MK1200G LNG 
Boise Locomotive Operations 
By Dennis L. Nott 

Locomotive Update 
Powered Switcher 

In early 1992, the Boise Locomotive Company (formerly Morrison Knudsen Rail Corporation) perceived a need for development of a new, highly efficient, switcher locomotive as a replacement for North America's aging switching fleet.  Paramount in the decision to develop a new switcher locomotive was the desire to incorporate state of the art control systems for enhanced tractive effort, economical operation and maintenance and superior environmental performance.  To this end Boise Locomotive Company formed a strategic alliance with Caterpillar, Inc., to design and produce North America's first microprocessor controlled 1,200 HP locomotive fueled entirely by liquefied natural gas (LNG), the MK1200G.
In 1993 the Boise Locomotive Company was approached by the Union Pacific Railroad (UP) and the Atchison, Topeka and Santa Fe Railway (now part of the Burlington Northern Santa Fe, BNSF) to produce two MKI200G locomotives for each company for use by each railroad as an LNG demonstration project in the Los Angeles Basin.  This resulted in the delivery of locomotive UP 1298 and LTP 1299 to the Union Pacific in August of 1994 and ATSF 1200 and ATSF 1201 to the Burlington Northern Santa Fe in December of 1994.  The Union Pacific 1200Gs went into service on September 22, 1994 and the ATSF 1200Gs on December 5, 1994. 

The Boise Locomotive Company has designed several operational and safety improvements over existing switchers in the new MK1200G switchers with: 
The Caterpillar G3516 spark ignited, turbocharged - aftercooled (SITA) LNG fueled V- 16 engine that produces the lowest NOx emissions of any engine of its class. 
Modern electrical rotating equipment, including electric motor drive for the air compressor, supplied by KATO Engineering, a division of Reliance Electric/Rockwell. 
A Boise Locomotive Company designed state-of-the-art microprocessor locomotive control system for superior traction and engine control. 
An advanced LNG fuel management system of cryogenic tanks, process piping, vaporizer and controls designed by Minnesota Valley Engineering (MVE). 
A modern, high visibility ergonomically designed cab. 
Excellent collision protection for short, nose end of locomotive. 
Six-row mechanically bonded radiator cores that remove heat from separate jacket water and aftercooler circuits that are cooled by two 48-inch electrically driven cooling fans. 

Two axle Blomberg type trucks with 40 inch wheels, G-G type journal bearings, 62:15 gear ratio, and clasp composition brakes providing superior ride, tracking and braking. 

(Slide general arrangement) 
Locomotive Type: 
 AAR Designation B-B  Industry designation 0440 
 Nominal dimensions and capacities are as follows: 
 Length, coupler to coupler  56 ft. 2 in. 
  Length between bolster centers 31 ft. 0 in. 
  Weight, loaded   236,000 lbs.
  Fuel capacity, LNG   1,400 gals. 
  Sand capacity    50 cu. ft, 
  Cooling water capacity  190 gals. 
  Lube oil capacity   219 gals. 

Curve negotiation: 
Minimum curve coupled to car              150 ft. 
Minimum curve coupled to locomotive 274 ft, 

 Traction motors 4 
 Type DC, series wound, axle hung 
 Gear ratio 62:15 
 Wheels 40 in. 

(Slide tractive effort) 

Performance data is as follows: 
 Engine RPM 1,500 
 Fuel LNG 
 Traction HP 1,200 
 Maximum speed 70 MPH 
 Minimum continuous speed 6.2 MPH 
 Minimum continuous tractive effort 60,000 lbs. 

The Caterpillar G3516 SITA engine is a mature design natural gas engine used in thousands of applications throughout the world, but their primary use has been in the stationary generating plant application.  The application of the G3516 SITA engine to the MK1200G locomotive is the first time this engine was used in a locomotive, or a variable load situation. Caterpillar took two years to enhance the design of the engine to meet the demands of this application. 

