African Fusion June 2015

at source solutions safe and environmentally responsible way,” he advises. available with three dust collection variations, Filtermax, FMC andMJC, and are installed with all of the ducting

Small and mobile fume extraction While Envirox offers solutions for gen- eral industry – including plasma cutting extraction systems, oil-mist filtration on the CNC side, and complete work- shop systems that can extract dust off the floor to keep it clean – “our niche focus in South Africa is welding fume. We offer everything from small (0.7 to 2.2 kW) mobile systems for occasional welding, to very large systems extracting 20 000 m 3 /h or more,” says Hoon. Nederman portable fans are simple and powerful extractor units. They are compact and easy-to-use with multiple inlet and outlet connection options. The smallest is the Fume Eliminator, which is a small, lightweight, portable unit designed to be carried to the working area. These units provide an airflow of 150 m 3 /h, use disposable cartridge- type filters and are ideal for on-torch extraction. FilterCart is another mobile extractionand filter unit for lightwelding applications. These come with an arm length of 2.0 or 3.0 m and are suitable for up to 1 050 m 3 /h over a filter area of 35 m 2 . Where a mobile solution for con- tinuous welding and dust extraction is required – for large fabrications on an open shop floor, for example – Neder- man has developed the Filterbox, which can be used with more that one extraction arm. “These systems have a self cleaning filter that operates via reverse pulse compressed air, along with a scraper. As with large-scale dust collectors, the dust is dropped into a collector below the unit for safe disposal after use,” Hoon tells African Fusion , adding that these Nederman systems are “among the most cost effective small system available” and the range can be “customised to suit almost any workshop application”. Twelve Nederman mobile filtration systems have recently been supplied to Kumba IronOre for itswelding activities, to overcome the limitation of a 3.0 m radius arm. Centralised extraction and filtration systems Nederman centralised systems are

extraction arms and fans required for each particular application. “At the starting point of the design of a fume extraction system is Nederman’s NetQuote de- sign software. Basedonabasic

specification, this ‘app’ can produce a 3D drawing of a fume extraction system

within 10 minutes, including all of the fan, ducting and extraction arm sizes. The software will also produce system performance curves that show the re- lationship between pressure, flow and power for different operating points,” Hoon says. Highlighting Envirox’s capability, according to Herteberger is

Centralised systems such as Murray and Roberts’ installation at the Medupi Welder Training Centre use variable speed drives (VSDs) on the fans. When a welder begins to weld, the damper in the telescopic extraction arm automatically opens to allow the fume to be extracted. On opening, a signal is sent to the VSD to increase the fan speed and accommodate the additional flow. Nederman’s FilterMax DF solution is a modular, efficient and compact centralised solution for dust and fume problems with

the centralised ex- traction installation at Murray and Rob- ert’s Medupi welder training centre in Lep- halale. “This is our biggest installation to-date. It consists of two independent 18.5 kWsystems, with 30 telescopic arms connected to each system. “To cater for the variation in the num- ber of welders being trained at any one time, Murray andRoberts chose

capacity to handle up to 13 000 m 3 /h from a single unit.

almost every workshop has a welder on its premises,” says Hoon. “The OHS Act specifies that youmust create a safe environment for your employees, while ISO 14000 specifies the exact allowable values. All European companies are now tending to adopt these globally accepted standards and even our mines are mindful of the air their workers are breathing. “We are proud promoters of at- source solutions. Not only is this safer, but it also saves energy, because less airflow is needed. Nederman’s at-source solutions range from the most cost ef- fective portable and mobile solutions available through to very large, modern andhighly efficient centraliseddesigns,” he concludes.

to use variable speed drives (VSDs) on the fans of both systems. When awelder begins to weld, the damper in the tele- scopic extraction arm automatically opens to allow the fume to be extracted. On opening, a signal is sent to the VSD to increase the fan speed and accom- modate the additional flow. So the fan speed adjusts to the total extraction requirement, speeding up when more welders are busy and slowing down as eachwelder stopswelding. This ensures that the energy use of the systemmatch- es the extraction demand and that the fan is never running at an unnecessary speed,” Herteberger explains. “These systems are necessary for welding operations to comply with health and safety regulations – and

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June 2015

AFRICAN FUSION