A typical floor mounted bag extraction system where the customer can spend more time emptying bags than machining


Ranheat Engineering is a leading UK manufacturer of wood combustion equipment. As the company’s MD Chris Franklin explains in his latest in a series of articles exclusively for Furniture and Joinery Production, he looks at converting bag mounted dust extraction systems to use with a new silo and heating system.

“The above shows a typical floor mounted bag extraction system where the customer spends more time emptying bags than machining – normally, this happens when a new CNC router is installed,” explains Chris.

“Depending on the physical size of the filter it is mounted on a Ranheat 3m or 4m diameter silo of between 14- and 50m3 storage capacity. In the shed on the right was an existing small warm air heater trying to use bags of dust, it was too slow and too labour intensive. The workforce hated changing the bags and hated tipping them into a hopper by hand. It was also a huge Health & Safety issue with masks and overalls needed. A very unpleasant job!

“Ranheat don’t make or install dust extraction systems, but used a local dust extraction contractor to modify the ducting. The system was to replace a hand loaded off-cut burner and a small hand loaded silo as a dust burner.

“This is the same filter with the bag plenum removed and bolted directly onto a flanged upstand on the silo roof. The silo is fitted with accredited silo burst panels on the dirty side of the filter. An automatically-fed 150kW warm air system was installed fed from the new silo of 21m3. The existing six-bag extraction system held only just over 1.5m3 of extracted dust before the bags needed changing.

“The need to constantly change bags meant that production was often interrupted for ½ hour each time the bags needed changing. Often the bags were forgotten and then overfilled resulting in hazardous dust spillages. The new storage silo means that the production can run uninterrupted, and the waste can be burnt 24/7.

“This represented a huge saving in labour, not only in changing the bags but hand loading the dust and off-cuts. The factory was also warm in the cold winter mornings, The summer winter diverter means the plant can run all the year round for the safe and effective disposal of fine MDF dusts from high speed machining.

“Mounted under the conical silo out-feeder there are two Rotary valves. There is also a small cartridge filter on the transfer screw (inclined) the second rotary valve is between the transfer screw and the feed stoker. This long feed screw and twin rotary valves, ensures no air is transferred from the extraction system to the heater (150, 240, 300, 450 or 600kW) Note heavy duty bends on duct as customer had installed a hogger to deal with off-cuts – no more hand loading on this site!”