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Thread: 6"/150mm ducting advice
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14th June 2019, 11:40 PM #1New Member
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6"/150mm ducting advice
Hello, I'm new to the forum, but have been lurking for a long time. Currently installing dust extraction in my home workshop and wondering if anyone has found a solution my current problem...
I'm planning on using 150mm DWV or SW PVC (160mm OD) for the main line and then flex pipe for the machine connections.
But, here in Tasmania, I can only find 150mm ID flex pipe. Has anyone found a reducer/spigot that could be used to join the PVC to flex pipe, or am I best to order 160mm flex pipe from the mainland?
Cheers!
Simon
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14th June 2019 11:40 PM # ADSGoogle Adsense Advertisement
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15th June 2019, 02:08 AM #2GOLD MEMBER
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Welcome to the forum Simon.
I can't help with your question but feel I should mention that you should keep the flex hose to the minimum. It has approximately three times the internal resistance to airflow when compared to smooth wall pipe. So 3 meters of hose would be equivalent to 9 meters of pipe. That's a performance killer especially if you are using a smaller dusty.
This site has a very good Dust Extraction forum where you can get answers to your questions and information in general.
Pete
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15th June 2019, 09:36 AM #3.
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Most of the flex to PVC joints in my shed are done using a PVC threaded capped coupler.
photos here Improving machine cabinet dust ports
This turns the flex end into a short female stub of solid PVC that can just be pushed over the end of standard 150mm PVC ducting.
It also means it can easily be pulled off again and used for vacuuming up around the machine or more easily moving a machine around.
For a schematic look here Improving machine cabinet dust ports
Sure they cost money but the ease of connection and disconnection and no more ragged ends of flex.
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15th June 2019, 04:58 PM #4New Member
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Thanks - that looks like a good solution. After some more searching I also found 150mm DWV slab repair couplings that have a 150mm OD to fit inside 150mm PVC/flex. Issue with that would be that the ID would be reduced below 150mm, but maybe not enough to affect flow much.
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16th June 2019, 10:56 PM #5SENIOR MEMBER
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I used a heat gun and a mould to reduce the diameter. Worked well but was a lot of effort for the outcome. Wish I had found the couplings or possibly paid the extra for the 160mm hose!
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17th June 2019, 10:09 AM #6SENIOR MEMBER
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While there's a discussion on PVC ducting, I'd like to ask about using it as I've been told PVC is susceptible to static electricity and when you have wood dust flowing through it, that's a nice recipe for an explosion. How do people prevent that from happening?
I cut it twice and it's still to short.
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17th June 2019, 10:28 AM #7.
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This is a bit of an old wives tale.
The physics says an explosion is near impossible for a number of reasons.
1) As soon as the smallest unit of static charge is produced inside a duct it moves to the outside of the ducting. This is because electrical charge move as far apart as possible from every other like charge in the vicinity. This results in the charges accumulating on the outside of the ducting where they do little except annoy some users who touch the ducting. It's the same reason why in a thunderstorm sheltering in the inside of a car is safer that underneath the car.
2) The "boot" that people occasionally get from PVC DE systems is simply not large enough to produce a spark that is big enough to start an explosion. This is because PVC is a poor conductor so when you ground or touch charged PVC the charge drained away are very local (ie a radius of mm) and very small. Sure its enough give you a tickle but not enough to start a bang.
3) The optimum sawdust/air ratio for an explosion occurs within a narrow range and sawdust within a ducting system is very rarely uniform enough both in terms of a sawdust particle size distribution or across volume/space to sustain an explosion.
There has never been an explosion reported in a PVC ducting system but their have been fires. This typically occurs when a hot or burning piece of material is sucked up and lands in the dust bag and AWAY IT GOES.
None of this is to say it's impossible, however there are other risks in a workshop that folks should be more concerned about.
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17th June 2019, 01:36 PM #8New Member
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From what I’ve read online, the chances of a situation where explosive conditions would arise is minimal and then wouldn’t there be more chance of a spark caused by metal hitting the impeller be a more likely ignition source than static discharge?
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17th June 2019, 04:57 PM #9GOLD MEMBER
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A couple links about the myth and why it wouldn't happen in a small system. Good to be concerned and asking the questions.
WoodCentral Articles & Reviews
Why dust explosions in a home woodshop are just a myth
Pete
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24th June 2019, 09:34 PM #10New Member
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If you use pliers and carefully pull out about 4 loops of wire out of the flex. You can then pull it over the 150pvc with a little wriggling. Then a hose clamp on that and you have a perfect connection
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