Sellafield advances materials handling facilities

Sellafield, UK - Sellafield Sites Ltd is currently constructing a new product and residue store (SPRS) at the Sellafield site. The facility will provides transfer, receipt, inspection, storage and retrieval of product arising from the Thorp and Magnox operations.

The contract for the design of the facilities receipt, transfer, inspection and storage systems went to BNS Nuclear Services, which then engaged Excel Automation to provide the design of one of the building's import/export stillage conveying systems.

BNS Nuclear Services subsequently won the contract to supply and manufacture all the mechanical handling plant and equipment for the facility. It awarded the contract for the import/export stillage conveying system to Excel , which arranged for the system to be fully assembled, cabled and tested in its Worcester factory. 

Excel's work included a ‘setting to work’ exercise, using a temporary control system and dummy storage equipment to simulate the actual storage equipment being transported from a simulated transport vehicle tailgate, through the whole system, and back to the tailgate. Following the simulation tests, maintenance trials were carried out and the system was signed off and approved by BNS Nuclear Services for delivery to site.

The import /export stillage conveying system, comprising an import/export bay, marshalling area and loading/unloading area, was required to carry secure transport containers that are delivered to the SPRS building. The Excel design features a quantity of chain driven powered roller conveyors, a shuttle car system and a scissor lift complete with powered roller conveyor.

Each powered roller conveyor has either a standby drive or manual crank arm drive facility in case of a drive failure or power outage. All conveyor equipment is designed to handle a capacity of 3,000kgs. The site transport vehicle reverses into a designated position alongside the scissor lift conveyor and, when in position, its tailgate is lowered. An off-board receiving conveyor is raised level with the tailgate rollers using a scissor lift with hydraulic power pack.

The scissor lift conveyor is mounted on a floating table top that extends and retracts pneumatically to enable the transfer of stillage from the transport vehicle. Pneumatically powered side rollers centralise the floating top to align with the tailgate, and electrically powered side arms pull or push stillages over the transport vehicle’s tailgate gravity roller section, depending on whether stillages are being imported or exported from the Facility.

When importing stillages, the transport vehicle powers single stillages to a position on the tailgate and the scissor lift side arm arrangement moves towards the transport vehicle with shot bolts retracted. With the side arms fully extended, the shot bolts are pneumatically extended behind the front end posts of the stillages. The scissor lift conveyor starts up as the side arms pull stillages onto the scissor lift, and the conveyor transfers them to an ‘import’ sensor switch at which point it stops.

During this movement the shot bolts retract as the side arms come to their own stop position. The floating top retracts and the feed height adjusts via the scissor lift assembly to align with the in-feed conveyor system. The stillage is fed into the SPRS Marshalling Area via a powered roller conveyor operating within an airlock enclosure.

In the marshalling area, a shuttle car, complete with powered roller conveyor and running on steel rails set into the floor, moves from a ‘home’ position at the end of the track to an import roller conveyor adjacent to the airlock doors. The shuttle car receives the stillage from the in-feed conveyor and transfers it into the marshalling area, which comprises two load/unload conveyors and seven park conveyors.

If the load/unload conveyors are not available, the shuttle car will take the stillage to one of seven park conveyors to await transfer onto the load/unload conveyor at a later date.

As stillages travel towards the end of the load/unload conveyor three sensors stop them to within +/-20 mm, enabling each Safkeg to be aligned with an overhead lifting beam for subsequent removal. When stillages leave the handling area, they move back through the system to the transport vehicle on the import/export conveyor or park conveyors. In most respects the export sequence is the reverse of the import sequence.