More safety with advanced screening media installation system

Mining since 1970s − from domestic into large export-producing site

Ravensworth open cut operations is located in the NSW Hunter Valley, between the towns of Muswellbrook and Singleton, Australia. It incorporates the open cut mine and a coal handling and preparation plant (CHPP). The mine is a joint venture between Itochu Corporation (10%) and Glencore plc (90%). The CHPP assets are owned by the joint venture and operated by Glencore. Mining was established at Ravensworth in the early 1970s. The open cut operation was originally a domestic concern, but has grown into a large export-producing site, processing around 14 million tonnes per annum.

Coal is moved from the mining areas via internal coal haul roads. It is then crushed by rotary sizers before being transported by conveyor belt systems to the Ravensworth CHPP. While most of the plant’s production is destined for export, mainly to Asia, some thermal coal is also delivered to the Bayswater and Liddell Power stations for domestic power generation.

Ravensworth produces both thermal and semi-soft coking (metallurgical) coal. The thermal coal product is highly volatile with strong combustion characteristics and is widely used for power generation as well as for general industrial use. The facility’s metallurgical coal is used in steelmaking blast furnaces as a component in the coke blend. The semi-soft coal is low in ash and sulphur with attractive coking properties.

Safety − the highest priority

Mining and quarrying can be very hazardous activities, so companies involved in these industries are extremely focused on ensuring the health and safety of their people. Ravensworth Operations employs around 800 people and according to Operations Manager Tony Morris, the safety of its employees is the company’s top priority. 

“We continue to investigate and implement new safety systems and controls to minimize the risk to our employees. The ultimate goal of Glencore’s ‘SafeCoal’ program is the production of coal with the certainty that there will be no fatalities or injuries to people working in or around our operations.” 

Taking worker safety seriously

As CHPP Manager with overall responsibility for Glencore’s Ravensworth coal preparation facility, Phil Enderby takes worker safety very seriously. A veteran of the coal mining industry, Enderby has been with Glencore since it merged with Xstrata in 2013, and in the coal preparation industry for about 22 years. Having started with BHP at the steelworks as an electrician, he also studied electrical engineering. Phil moved into coal preparation in 1996 at Dartbrook Coal then moved to Bulga, and finally to Ravensworth. He has extensive experience in all aspects of coal preparation including electrical engineering, electrical and mechanical maintenance, as well as process engineering, and has been the manager of the Ravensworth CHPP for almost five years.

“One of our main safety concerns are the risks involved with the amount of maintenance that is required,” he said. “There are many tasks that involve a lot of planning, assessment and control of risk, and we like to get the guys to think about why they are being safe."

“It’s not just about compliance – we want them to think about what they value in life outside of their work, so that these thoughts are with them when they are doing their risk assessments.”

“They may have kids, be looking forward to a holiday with the family, etc. and you can only do that if you are healthy. We encourage the guys to think about these things and remember that there is always a good reason to keep safety front-of-mind.”

Hammers a major risk

Due to the hands-on nature of much of the maintenance work in industrial facilities such as coal preparation plants, hand injuries are the most common injury encountered, and of these a significant proportion comes from the use of hammers.

As a result, senior management at Glencore set a challenge, beginning at CHPPs, to eliminate the use of hammers at all of its facilities. Phil Enderby took on the challenge.

“It is no mean feat to eliminate the use of hammers,” he said. “It’s a big challenge because hammers are used everywhere. Where was one of our biggest risk with hammers? Maintaining the screen media. When you look at the positions the guys are in – using hammers when maintaining the screens – you can see that there are significant safety risks.”

The importance of the screens

Because the raw coal from the mine contains impurities such as sand and rock, and often has a significant variability in terms of size, it must be washed and crushed to product specification. Screens play an important role in grading (size separation) and dewatering the coal.

“At the end of the day, in coal preparation screening is very important,” said Enderby. “We have 22 screens here. If they are not working efficiently and effectively, product can be misplaced to reject and vice versa, affecting yield, product quality and revenue, so it is very important that every screen is doing its job.”

The screens in use at the Ravensworth CHPP range in size from 4.2 m wide by 7 m long, down to smaller machines 1.8 m wide. Each screen has decks made up of removable screening media panels 300 x 600 mm in size.

Screen maintenance is currently scheduled every two weeks. Technicians are required to get onto the screen decks to examine every single screen panel and assess the aperture size. The panels are replaced according to the wear of the apertures so that Ravensworth can optimize the life of the panels without compromising screening efficiency. The maintenance involves from six to eight people every maintenance day, and can take between eight and ten hours to complete. If the panels are not checked correctly, there is a chance of panel failure in the following two weeks, causing poor efficiency, lower plant yield and plant downtime.

Ergonomics and safety risk

The removal and replacement of screen panels typically involves the use of a 3lb (1.25kg) hammer to drive the tip of a demolition screwdriver between panels to lever them out, thus allowing technicians to clean, inspect and replace them. Panels are then hammered back into place. All this is done while the technician is lying in narrow areas on the screen deck. Ergonomically, the job is quite challenging and physically exertive.