The basic engine features are: 
16 cylinder - 60oV configuration 
Turbocharged - aftercooled 
4 - stroke cycle 
Spark ignited 
11.1 compression ratio 
1,350 BHP @ 1,500 rpm 
Low firing pressures 
170 mm bore and 190 mm stroke 
2 - intake and 2 - exhaust valves per cylinder 

Electronic ignition system (EIS) 
Air/fuel ratio control 
Fast transient response 
Trouble shooting and maintenance capabilities 

The G3516 SITA engine is unique from diesel counterparts because of the low pressure LNG gas delivery system and spark ignition system.  The G3516 uses low-pressure (40-psi) gas flow out of the initial Acme gas regulator.  The gas then flows to the Sprauge regulator that regulates the gas to the engine at 6 to 8 inches of water at idle (increases with engine speed).  The gas flows to the engine through a carburetor and is spark ignited by a spark plug within the cylinder.  The 1200G runs on pure LNG and does not require diesel fuel to be mixed with the LNG as do high pressure (3,000 psi) direct injected systems that were tested in high horsepower locomotives in 1995 and 1996. 

(Slide emissions performance) 
The emissions performance of the Caterpillar G3516 SITA engine is as follows: 
ISO 8178-1 Conditions 
 Oxides of Nitrogen (NOx) 2.0 
 Carbon Monoxide (CO) 1.9 
 Hydrocarbons   (HC) 2.8 
 Particulates   .08 


The fuel system on the 1200G can be divided into three (3) primary systems: the fuel tanks, process piping, valves, and the LNG vaporizer. 

(Fuel tank slides) 

Fuel tanks of the 1200G must be cylindrical to provide the strength necessary to store the fuel because LNG is a cryogenic material under low to moderate pressure when stored.  The fuel storage system on the 1200G is three separate interconnected tanks with a total capacity of 1,400 gallons of LNG.  There is one tank of 900 gallons in the middle of the tank system and two outer tanks of 250 gallons each.  Because of the cylindrical design required the space normally occupied by a conventional fuel tank on the locomotive could not be efficiently utilized resulting in the lower fuel capacity of the 1200G.  Under normal operating conditions the 1,400 gallons of LNG is equivalent to about 900 gallons of diesel fuel on a diesel-powered switcher.
The inner shell of each tank is fabricated from 1/4-inch thick, ASTM 304 stainless steel to hold the temperature of the LNG at approximately -260 degrees F.  The inner shell is blanketed with approximately 1-1/2 inches of an aerospace developed insulation material and then installed in a high strength carbon steel (ASTM A572) outer shell of 1/2 inch thick that provides the tank structural integrity. 
After the outer tank is capped and sealed the insulated space between the inner and outer tanks is vacuum pumped to improve the insulating capabilities of the system.  All three tanks sit in a tank cradle that is attached to the frame of the locomotive.  The dynamic load capability of the fuel tank system is 10G in all directions.  In addition, the bottom of the tank cradle is protected from derailment puncture by a steel skid plate.  Fuel level monitoring is accomplished with capacitance tubes in each of the LNG tanks. 

Process piping on the system is simplified by the fact that the G3516 engine is a low-pressure engine.  When the fuel tanks are fully loaded, the saturation pressure of the LNG is 70 to 100 psi. This means that the pressure of the evaporated gas alone will provide enough gas pressure to run the engine without the use of pumps.  The process piping and Swaglock fittings are Schedule 40 stainless steel and all valves on the tank system are all made of bronze because of the cryogenic nature of the fuel.  There are three separate process piping and valve systems on the MK1200G: the LNG fill and off load piping; the LNG fuel tank to engine supply piping; and the gaseous fuel and vent pipe system (discussed later under Safety).  All piping and fittings at the end of the fuel tanks are protected by a steel collision plate. 
The final component of the fuel system is the liquid-heated vaporizer.  The purpose of the vaporizer is to assist the vaporization of the liquefied LNG as the fuel supply depletes in the fuel tanks.  The vaporizer is a cylindrical liquid - to - liquid heat exchanger that uses engine coolant water to raise the temperature of the LNG to aid evaporation. 

(Slides rotating equipment) 

The main traction alternator is a KATO 8P6.5-3000, coupled to the engine by a flexible coupling.  AC power is rectified to the rated 1,050 VDC and 4,000 amps continuous output with an intermittent capacity of 6,000 amps.  The traction alternator receives excitation from the companion alternator. It is ventilated by an internal, direct drive cooling system.  The traction alternator is also of double bearing design to increase reliability and life. 

The companion and auxiliary alternators are combined into one housing which is coupled to the engine crankshaft through a 1:1.33 gear ratio. 

The companion alternator is a 130 kW, KATO series 6P2-1450 revolving field machine equipped with slip rings and brushes.  AC is output at a rated 183 VAC, 100 Hz, 3-phase power at 2,000 RPM.  Excitation to the main field is provided by the auxiliary alternator. 

