[2] The plaintiff manufactured and supplied to the defendant certain mineral processing and other associated equipment which comprised an essential part of the mine plant. The equipment comprised Barmac vertical spindle impact crushers, vertical regrind mills, high frequency screens, pumps, secondary crushers, vertical screens and vibrating feeders.
[3] During the period July 1997 to December 1997 the plaintiff supplied spare parts for use in repair and maintenance work on the Barmac crushers and secondary crushers and other processing equipment it had supplied to the defendant. The plaintiff sent invoices to the defendant in respect of those materials in sums totaling $264,042.36, which remain unpaid. The invoiced sums accrued due thirty days after invoice.
[4] On 12 December 1997, Administrators, pursuant to Part 5.3A Division 2 of the Corporations Law, were appointed as Administrators of the defendant.
[5] On 24 December 1997 in purported pursuance of the Workmen's Liens Act NT the plaintiff lodged a Notice of Contractor's Lien with the Registrar-General of the Northern Territory against the defendant's estate and interest in Mineral Lease (Northern) 1077 in respect of the unpaid monies. In these proceedings the plaintiff seeks judgment in the sum of $264,042.36 for goods supplied and an order enforcing the claimed lien. The defendant, whilst eventually admitting the monetary claim, denies that the plaintiff was entitled to a lien over the defendant's interest in the Mineral Lease. In particular the plaintiff asserts and the defendant denies that the Barmac vertical spindle impact crushers and other processing equipment for which spare parts were supplied by the plaintiff to the defendant constituted fixtures to the land. In short, subject to one argument I shall notice shortly, the question is whether the plaintiff supplied materials in connection with work done or to be done to "fixtures" for the purposes of the Workmen's Liens Act NT.
[6] The preliminary stages of the mining operation at Mount Todd commenced in mid 1992. Production commenced in late 1993.
[7] A method known as the heap leach method was adopted by the defendant for the recovery of gold in the early stages of the mine's development. First, the raw rock was mined from the pit. The size of mined ore varied greatly from one cubic metre lumps down to less than one millimetre. The ore was then reduced in size through three stages of crushing into finer ore of nominally less than eight millimetres in size. The crushed ore was then stockpiled on a leach pad where it was continuously doused with chemicals to leach the gold from the ore. Finally, the leachate collected continuously from the leach pad was separated from the chemicals and the recovery process was complete. These steps of the production process proceeded simultaneously as the raw ore was continuously being mined.
[8] This method of production continued up to a later phase of operation when the plant was substantially upgraded by the addition of a fourth crushing stage, two milling stages and a more complex extraction and recovery stage.
[9] The mining equipment supplied by the plaintiff to Mount Todd was used in relation to the crushing, screening, feeding, milling and extraction processes.
[10] In the later phase crushing stage raw ore was fed into a primary crusher from where it was discharged via a conveyor to a primary crushed ore stockpile. The rock comprising the primary crushed ore stockpile was recovered by reclaim feeders below the stockpile. The recovered ore via a series of conveyors, surge bins and feeders was then passed across three vibrating screens, called secondary screens, for the purpose of separating the ore by size. The larger oversize ore was fed into three secondary crushers and the smaller ore was fed via a conveyor and surge bins into eleven tertiary crushers. The tertiary crushers were designed for crushing ore of less than thirty millimetres. The rock discharged from the secondary crushers was recirculated back over the secondary screens. The rock from the tertiary crushers was via a series of conveyors and feeders passed across another series of four vibrating screens, called tertiary screens, separating the ore by size. The oversize ore was recirculated back to the tertiary crushers and the finer ore less than eight millimetres was fed into the quaternary crushing circuit. The rock discharged from the quaternary crushers was via a conveyor and surge bins passed across a series of vibrating screens, called quaternary screens, separating the ore by size. The oversize ore was recirculated back to the quaternary crushers and the finer ore was then sent to a fine ore stockpile prior to the milling stage.
[11] During the milling stage the ore from the fine ore stockpile was recovered by reclaim feeders below the stockpile and fed into three ball mills. The ball mills ground the ore into a micron size material to accommodate further processing in the extraction and recovery stages. It was intended in the plant design that the oversize product from the ball mills after separation by hydro-cyclones was fed into a vertimill which would grind the oversize ore into a finer product. The vertimill although commissioned was never operated continuously as part of the size reduction process.
[12] During the extraction stage the material from the mills was exposed to various chemicals, referred to as a carbon in leach process, which caused gold particles to separate from the ore and attach themselves to carbon particles. The gold particles were subsequently separated from the carbon particles and the extraction stage was complete.
