In the penultimate episode in this series on dust extraction, I’ll be examining the basic requirements that should be taken into consideration when setting up an extraction system in the hobby workshop of about a single garage size. The regulations imposed on a trade workshop don’t apply, but, even so, the prudent hobbyist should always be mindful to try and achieve ‘best practice’…which may or may not be possible or practical.
Table saws, planer thicknessers and some other machines usually have a dust port of 100mm and this is probably the most common size of ducting that’s used in a hobby workshop. It’s also the same size that will fit most chip extractors. Where individual machines have an extraction port which is smaller than 100mm, they are best connected to a separate low volume, high pressure (LVHP) vacuum extractor such as the excellent NVD750 or NV750. This is because workshop chip extractors generate a high volume of airflow but with low pressure (HVLP), which makes them unsuitable for use with small diameter inlet hoses. A reduction below 75mm diameter is not recommended. The mesh size of the filter bag on a chip extractor needs to be relatively coarse to allow the high volume of air to pass through and thus they are not suitable for filtering out the very fine dust produced by sanding machines. Owing to the high surface area, fitting a cartridge filter equipped with deep pleats improves the level of filtration without impeding the airflow.
A vacuum cleaner should also be used to clean the ‘shop floor of accumulated detritus and debris; a far better way of cleaning than using a dustpan, which throws a cloud of fine dust into your lungs as the brush is enthusiastically pushed across the floor. Should funding permit, Numatic also produce a cleaning kit for their machines.
Look firstly at the number of machines in the proposed system, the type of dust they’ll generate (planer chippings, sawdust, fine dust or a combination of all three) and the size of the outlet port, which should be 100mm.
Making the assumption that one of our Hobby range of HVLP chip extractors is going to be the ‘prime mover’, which one is best?
Using the standard 100mm ducted system, an airflow of 700m3/hr is the minimum requirement for one machine, thus for a very simple installation the AWEDE2 & Filter Cartridge (1 micron) to handle finer dusts is recommended. When more machines are included in the system (and hence a longer pipe run), it’s better to install a bigger extractor such as the FM300BC & Filter Cartridge (1 micron), bearing in mind that there will be increased airflow losses with a more complex system.
It’s quite difficult to work out precisely what components will be needed, but a great place to start is with the 100mm Dust Extraction Kit. It’s inevitable that you’ll have bits and pieces left over and you may (as I did) have to order additional parts as you need them. The ‘T’ junctions included in the kit should be replaced with ‘Y’ junctions and extra 45° sections (see bullet 5 below). It should be noted that from April 2017, ‘Y’ junctions, rather than ‘T’, will be standard in this kit.
Using bullet points, this is the basic procedure:
• Keep it simple; don’t over complicate the pipe run.
• Keep it straight, with as few bends as possible.
• Position the extractor so that the ducting run is as short as possible. Longer ducting introduces undesirable losses.
• Keep flexible ducting to a minimum. If the machine can’t be connected to the system with solid ducting then only use flexible hose for the final part.
• Branches joining the duct should do so at a maximum angle of 45°. When branches join the main duct they should ideally enter at the side or the top at a maximum angle of 45° towards the direction of flow.
• Fit blast gates to maximise efficiency and balance the system. Aluminium blast gates are preferable as they isolate individual machines and ensure maximum airflow. They should be installed the right way round and with the gate facing downwards.
• Avoid leaks! A system with air losses caused by leaking connections is one that’s not working at maximum efficiency. Fortunately, this is easy to correct with a turn or two of duct tape (hence its name) and the judicious application of a few cable ties. A more permanent seal could be made with a smear of silicon before assembly.
In the final episode of this series on dust extraction, I intend to revisit my own system, which has to manage planer chippings, sawdust from the bandsaw and fine dust from the Jet 16-32 Drum Sander, Jet JDS-12 Disc Sander and the ATVS1628 lathe. My Jet pillar drill, which is similar to the current model, is not yet connected to the system and this will be a future project later on in the year. I’ve made a few substantial changes to the system and my dust collection regimes in general which I hope will make a difference.