Precise Anode Beam Positioning from Power Jacks

UK Manufacturer Power Jacks has been a supplier to the Primary Aluminium Industry for Anode Beam Positioning Systems ever since the very first commercial smelters were established.

Based near Aberdeen in Scotland, at the heart of the North Sea Oil & Gas industry, the company manufactures for a diverse range of industries where lifting and position solutions are required and exports its products to more than 70 countries worldwide.

The products are supplied to end users and OEM’s in various sectors including Energy, Industrial Automation, Defence, Medical, Transport and Civil Engineering.

The Company was presented with a Queens award for Enterprise in International Trade in 2011.

The company’s product portfolio includes screw jacks, actuators and lead screws that offer an electromechanical alternative to hydraulic actuation for positioning applications with loads from a few kilograms to hundreds of tonnes.

Electromechanical solutions can provide significant advantages over hydraulics, not least removing the need for expensive hydraulic pumps and pipework, but also where there is a demand for increased safety (in the event of power loss, screw jacks can be self-locking), the need for machinery to operate with better energy efficiency, machinery that operates with greater levels of precision, less maintenance or manual intervention,

and also providing cleaner and quieter solutions.

While users normally associate the term ‘jack’ with lifting, the company is keen to emphasise that its products are used for many different applications in industry. As well as lifting and lowering, the products are equally used for tilting and pivoting, rolling, locking/unlocking and tensioning of loads in any direction.

The energy sector is a key market for the company with many applications in the Oil and Gas industry, both topside and subsea with bespoke pressure compensated products operating successfully 3000m below the surface on the seabed. Applications in renewable energy include wind, wave and increasingly solar energy where they are used to position mirrors (or heliostats) in large solar arrays.

For the Primary Aluminium industry, in particular aluminium smelter pot rooms, screw jack systems are the tried and proven method for the lowering

Hydro

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and precise positioning of the anodes and anode beams and also for “high-jacking” of frozen pots. The same method is used in both Soderburg and Prebake although jack styles and configurations vary depending on the technology employed.

The screw jacks can be individually motorised or mechanically linked through a combination of transmission elements and the anodes are positioned via an electronic control system.

The company says it has more than 15,000 units deployed in smelters around the world. Lifetime spares generally represent less than 1% of the total capital investment over the lifetime of the products being least 35 years.

This demonstrates the quality and reliability of the products in what is an integral function of the potroom operation.

For positioning the anode beam on a reduction cell, the company designs

products to cope with the harsh operating environment encountered in an aluminium smelter.

The use of special alloys and heavy duty sealing arrangements protect the product from abrasive alumina dust to ensure durability.

Products are designed that allow specifically for side-loading stresses caused by thermal expansions on the superstructures with either tilting or swivel mechanisms, used extensively in pre-bakes where the beam is not self-supported, allowing for pivoting movement in the lifting screw from the vertical in any direction.

Power Jacks has developed products to suit reduction cells derived from all the major PB technologies including Alcoa, Alusuisse, Dubal, Hydro, Kaiser, Pechiney, Reynolds, VAW and others. In tailoring a product to fit within the OEM’s superstructure, Power Jacks aim is to minimise potline cost and support the client to maximise yields.

The company says that while reduction cell amperages have increased significantly as has the carbon area with the use of larger anodes, there is scope to optimise the anode-cathode interface.

Power Jacks believes that as many smelters constructed 40 – 50 years ago will ultimately need to replace their anode beam positioning systems, new technology could offer the industry greater positional accuracy that could lead to significantly reduced running costs.

In pre-bakes, the anodecathode interface should ideally remain constant at a level where the voltage maintained is as close as possible to the theoretical tension imposed by the electrochemical reaction and the Faraday efficiency is highest.

If the interface is too high, parasite Joule effect causes heat losses in the bath. If too short, the same occurs in the anode and stem.

Dubal

Dubal

Alusuisse

Pechiney

59AWJ 2014

www.powerjacks.com

Traditional jacking systems adjust periodically the interface by lowering the anode system. This frequency in a pre-bake is generally much lower than the alumina feed frequency which itself provokes a change in bath resistance and justifies an adjustment.

Without going into print on details, the company claims that a new design of anode jacking system could offer both greater positional accuracy, continuous duty cycles and load feedback information enabling the anode to be adjusted in conjunction with the alumina feed.

Power Jacks is interested in talking to aluminium smelters willing to act as partners for the new technology.

In addition to new installations, the company offers of all existing anode beam positioning systems in the field whatever the origin. It recognises the need to eliminate downtime and will work with smelters to offer fast repairs and to establish annual spares requirements.

Author: Bruce Bultitude,

Managing Director,

Power Jacks Ltd.

Contact:

bruce.bultitude@powerjacks.com

www.powerjacks.com