederick Moreno wrote: Insulation wrapped on exhaust pipes and coatings that reduce the surface = thermal emissivity both raise exhaust pipe temperature.=20 =20 So what?=20 =20 At these temperatures, the strength of the 321 stainless steel = generally used in exhaust pipes is dropping like a rock - small = temperature increases result in big strength decreases - and creep = resistance drops even faster. =20 Oxidation is also increasing dramatically with temperature.=20 =20 In short, the exhaust pipes will fail much, much sooner due to cracking = or wall thinning. If you are driving a turbo, you run a double risk = because of the high pressures inside the exhaust pipes upstream of the = turbo that stress tubing walls more and create blow torches when cracks = form.=20 =20 In short, don't do it unless you pledge to inspect the pipes more often, = like every time the cowl is off, and unwrap the pipes for a very careful = inspection at EVERY annual.=20 =20 Data below. Out of curiosity I made an Excel plot, attached. It makes = the point even better than the table below. Creep strength virtually = zero at 800C =3D 1432F =20 Sorry 'bout that. =20 Fred Moreno =20 2. Properties at Elevated Temperatures=20 Short Time Elevated Temperature Tensile Strength Temperature, oC 600 650 700 750 800 850 Tensile Strength, MPa 390 329 280 230 190 140 Creep data=20 Stress to develop a creep rate of 1% in the indicated time at the = indicated temperature. Time Temperature oC 550 600 650 700 800 10 000 h Stress MPa 180 100 70 40 10 100 000 h Stress MPa 120 80 50 25 5 Creep Rupture Stress Time Temperature oC 500 600 650 700 800 1 000 h Stress MPa 270 180 140 70 30 10 000 h Stress MPa 240 130 90 50 10 100 000 h Stress MPa 200 90 50 15 5 =20 =20 Subject: Re: [LML] Re: Ceramic exhaust coatings =20 One other thought, I have heard both sides of this argument before as = well. I also heard it is nearly impossible to weld / repair pipes with = this coating. I found a solution that solved the problem cheaply without = making the pipes more difficult to weld. I wrapped my entire exhaust = system with hot rod exhaust wrap. I bought it at the local auto parts = store in the 1" width. Spruce sells it as well. I tested the stuff with = a torch in the hangar on my hand and was amazed how well it insulates. I = have 2 layers in some very hot places on the pipes. In addition to = reducing the inner cowl temps, It also tames the vibration of the pipes = and reduces noise.=20 Cheap, relatively light and effective... Fwiw. <321 SST strength vs temp.xlsx>-- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html --Apple-Mail-100-521895195 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii That data makes it pretty clear.
I had a = mechanical engineer/metallurgist friend who was a pilot at one point. =   His comment on the equipment was "Airplanes barely work. =  Helicopters don't work"   I think this exhaust situation is = an example of "barely work".   Those margins are really = thin.

So does this also mean that it is better = to paint stainless black than leave it = shiny?

Colyn

On Jan 15, = 2012, at 10:39 AM, Frederick Moreno wrote:

 don't= do it unless you pledge to inspect the pipes more = often, like every time the cowl is off, and unwrap the = pipes for a very careful inspection at EVERY = annual. 
 
Data below.  Out of = curiosity I made an Excel plot, attached.  It makes = the point even better than the table below.   Creep = strength virtually = zero at = 800C =3D 1432F
 
Sorry 'bout = that.
 
Fred = Moreno
 

2. Properties at Elevated = Temperatures 
Short Time Elevated Temperature Tensile = Strength

Temperature, oC= 600650700750800850
Tensile Strength, MPa390329280230190140

Creep = data 
Stress to develop a creep rate of 1% in the = indicated time at the indicated temperature.

TimeTemperature oC= 550600650700800
10 000 hStress MPa180100704010
100 000 hStress MPa1208050255

Creep = Rupture Stress

TimeTemperature oC= 500600650700800
1 000 hStress MPa2701801407030
10 000 hStress MPa240130905010
100 000 hStress MPa2009050155
 
 
Subject: Re: [LML] Re: Ceramic = exhaust coatings
 
One other thought, I have heard both sides = of this argument before as well. I also heard it is nearly impossible to = weld / repair pipes with this coating. I found a solution that solved = the problem cheaply without making the pipes more difficult to weld. I = wrapped my entire exhaust system with hot rod exhaust wrap. I bought it = at the local auto parts store in the 1" width. Spruce sells it as well. = I tested the stuff with a torch in the hangar on my hand and was amazed = how well it insulates. I have 2 layers in some very hot places on the = pipes. In addition to reducing the inner cowl temps, It also tames the = vibration of the pipes and reduces noise. 
Cheap, = relatively light and = effective...
Fwiw.

<321 SST strength vs temp.xlsx>--
For archives and = unsub http://mail.= lancaironline.net:81/lists/lml/List.html

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