“The biggest problem is the ergonomics of crawling around in a small space over the screen deck,” said Enderby. “The risk is associated with the use of hammers and other tools in an awkward position.”

Reducing the need for hammers

Enderby has been involved in the Australian Coal Association Research Program (ACARP), totally funded by the black coal industry, for over 12 years. “ACARP is all about enabling researchers to identify opportunities to improve the way we do business,” he said. “In relation to coal preparation, the research includes projects to improve efficiency and safety, as well as looking at environmental and community concerns.”

Enderby approached Metso to find out if it was possible to develop a system that didn’t rely on hammers for the installation and removal of screening media. Metso responded with an initial design. ”It was only a prototype at that stage,” he said. “When they first showed us the prototype, my mechanical engineer Mark Prosser and I had a few concerns, so we had some discussions about different aspects of the system and how it could be improved. Metso took our comments on-board and redesigned the prototype.”

The implementation involved an extensive change management process

“First and foremost, we had to make sure the hammerless system didn’t introduce any new risks for personnel. We also had to ensure that it didn’t impact screen efficiency, and that the screen itself was not compromised and its life reduced,” he explained. Once Metso had refined its prototype, the system was initially tested at the CHPP on the operating deck of a vibrating screen that wasn’t in use for production at the time, where it performed well for 3-4 weeks.

Traditional screening media panels are held in place by the compression of their polyurethane surrounds which clip onto a mounting strip, hence the necessity to lever them out using a demolition screwdriver which is driven in between the panels with a 3lb hammer. With the new system, the polyurethane surrounds of the panels have been modified with a recess that fits around a locating block on a newly-designed mounting strip. A tapered bottom on the polyurethane edge allows the panels to slip easily into place. A 1220mm long top protection cover strip locks the panels into place with M16 hex head bolts. The bolt heads are protected from impact from the coal by deflectors built into the strip.

Screening media panels are simply removed by unscrewing the retaining bolts with a battery-powered rattle gun, lifting off the protection strips, and lifting out the panels. This procedure is reversed for the installation of replacement panels.

According to Enderby, the tests on the offline screen were encouraging. “The panels stayed in place, which gave me the confidence to install the system in a live section of the plant where we were putting coal over the top. We first installed the trial mounting system in the low-wear areas of the deck,” he explains. “It wasn’t all plain sailing – we had some challenges, and Metso had to do more R&D to fix some issues, but at the end of the day it worked very well.”

The Ravensworth facility has implemented the new screening media across 16 of its 22 screens in two sections of the plant. A third section is currently undergoing a general upgrade, which will include the new media if it continues to perform well in the other sections. Enderby set three criteria to determine if the new screen media was a success: improved safety, no compromise in efficiency, and no impact on screen integrity.

“We had to assess whether it has had a positive impact on safety, and it categorically has. We have virtually eliminated the use of hammers in screen maintenance, which is a very positive safety outcome for the guys,” he explained. “The efficiency hasn’t been compromised either. In fact, although it is hard to quantify, it is incrementally better than before, because each screen panel has a slightly more open screen area.

“So far, there has also been no impact on screen integrity. The time taken to change a single screen panel may be about 30 seconds longer, but in the end the cost of, say, one extra man-hour over 100 panels is well worth it to ensure greater safety for our workers.”

Success through partnership

The development of this new, safer, screen media fixing system is the product of a strong, enduring partnership between Metso and Glencore. In working together, they have eliminated the risks associated with hitting a demolition screwdriver with a hammer during screen maintenance activities.

“Metso has been absolutely instrumental in the development of this system, taking on board comments from Mark Prosser and I about challenges with different methods of attaching the screen media,” said Enderby. “It hasn’t all been plain sailing of course – there have been various challenges along the way, especially in the testing phase. We had to be very patient, and Metso was very proactive in dealing with issues that arose."

“It was challenging for me – and the business – to continue to support it, but when I looked at the end goal of eliminating hammers, it encouraged me to persist. At the end of the day it has worked very well. Metso was open and honest with us all the way through the process.”

A leap forward for the industry

In the end, what Glencore and Metso have achieved together is something that can benefit the entire industry. “Metso’s people have been excellent from the beginning,” said Enderby. “Their knowledge and their passion to look at this new screen media mounting system demonstrates that the Metso guys want to improve our industry. And while it is a business opportunity for Metso, in the big scheme of things it is improving the safety of coal processing.”

“At Glencore, we’re always looking for opportunities to improve safety and to have a supplier that is on the same page as us, means that we can go a long way working in partnership with them. I am only too happy to offer my team’s advice to help suppliers like Metso develop safer systems.”

Keith Blair, Metso’s Screen Media Solutions Technical Manager – East Coast, summed up the impact of the new system: “What we’ve created in this hammerless screen media system is so simple, that it can readily adapt to almost any modular screen in the mining industry."

"We see huge potential for improving safety, by reducing both hammer strike and fatigue-related injuries during screen media change-outs for workers across all mining sectors.”

In addition to the customized system designed for Ravensworth, we have introduced a hammerless screening media attachment system for dry applications with even quicker installation times, available globally. Watch the video.