The auxiliary alternator is an 18 kW KATO series 6P2-0500, revolving field machine. 55 VAC is rectified and output is rated at 74 VDC.  The exciter field is controlled by the voltage regulator by a VR 10 card. 

Four D78B traction motors are connected in full parallel with no motor or alternator transition required. 

(Slide microprocessor) 

The 1200G use a MK-LOC microprocessor control system to control excitation/load control, adhesion engine control, diagnostics systems and LNG gas leak detection and control. 
The excitation control system regulates the traction alternator output.  It is linked to the adhesion control system, which optimizes available adhesion.  Load control maintains horsepower in accordance with the locomotive's tractive effort characteristics. 
The adhesion control system provides smooth, uniform wheel creep action to maximize adhesion for any locomotive and track condition.  Wheel rotation rate signals are received from hub mounted axle generators. 
The engine control system maintains accurate engine speeds of plus or minus 1%.  Engine speeds are set to maximize fuel economy and avoid resonant vibrations for each throttle position.  Engine control provides low idle, hot engine protection and automatic fan sequencing. 
The diagnostics system monitors the locomotive performance, stores all critical information, and provides a historical fault log to service personnel for quick troubleshooting and maintenance turnaround.  The system reacts to a full range of fault and trending conditions and signals critical events that require operator action.  The microprocessor's command procedures and fault logs are stored in software, hardware, and nonvolatile memory.  If required, service information can be displayed on the onboard computer screen, displayed on a portable interface display or off-loaded to a remote terminal. 
The 1200G also have continuously powered methane detectors that provide input to the microprocessor control system that will activate engine shut down and warning systems. 

(Slide of cab) 

The 1200G were designed with numerous features for crew safety and comfort.  The cab design allows adequate room for normal crew movement within the cab as well as space for a refrigerator and steps down to the short nose if a toilet is installed there.  The cab meets all AAR clean cab requirements.  The under-floor mounted HVAC system also provides the crew with a clean and comfortable environment in which to work. 

The cab was designed to provide the engineer and other crew members with excellent 360 degree visibility.  The short nose of the locomotive is lower and slopes down for larger windows could be installed.  Another window over the long hood of the locomotive affords the crew additional visibility in that direction.  The engineer's view is enhanced by the raised platform that the control stand sits on. 
The cab is also insulated against noise. It has excellent sound characteristics of 60 - 75 decibels under normal operating conditions. 

(Slide of anti climber and collision post) 

The 1200G is also built with an anti climber and 16 inch deep I beam collision posts on the short hood end for extra crew protection in the case of collision with other railroad equipment or at railroad - highway grade crossings.  All collision protection meets AAR S-580 requirements. 
There are several safety features incorporated in the LNG fuel system even though that LNG is difficult to ignite because of the very narrow range of the air to fuel ratio that is required.  Excess heat and fuel pressure (greater than 80 psi) are removed by an economizer regulator that draws vapor from the top of the tanks while the engine is running and passes the vapor to the engine.  When the engine is shut down the road relief regulator slowly vents vapor that is produced in the tank (120-psi) through a vent at the top of the locomotive's long hood.  This condition usually occurs when the locomotive has been sitting for prolonged periods without use and consequently, the fuel begins to boil off increasing vapor pressure.  There are five 220 psi relief vent valves on the locomotive; three on the vent tree inside the locomotive car body and two on the fuel tank system.  The vent tree also has two 270 psi burst discs.  The vaporizer has an 18-psi burst disc on the water side of the cooling system should a leak develop within the vaporizer. 
The locomotive is equipped with six methane sensors for gas detection that work through the microprocessor.  Methane sensors are located at each end of the fuel tanks: one below the radiators above the air compressor and one above the auxiliary generator on the expansion tank. In addition, one in the fresh air compartments below the inertial filter and one in the cab.  All of the sensors on the BNSF 1200Gs are set to activate at a 10% Lower Explosive Limit (LEL) alarm level.  Those on the UP 1200Gs are set at a 20% LEL.  The sensors on all 1200Gs are set up for non-intrusive calibration.  The sensors provide uninterrupted alarm capability with both audible and visual warnings.  In the case of an alarm, strobe lights at each end of the locomotive (one on long hood end and one on each side of the cab) are activated and an audible sound warning is activated in the cab.  There also is a normal compliment of standard, locomotive emergency, fuel cut-off buttons on the locomotive. 

