Booyco Electronics has introduced the first locally designed and manufactured IS certified USB to RS485 media converter – suitable and readily available for general use on the South African market. This innovative new converter complements Booyco Electronic’s existing range of IS products which are available on an “off the shelf” basis, or as part of a comprehensive installation. Intrinsic safety (IS) is a protection technique for safe operation of electronic equipment in explosive atmospheres and under irregular operating conditions. The concept was developed for safe operation of process control instrumentation in hazardous areas.
As a discipline, it is an application of inherent safety in instrumentation. The theory behind intrinsic safety is to ensure that the available electrical and thermal energy in the system is always low enough that ignition of the
hazardous atmosphere cannot occur.
“As technology advances important communication hardware, such as the standard serial communication port, is now a specialised after market add-on to portable and desktop model computers,” Booyco Electronic’s Jaco du Plessis, explains. “This has made it increasingly difficult to interface with serial devices – calling for the installation of different kinds of media converters coupled together for successful communication to serial devices such as PLCs and belt drives.
“When it comes to IS applications, this task appears almost impossible. For IS loops to be approved certified serial isolators, IS barriers and IS power supply units must be used in the installation. .
“To address these requirements, Booyco Electronics has developed an USB to RS485 media converter, certified IS for associated apparatus category ‘ia’ Group I / IIC, for a T4 temperature class,” Du Plessis says. “This means when the unit is installed outside a hazardous area, it is now possible to communicate directly to IS serial devices installed in hazardous areas without the unit having to be in an explosion proof enclosure. Only when the unit is installed in a hazardous area must it be contained in an explosion proof enclosure. There is no need for external serial isolators or barriers, or even additional IS power supply units.”
The unit is powered directly from the USB port on a PC. The serial communication is able to operate up to distances of 1200 metres (cable dependant). Easy-to-understand LEDs indicate the power status and TX/RX transmission on the serial communication lines, clearly indicating if there is communication on the line.
“Booyco Electronics offers the market the most advanced IS solutions,” Du Plessis says. “Our products are certified by an independent Certified Testing Laboratory endorsed by SANAS, in compliance with national IS standards.”
Booyco Electronic’s IS RS485 Barrier serves as an isolation barrier on a serial communication bus between a non-hazardous and hazardous area in a mine or plant environment. The unit, approved for Group I and IIC, is powered from a 12 to 24 V DC power supply. Any RS485 based communication can be isolated by this unit, as it is protocol independent. The barrier simply relays the data strings it receives. If the unit is destined for installation in a hazardous area, it must be installed in an explosion proof enclosure.
“Only low voltages and currents should be allowed to enter the hazardous area and all electric supply and signal wires must be protected by safety barriers, such as the Booyco IS RS485 unit,” Du Plessis says. “An alternative type of barrier known as a galvanic isolation barrier may also be used. In normal uses, electrical equipment often creates internal tiny sparks in switches, motor brushes, connectors and in other places. Sparks
like this can ignite flammable substances present in air and must be eliminated at all costs from hazardous zones in the underground mining environment.”
The company’s IS offering includes an active high power, 2 A at 12 V IS Power Supply Unit (IS PSU) suitable for providing items in hazardous areas with various DC IS power. The IS PSU includes overload protection and isolates the load from the power supply when an overload occurs.
The use of alternative battery technology has produced Booyco Electronics’ IS uninterruptable power supply (UPS) which offers reliable performance under even the harshest operating conditions. The IS UPS is locally
manufactured under stringent quality management systems and meets all the statutory regulations pertaining to IS equipment. Du Plessis comments that while there are many UPS systems available on the market, few of these are intrinsically safe and suitable for underground use.
The Booyco IS UPS is able to deliver 2 A at 12 Volt for extended distances up to 2 km. To cater for individual application requirements, the units can be supplied in multiple outputs. The various models available deliver backup power up to 80 A/h. The IS UPS is suitable for a spectrum of critical applications, including maintaining communications systems and gas detection systems.
“An important aspect of intrinsic safety is controlling abnormal small component temperatures,” he comments. “Under certain fault conditions – such as an internal short inside a semiconductor device – the temperature of a component case can rise to a much higher level than in normal use. Safeguards such as current limiting by resistors and fuses must be employed to ensure that under no circumstances can a component reach a temperature that could cause auto-ignition of a combustible atmosphere.”
“No single field device or wiring is intrinsically safe by itself, except for hermetically sealed battery operated, self contained devices,” Du Plessis says, “but is intrinsically safe only when employed in a properly designed IS system. All items of equipment we manufacture for underground gas detection systems are compliant with SANAS regulations and we have batch approval certificates for all these products. And, since we produce the full range of IS equipment, at Booyco we are also able to conduct on-site IS loop certification for our customers.
“These capabilities give us full confidence in the products we produce to sustain and improve mine safety.”