[13] The plaintiff supplied various equipment to Mount Todd during the period 1993-1997. The equipment supplied included:
[14] A Barmac is a rock crushing machine designed for use in the mining and quarrying industries. Barmacs were used in both the tertiary and quaternary crushing stages of the defendant's mining operation. In the third stage it was used to reduce ore from a size of approximately thirty millimetres to a size of eight millimetres. In the fourth stage it was used to reduce ore from a size of eight millimetres to a size of three millimetres.
[15] The Barmac is a vertical spindle impact crusher. It uses the impact velocity of rock on rock to achieve its crushing action. This is achieved by the use of a rotor which spins at up to twelve hundred revolutions per minute. The feed material enters the centre to the rotor and exits through discharge ports in the outer circumference. Barmacs are supplied with feed material through a feeder. As the rock exits the rotor it impacts on other rocks in the crushing chamber.
[16] The Barmacs supplied to Mount Todd are duopacters. In duopacter models, a second stream of material in a controlled quantity is introduced via a cascade feed system into the crushing chamber turbulence. This improves the energy transfer between the particles, and in combination with the rotor diameter and speed, can increase the quantity of ore being crushed without increasing the energy level required.
[17] A Barmac, when new and unused, weighs approximately thirteen tonnes with a stand fitted. Once used, its weight increases to approximately fifteen tonnes, because extraneous ore becomes trapped inside the crusher. Each Barmac is approximately three metres high by two and one half metres wide by three metres long. A Barmac comprises four main sections:
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(a) A feed hopper into which the ore is introduced;
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(b) the crushing chamber;
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(c) the transmission housing assembly housing the bearing cartridge and supporting the two drive motors; and
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(d) the rotor.
[18] The Barmac crusher is protected by a number of wear parts. Wear parts are "sacrificial linings" which require replacement as they wear away in order to preserve the life of the rotor and protect the integrity of the major components of the crusher which are expensive and time consuming to repair. Some of the most common wear parts are:
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(a) The liner plates which protect the upper and lower sections of the rotor from abrasion;
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(b) The distributor plate which is the first point of impact for rocks entering the rotor;
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(c) Rock tips. These are lined with tungsten which takes most of the wear as the rock slides out of the rotor discharge port. Without the rotor tip insert the rock would slice the rotor in half within thirty minutes of continuous operation.
[19] Wear parts are those parts which have immediate contact with the ore to be crushed. Each of these parts is designed to be changed without the need to dismantle the entire Barmac. They are replaceable without the need to remove the machine.
[20] Although the Barmacs can be run independently of one another, they cannot be operated effectively unless operated simultaneously with vibrating screens in a closed circuit.
[21] During the period 1993 - 1996 the plaintiff supplied nineteen Barmacs each with a support stand and two two hundred and twenty kilowatt drive motors.
[22] Each of these nineteen Barmacs was bolted to a frame and mounted into a support stand on anti-vibration mounts. Each frame and stand is constructed from fabricated steel, and is approximately two and one half metres wide, two and one half metres long and one and one half metres high. Each frame and support stand are in turn attached to a larger support structure and housing which respectively supports and encases the Barmac, the feeder and the feed bin structure. The support structure and housing encases the Barmacs, feeders, surge bins and other equipment in each of the sections.
[23] The Barmacs were standard heavy duty mining machines. They were supplied with their own support frame, which was bolted directly into the supporting structural steel work of the tertiary crushing station. The footing of the supporting structural steel work was embedded into the ground with concrete. The supporting structural steel work surge bin and feeders were not supplied by the plaintiff, but were purpose designed, manufactured and constructed by others for the installation of the Barmac crushers at Mount Todd at the time the Barmacs were supplied.
[24] Each section of the Barmacs were aligned on a stand within a continuous steel housing structure. Above each series of Barmacs is a feed bin structure which had a four to five thousand tonne rock capacity in relation to the tertiary section, and an eight to ten thousand tonne capacity in relation to the quaternary section. The feed bin was fed by a feed tripper conveyor belt, which was located above the feed bin. The feed bins had a series of five or eight outlets depending on whether it was in the tertiary or quaternary section. Each outlet had a separate belt feeder which controls the flow of rock into each Barmac. The rock was crushed in each Barmac and discharged through a shute below the floor level onto a discharge conveyor belt whereby it was conveyed to the screening circuit.
[25] The dimensions of the tertiary circuit were approximately sixteen metres high, thirty five to forty metres long and eight to ten metres wide. It weighed many hundreds of tonnes. It was built to withstand cyclonic conditions, and was therefore particularly heavy. The entire structure was attached to the ground by steel columns bolted to concrete foundations set in the ground.
[26] The dimensions of the quaternary circuit were approximately sixteen metres high, twenty four to twenty five metres long and eight to ten metres wide. It weighed several hundreds of tonnes.
