The following originally appeared in the May 11, 1994 issue
of FLIMSIES (One time North American serial rights granted, 
all other rights retained.) in anticipation of the arrival
of two new switch engines for the Union Pacific's Southern
California operations.  These were delayed but have now
arrived and news items should begin appearing on their test
performance.  The following is to better understand the use
of Liquified Natural Gas (LNG) as a locomotive fuel. A
photograph of locomotive No. 1299 is in 1299.GIF, library 5.
 
                     LNG, The Cool Fuel
                             by
                       Carl M. Lathrop
     Natural gas  transported in some two million miles of
high pressure pipelines has heated our homes, generated our
electric power and served industry.  It is beginning now to
take its turn at fueling locomotives on our railroads. 
Union Pacific has entered this  developing field of fuel
utilization seeking ways to reduce both operating costs and
stack emissions.  Locomotives designed specifically for this
clean burning fuel have been ordered from the three major
suppliers and performance tests will begin in 1994.
     Morrison-Knudsen Corporation, as one of the three, will
enter the field with their MK 1200 G locomotive powered by a
Caterpillar G3516 SITA four-stroke spark ignited engine
specifically designed for natural gas fuel.  EMD and General
Electric will be using adaptations of their respective
diesel cycle engines modified to burn up to 95% natural gas.
A similar approach has been taken by Burlington Northern
and this will be explored separately.
     The two machines being supplied by M-K are self
contained in that the usual diesel fuel tanks will be
replaced with 1400 gallon cryogenic tanks to carry the LNG. 
The EMD and GE sets of two engines each will be hauling
liquid fuel tenders not unlike conventional tank cars in
appearance but of vastly different design for operation at
-259 deg F.
     There are enough differences in the two approaches to
make it desirable to talk about them separately.  Since the
M-K units are totally fueled by LNG they will be looked at
first.
     While standing out in the weeds to watch the train go
by most observers look at the locomotive as just another
"diesel".  Rudolph Diesel's invention has become so
commonplace as to have added a new word to the lexicon of
railroading with a generic term, diesel engine.  Sometimes
we forget that Nickolaus August Otto began building internal
combustion engines as an improvement over the reciprocating
steam engine, as did Diesel but with quite a different
approach. 
     Basically the difference is in the ignition system. 
The original Otto cycle used a separately heated hot tube as
the ignitor with electric spark for ignition being
introduced at the turn of the century by a San Francisco
marine engine builder.  Rudolph Diesel, on the other hand,
used the heat of compression to ignite the fuel.  The M-K
units are Otto cycle while the EMD and GE engines, before
modification, are Diesel cycle.
     Some of the railroads have been repowering their older
diesel locomotives with new Caterpillar diesel power plants
as an upgrade.  At the same time Caterpillar manufacture
other engines suitable for other fuels.  They can supply
their customers with engines that operate on gaseous fuels. 
These engines have found their way into the oil fields and
gas pipeline stations using the indigenous gas as fuel.  It
was, therefore, a rather easy and natural step to power a
locomotive whose fuel tanks contained LNG.  This is true
since as far as the engine is concerned it is looking at a
97% methane gas in the gaseous state at 60 deg F and 50
psig.
     M-K are installing double wall fuel tanks on these
switchers.  The outer tank is carbon steel while the inner
tank is stainless steel with a composite heat insulation
barrier in between the two tanks.  The LNG is at about -200
deg F and 50 psig.  It enters a vaporizer as a liquid and
heat from the engine's cooling system causes it to boil and
is further heated to 60 deg for introduction into the
Caterpillar engines.  This is a dead end fuel system and not
a circulating system as with conventional diesel fuel
systems. Tank pressure is maintained by a recirculating
economizer circuit.
     These engines can be characterized as lean burn engines
and, therefore, one would expect stack emissions to be lower
than with conventional diesel engines burning #2 diesel
fuel.  A contributing factor to the lower NOx is the lower
combustion zone temperatures with the gas fuel.  On the
other hand, one must remember that LNG is not a high energy
fuel compared to diesel fuel.  In fact, the fuel system must
handle 60% more liquid thus requiring 60% more fuel tank
capacity for the same operating hours between refueling
stops.

