VII PTNSS Congress - 27th-29th June 2017
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Aftertreatment with DPF, Inspection & Maintenance, The Policy

Engine life and emission stability of diesel engines with exhaust emission after-treatment devices depend mainly on maintenance. It must be a periodic routine and emission control has to be an integrated part of maintenance. Thus emission stability can be achieved and overall running costs be reduced by preventive repair, avoidance of operation interruptions etc.
 
Since DPF system failures or tampering might increase the PM emission by two orders of magnitude, periodic checks are necessary. An important tool for a regular emission check during the vehicle maintenance, for roadside measurements and official periodic checks, are fast, handheld, accurate and certified PN measurement devices. PN measurements at low idle are sufficient accurate even to verify the filter efficiency if necessary by measuring also upstream of the filter, to detect small repairable DPF defects and also engine malfunctions.
 
Besides an on-road or on-site supervision by the authorities, different organization models for I & M are applied. Periodic checks might be made by test-only-stations, run by the authorities or an authorized private organization. Or private test+repair-stations or even the vehicle user or the fleet owner does the check and just in case the necessary repairs/re-adjustments. The most important engine system data and the inspection activities should be documented in an individual inspection document. The elements and the procedures of a chosen I&M concepts have to be defined by the authorities.
 
PN emissions above a given limit can be caused not only be a failed filter. In the case of a CRT system the reason for an insufficient filter efficiency might also be a DOC, inhibited by thermal or chemical poisoning or contamination. With a CO measurement during a load step up to about 250°C the conversion capability of the DOC can thus determined. Not only the PN measuring instruments but also sensors for measuring CO (and NOx) should correspond to guidelines like the ones of the Swiss Federal Office for Metrology (METAS). A simple and practicable DOC check is actually in the test phase.
 
The filter system must be monitored with regard to overload and filter damage. Today’s datalogger measure and store data, produce alerts (e.g. with a red light at the dashboard) and are able to send them by GSM or local WLAN to a central monitoring station. This will allow fleet owners the monitoring of functions, alerts, failure diagnostics and to generate statistics of DPF and vehicle operation, vehicle and filter comparisons and prediction of maintenance needs.
Topic: Engine accessories and equipment
Author: Thomas Lutz
Co-authors: