industry Tis was dealt with through several approaches. To begin


with, the omnidirectional antenna on the administration area site was replaced with a 16·5dBi panel antenna, to beam the signal towards the production areas, improving coverage and receive sensitivity. Signals to the rear of the panel were correspondingly reduced, but this did not matter because there were no users on that side. In addition, it was necessary to increase the receive


sensitivity at the radio sites. “Engineers from Teltronic came here – three or four engineers came here – and we spent a lot of days, weeks, in fact, making some adjustments”, Mr Gagno recalled. “Tat’s why we changed the omni antenna to the panel antenna and we changed the sensitivity. We wanted it to be not –97dB but –102dB, to make it possible to talk inside the buildings. “As you saw, we have many ferromagnetic buildings, so the


coverage was not good. But now we did it, and it’s working very good.” Te use of powerful 3 watt handportables in combination


with the 75 watt base station sites also helped to overcome the noise. And the lockup problem was solved through a software adjustment. “We asked Teltronic to change the way the system communicates, the handshake, and they did it. So it was no more broken, because it tries many times without going to searching state. So even if the signal does not arrive, the system retries. We could work with this level of sensitivity – it was not blocking the system. We wanted to make it transparent to the user so the user did not have to turn off the radio.” Another improvement, devised by Teltronic, was a


keyboard short-cut so that users who needed to be in touch with several talkgroups could scan them at the touch of a button, for fast access. Tis was a special development for ArcelorMittal.


One important provision of the agreement with Teltronic


concerns servicing the radios. “We can maintain them here on our site”, said José Martins. “Tat makes us capable to fix stuff and keep them working. We have a laboratory here and Teltronic has a laboratory in Bahia [Brazil]. Part is done here and part is done in Bahia – and part in Spain.”


Next steps With a plant and a radio system of such a size, there is always more work to be done. Next items on the communication team’s wish list include radio terminals which are more dust- proof (Teltronic is working on this) and improved accessories for specialized groups of radio users. “In some places they need to use a mask for gases and things like this so we have to have another way to talk”, Mr Gagno said. “We tried to use osseous [bone conduction] microphones but they were not very good for us, so we are still studying this solution.” Also on the agenda is the plant’s railway system. TETRA


radio installations are needed in the driver’s cab for the locomotive operators, but in addition it is proposed to convert the train-monitoring system to TETRA. At present, radio transponders on the track and on the trucks are read by antennas on the locomotive and relayed via the analogue radio system to an operator, who can then view the location of each train. Tis system reports a train’s position when it passes a


transponder, but does not track it metre by metre. Te team plans to test a GPS receiver in one locomotive to see how well it works – but because some of the tracks run only one metre apart, the GPS signal will not be precise enough to show exactly which one a train is on. But with the change to TETRA for relaying the positional


data, it will at last be possible to shut down the old analogue radio system.


From coal to coke with TETRA E


levated above ground and resembling a giant shelf of books, the plant’s array of coke ovens highlights some of the kind of communication requirements found on


the plant. Each huge compartment is a separate oven, loaded from above with coal by a conveyor belt. After some 20 hours of roasting to release the gas and tar, the glowing coke is pushed by a machine from one side through a door on the far side and dumped into a waiting truck, hauled into position by a locomotive sounding a two-tone warning siren. Then the operators move on to empty the next oven. “The machine stops in front of the furnace and all the


The driver of this immense locomotive relies on a TETRA radio (seen to the right of the main control panel) to take instructions from an operator stationed on the far side of the coke ovens


time he goes and comes back”, explains Antônio Gagno. “But the operator at the side cannot see the operator on the other side. So they have to communicate: ‘OK, I am at the position’ – ‘OK, you can start taking off the material’. And they do it every minute. It’s very critical because they cannot start taking off the material if the locomotive is not ready to receive the material.”


When the oven has been emptied, the flaming truckload is raised on an elevator as high as a small


apartment building for the coke inside to be quenched and cooled with nitrogen. This is extracted from the air in a plant elsewhere on the site. Looking up at the furnaces, Mr Gagno points out that reliable radio coverage is essential in this area,


and that the signal must reach both sides of this immense steel structure. “This operation is a typical one because it is very critical”, he says. “All the stop and go commands are made by radio. Other areas use PLCs and other controllers, automatic controllers, but this one is still by radio.”


14


Beneath the massive coke ovens: for safety,


reliable radio coverage is vital in this critical area


TE TRA TODAY Issue 6 2012


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