Underframe Washer at Tyseley Light Maintenance Depot - Hyder Consulting Case Study
Before maintenance work is carried out on a train, its underframe needs thorough washing - because it is so caked with filth picked up from the tracks on which it has run many hundreds of miles. In the UK Railway Industry, underframe washing is usually carried out in a shed with a pit that is as long as the train. A mechanized trolley runs up and down the length of the pit, spray-washing the underframe of the train with water/chemicals/detergents.
At Birmingham Tyseley Depot, this mechanized wash arrangement was most ineffective. So, it had to be supplemented - with hand-lancing. Operatives found this work very unpleasant. It was also a threat to their health - the spray rebound off the underframe was filth-laden. Typically, to wash a 3-car train would take about 3 hours and would need some 30,000 lit of hot water. Dirty wash-water used to clog the drains and cause regular flooding of the wash-shed.
Maintrain, the Depot Facility Operator made representations to NetworkRail. It was agreed that a new underframe washer was needed. In early-2005, a design-and-build contract was awarded to GallifordTry Construction. They appointed Hyder Consulting as their Designer. The Works had to be designed to suit equipment/plant from a specialist supplier, Ceccato SpA, and consisted of the following.
The layout of the Works was constrained by land availability. Structures had to be squeezed into space between existing tracks.
Construction was constrained by operational requirements of a busy rail depot. In daily consultation with the Depot Facility Operator, work had to be programmed around frequent train movements.
A radical new concept was adopted as regards the new underframe washer - a complete change from what had been previously used by the UK Railway Industry. A custom-built wash-shed was not required, merely a bespoke wash-apron - only 8.0m x 7.2m in footprint - on the line of an existing track. Jet-wash nozzles (both static and rotating) are fixed to this apron, rather than to a travelling trolley.
The track was re-laid on special supports on this apron. An underground transition slab was constructed at the approach to the apron, to accommodate the change from ballasted-track to slab-track.
A new services building was located some distance away from the wash-apron. Gas, electricity and water services are conveyed to this building via a custom-built gantry over an existing track. The steel gantry was hot-dip galvanized, to avoid the need for future painting – for which a track-possession would be necessary.
The services building was constructed with factory-manufactured GRP-panels. This ensured speedy line-side assembly of an inexpensive but functional structure. The services building is lit/ventilated. A plant/equipment-room houses compressor/pumps/switchgear. A boiler-room houses an industrial gas-fired boiler.
Hot water/wash chemicals/detergents are pumped under high-pressure from the services building to the wash-apron.
The automated wash operation requires the train to make slow passes over the wash-apron. As it passes, high-pressure jets spray its underframe, cleaning it thoroughly.
To wash a 3-car train now needs only 600 lit of hot water (a saving of 98% from previously) and takes just 7 minutes (a saving of 96% from previously). Far less detergent than before is needed. The Depot Facility Operator is very pleased that train underframes are washed much more thoroughly than in the past.
The project is estimated to achieve a total carbon emissions reduction of 550T CO2/year. The considerable savings in consumables are sufficient to repay the initial capital outlay within 5 years.
The very dirty effluent from the train washer gravitates to a deep sump under the wash-apron. From here, a submersible pump delivers it, via underground (including under-track) pipework, to line-side settlement tanks in series. These reinforced concrete tanks are square in cross-section (instead of circular - for ease of construction) and are at ground level. Underground tanks would have required expensive ground support at this between-tracks location. All pipe inserts into the tanks are of stainless steel - to avoid corrosion of these inaccessible components.
Treatment in the line-side treatment works consists of settlement/oil-skimming/chemical dosing and filtration through activated-carbon. The resulting final effluent is of a quality that could be discharged to a watercourse. However, it is disposed of by pumping into the foul water sewer system.
Sludge from the treatment works is stored in a 12m3-capacity tank. Decanted liquid from this tank is periodically returned to the treatment works. Sludge is tankered off-site every 3 months. It does not consolidate in the interim because is kept in suspension by means of compressed air that is bubbled through a sparge laid on the floor. This aeration of the sludge also minimizes odour nuisance.
Underframe washing at Tyseley Depot is much speedier and more thorough than previously. Many more trains are maintained on a planned basis, now that accurate time/productivity predictions are possible as regards underframe washing. Consequently, the West Midlands community benefits from having more reliable trains to commute by.
The £0.8M project was successfully completed on time and to budget. It won the ICE West Midlands Innovation Award 2006 ‘for an outstanding example of a Civil Engineering project completed in 2006’ and was a finalist for the Environment Agency Water Efficiency Awards 2007 – in the industry & business category – where it was adjudged to ‘make a massive impact on reducing water use and deserving of recognition’. The project has now been short-listed for an edie environmental excellence award – in the carbon-reduction project category. The winners will be announced shortly, at an official awards ceremony.
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Case study related to: Awards for Environmental Excellence
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Last updated 05/02/2008