Generator installation with jet fuel 1

[supadupachalupa]

Guys/Gals,

I'm currently working on a project to design a generator plant for an airport. The units are to typically run on diesel fuel but can be run on jet fuel in case of an emergency.
Does anyone have any experience regarding this type of installation?
Specifically, do the generators need to be constructed to Class 1, Division 2 standards?
Any other tips or notes regarding your installation you would like to share?

Thanks in advance,
Dennis

 

[dpc]

It should be similar to Diesel, but you'll need to consult applicable NFPA standards. We have a pretty good NFPA forum on this site. You might want to post a specific question there.

 

[oldfieldguy]

Work with the manufacturer of the prime movers to verify the operation on jet fuels.

old field guy

 

[waross]

Here are some John Deere fuel recomendations which may apply;..

John Deere engines will also operate on lower viscosity fuels. However, with rotary pumps, as fuel viscosity decreases, fuel flow to the engine decreases resulting in lower power. Engine response, load recovery, and starting time are adversely affected. The reduced lubricating properties of lower viscosity fuels may also reduce pump life unless special internal parts are used.
Engines which use in-line pumps are also sensitive to lower viscosity fuels, resulting in reduced power. In-line pump components are not as sensitive to wear as rotary pump components since in-line parts are lubricated by engine oil.
Engine operation using extremely low viscosity fuels such as JP-4 and Jet B is not recommended. Significant fuel injection equipment wear results from use of fuels with viscosities below 2.0 centistokes. If JP-4 is used, viscosity must be raised by adding 10%-20% new lube oil by volume and 0.2%-1% cetane improver such as hexyl nitrate. Even with these additives to raise viscosity and cetane number, a performance loss should be expected.
The use of high specific gravity fuels (lower API) could result in power levels exceeding the engines approved power rating. Operation above the approved engine power level will result in reduced engine life and increased operating costs.
In general, ‘light’ fuels may give poor low-load / highspeed
performance, poor injection system lubrication, lower power, and poorer startability. ‘Heavy’ fuels may cause fuel filter plugging at low temperature, poor starting, additional combustion zone deposits and higher wear due to higher sulfur levels. Pretreatment of ‘heavy’ fuels may be required, such as prefiltering, water separation, and heating. Contact Sales Engineering if use of other than recommended fuels is anticipated. The following tables summarize various fuels, comments concerning modifications required to maintain pump and engine life, and performance effects that may be encountered.

Diesel Fuels
No. 2-D Recommended fuel. Recommended for ambients above 40°F (5°C).
No. 1-D Recommended for ambients below 40°F (5°C). Power loss up to 5% can be expected due to lower viscosity.
DF-A U.S. Federal Specification, arctic grade. Power loss up to 6% can be expected. Injection pumps may exhibit increased component wear with extended use of this fuel due to high dewaxing and low viscosity. Special transfer pump and drive component parts are required for Stanadyne injection pumps. Stanadyne Gen-set pumps also require special governor components. Stanadyne fuel injection pump options identified as “Jet A, JP5/JP8 Fuel Capable” are equipped with the required parts. Standard Stanadyne pumps can be converted by installing a Stanadyne Arctic conversion kit. Special components are not required for Lucas-CAV injection pumps.

Aviation Fuels
Jet A Lower viscosity and density than base fuel No. 2-D. power loss up to 10% can be expected. Injection pumps may exhibit increased component wear with extended use of this fuel. Special transfer pump and drive component parts are
required for Stanadyne injection pumps. Special components are not required for Lucas-CAV injection pumps. See DF-A comments for details.
Jet A-1 See Jet A and DF-A comments. Power loss up to 10% can be expected.
Jet B Not Recommended. Lower density and extremely low viscosity compared to base fuel No. 2-D will result in greatly accelerated injection pump wear, poor starting, and a power loss of up to 14%.
Jet B may be used on pumps with Stanadyne injection pumps with special hardened parts for up to 300 hours as an emergency fuel only. Hot starting could be extremely difficult or impossible without priming. Lucas-CAV injection
pumps should not be used with Jet-B fuel, even for emergency operation.
JP-4 Not Recommended. Military equivalent of Jet B. See Jet B comments. Power loss up to 14% can be expected. JP-4 may be used on Stanadyne pumps with special hardened parts up to 300 hours as an emergency fuel only. Lucas-CAV injection pumps should not be used with JP-4 fuel, even for emergency operation.
JP-5 See Jet A and DF-A comments. Power loss up to 9% can be expected.
JP-7 See Jet A and DF-A comments. Power loss up to 10% can be expected.

You may want to consider locating a suitable additive to improve lubricity for Jet fuel. I hope this will prepare you to discuss Jet fuel issues with the engine and/or injector system manufacturers.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

I have done a number of sites using CAT engines running on aviation fuel at military sites.

At those sites we had no special issues with installation or code like Class 1 Div 2. Our primary problems were with fuel lubricity and power derate. The normally allowed maximum fuel temperature of 150 degrees F (with #2 diesel fuel) delivered to the injectors was no longer valid with the jet fuel, we found we had to keep the fuel temp below 95 F to the injectors for these engines, which meant about 70 degrees F to the inlet of the fuel transfer pump. Otherwise we had very poor fuel delivery system service life, mainly due to plunger and barrel sticking.

Since introduction of low sulphur fuels, fuel system components have appeared to become more resistant to problems caused by low viscosity fuel. But I still see issues time to time, especially with prime power units in higher ambient conditions.

At some sites we had to go as far as refrigerated fuel coolers to keep injectors alive for a year.

Additives are a possiblity, but at many sites I have been at no changes to the fuel was allowed that may affect the operation of aircraft engines, since the fear was always there that somehow the fuels might get mixed.

The manufacturer of the engines you are getting should have specific recommendations like Bill referenced from John Deere above.

 

[waross]

catserveng, Will a day tank with no easy return to the main fuel storage, with a dosing pump for additives be acceptable at most sites?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[alehman]

The key to hazardous area determination is the flash point of the fuel. Usually you can get that from an MSDS sheet. Then go to NFPA.

Bill - Based on catserveng's comments, you may need a fuel cooler. Need to look at the flow rates, supply and return temps, size of day tank, etc. to determine for sure. Fuel coolers are common even for #2 where day tanks are small and have no return to the main tank for diluting hot fuel.

Alan
----
"It’s always fun to do the impossible." - Walt Disney

 

[catserveng]

Bill,

The Navy was pretty hard core about not "modifying" the fuel. We did a couple of stations in the Channel Islands and ended up with fuel chillers on those, as well as some units we put together for tactical deployment systems for the Air Force. We also ended using fuel chillers on a site in the desert when ultra-low sulphur fuel first came out, we were only getting 500 hours before the injectors started sticking. Since then CAT has made a number of changes/improvements so ULSD doesn't appear to be a problem anymore.

I was at Kwajalen a while back, we (actually former employer) have larger engines running on JP5, they have oversized air to fuel coolers and for the most part they do ok, but let them get a little dirty and it's a batch of injectors.

Also the fuel cooling did nothing to help the fuel density/power derate. The engine meters fuel by volume, if your fuel is less dense=less power, and usually we were not allowed to change fuel settings. Of course with the newer electronic engines it's completely out of anyones hands.

CAT and Cummins both had special ratings for tactical equipment using aviation fuel, but I don't know if a commercial user could get those ratings.

Of course with a standby set most folks just take there chances, most air districts in So Cal limit non-emergency run time to about 22 hours/year, and since power in this part of the world is pretty darn reliable, actual annual runtimes are low and customers out here take lots of chances to save a few bucks.

Hope that helps, Mike