THE ROAD UNITS
     EMD will modify two of their SD-60M 3,800 horsepower
units and GE will be using two of their Dash 8 4,000
horsepower machines.  These will be the road units for
service anywhere on the system as this part of the program.
     Both builders will, in effect, be providing their
conventional diesel engined locomotive to which has been
added a second fuel system.  To extend their operating range
and to provide for the second fuel each set will be provided
with a fuel tank car of unique design.  The LNG will be
pumped from the tender by two submerged pumps delivering the
liquid fuel to another pump on the locomotive where the
pressure will be increased to 1,000 psig. Here it will be
vaporized and directed to the second fuel rack for timed
intermediate high pressure injection into the cylinders. 
This is a circulating system not unlike the diesel fuel
system with any surplus liquid over need being  returned to
the tender tank.
     Diesel fuel  will become the auxiliary fuel or,
perhaps, should be termed the ignntion fuel.  It will be
fired at a rate of about 5% of full load fuel requirements. 
At idle it will be 100% of the fuel consumed.  This constant
level is the ignition source for the LNG.  With gas becoming
the primary fuel which is not ignited by compression
temperature rise would seem to convert these "diesels" to
the Otto cycle.
     The tender tank car for fuel is the work of Process
Engineering of Plaistow, New Hampshire.  The 30,000 gallon
capacity vessel is a double wall pressure vessel with
insulating material in the space between the concentric
vessels.  The designers catered to the needs of safety in
this unusual situation by developing several features
recognizing the possibilities of derailment.

OTHERS ARE IN THE LNG FIELD
     Air Products  Corporation of Allentown, PA, have been
working with Burlington Northern for the past six years in a
program to move this type fuel into the railroad industry. 
Two EMD locomotives were modified by an outside contractor
who added a second and parallel fuel system.  Air Products &
Chemicals Inc. regularly move liquified gases in their fleet
of tank cars and have modified two cars to be the fuel
tenders in this operation.
     Vaporizers and control equipments were installed on the
tenders with the fuel being moved across the couplings to
the engines as a gas.  It is a low pressure operation with
the fuel being injected into the cylinders at the bottom of
the  stroke to be then compressed during the compression
stroke.  A small amount of diesel fuel is injected at the
end of compression to be ignited in the usual manner and be
the ignition source for the gas fuel as in the Otto cycle. 
     Conventional pipeline gas is processed to remove inerts
such as carbon dioxide and helium before being liquified,
stored and transported for trackside refueling.  Field
testing in coal drags has accumulated over a year's worth of
operating data.

THE OTHER SIDE OF THE COIN
     There would appear to be some interesting possibilities
for natural gas off in the future.  Something like 40% of
the world's hydrocarbon reserves are natural gas.  It has
been estimated that there are over 1,500 trillion cubic feet
available.  Unfortunately about half are in remote areas and
not near to the markets.  Long distance, high pressure,
pipelines are a solution for continental sources and
destinations, however, many of the gas fields are beyond our
borders and far across vast oceans.
     Transporting this gas by LNG tankers has met with mixed
success and has not achieved universal acceptance.  On the
other hand processes such as Exxon's AGC21 conversion
process is capable of converting natural gas to a white
crude oil transportable in conventional ways.  This
synthetic liquid can yield a wide range of high quality
transportation fuel products.  As with most of the synthetic
fuels ventures the economics of crude oil pricing dictated
by OPEC place these just out of reach.  A few dollars
increase in the delivered price of crude and the break even
figure is reached.
     The bottom line in fuel costs is in units of dollars
per million Btu delivered to the consumer.  The LNG of our
interest will, generally, come from pipeline natural gas. 
For the most part this is not a spot market but a long term
contract market with the consequent stability of price.  
     The end product of any LNG liquefaction step is
essentially methane with the 3% to 5% undesirable
constituents having been removed.  This liquefaction step
represents an add-on cost to the market price of the natural
gas both of which will have a bearing on the point where
there is a break even with  conventional diesel fuel
marketed as a commodity and not as a specialty fuel. 
     There are, however, other considerations that must be
factored into the case.  Improved maintenance costs are
certainly an economic consideration.  Reduced stack
emissions chargeable to the new fuel are probably going to
be an imponderable factor that management will likely need
to accept as a necessary consequence of doing business in an
air quality sensitive area.
                            -end-