The “Banana APU” – RAPU2174: Advanced Auxiliary Power for Locomotive Efficiency

The RAPU2174 Auxiliary Power Unit (APU) is a compact, diesel-driven “genset”, engineered to minimize main engine idle time, reduce fuel consumption, and protect critical locomotive components. Designed for dependable year-round operation, the RAPU2174 delivers substantial operational savings while enhancing locomotive reliability and environmental performance.

Locomotive in the cold

© INPS Group

System Features

• Integrated Heating & Cooling: Water/coolant heat exchanger provides main engine heating and cooling for optimal thermal balance.
• Complete Pump Integration: Incorporates locomotive water pump, lube oil pump, and fuel supply/return systems.
• Battery Support: Automatically charges locomotive batteries during APU operation.
• Independent Systems: Features a self-contained engine oil system for simplified maintenance.
• Remote Monitoring: Cellular/GPS-enabled tracking with fault indication for real- time diagnostics.
• Automatic Operation: Starts and shuts down based on coolant temperature, battery voltage, or operator command.
• Enhanced Protection: Automatic safeguards against high temperature, low oil pressure, and over-crank conditions.
• Freeze Protection: Equipped with Guru® Valves for main engine coolant protection.

Banana APU

© INPS Group

Operating Characteristics

The RAPU2174 operates in a “sentry mode” when the main engine is shut down, automatically activating under specific conditions:

• Temperature-Based Start: Engages when coolant temperature falls below 80°F, maintaining engine warmth and battery charge.
• Battery-Based Start: Activates when battery voltage drops below 62 V.
• Manual Override: Allows operator-controlled start-up outside of automated functions.

Fuel and Cost Savings

Field testing confirms an average 83% reduction in fuel consumption compared to main engine idling. During cold weather operation, the APU typically runs only 30–40% of shutdown time, consuming less than 0.5 Gal/hr of fuel—up to 90% less than the main engine.

• Example: Over 2,190 idle hours annually, fuel waste without an APU can exceed 11,000 Gallons per locomotive.
• Payback Period: Typically achieved in under one year, depending on duty cycle and climate conditions.

Noise Reduction

The RAPU2174 operates at exceptionally low noise levels. With the locomotive car body doors closed, APU noise is virtually indistinguishable from background levels at a distance of 100 feet—ideal for yard and terminal environments.

Efficiency • Reliability • Sustainability

The Banana APU – RAPU2174 delivers proven fuel savings, reduced emissions, and extended engine life—helping rail operators meet performance, environmental, and economic objectives with confidence.

Julie Biscoe, Operations Manager, INPS Group said:

Stocked in the USA and Canada. Save on fuel, and idling emissions. Be prepared for the upcoming, ever-changing winters.

This article was originally written by INPS Group.

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