Ball screw jacks offer advantages over hydraulic rams

As part of the decommissioning project for Chapelcross Magnox Power Station, BNS Nuclear Services was commissioned to develop and construct a Graphite Handling System and awarded Power Jacks the contract to supply 50kn E series ball screw jacks. Power Jacks' longstanding history of supplying quality products on time and within budget was one of the many factors why the company won the contract.

The Graphite Handling System was developed to retrieve graphite components, capping pieces and thermocouples from inside the reactors, crush them to reduce their size and deposit them into shielded flasks. The machine itself houses four types of flask, each with different thicknesses of shielding. The material is deposited into the selected flask depending on its level of radioactivity, with the selection made by the Graphite Handling System.

Power Jacks ball screw jacks were specified to raise and lower the flasks in operation and to drive the crushing jaws, as typical hydraulics were unsuitable.

Mode of operation

In operation the Crusher and Twin Hoist unit are positioned over the reactor stand pipe. A grab is selected, depending on the type of material to be removed, and then lowered through the Crusher into the reactor to pick up a component. The Hoist is then raised and the component deposited in the Crusher. The crusher is taken to the flask filling station and connected to its supplies.

Three 50kN screw jacks - complete with a bevel gearbox and motor from Power Jacks - drive the Crusher jaws reduce the size of the component. The selected Flask is raised into the docking position by two 50kN long-travel screw jacks, also supplied by Power Jacks complete with a bevel gearbox and motor. The crushed component is deposited into the flask, which is then returned to its storage position.

Power Jacks Group has been supplying products and a continuous aftersales support services to BNS Services for over 38 years. This test of time acknowledges Power Jacks' commitment to providing exceptionally high business standards to its clients in the UK and overseas.

A spokesman from BNS Nuclear Services says: "Our products are designed to meet a range of bespoke customer requirements and Power Jacks has always sought to be involved at the early stages of our project delivery during the design phase. Power Jacks' active involvement at this stage of the project provides benefits to both BNS Nuclear Services and our clients."

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