EAND | Engineering Analysis and Design

The EAND Papers – No.2: A Mild Case of Mill Ennui

There has been one useful side effect of writing these little articles on LinkedIn. They sometimes feel futile. I write them, fiddle with them, question their value, decide no one will read them, then keep going anyway. This is not an efficient process. It is, however, familiar. The real value …

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The EAND Papers – No.1: The “Magic” of Mill Design

This photo is not a ball mill. It is a very naughty expansion in a piping system. At first glance, the photo …

Cadia GMD Stator: Preface

The remedial design of the stator of the gearless mill drive (GMD) of the 40 ft SAG mill at Cadia Hill was …

Cadia GMD Stator: Observed Behaviour and Modelling

The Stator Behaviour The Cadia SAG mill diameter is 40 ft and the ring motor that drives the mill is rated at …

Other Investigations of the Cadia Vibrations

In preparation

Insurability of Large Gearless Mill Drives (GMDs)

ABB’s and Zurich Risk Services’ concept of a 24 h repair cycle in ring motors for GMDs is reviewed. The application of this concept to winding design is shown to be counterproductive.

The Boddington Ball Mills

No-one publishes good news as it doesn’t sell. Yet there is a lot to learn from jobs done well. The Boddington ball mills represent just that – a job done well by all. The set up of the job was the key.

Mill Castings – QC – Consultants

It is a terrible waste in terms of energy, cost, human effort, damage to the environment, etc., to scrap a mill casting. However sometimes, this is necessary and it does not take an expert in quality control to see why. The assessment of flaws in castings using fracture mechanics seems to be too conservative but there is no credible alternative proposed by mill vendors at present. There is a need for independent, openly published research into a less conservative approach for casting flaw assessment and this would be useful to Owners and vendors alike.

Grinding Mill Foundations

Mill system analysis is just as important, if not more important, for gear driven mills than for gearless driven mills. The aim of the two analyses is different. For one mill type, the aim is to stop the foundation from vibrating or deflecting excessively, For the other mill type, the aim is to prevent the ring motor from doing so. Some failures and issues relevant to mill system design are presented.

Cadia Girth Gear Failures

Three investigations into the Cadia gear failures are reviewed. The first and third investigations showed that the location of the failures can only be explained by the thermal expansion of the gear. The second investigation shows that pinion diameter was a primary contributor to the failure and that T-shaped gears have better load distribution than Y-shaped gears. In any case, the cause of the gear failures was a design fault.