SMC delivers gains when the dust has settled

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Lots of products are destined to sit and gather dust, but for SMC Corporation it’s not a criticism, but a design feature.

Dust capture is important part of maintaining a clean mine site. The process of keeping dust to a minimum onsite is generally achieved through the use of elaborate filtration systems that use large filters to trap dust.

This dust can come from a variety of sources, whether it be silica, cement, coal, sawdust or sand, accumulating on filter bags until they become caked with dust over time.

This interferes with the overall efficiency of the filtration operation if it isn’t removed and eventually lead to issues like blinding, which require expensive periods of downtime to fix. As such, it is important that the filter bags or cartridges are cleaned at required intervals to ensure operations run smoothly.

This bag-cleaning process is usually performed with air valves that blow compressed pulses of air into the bag to create a shock wave which causes the bag to flex and fracture the dust cake.Typical examples of these valves include industrial-strength 2/2-way air pilot or solenoid valves that are capable of supplying between 45,000-110,000 litres per minute of compressed air. Having the capability of producing such a high flow provides a short and sharp air pulse for the best shockwave possible.

“That shock of air is important,” explains Vince Marcucci, ANZ resources manager at SMC. “The higher the pressure (without over-pressuring) for a short period of time, the greater the shockwave and the greater the ability to remove dust from the outside of the bag.

“However, you don’t want to leave it on for a long period of time as you end up with unnecessarily excessive air consumption.”

While it is cheaper to maintain efficient bag-cleaning processes with these valves than suffer a potential breakdown, the dust removal process can still involve significant energy costs, particularly when a bag house could have six or more valves, with hundreds of valves at any one facility.

In response to this inefficiency, SMC Corporation has developed a valve technology – the JSXF – that includes a fast closure and response that can pump large volumes of air at a higher pressure for a short period of time. This is sufficient to create a shockwave that cleans the bag effectively while reducing compressed air energy costs.

Where most valves are rated to stand up to around one million cycles, SMC’s JSXF valves are rated to at least 10 million cycles.

Marcucci estimates that with a six-valve system and an operation sequence of every eight seconds, working 16 hours a day, six days a week, 50 weeks a year, this could translate to over 20 years of working life before replacement is required.

The systems that allow the valves to last for such a long time include the removal of the springs (a typical feature in other air valves) and addition of a high-strength elastomer diaphragm (which can’t be accidentally inverted). These springs are also prone to mechanical failure and breakage over time.

Since the valves are typically mounted high on a tower, SMC designed them with reliability in mind from the outset to maintain service life in between intervals. That serves the client not only from the labour perspective but also spare parts.

“The traditional diaphragm is a thin rubber sheet material that requires a spring to sit behind it to ensure the diaphragm is closed on initial startup,” Marcucci says.

“With the removal of the spring the high-strength durable elastomer diaphragm that we used has eliminated a failure point. We also find that the soft rubber is prone to splitting or cracking as well.”

The JSXF valve also comes with two different types of fitting suitable for different connectors. One is direct mount with threaded connections and the other a compression fitting also known as a dresser nut.

By using a high-strength diaphragm the need for an internal spring is nullified, a design decision that has delivered air consumption reductions of up to 35 per cent and increased peak impact pressure by 15 per cent during testing.

Overall, SMC has designed the JSXF valve to be adaptable to a host of different situations.

“This valve is suitable for any facility where a ‘bag house’ is used for the collection of dust,” he says. “This includes coal, iron ore and mineral mines; concrete batching plants; waste and recycling; gas turbines in power generation; pulp and paper; and the wider market.”

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