The Union Pacific locomotives, UP 1298 and UP 1299, are currently assigned to the UP's Commerce Yard just east of downtown Los Angeles, California.  Both units are assigned to general switching duties within the confines of the yard.  The UP performs all [sent] maintenance and servicing functions, except fueling, to the locomotives with UP forces. 

Since the maintenance is performed by the Union Pacific, Boise Locomotive Company has a more limited access to the two locomotives.  In addition, the two Union Pacific 1200Gs are equipped with a GPS system interfaced with the 1200Gs micro processor system. Because of this, the UP does not download the microprocessor data on a regular basis.  However, the Union Pacific did download the duty cycle of UP 1299 for the period of September 4, 1996, and January 31, 1997.  Officials of the Union Pacific and Boise Locomotive Company feel that this download represents a typical duty cycle for the two Union Pacific 1200Gs.  Through December 31, 1996, the UP 1298 engine operated 7,219 hours, averaging 8.68 hours for each day in service.  For the same period, the UP 1299 had 6,934 engine hours averaging of 8.33 hours for each in service day. 

The Burlington Northern Santa Fe locomotives, ATSF 1200 and ATSF 1201, are currently assigned to BNSF Hobart just east of downtown Los Angeles, California.  Both units have been assigned to general switching duties within the confines of the yard until February of 1997.  In February of 1997, the units were assigned to switching and local duty on the Los Angeles Junction Railway (LAJ) in Vernon, California, a subsidiary of the BNSF.  All maintenance and servicing, except fueling, is performed by the Boise Locomotive Company at the LAJ facility a short distance from Hobart Yard

Limitations noted by the Burlington Northern Santa Fe are 1200 HP for traction and the fuel tank size limits the locomotives to yard service, because the units need to be operated near their fueling stations. 
The BNSF is pleased with the tractive effort of the 1200G.  On August 15, 1995, a tractive effort test was conducted by the ATSF on a 2.0% grade at mile post 27.0 on the Lucerne Valley Subdivision with ATSF 1201.  The test location is at approximately 4100 feet elevation and the temperatures during the test time varied from 90oF to 96oF.  Under those conditions the 1201 produced slightly over 1000 HP.  The test was conducted using test car ATSF 83 plus 19 loaded ballast cars with weights as shown: 

Locomotive car number  gross scale weight 
Locomotive ATSF 1201 121.78 tons 
Test Car ATSF 83 85.00 tons 
Ballast Car ATSF 177037 94.05 tons 
Ballast Car ATSF 176926  92.65 tons 
Ballast Car ATSF 177183 91.10 tons 
Ballast Car ATSF 177257  92.95 tons 
Ballast Car ATSF 176945  95.75 tons 
Ballast Car ATSF 177084  92.50 tons 
Ballast Car ATSF 177376  94.40 tons 
Ballast Car ATSF 177482  96.85 tons 
Ballast Car ATSF 177586  94.35 tons 
Ballast Car ATSF 177963  128.65 tons 
Ballast Car ATSF 177047  94.80 tons 
Ballast Car ATSF 177212  91.65 tons 
Ballast Car ATSF 177893  114.45 tons 
Ballast Car ATSF 177132  93.80 tons 
Ballast Car ATSF 177681  92.95 tons 
Ballast Car ATSF 177116  95.55 tons 
Ballast Car ATSF 177469 94.60 tons 
Ballast Car ATSF 177917 108.65 tons 

The results of the test are as follows: 

1   1201/   10 cars 7.8 39,000 .18 
2 1201/     11 cars 6.6 44,400 .20 
3 1201/     13 cars 5.1 52,300 .23 
4  1201/    15 cars 3.6 61,000 .27 
5  1201/    17 cars 2.9 68,800 .30 
6  1201/    19 cars Stalled 
7  1201/    18 cars Stalled 

Note: Adhesion coefficient "u" includes locomotive resistance. 
Duty cycles of each unit downloaded from February 14, 1996, through September 30, 1996 are virtually identical. 
Officials of the Burlington Northern Santa Fe and the Boise Locomotive Company feel this duty cycle represents a typical operation of the two 1200Gs. 

Through December 3,1996, the ATSF 1200 engine had operated 10,610 hours for an average of 14.53 hours for each day in service.  For the same period, ATSF 1201 had 10,592 engine hours averaging 14.51 hours for each in service day. 


