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Steam sheds were invariably located near stations, goods depots or marshalling yards. They provided the facilities to prepare locomotives and return them to service. The ultimate aim was to have the engines available for work for the maximum time each day. The depots designed along the lines of the above made it possible to receive the engines and process them through the system as quickly as possible.
When a locomotive arrived at the depot the servicing process began. Water and coal were checked and replenished, ash and char were emptied from the smokebox and the fire was cleaned. running repairs were then carried out.
There were three main types of depot layouts:
straight dead-end, straight double-end (like 6G), and roundhouse.
Each layout had it's advantages and disadvantages.
Straight dead-end, by nature of the one entrance design, were only suitable for small depots . Locomotives had to be stored in reverse order until needed.
Straight double-ended (like 6G), in which engines passed through in one direction , were much more flexible and efficient.
Roundhouse design had engines grouped around a central turntable, which was also very flexible but very expensive to build and totally reliant on the continued running of the turntable, which could be vulnerable to breakdown, leaving engines stranded inside the shed.
The best layouts of depot yards allowed engines to move through the servicing procedure in one direction. Many depots could not offer this pattern and delays and conflicting traffic movements were common. It was also desirable for coal and ash wagons to be able to be shunted without disrupting engine movements. Engines could be held up if it wasn't possible to by-pass the coaling stage and ash pits , which were the slowest operations carried out
during routine servicing.
In the 1930's the LMS and LNER regions undertook a major modernization program in order to bring their depots in line with the accepted layout design, and to improve efficiency.
STEAM DEPOT EQUIPMENT AND SERVICING TASKS
ASH DISPOSAL
The disposal of ash and clinker was , by far , the biggest problem a steam depot had to contend with. A steam locomotive could produce up to half a ton of it after a days working.
In the early part of the century there were two systems for ash disposal used by steam depots.
The LMS favoured the cleaning of fires and ash pans into tramway tubs running in ,and alongside, the ashpit. These tubs were tipped into an underground skip, positioned towards one end of the ash pit, from where the deposits were raised by bucket conveyor to an elevated bunker to be dropped into wagons to be taken away. On the LNER ash and clinker were dropped from the locomotive, through grids into a deep wet-ashpit below the rails (wet ash being easier to handle). The wet-ashpit was regularly emptied by lifting the grids and removing the deposits with a grab-crane.
WASHING OUT
To prevent the build up of scale, which impaired performance, locomotive boilers needed to be "washed out" on a regular basis . If the boiler was hot when washing out was performed the boiler was emptied of steam and hot water, from a hose through a blow-off cock , at the base of the firebox , into a static plant. The hot water, under pressure and after filtration, was used to wash out the boiler. Steam heated cold water was then used for refilling the boiler after washing out.
High pressure (about 60lb psi) water mains were required at the washing out points for washing out cold; a suitable booster pump fed these mains.
SAND DRYING
The use of sand , sprayed onto the track in front of the driving wheels , was essential for grip in wet or greasy conditions. The sand had to be free from stones ,and dry , for it to flow freely from the loco's sand box onto the rails.
Sand was kept dry in the depot's sand furnace many of which were inefficient and wasted fuel. When a depot was modernized , the furnace was replaced by a semi-automatic coke-fired drying plant. These were more efficient and needed less attention than the older furnaces. The sand was filtered through gratings which removed any stones.
Traditionally sand was carried by the crew from the furnace to the locomotive in buckets with large pouring spouts .
But some larger depot's , notably , on the LNER, installed overhead hoppers above the preparation pits from which the sand was drawn through hoses. Sand was blown by air through a pipe to the hoppers.
WHEEL DROPS
The removal of wheels from a locomotive was one of the heaviest tasks undertaken at steam depot's. Any occurrence of a hot axle box required removal of a pair of wheels.
Lifting the engine ,particularly by hand-operated sheer legs or gantry , which was all that was available at many larger depot's was time consuming and imposed extra strain on the frames.
Major depot's were equipped with a wheel drop. Either electrically or hydraulically powered. The engine ran over the drop table and the affected wheels were lowered well below rail level. Temporary rails were positioned to bridge the gap and the engine was then drawn clear. The wheels could then be rolled away for attention. The wheel drop table was long enough to drop a complete bogie.
The wheel drop at 6G [Norman Kneale]