A special feature of E-S-S’s designs is their sparing use of network capacity. “Bandwidth is money”, explains Johan Hoolsema, the company’s general manager. “So we’ve really been looking, from an application point of view, to send the least amount of data without losing integrity.

“We understand the networks, we understand the application, so we can provide the lowest bandwidth for the networks.”

Free of contention

With many monitoring protocols, Johan explains, the central station constantly polls the remote terminal units (RTUs) to request their status. But queries and the responses can generate heavy radio traffic. So instead, E-S-S focuses on detecting changes of state, and reporting only those.

This approach, Johan says, is especially suited to TETRA because the network itself can take care of gathering all the data. “The network is handling the collisions for me”, he says. “You don’t have to do it in our system because that takes, again, a lot of bandwidth.

“Five RTUs or 10 RTUs can send data, and the network will handle it. In our RTU, if I send data, I will get a confirmation back (an ACK); if I’m getting a NAK, I’ll ask again. It’s a very simple mechanism.”

All this low-bandwidth interaction takes place over the control channel of the TETRA system, where it will not be in competition with other data or voice traffic being carried by the system.

E-S-S’s equipment can interface with terminals from a variety of radio manufacturers, but at the Sasol sites it connects to the Rohde & Schwarz (Hytera) TETRA infrastructure. Besides monitoring the pulse of the radio network, it also monitors physical installations such as the external radio sites. “In South Africa, you will see up here a lot of fencing and electrical gates”, Johan Hoolsema says. “If you go typically to a high site, you don’t want to climb out of the car. It could be dangerous – you might be robbed.

“So what does the guy want to do? He wants to take his TETRA radio and open the catch remotely. Or he phones into the control room and says, ‘Please open the gate’. You don’t climb out of your car. If it’s dark, they can remotely activate all the spotlights. They know if there are any movements from the alarm system. And then they will grant you access to go into the site.

“Once you’re in the site, they close the gates. So the personnel are safe.”

Managing radio change

When developing any new system, a key factor is to manage expectations, according to project manager Christo Kriek. “One of the guys that were on my project was a dedicated change management person”, he says. “He was there for one full day a week. It cost me a span of money but I never had a problem with anybody accepting the system when we did the implementation.”

Christo offers another important piece of advice. “Make sure that there is a service level agreement (SLA) in place with your service providers and with your customer”, he urges. “You should have an SLA in place which says, ‘Guys, if this thing goes off and you don’t find a signal, first phone this number. Don’t go the next day and talk to your boss’ – who will talk to the section leader, who will talk to the area leader – and then three weeks down the line we have a problem. It’s too late.

“Of course, if the system fixes itself, you will not know what the problem was, and it’s too late to follow up. So that is an extremely important thing – aftercare!

“This is a system, and a system needs to be managed. You have to put management principles in place, and then you will not have half the trouble – not half the trouble!”

Step by step, from coal to motor fuel