Pacific Automation knows its mining customers require reliable equipment, which is why it has developed a smart pull wire solution.
Water poses a problem for pull wire switches. If it gets inside a switch’s enclosure, fluctuations in temperature can lead to trapped humidity.
Similarly, if dust manages to work its way into a switch’s enclosure, it can accumulate over time. Either can corrode important contacts inside the enclosure over time, especially if there is a lot of vibration. Unfortunately, Australian mines have the perfect cocktail for things to go wrong: hot days, cold nights, dusty environments and equipment that creates near-nonstop vibration.
When the current flowing through the switch does not reach the correct contact point, it can cause a nuisance trip, grinding everything to a halt and causing headaches throughout the process.
On shorter conveyor belts, finding the culprit may be relatively simple. However, if the conveyor spans 20 kilometres (km), it becomes much more difficult to find the fault.
Pacific Automation product manager for conveyor control and mining Johan Blignaut told ABHR these nuisance trips were a major concern for engineers.
“If your equipment isn’t reliable, it could be potentially unsafe,” he said. “Unreliable equipment also leads to unplanned downtime and loss of money due to process stoppages.”
Blignaut has more than 30 years of experience working as a field engineer in the mining industry. This extensive career has given him a deep understanding of what causes equipment to fail and how to prevent it.
When it comes to pull wire switches, he said recurring issues stemmed from three key areas: loose wire connections, exposed switch contacts prone to corrosion, and slack wire tripping caused by thermal expansion and contraction of the lanyard wire.
Pacific Automation’s Smart Series pull wire switches are designed to avoid this issue entirely. Featuring a Weidmüller A-Series push-in terminal, the switches use spring-tension technology that grips tighter with movement, making them impervious to vibration and thermal cycling.
Contacts inside the switch are IP67-rated and fully epoxied, preventing corrosion even in extreme moisture or dust. Each contact connects directly to a fly lead, which is then fed into the spring terminals, adding a second layer of protection. Internal springs inside the switch body have also been eliminated, eliminating the problem of slack-wire tripping.
Blignaut said the Smart Series maintains its IP67 rating for long periods of time, thanks to high-quality seals and O-rings.
“Other products may have the same IP rating, but they don’t last. If the seal becomes compromised, the rating isn’t good anymore,” he said.
“Even if dust gets into the enclosure, the switch by itself is IP67, which protects it. No dust can actually get into the switch.
“We had an installation that had been in operation for around 15 years. When it was opened up for an inspection, it looked brand new – the inside was still shiny. If there had been a failure, you would have seen signs of water or dust, but this switch was like new.”
Due to their construction, the Smart Series pull wire switches require little maintenance.
To assist mines with regular maintenance, the company introduced a tension indicator that aligns with the AS/NZS 4024.3610:2015 safety standard, giving operators a visual confirmation that tension is within a compliant range.
Blignaut said the system has proven itself in the field.
“A major mine in Western Australia recently installed a full conveyor safety package, including our Smart pull wire switches,” he said.
“They previously had so many problems with their old system. Since installing ours, they’ve had zero nuisance trips.
“The client was so impressed that all future upgrades and new projects will be standardised across operations with the system.”
