Increase in axle load of freight wagons

CC LOADING In order to enhance throughput to meet increasing traffic demands, Board has permitted running of BOXN & BOXNHS wagons loaded up to CC+8+2(axle load of 22.82t) at maximum permitted speed of 60 kmph on identified iron/other ores routes w.e.f. May,05 as a pilot project for a period of one year initially (currency of the project has been extended up to June,08). Initially,16 routes were identified for such operation. Gradually, more routes were cleared totaling to 34 routes up to March,07 on ER, SER, SCR, SWR, ECoR, SECR, SR & WCR as per list in the annexure I. However, a number of precautions and monitoring mechanisms have been prescribed for these trains.

CC +6+2 LOADING To achieve further augmentation in throughput, Board has approved universalisation of running of CC+6+2 t loaded BOXN,BOXNHS,BOBR,BOBRN,BCN, BCNA, BCNAHS & BOST wagons for carrying coal,cement,rice,sugar etc. at maximum permitted speed of 60 kmph, except some sections where it will be restricted. Restricted sections are given at Annexure II. In case of emergencies such as accidents etc. running of CC+6+2 loaded wagons in some restricted sections can be permitted. This shall be done at the level of PCE, who will advise suitable speed restrictions keeping in view the condition of fixed infrastructure. The precautions and monitoring prescribed for these sections are essentially similar to those prescribed for CC+8+2 axle load.

Precautions and Monitoring Mechanisms –Installation of electronic in-motion weigh-bridges at loading points to stop overloading. –Installation of adequate number of Wheel Impact Load Detectors (WILD) for recording of loading spectrum passing over track. –Ultrasonic testing of rails for detection of gauge corner cracks. –Quarterly review of the project by a multidisciplinary committee comprising of PHODs under GM of Zonal Railway. –Monitoring of defect generation rates in rails and welds based on USFD testing. –Monitoring systems to be installed at identified Bridges. –More frequent track recording to monitor track geometry.

Important technical parameters i)Track structure: Minimum 52/60kg 72 UTS rails, sleeper density M+7 and depth of ballast cushion 250mm with a clear cushion of 100mm for running of these freight trains at maximum permissible speed of 60 Kmph. In case of 90R rails, maximum speed permitted shall not exceed 30 Kmph. ii)Bridges: Mostly of BGML standards are available on these sections.

Specific items for action,monitoring & recording observations TRACK i)90R rails should be replaced expeditiously as possible. While renewing rails, rails of 90 UTS may be used from overall economics consideration as rail life will get shortened due to increased stresses. ii)Similarly, while replacing sleepers, sleeper density of 1660/km may be provided. iii)Ballasting will have to be given thrust. iv)Structural integrity of fastenings has to be ensured especially rubber pads.

Specific items for action,monitoring & recording observations v). As a good maintenance practice,it may be desirable to destress LWRs twice every year, once before winter and again before summer especially in Zone III & Zone IV. Behaviour of LWRs would have be watched critically and data collected.

Specific items for action,monitoring & recording observations (Contd.) vi) Due to increase in lateral forces on curves, increased deterioration in lateral alignment would occur. Hence, curves may have to be inspected more frequently.

Specific items for action,monitoring & recording observations (Contd.) vii)Due to increased bogie rotational resistance, rail-wear on curves will increase. Rail profile would be required to be monitored to understand rail-wear pattern. On curves, increased angular wear may be dangerous and need to be watched. The observations of rail wear will be useful in decisions for rail replacement.

Specific items for action,monitoring & recording observations (Contd.) viii) Due to increased load,rolling contact fatigue (RCF) defects viz. head checks & gauge corner cracking would occur resulting in more rail failures. USFD examination of rails at more frequent interval would be required to be done. As a preventive measure, rail grinding will be helpful to eliminate such defects.

Specific items for actions,monitoring & recording observations (Contd.) ix) Rail/wheel impact forces due to defects in the rail/wheel surface, viz. dip at rail joint, cup formation in AT welds, flat tyres, out of round wheels will increase damage to rail-heads, fishplates, bolt-holes and fish-bolts, sleepers & ballast. These will cause increased deterioration in track geometry. Since the track is going be overstressed, Wheel Impact Load Detectors should be installed at suitable locations to prevent further overstressing.

Specific items for action,monitoring & recording observations (Contd.) x) Rail corrugations may develop due to high dynamic forces. These would have to be monitored and if necessary, rail grinding may be done to eliminate the same.

Specific items for action,monitoring & recording observations (Contd.) xi) Points & crossings maintenance activities will get increased viz. packing, correction to alignment/level, replacement/ reconditioning of switches & crossings. Due to increased bogie rotational resistance, the increased lateral forces may increase the tendency of derailment on a weak turn-in/turn-out curve, by gauge spreading. Thus, P&C will require close monitoring.

Specific items for action,monitoring & recording observations (Contd.) xii) Transitions, viz. bridge approaches, level crossings, culverts, tunnels etc., where the track stiffness changes abruptly, will require special monitoring due to abrupt change in vertical dynamics of heavy wheels.

Specific items for action,monitoring & recording observations (Contd.) FORMATION: Weak stretches of formation would have to be rehabilitated by providing blanket layer as given in RDSO Guideline GE:G-6. Till such time it is done, frequent monitoring of the track geometry at such locations should be done.

Specific items for monitoring & recording observations (Contd.) BRIDGES: Each bridge would have to be evaluated as an individual identity reg. safety vis-a-vis its physical condition. Speed restriction may have to be imposed from safety consideration,if required. Rehabilitation/strengthening should be carried out as per the increased trailing loading density of 8.51 t/m. Sample & vulnerable bridges should be got instruemented through specialised agencies. NDT tests may be carried periodically.

Specific items for monitoring & recording observations (Contd.) Extra maintenance effort would be required due to increase in inspection,monitoring,maintenace of track,formation and bridges. Therefore, a proper record should be kept & costs worked out so that proper evaluation can be done at the end of the pilot project.

Conclusion RDSO should be associated in the studies and monitoring exercises. Railways should put in place the monitoring mechanism by the Monitoring Committee comprising of PCE/CE,CME,COM under GM. Instructions for installation and functioning of weigh bridges for detecting overloading of wagons have to be meticulously observed