VariNOx® VN,

Common issues

• Catalyst fouling or soot deposition reducing NOx conversion efficiency
• Reductant (urea/ammonia solution) injector nozzle clogging or wear, affecting dosing accuracy
• Ammonia slip from over-dosing or catalyst degradation
• Exhaust temperature outside the catalyst's effective window, reducing conversion
• Corrosion in the reactor housing or ducting from condensation at low engine load
• Dosing pump or control unit faults
• Catalyst element cracking or erosion from thermal cycling

Inspection checklist

• Check catalyst condition and back-pressure at maker-specified intervals
• Inspect and test injector nozzle dosing accuracy
• Verify reductant quality and concentration
• Check exhaust temperature and NOx/NH3 slip sensor calibration
• Inspect reactor housing and ducting for corrosion or leakage
• Verify dosing pump operation and control system alarms
• Check insulation/lagging condition around hot sections
• Confirm reductant tank and heating arrangement (cold-climate operation) functions correctly

Service intervals

Critical spares

• Reductant injector nozzle
• Dosing pump seal/diaphragm kit
• Reductant filter
• Temperature and NOx/NH3 sensor
• Catalyst element (when within its renewal window)

Safety

• Hot exhaust ducting and reactor surfaces
• Reductant (urea/ammonia solution) is an irritant - ensure ventilation when handling in enclosed spaces
• Pressurized dosing lines
• Working near a running exhaust system

Class survey

This unit's marine equipment database category on this listing is recorded as steering gear, which does not match its known function; the notes above describe the SCR/NOx-abatement system this product actually is, based on the manufacturer and product name. Please verify and correct the category before publishing. SCR systems supporting NOx Tier III compliance are subject to class/flag verification of the NOx Technical File and On-Board NOx Verification Procedure; survey typically checks catalyst condition, dosing system calibration records and continuous monitoring/alarm functionality.