All fueling of the two BNSF 1200Gs is done at a modular TVAC fueling station that has been installed at LAJ locomotive service track in Vernon.  This type of fueling station was chosen for its low cost of installation, based on low volumes of LNG the two BNSF units would be using. 
The TVAC cryogenic pressure vessel capacity of 5,300 gallons of LNG.  The vessel is a double wall pressure vessel with vacuum insulation capable of storing LNG at low pressures for several days.  The vessel has pressure relief valves and vents to release vapor pressure inside the tank.  Tanks of this size will normally hold the LNG for 5 - 10 days before venting depending on the tanks volume and the pressure upon delivery of the LNG.  The vessel is housed in a frame conforming to the specifications for an ISO container.  All fuel transfer equipment is skid mounted and placed next to the pressure vessel.  Instrumentation includes both mechanical and electrical pressure gauges and level indicators.  This system will deliver between 40 and 50 gpm at pressures between 120 and 150 psi. 
The system at the LAJ site has been permanently installed on concrete pads with a concrete, spill retaining wall built completely around the equipment to meet local codes. 

Fueling of each locomotive is typically done once per week.  The locomotives are spotted at the TVAC (each locomotive has a fuel fill on each side) and the fuel fill nozzle from the TVAC is attached to the fuel tank receptacle.  The LNG enters each tank through a top, fill spray bar distributed through the vapor space to immediately reduce tank pressure to the saturation pressure of the incoming liquid.  This eliminates the need for venting the tank while fueling. 
Low volume pumped by the TVAC 
Safety checks are performed on the system prior to and after fueling. The time it takes to condition the fuel before pumping can take up to 40 minutes to fuel the first locomotive and 20 to 30 minutes for the second locomotive. 

All fuel is delivered by truck to the TVAC. 

Total fuel used from start up of fueling operation in December of 1994 through September 30, 1996, (last date of fuel reconciliation of fuel deliveries to inventory) is 291,783 gallons: An average of 217.75 gallons per day per locomotive for the period. 


Locomotive fueling for both Union Pacific 1200G switchers is done at UP LNG fueling station located within Commerce Yard.  While the system and fueling process is the same as with the TVAC at the LAJ, UTP was designed as permanent facility capable of dispensing LNG to large volume road locomotives and all equipment is therefore sized accordingly. 

The fueling station at the UP consists of a permanent 55,000 gallon, 50 psi, LNG bulk storage tank that can be filled by truck or rail car.  From the main, bulk storage tank, the fuel is pumped to a 3,000 gallon, 250 psi, LNG Transfer Tank where the fuel is conditioned prior to filling the locomotives.  From the LNG Transfer Tank the fuel is pumped to the locomotives at 250 psi at a rate of approximately 100 gallons per minute.  Fueling each 1200G at the UP typically takes approximately 25 minutes for the first locomotive and 15 minutes for the second locomotive. 
The total fuel used from start of locomotive fueling on September 22, 1994, through September 30, 1996, (last date of reconciliation of fuel deliveries to inventory) is 239,383 gallons.  This is an average of 161.96 gallons per day per locomotive. 


While the fueling systems at both locations are different, the procedure for fueling the locomotives does not differ at either location.  However, the LNG fueling procedure does differ from the normal, diesel fuel procedure.  The LNG fueling procedure is as follows: 

"Blue flag" the locomotive. 
Shut down the locomotive engine. 
Ground the locomotive by attaching ground cable from locomotive fuel tank to ground stake. 
Cool down the fuel pump and fill equipment by circulating (normally aspirate) fuel. 
This procedure allows the liquid gas to reduce the temperature of the pumping and filling equipment so that the liquid LNG does not become vapor when it flows through warmer equipment. 
After cooling the special cryogenic fill connector on the fuel station side it is connected to the special cryogenic fuel fill on the locomotive. 
Before pumping fuel into the locomotive, the road relief valve on the locomotive must be closed to prevent vapor pressures from spiking and damaging the regulator. 
Begin fueling and fill locomotive until the pressure gauge spikes. 

After tanks are full, shut down fuel station pumping system. 

Open locomotive load relief, valve on locomotive. 
Remove fueling station, fill connection from locomotive. 
Remove grounding cable from locomotive. 
Start locomotive. 
Remove blue flag. 


