INTRO: Diesel traction offers flexibility for international freight operation in a liberalised European market, but railways need to maintain their green credentials at a time of growing environmental awareness and ever-stricter emissions limits. Revised UIC emissions standards offer an alternative to individual tests by national approval authorities

BYLINE: Hans Paukert

Project Manager, European Railway Research Institute

WITH the revision of UIC Leaflet 623 Approval of Diesel Engines by the European Rail Research Institute, an important step has been taken towards the establishment of European standards for diesel exhaust gas emission limits in rail traction applications. Since the strictest rules become meaningless if they are not applied, it is hoped that the revised Leaflet 623-2 will remove the need for additional exhaust gas tests by national approval authorities if a UIC approval certificate can be obtained for the engine under examination.

During the 1970s and early 1980s the European railways’ continued appetite for electrification impacted on diesel traction, which suffered a diminishing role. As a consequence, the application of type approval for diesel engines to UIC specifications became less significant.

This situation changed in the late 1980s, when heightened environmental awareness prompted the railways to establish an ERRI Study Group (S1015). The remit was to examine exhaust gas emission behaviour of diesel engines used for rail traction and to define future pollutant limits, as established in the USA by the Environmental Protection Agency (RG 9.96 p569).

Large differences in ratings and duty cycles preclude European road vehicle specifications, Euro I, II and (III), from being applied to rail operations. Typically, road vehicles do not exceed 500 kW. Their idling period is only 10 to 15% of operating time, compared with 50 to 60% for rail applications. Similarly the partial load range, representing 70 to 85% of the road vehicle’s duty cycle, is considerably lower for rail traction at about 10 to 15%. Full-load range accounts for only 5 to 15% of road use, whereas this is 25 to 30% for railway vehicles.

An ISO Standard, 8178/4, Cycle F, taking into account the different duty cycles of rail vehicles, was developed to determine pollutant output. Euro I, II and (III) exhaust gas values are hardly relevant for diesel engines used for rail traction, because it is not possible to convert the results obtained by the two methods.

Tougher limits

In 1992 ERRI published report S1015P/RP1, containing proposals for future permissible limits for carbon monoxide (CO), hydrocarbons (HC) and nitrous oxides (NOx) in diesel emissions. These limiting values have been incorporated in UIC Leaflet 623-2, so that mandatory exhaust gas emission limits may be enforced across national boundaries.

In the course of this work, we found that it was necessary to completely revise Leaflet 623, since most of its conditions were no longer relevant and it did not make provision for computer-assisted monitoring of test runs or associated computer-controlled testing. Other specifications were similarly outdated, such as the use during approval testing of fuel with a high sulphur content in order to ensure the engine could run properly on inferior qualities of diesel such as those sometimes used outside Europe. The option to carry out a 4000 to 5000h service test in place of an endurance test was removed, as such a lengthy service test is simply impossible to monitor.

From 1993 further developments strengthened the validity of applying the UIC specifications. Under European Union guidelines for the submission of tenders to supply new rolling stock, a test report certifying UIC approval of an engine to Leaflet 623 represented a guarantee of its suitability for rail use and compliance with emission limits. It was often the only objective option for comparing products in a competitive market.

Work on the revision of Leaflet 623 was completed in 1996, with the revised Leaflet 623-2 in force since July 1 1997. The most significant outcome was that permissible emissions were considerably reduced in comparison with limits proposed in 1993 at the start of the revision process (Fig 1). An exception is the Bosch-Index measuring smoke emission characteristics, which in 1993 was set at its most rigorous level (1·0, equivalent to ’clear smoke’) and remained unchanged in 1997.

CAPTION: French National Railways’ Class 72000 C-C diesel locos have been blamed for high levels of emissions from the depot at La Villette which serves Paris Est. Favoured countermeasure is to re-engine them with a modern power unit

CAPTION: An Anglo-Belgian Corp 6-cylinder engine rated at 1150 kW, of the type to be used in the new Siemens-built diesel shunters for SNCB, was instrumented for approval testing for compliance with UIC623

CAPTION: Fig 1. Reductions in permissible pollutant emission levels from 1993 (red) to 1997 (orange)(Index 1993 = 100%)