Dust extraction size 125mm>100mm on ducting? or keep to 100mm throughout

[Hsmith192]

Hi everyone,

I want to make my dust extraction as efficient as possible over 4 m. I'm struggling to choose between 125mm ducting or 100 ducting.

I've got a 125mm port on the cyclone which has an adaptor on that can take two 100mm.

So, would I need to use 125mm for the main ducting and drop down to 100mm for each machine with flexible pvc pipe for the last meter?
Or do i go with 100m pipe throughout with 100mm flexible pipe for the last meter leading to the machines?

I will use blast gates and it will be rare that more than one machine will be used at any given time.

What do you guys think?

 

[PAC1]

The latter. Keep the ducting as large as possible as long as possible.

 

[Hsmith192]

The latter. Keep the ducting as large as possible as long as possible.

Thanks, In that case I should also have drop downs to 125mm and then use 100mm flexible pipe to join to the machine.

 

[Inspector]

You should actually open the machine ports to 125mm and use 125 straight through. The more air you can flow the better. The exception being your table saw. That should have the 125mm split to 2 x 100mm. One for the cabinet and the other overhead on the blade guard. Use as little hose as possible as it has three times the resistance as duct. One metre of hose equals 3 metres of duct.

Pete

 

[Hsmith192]

Thank you for your comment. I don't have the table saw just yet but in relation to the ports, can I use adaptors or do I have to change the ports as they are 100mm ports as standard?

 

[Hsmith192]

You should actually open the machine ports to 125mm and use 125 straight through. The more air you can flow the better. The exception being your table saw. That should have the 125mm split to 2 x 100mm. One for the cabinet and the other overhead on the blade guard. Use as little hose as possible as it has three times the resistance as duct. One metre of hose equals 3 metres of duct.

Pete

Thank you for your comment. I don't have the table saw just yet but in relation to the ports, can I use adaptors or do I have to change the ports as they are 100mm ports as standard?

 

[PAC1]

Just as a quick rule of thumb. People look at this choice and say well 125mm is only 25mm bigger than 100mm so it is only a a quarter more air that can pass along the duct. That is wrong it is very nearly double the amount of air.

 

[J-G]

Just as a quick rule of thumb. People look at this choice and say well 125mm is only 25mm bigger than 100mm so it is only a a quarter more air that can pass along the duct. That is wrong it is very nearly double the amount of air.

It's actually 156% - still a big difference but not 'nearly double'.

 

[Inspector]

I know the ports are supplied with 100mm openings but they are too small to capture fine dust. They should be bigger so you have to do some cutting. If you are only concerned with dust you can see then the supplied ports will work but you’ll need to wear a respirator while working. That fine dust hangs in the air for hours. If you want to learn why see search “Bill Pentz dust collection” and spend a few days reading.

Pete

 

[PAC1]

It's actually 156% - still a big difference but not 'nearly double'.

The cross sectional area is 156% but you also need to factor in the reduction in flow caused by the reducer etc and the practical difference is that nearly double the amount of air will flow per minute or hour through the 125mm duct as will in the 100mm. If it is a branch it can be even more.

 

[mccpe]

in relation to the ports, can I use adaptors or do I have to change the ports as they are 100mm ports as standard?

I have that extractor. 125mm steel ducting and 125mm flexible everywhere. At each machine I convert from the machine diameter (100 on some, 150 on the saw) to the 125mm. I have a short length of 125 flexible between the extractor and the steel duct.

The converters are either plastic or steel depending on what I thought best.

Www.dustspares.co.uk for steel duct and joints, blast gates, etc. EBay for flexible and various places for plastic adapters.

 

[Keith 66]

One metre of hose equals 3 metres of duct. Pete

I never realised that, at my last school the circ saw had two vacumm cleaners coupled to it with 35mm bore ducts, this when the machines lower port was 100mm & crown port 63mm, It was completely inefectual. However every year it passed its lev test!
The lev engineer also stated duct size was 38mm having measured the outside diameter of the corrugations.
Service providers dont have a clue. I left after 5 years of trying to get them to fit decent extraction.