The Boddington Ball Mills

You don’t get enough good news stories these days probably because it doesn’t sell.  We are going to put up good news stories though.  The Boddington plant is now about 6 years old now, so it is not “news” any more.  However, the project was a great one for us in terms of how it was set up and how it turned out.

Specifically, this post is about the procurement of the ball mills for Boddington in Western Australia.  The initial scope asked for four 26 ft by 44.5 ft  ball mills with pad bearings that were supported on pad bearings.  The mills are gear driven by twin pinion 7.8 MW drives.  These are some of the largest ball mills in the world.

Everything that could go right in this supply did go right.   Why?

1 – Owner’s Team

The Owner, Newmont, put together a great team starting with project director, Tom McCully; engineering manager, Simon Briggs; and principal engineering guru, Ian Edwards (now at Chemech Consulting).

The best way to describe EAnD’s role is that of “technical custodian” for the mills, crushers, HPGRs and their foundations.  All the technical issues related to the mill rotating elements and bearings and the QA were our responsibility.

The team knew what was required.  New specifications for mills were written under the banner of EAnD but 90% of these documents were created by Ian Edwards.  Boddington wanted the best mills, with low stress ranges and the best sub-suppliers.  The technical specifications clearly defined what was required and the pre-award negotiations ensured that the tenderers knew what was required.

2 – Vendor and Sub-Suppliers

The successful vendor was Metso.  We don’t want to make you all groan as this is not an advertisement for Metso, but when a company gets something right, they should be commended for it.  There is no doubt here that Metso did do a great job on the grinding mills for Boddington.

The Owner’s team had a list of preferred sub-suppliers for the mills.  This list was based on previous experience on projects.  Metso agreed to use the sub-suppliers on the list for almost all components.  Where an alternative sub-supplier was proposed by Metso, and there was one, it was accepted on the basis that the sub-supplier had supplied the required components for mills in the recent past with very few rejects.

3 – Specification and Design

The specification included specific design criteria for allowable stress ranges in welds that were lower than those used by US mill vendors.  In addition, the configuration and details of the lube systems were specified to what Metso later called an “Australianised” design.  Two specific QA/QC requirements relating to dross and threshold stress intensity in castings were not as strict as those found in some specifications in the industry.  These relaxed requirements were aimed at avoiding unnecessary conflict and were based on test data from a number of sources including open literature.  All the requirements were clear in the tender documents and Newmont paid for these where they represented an additional cost to the vendor’s standard design.  There was no expectation that the costs associated with any specific requirements in the specifications would be absorbed by the vendor.  In fact, the cost of these requirements was not significant.

So, what happened?  Hold on to your hats …  cooperation!  Metso agreed to the specification requirements with some minor changes.  The mill shells were designed to conform to the stresses in the specification.  The lubrication system was made according to Ian Edwards’ “Australian spec”.  The QA was done as required.  Access for inspectors from the Owner’s team was granted to all sub-suppliers with no restriction.  The sub-suppliers were excellent.

3.1 Design Issues

The allowable stress ranges at the can-to-can flanges were exceeded in the original design according to our design audit.  There were a few emails exchanged between Metso and EAnD on whether the stress ranges were real and if the joints would pry open.  However, a small change to the weld design proposed by EAnD that would result in conforming weld design was implemented by Metso and that was it.

The only fly in the ointment was getting drawings to enable us to undertake a design audit.  This period in the 2000s was when the US vendors started to worry about their IP and “potential” competitors.  Fortunately, what now seems to have become a paranoia, was only beginning back then and contracts were already signed, so the drawings were supplied eventually.  More on this below.

4 – Quality Surveillance

The Owner’s team intention in selecting a specific set of sub-suppliers was to make sure that the capabilities of these sub-suppliers were such that there would be a very low likelihood of faults, errors or rejection of components.  We are not listing who the sub-suppliers were here because it could be twisted to imply that all factories that did not supply on Boddington were unacceptable and this is not so.

One advantage of these selections was that we were able to do just a few inspections in the chosen factories rather than going to each witness point on the ITPs because the products supplied were of consistent quality.  The disadvantages?  We didn’t get to visit these places enough just to enjoy the pleasure of seeing a job being done well.

AFTERWARD

We are not fooling ourselves here or gilding the lily.  The Owner-Vendor relationship overall was not all “lovey-dovey”.  We are restricting this “good news” story here to the mills.  The reason why the Boddington ball mill supply went so well was that there were no major design or manufacturing difficulties.  Usually, a few problems have to occur before the relationship between Owner and vendor goes pear-shaped.  However, the good technical specification; the in-depth knowledge of design and manufacturing issues on the Owner’s team; the choice of sub-suppliers by the Owner; and the cooperation of people in Metso’s grinding mill division (viz., Svalbonas) helped to avoid manufacturing and design problems.

We recognise that Boddington was purchased at the right time when sub-suppliers could be selected without resulting undue delay due to shop loading and that this was a luxury during the mining construction boom.  Right now though there is a glut of manufacturing capacity so, if you are buying a mill, spend a bit more, learn about the design and manufacture, pre-qualify sub-suppliers and make some choices for yourselves rather than leaving it all up to the vendors to decide where to source the mill components.  It will save you in the long-run.

The mill vendors from the US continue to become more and more concerned in terms of the potential for design auditors to turn into competitors.  Sometimes, we find this a bit hard to take as it delays work and if a problem is encountered, all hell breaks loose because it is already too late to sort it out simply.  It is not as if we do not find mistakes.  We don’t find them on all mill jobs but we do on more than 50% of them and some are major.  We recognise that IP is a serious issue for these companies and have always done so but it does look like paranoia sometimes.

So there you have it.  A good project for everyone involved.  One to look back on as part of the good old days!