The Boise Locomotive Company worked closely with Caterpillar to develop a scheduled maintenance program for the 1200G prior to the delivery of the units to both railroads.  The 1200G is a locomotive that, for all purposes, is state-of-the-art in all respects when compared to other new DC motored locomotives being delivered with the only major difference being the state-of-the-art LNG engine and fuel system.  Therefore, Boise Locomotive Company's recommended scheduled maintenance cycle for the 1200G is the same as would be recommended for any new DC motored locomotive with the exception of the LNG differences. 

Boise Locomotive Company's initial scheduled maintenance for the Caterpillar 3516 SITA engine and fuel system was conservative and with experience and time most of the maintenance functions scheduled on a 92 day basis have been extended out.  Functions that are over and above a typical diesel powered locomotive 92-day inspection are as follows: 

 Additional Inspection Requirements - 92 Day Inspection
 Man Hours/ 
 Function Interval 
 Calibrate methane detectors 1.0 
 Calibrate ignition timing 1.0 
 Total additional man hours 92 day inspection 2.0 

From experience, Boise Locomotive Company has determined that the following additional maintenance functions are required for the 1200G LNG switcher on an annual basis: 

 Function Man Hours/  Interval 
 Change oil as required by analysis not to exceed 1 year 2.0 
 Drain aftercooler condensation 0.5 
 Clean/set spark plug gap and adjust engine valve lash 8.0 
 Inspect fuel system valves/fittings and leak test 4.0 
 Replace gas regulator 1.0 
Replace burst disks                                                      1.0 
Total additional man hours annual                                     16.5 

All four 1200G locomotives have now been in service for over two years.  Several items planned for replacement during the annual inspection and two-year inspection were not necessary.  Boise Locomotive Company is continually monitoring the performance of the following items to determine the optimum maintenance interval: 

Replace spark plugs. 
Replace oxygen sensors. 
Replace engine thermostats. 
Replace jacket water pump. 
Replace aftercooler water pump. 
Replace carburetor. 
Replace starter motors. 
Replace coolant. 
Replace water temperature thermostats. 

All scheduled maintenance is still in the evaluation process.  It is Boise Locomotive Company's goal to extend all maintenance functions as long as possible, however, different operating conditions may dictate revisions to the scheduled maintenance work scope and schedule. 


Since the units were put in service, each Union Pacific 1200G has been in operation for 863 days through January 31, 1997.  Each BNSF 1200G have been in service for 789 days through January 31, 1997.  During the period of operation through January 31, 1997, there were 114 defects reported on all four 1200Gs.  Failures reported are listed in ANNEX 1. An analysis of the 114 reported defects breaks down as follows: 

Defect reported, none found                17                 14.9% 
Auxiliary generator problems                15                 13.2% 
Fuel system/fuel pressure                      14                 12.3% 
Control system/Microprocessor            13                 11.4% 
Sensors/probes                                     12                 10.5% 
Engine/Engine control module                10                   8.8% 
Engine no start                                        9                   7.9% 
No load                                                  8                   7.0% 
Sanders                                                  3                    2.6% 
Air system                                               3                   2.6% 
Cooling fans                                             2                  1.8% 
Operator caused                                      1                   0.9% 
Other single events                                   7                  6.1% 
Totals                                                  114 100.0% 

The largest category of defects reported was 14.9% where defects were reported and none were found.  Traditionally, there will always be some defects reported with no defects found. However, the Boise Locomotive Company feels that the large number of reports of this type on the 1200Gs is due to the prototype-type nature of the locomotives.  Because the 1200Gs have a new engine system, fuel system and control system entirely different from any that Boise Locomotive Company has ever produced there were probably several instances where the operator's noted a problem where the operator description, the maintainer's experience or lack of proper diagnostics from the micro lead to no defect being found.  A prime example of this is the backfire problem reported several times, but no defect was found until a later date. 
The auxiliary generator defects at 13.2% of the reported defects took several months to solve and the root cause of the defect was not related to the auxiliary generator itself.  It was found that air born debris was in the car body near the auxiliary generator.  This debris was being ingested by the auxiliary generator causing the brushes, commutator and slip rings to be coated with a film of dirt.  To eliminate the problem Boise Locomotive Company installed impingement filters over the air vents on the auxiliary generator housing.  Since the installation of the impingement filters, there have been no auxiliary generator defects. 
The fuel pressure, fuel system and some of the no load defects were for the most part due to problems with the LNG regulator (regulator plunger sticking).   Two of the most serious LNG leak problems occurred when the plunger on the LNG regulator failed to close when the locomotives would not start.  This allowed LNG gas to flow through the intake system, through the turbochargers into the fresh air room setting off the methane detectors.  To eliminate this from occurring again Boise Locomotive Company revised the coding on the microprocessor to have the gas valve to the regulator shut off if the engine does not start.  In addition, it is Boise Locomotive Company's recommendation that the regulator be changed out at every annual inspection since the plunger on the regulator will eventually stick even when not in an engine start mode.  Since the regulators have been changed on a regular basis, the fuel system problems have not occurred.  A design change to the fuel regulator is being investigated at this time. 

