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	A major benefit of the radioactive tracer oil consumption method is that it provides reliable data for measurements taken over short periods of time.

For 50 years, radioactive tracer techniques have been used at Southwest Research Institute (SwRI) to make highly accurate and sensitive real-time wear measurements in operating engines. These capabilities are particularly important because of the harsh operating and environmental conditions imposed on today's high-performance engines in which performance as well as low emissions levels increasingly depend on close-tolerance operation with minimal wear.

Advantages of Radioactive Tracer Technology

Using sophisticated instrumentation, SwRI engineers study real-time wear to detect wear and wear rate changes instantly. Advantages of radioactive tracer measurement techniques include:

• Cost-effective tests

• Repeatable measurements

• Real-time wear data

  	Wear is measured as a function of lubricant and engine operation parameters using bulk-activated rings and connecting rod bearings in a test engine.

• Meaningful results for short tests

• Easily measured transients

• Identification of cause and effect relationships

• Association of wear with specific design parameters, fuel and lubricant characteristics, and engine operating conditions

Purpose of Radioactive Tracer Technology

Two radioactive tracer techniques are typically used to measure internal combustion engine component wear:

• Bulk activation

• Surface- or thin-layer activation (SLA/TLA)

SwRI selects the appropriate method based on specific test objectives, component metallurgy, and configuration or site particulars.

To measure wear in operating engines, specific components are first irradiated in a nuclear reactor. During wear testing, abraded material is measured using the resulting traceable isotopes.

Bulk Activation

For bulk-activation testing, components are neutron (n) irradiated in a research reactor and installed in a test engine. As irradiated particles abrade from these components during engine operation, specific radionuclides serve as detectable tracers in the lubricant or cooling water.

SwRI measures radiation from these particles using a gamma ray spectrometer; the radiation detected is proportional to the mass of the abraded material in the circulating fluids. Multiple radionuclides can be measured simultaneously, allowing wear from multiple parts or surfaces to be measured during a single test.
 

SwRI Vehicle Systems Research Department staff study the impact of dust ingestion on engine wear using upstream dust particle sizing and radioactive tracer analysis.

SwRI maps natural gas engine wear as a function of speed, load, coolant temperature, and oil type.		Using bulk radioactive tracer methods, SwRI measures transient piston ring wear associated with speed and load changes.

Radioactive tracer wear testing can be applied to virtually any metal part that provides suitable radionuclides when irradiated. In addition to engine components, transmission gears and hydraulic pump parts are ideal candidates.		Using surface-layer activation, SwRI measures in situ piston ring wear as a function of liner surface treatment in a diesel engine.

Surface- or Thin-Layer Activation

Using SLA/TLA techniques, components are bombarded with a high-energy beam of charged particles to activate a thin layer of atoms on the component surface. Wear is measured by monitoring a decrease in the component's radioactivity or an increase in the radioactivity of debris collecting in a fluid filter.

Radioactive Tracer Experience

The SwRI radioactive tracer techniques provide cost-effective, accurate, real-time data, detecting minute wear changes without disassembly and physical inspection, to study component wear during transient and steady-state conditions.

Past SwRI radioactive tracer measurement projects include:

• Measuring piston ring wear associated with changes in engine speed, load, and operating temperature; fuel and lubricant quality and type; and internal and external contamination

• Measuring fuel injector wear associated with component metallurgy, fuel quality, and contaminant level

• Evaluating diesel engine cylinder liner wear correlating to liner design, material, and lubrication

• Investigating engine wear sensitivity to fuel, lube oil, and air filtration

• Measuring engine wear associated with dust contamination to determine relationships between component wear, particle size, and filtration level

• Studying filter performance and filter test procedures using irradiated standardized test dusts

• Comparing component wear for an engine operating alternately on natural gas and gasoline

For more information about real-time wear measurement using radioactive tracer technology capabilities at SwRI or how you can contract with SwRI, please contact  Martin B. Treuhaft at mtreuhaft@swri.org or (210) 522-2626.

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

September 20, 2008