Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Thu, 11 Nov 2004 18:50:19 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m18.mx.aol.com ([64.12.138.208] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 528073 for lml@lancaironline.net; Thu, 11 Nov 2004 14:51:35 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.138.208; envelope-from=REHBINC@aol.com Received: from REHBINC@aol.com by imo-m18.mx.aol.com (mail_out_v37_r3.8.) id q.158.437c20f6 (3924) for ; Thu, 11 Nov 2004 14:50:50 -0500 (EST) From: REHBINC@aol.com X-Original-Message-ID: <158.437c20f6.2ec51c9a@aol.com> X-Original-Date: Thu, 11 Nov 2004 14:50:50 EST Subject: Re: [LML] Re: Halon fire extinguishers X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1100202650" X-Mailer: 9.0 for Windows sub 5114 -------------------------------1100202650 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 11/10/2004 4:56:35 PM Eastern Standard Time, lancair@ustek.com writes: > While we are on the subject of temperatures, the autoignition > temperature for av gas is 440 C, for diesel is 230 C and for polyester > is 560 C. Motor oil should be similar to diesel. If anyone is > interested... Rob, I (think that I) had read that the Navy does not want av gas on board ship because it is more of a fire problem compared to jet fuel, and I believe that jet fuel and diesel are interchangeable. Are our turbine brothers carrying around that much greater risk? Robert M. Simon, ES-P N301ES Robert, Jet A is essentially kerosene and almost identical to No. 1 fuel oil. I think the main difference is that kerosene is a bit cleaner. The big hazard with av gas over Jet A is in the flash point. For av gas the flash point is -50 F, for Jet A it is between 110 and 150 F. If the fuel is significantly below the flash point, the liquid cannot generate flammable vapor concentrations. In this situation, a spark or hot surface cannot ignite the vapors. If the fuel is significantly above the flash point, a spark with sufficient energy or a surface exceeding the autoignition temperature will ignite the vapors if the air fuel ratio is right. At the flash point, ignition depends on the surrounding conditions. Since the temperature aboard ship is never going to be below -50 F, any leak or open container of av gas is going to release flammable vapors which may come in contact with an ignition source. If the navy specifies their Jet A to have a flash point of say 130 F (I don't know what their spec is or if they even use Jet A), then as long as the temperatures are kept below 120 F there should be no flammable vapors generated. Just don't spill any on a hot exhaust manifold. However, once gasoline and jet fuel/diesel fuel are vaporized in flammable mixtures, it is MUCH easier to ignite jet/diesel than gas. The reason I presented those autoignition temperatures was to give some idea how much a fire scene must cool before the extinguishing agent is lost in order to prevent reignition from occurring. As for whether the turbine drivers have an increased risk of fire, I don't know the answer. Certainly the risks are different. For instance, the head space in a gasoline fuel tank is generally too rich to burn at any altitude you might fly. However, the head space on a jet A tank generally starts out too lean to burn on the ground. But, as the altitude increases it will likely enter the flammable range. Remember the center fuel tank issue on TWA 007. Also note that the flash point drops with increased altitude. Rob -------------------------------1100202650 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 11/10/2004 4:56:35 PM Eastern Standard Time, lancair= @ustek.com writes:

> While we are on the subject of temperatur= es, the autoignition
> temperature for av gas is 440 C, for diesel is= 230 C and for polyester
> is 560 C. Motor oil should be similar to d= iesel. If anyone is
> interested...

Rob,

I (thi= nk that I) had read that the Navy does not want av gas on board
ship bec= ause it is more of a fire problem compared to jet fuel, and I
believe th= at jet fuel and diesel are interchangeable. Are our turbine
brothe= rs carrying around that much greater risk?

Robert M. Simon, ES-P= N301ES

Robert,

Jet A is essentially kerosene and almost identical to No. 1 fuel oil. I= think the main difference is that kerosene is a bit cleaner.

The big hazard with av gas over Jet A is in the flash point. For av gas= the flash point is -50 F, for Jet A it is between 110 and 150 F.

If the fuel is significantly below the flash point, the liquid cannot g= enerate flammable vapor concentrations. In this situation, a spark or hot su= rface cannot ignite the vapors. If the fuel is significantly above the flash= point, a spark with sufficient energy or a surface exceeding the autoigniti= on temperature will ignite the vapors if the air fuel ratio is right. At the= flash point, ignition depends on the surrounding conditions.

Since the temperature aboard ship is never going to be below -50 F, any= leak or open container of av gas is going to release flammable vapors=20= which may come in contact with an ignition source. If the navy specifies the= ir Jet A to have a flash point of say 130 F (I don't know what their spec is= or if they even use Jet A), then as long as the temperatures are kept below= 120 F there should be no flammable vapors generated. Just don't spill = any on a hot exhaust manifold.

However, once gasoline and jet fuel/diesel fuel are vaporized in flamma= ble mixtures, it is MUCH easier to ignite jet/diesel than gas.

The reason I presented those autoignition temperatures was to give some= idea how much a fire scene must cool before the extinguishing agent is lost= in order to prevent reignition from occurring.

As for whether the turbine drivers have an increased risk of fire, I do= n't know the answer. Certainly the risks are different. For instance, the he= ad space in a gasoline fuel tank is generally too rich to burn at any altitu= de you might fly. However, the head space on a jet A tank generally starts o= ut too lean to burn on the ground. But, as the altitude increases it will li= kely enter the flammable range. Remember the center fuel tank issue on TWA 0= 07. Also note that the flash point drops with increased altitude.

Rob

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