The manufacturing process is split into a number of stages outlined below.
Manufacture of reinforcement frames
The sleeper incorporates two pairs of four reinforcement bars anchored at the ends by a flat plate made the in factory.
The process includes receipt of raw materials, control of the sleeper’s dimensional quality, and the tensile testing included in our production Quality Plan.
The steel rods are already cut to size on delivery. Once delivered, they are fitted to the flat plate and the ends headed.
Now the twin reinforcements are ready to be built into the sleeper.
Concreting the sleeper
The first operation is to take an empty mould, which has a capacity for four sleepers to be concreted at the same time, and to add the release agent; the mould moves along the assembly line, where threaded pins are fitted to it.
The flat plate that the reinforcement is anchored to is fastened to the mould by means of clamping screws. Then hydraulic jacks start tensing while stress values are monitored and logged on the system. These hydraulic jacks are calibrated by an approved laboratory.
Then the mould moves on to the concreting booth, where it is placed on a vibrating table.
Curing takes place in steam chambers. The chamber is filled, closed and then curing begins.
This process is controlled independently for each chamber using digital and graphic logs.
Transfer of stress and mould release
Once the curing cycle has been completed, stress is transferred to the sleeper. Such stress transfer only takes place when the results of testing sample sleepers have been reviewed.
After that, anchoring pieces are attached to the sleeper, which is then transferred to the storage area.
Storage and shipment to site
Sleepers are stored in lanes organised by date. Transport to site is by train or road.
Sleepers are subjected to statutory shop testing, for which the factory includes a properly equipped laboratory.