[27] The Barmacs could be moved. Removal of the Barmacs from the site would involve the following steps:
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(a) the feed hopper would be cleaned out to remove the excess ore stored inside;
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(b) the top half of the Barmac would be lifted off;
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(c) the balance of the extraneous ore caught inside the Barmac would be cleaned out;
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(d) the electrics would be disconnected and the rotor assembly removed;
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(e) the Barmac would then be re-assembled without the rotor or the drive motors and drive pulleys;
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(f) each Barmac could be removed one at a time with the stand in place and it would require a crane to do so;
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(g) the feet, which would have remained in the structure/housing, would need to be removed;
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(h) the feet would then be re-affixed to the Barmac and the supporting stand, and transported to the new site by truck.
[28] All this could be achieved with reasonable facility. The plant incorporated overhead heavy duty gantry cranes capable of lifting the Barmacs into and out of their working stations.
[29] The plaintiff also supplied the defendant with three secondary crushers, three secondary screens, several carbon recovery and trash removal screens, a Vertimill and twenty six pumps.
[30] The secondary crushers were supplied in the seven major components namely the main shaft assembly, pinion shaft housing assembly, hydro set assembly lubricated system, motor, and top and bottom shell. These components, once assembled, were installed on the secondary crushing station which is located on a substantive steel tower approximately twenty five metres high.
[31] These secondary crushers were known as "84 inch hydrocones". Each hydrocone, which weighed approximately eighty four tonnes when empty was used to break ore down from approximately three hundred millimetres to thirty millimetres in a closed circuit with the secondary screens. A hydrocone is a cone crusher, a generic name for a particular style of compression crusher.
[32] The hydrocone crushers were assembled three in a row. Above each was a screen, which in turn was fed by a feed bin and conveyor. Below each bin was a discharge feeder. Ore was fed from a feeder into a vibrating screen and thence into the hydrocone crusher. All three crushers were built into a steel structure approximately twenty five metres high. This was the tallest structure on site with the exception of the ore stock pile. The feed bin elevated above the crushers had a capacity of between four to five tonnes. There was a substantial concrete component to the structure. The entire secondary crusher section would weigh thousands of tonnes.
[33] The secondary crushers were bolted directly to the steel structure of the secondary crushing station. That steel structure was designed to accommodate the vibration and out of balance dynamic forces encountered in the operation of cone crushers. Although removable, the size and the nature of the operation of the secondary crushers in the circuit meant that once installed, they were not readily moveable.
[34] The secondary screens were installed above the secondary crushers. Ore was fed out of a bin onto a belt feeder, which in turn fed the three screens.
[35] The screens measured approximately three metres by six metres and weighed approximately fourteen tonnes each.
[36] The screens included a drive mechanism which vibrated the screen permitting the screen to sort the material into the requisite size and to pass the larger material to the secondary crushers and the smaller material to the tertiary crushing circuit.
[37] Once the screens were located above the crushers they were bolted into the secondary station framework. They were not easily removable once installed because they were bolted down and other equipment required removal before the screens could be removed. All maintenance and works incorporating the materials supplied from time to time by the plaintiff into the secondary crushers and screens was necessarily done in situ.
[38] The pumps supplied by the plaintiff were of various models. Pumps are an integral part of the extraction and recovery plant process. The pumps were bolted down to fabricated steel bases and in turn to concrete foundations. They were attached to pipes to permit liquids to flow through them.
[39] All the items of equipment in question were plainly intended to form part of the gold mine plant for the indefinite life of the mine and were installed in situ for that purpose. The plain object and purpose for which the items in question were installed were their use for such time as they were needed. None of the equipment was removed from the site at any time the defendant operated the mine. The mining plant and equipment in question was sold by the defendant with the Mineral Lease in the sale of the Mount Todd Gold Mine as a going concern. The Mineral Lease in its terms requires mining plant and equipment to be removed at the expiry of the lease. Indeed s 185 Mining Act NT requires removal of all plant, machinery, engines and other equipment from the tenement at the end of the lease. The lease was for a term of fifty years. The mining operation commenced in 1993. It was expected to continue until about 2004. In fact it ceased late in 1997.
[40] The evidence before me establishes that the Barmac crushers and other equipment, whilst large and heavy, are nevertheless removable by crane and transportable once detached from the remainder of the plant and that it was and remains an economic proposition to sell and relocate that equipment as was and is common mining industry practice. Moreover removal of the equipment would not damage it. I should also mention that the sale of the mine by the defendant in February 1999 as a going concern specifically included transfer of the mine plant and equipment.
[41] Before turning to the parties' submissions it is convenient to set out material provisions of the Workmen's Liens Act NT. Section 2 provides, in part,