The bulk of the control system, microprocessor and some of the no load problems were attributed to digital output board #2.  This board was found to have an internal defect that has been corrected by the installation of an external, noise suppression circuit.  No other problems have occurred since the installation of the noise suppression circuits.  A new board is in development now that will eliminate the need for the noise suppression circuit. 

The defects associated with methane sensors and other probes were found to be directly related to moisture in the connections.  An improved sealing method at sensor and probe connections has all but eliminated this problem. 

The defects associated with the LNG engine are deemed to be of the infant mortality variety except for the backfire, Engine Control Module (ECNP and no start problems.  Boise Locomotive Company believes that the last three defects above are related to an inherent operational problem related to engine design.  The 3516 SITA LNG engine was originally designed as an electrical power generation engine that typically runs at full load continually.  From the duty cycles shown that appeared earlier it can be seen that the 1200G application of this engine is anything but a high, constant load application.  In fact, the predominant loading is in the idle position.  Boise Locomotive, in conjunction with Caterpillar, has determined that when the LNG engine is running at idle or low throttle positions, the turbo boost pressure is low enough to allow the downward stroke of the piston to create a vacuum in the cylinder.  This vacuum in turn was drawing oil past the valve umbrella seals, down the valve guides, into the cylinders resulting in oil deposits at the bottom of the head.  When the engine was operated in high load conditions these deposits would burn causing the ECM to sense an other than optimum engine operating condition causing the engine to pre-detonate and shut down.  The condition also allows deposits to form on the valve guides and valves and that may be causing cold start problems.  To date only one engine valve has been burnt on the ATSF 1200. 

Caterpillar has developed a revised head for the LNG engine that has tighter clearance on the valve guides, an improved seal with the single lip seal replaced by a multiple lip seal (equivalent to 60 lip rings per inch). In addition, the valves are of two angle design rather than the original single angle design.  A full set of these new design heads was installed on ATSF 1200 in January 1997, for testing.  To immediately mitigate the problem Boise Locomotive Company recommends that the 1200Gs be shut down when possible to reduce idling time. 
To adequately measure how the above defects have been dealt with during the service life of the 1200G, one can look at average days between failure.  From the in service date for each 1200G through the end of 1995 (1,716 in service days) 84 defects (including no defects found) were reported. This is an average days between reported failure of 20.42 days.  In 1996 (1,464 in service days), there were 30 defects (including no defects found) reported for an average days between reported defects of 48.83 days. 

However, of the 1996 defects reported, 27 occurred in the first six months.  From July 1, 1996, through January 31, 1997, (860 in service days) there have only been three reported defects for an average days between reported defects of 286.67 days. 
Availability of the units has not been tracked as the contracts that Boise Locomotive Company has with the Union Pacific and the Burlington Northern Santa Fe recognize that the 1200G are test locomotives.  Each contract contains clauses that allow the Boise Locomotive Company a limited period to make repairs and adjustments before an availability penalty applies.  In all cases, Boise Locomotive Company has made repairs to defects before the elapse time resulted in an availability penalty.  In most cases, repairs are made when the locomotives are in for fueling or servicing or during their scheduled maintenance. 


The 1200G test program on the Union Pacific and the Burlington Northern Santa Fe has been the only successful demonstration to date of the feasibility and safety of using LNG as an alternative fuel.  The 1200Gs have proven that a LNG powered switcher locomotive can be operated and maintained efficiently and safely much the same as conventional diesel powered switcher locomotive. 

I would like to thank the following individuals from the Boise Locomotive Company who have contributed information and their time in the preparation of this paper: 

David Brannan, Operations & Maintenance, BLC 
Doug Graybeal, Service Department, BLC 
Jim Larkin, Program Manager 1200G Program, BLC 
John Reynolds, Service Department, BLC 

I would also like to thank Mr. R. Bryan Morrison, formerly of the ATSF, for supplying the tractive effort test data performed by the ATSF.