Wolis - Wireless Online Loading Information System

Published 2010-03-01 00:00:00 | Updated 2010-03-01 23:23:28

Information shall be collected where it’s created and be delivered where it’s needed. This is where Wolis steps in.

”For thirty years I have been blind!” Olle said a few days before his retirement. Olle has been driving a loader in the mine for over thirty years. He was of course one of the persons who carried out the pilot tests of the loading system Wolis at the mining company LKAB.

25 to 30 loaders are rolling in triple-shift in Europe’s largest and smallest iron ore mines. These machines are driven by skilled personnel that manoeuvre the beasts in narrow drifts at high speed. The largest machine weighs 80 tons and has a bucket capacity of 25 tons. Some rumours say that the record is in excess of 50 tons, yet this has not been confirmed, but it is not totally unbelievable.

Quarrying, which started with an open-cast mine at the end of the19th century, is today completely based underground. This means that tunnel systems are created through the ore body where drill rigs drill upwards, with up to 60 m long holes in a fan-shaped pattern.

Each pattern contains 10-14 drill holes with a diameter of approximately 15 centimetres. Every drill hole is filled with a large charge of explosives. Five to ten charges are blasted every night, which gives 8-12 thousand tons of iron ore per charge. After the blasting, loading is started from the blasted patterns. This continues until all the iron ore from the pattern has been taken out.

Personnel in the leading position has for a long time had the ambition to make the loading personnel more involved in the whole quarrying process and not as it has been for a long time, partly isolated units, where decisions are made based more on feelings than on facts. The ambition has throughout the years been successful in many ways, but unfortunately failed in some parts.

Attempts to gather information about the process has been made. The numbers of buckets loaded from the blasts in the ore body has been counted manually. This gives a good total for the whole loading, but also, this method can differ a lot between separate loaders. Information has also been spread in many ways. ”Prayer” meetings, that’s what the morning meetings are called, has been held. Papers have been spread out among the drivers so they shall have enough information. Unfortunately this method doesn’t work because the drivers need updated information.

The next step was to weigh every bucket by measuring hydraulic pressure and transform that to weights. This has been done with a so called bucket scale. The scale has been connected to a memory stick and with the help of the driver; data has been transferred to the follow-up system at the end of the shift. The driver has at the same time been given access to information from the follow-up system so that he is able to create a survey of how far the loading work has progressed.

The solution in this case is that information about loading are collected both from the loader and the follow-up system and delivered to the drivers in the loader where they shall make their decisions according to the rules that have been agreed upon. This is where Wolis steps in.

Every drift (loading place) and shaft (unloading place) has been provided with RFID tags. The tags have been connected to the walls and the electronic identity has via the follow-up systems been coded to loading- and unloading places known by the follow-up systems.
Every loader has been provided with a:

• RFID reader which in high speed can decide the loaders logical position.
• Loader computer which through a local network in the loader can communicate with the RFID reader through TCP/IP. The computer also has a radio network (WLAN 802.11G) in order to through TCP/IP be able to communicate with the follow-up systems

The bucket scale has been connected to the Loader computer through RS-232 interface. This means that the loader computer can collect all information about what’s happening in the drift. Information about how many and how heavy buckets are being transported. When and where loading are taking place and of course when and where unloading is performed. All of this can the system later on, when driving through a place with radio contact (which is a science in itself, in this environment) synchronise with the follow-up systems. A lot of information can be transferred to the loaders down in the drift during this synchronisation. The entire collection and synchronisation of information is taking place automatically, without the aid of the driver.

When the loader is started, the help systems are started automatically. When the systems have been started the driver gets an information picture on the screen of the loader computer. This picture contains information which the driver easily can confirm; i.e. verify that the system finds the right area in the mine.

When the driver takes the loader to the first loading place, Wolis will position itself and immediately visualize the loading place on the drivers screen. The driver will immediately see how much has been loaded earlier from this place and an estimate of how much is left. The driver can also see what has been loaded; i.e. how much iron the earlier loadings contained. The geological cross section of the blasted pattern will also be shown to the driver. All these values are important to the driver in order to make the right decision about when the loading from this place shall be stopped. If the decision is made too early, the iron ore will be difficult to find later. If the decision is made too late, the production process will be strained due to large segments of granite. A simple rule has been defined: If you have loaded more than 80% of the theoretical amount of iron ore and the iron content is beneath 30% and falling, you shall terminate the loading from this pattern and make the drift ready for a new blast.

After the first month of pilot testing a follow-up was made of the results from loaders with Wolis in comparison to the loaders without Wolis. One question that was asked was; how great share of the finished load patterns followed the simple rule that had been defined. The comparison was carried out in two different places of the mine.

It was established that with a better support it was easier to decide according to facts.
One worry was that the iron content should sink when the total amount of ore from each pattern increased. A comparison was made for the period before, during and after the test period.

During the test period a peak content of iron was measured at 54 % mean value for one day. Except for this the iron content was unchanged with Wolis. However the loading extent increased from 121 to 170 % immediately when Wolis was introduced. The loading extent dropped immediately when the test period was over. This meant that from corresponding blasted patterns more ore was loaded without an increase of investments.

In addition, 15 minutes of administrative work at every ending and beginning of a shift have been saved. Now the driver can concentrate on driving the loader through the narrow drifts at high speed. And further more. The process control has improved. The driver of the loader has become more involved in the process.

”But finally I can see”, Olle 62 said and went on his well-earned retirement a few days later.

The changing of the process did not stop when Olle retired. Beyond the development of Wolis, the system has been put in operation in full scale in the mines in Malmberget and during next year the expansion of the system will continue with the mine in Kiruna.

Still, there are improvements to be done, such as calculation of iron contents, which to day is achieved through the knowledge of:

• the weight in the bucket
• the density on granite
• the density on iron
• the estimated mean volume in the bucket

The last-mentioned has been proven to give incorrect values in some situations The use of lasers with rotating mirrors that can scan the bucket and with help of ingenious algorithms calculate the buckets ”exact” loaded volume is under consideration. The thought is to implement this through a volume measuring station which is placed at the unloading station where a laser scanner recognize the bucket and will be able to calculate the loaded volume by sending out thousands of laser beams per second. By calculating angles and distances identification of a bucket is possible. The laser can identify how much material it is in the bucket by scanning the surface. This method is expected to improve the iron content measurement even more and take parts of our mines further in to the era of information technology

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Tags: Drilling, grouting and reinforcement, blasting, Mining and underground project management