New Dust Extractor ductwork.

[stigg]

Hi,
I have just agreed to buy a new (to me) dust extractor. It is a three bag 5.5Kw model. Don't know the make but like the Inventair or P&J models. The plan is to site it external to the workshop under a cover / small shed.
Does anyone have any advice about the ducting design?
I am thinking of 200mm duct down two sides (L shape) with a T half way down to service the other side. -I suppose that makes it an F shape. Drops to the machines will be either 150 or 100mm flex as most machines have to move on occasion. Shop is 10 x 5.5
I have been looking at various pressure calculators and trying to work out my TEL etc but maybe someone reading this has done this before? Don't want to buy the ducting to find it doesn't work in the end.
I have a few machines this will be hooked up to.: TableSaw, Bandsaw, Spindle, Mortice, Tenoner, drill etc etc.

Currently have an Axminster single bag mobile thing but it is always in the way and there is a great big cloud of dust blown into the air every time it starts and it doesn't really work all that great with my planer.
I did have a look through the forums but couldn't find anything quite the same s sorry if this is one of those questions AGAIN!
I will probably find it immediately after posting

Thanks
Dan

 

[Yojevol]

Hi,
I have just agreed to buy a new (to me) dust extractor. It is a three bag 5.5Kw model. Don't know the make but like the Inventair or P&J models. The plan is to site it external to the workshop under a cover / small shed.
Does anyone have any advice about the ducting design?
I am thinking of 200mm duct down two sides (L shape) with a T half way down to service the other side. -I suppose that makes it an F shape. Drops to the machines will be either 150 or 100mm flex as most machines have to move on occasion. Shop is 10 x 5.5
I have been looking at various pressure calculators and trying to work out my TEL etc but maybe someone reading this has done this before? Don't want to buy the ducting to find it doesn't work in the end.
I have a few machines this will be hooked up to.: TableSaw, Bandsaw, Spindle, Mortice, Tenoner, drill etc etc.

Currently have an Axminster single bag mobile thing but it is always in the way and there is a great big cloud of dust blown into the air every time it starts and it doesn't really work all that great with my planer.
I did have a look through the forums but couldn't find anything quite the same s sorry if this is one of those questions AGAIN!
I will probably find it immediately after posting

Thanks
Dan

200mm is way too large. I have a similar sized workshop with runs and spurs in 125 and 100mm ducts. There are about 8 terminal points controlled by blast gates. I assume you will be working alone with just one gate open at a time. The duct run needs to be as consistent as possible all the way from the machine back to the extractor in order to keep the air speed constant. If the speed suddenly drops due to increased duct size the dust load will fall out and collect on the bottom of the pipe. It will collect there until the effective cross sectional area is reduced enough to increase the airflow to such a speed that will maintain the dust in suspension again.
I suspect the DX is too large for a single machine running at any one time. It will be churning away doing very little work and may end up overheating.
Sorry to be a downer.
Brian

 

[Doug71]

You down want to get this wrong so I would get advice from someone like Dust Spares rather than trusting opinions on the internet. I'm sure they will design you a system for free if they think they might get a good sale from it.

https://www.dustspares.co.uk/

 

[stigg]

You down want to get this wrong so I would get advice from someone like Dust Spares rather than trusting opinions on the internet. I'm sure they will design you a system for free if they think they might get a good sale from it.

https://www.dustspares.co.uk/

I have been looking at dust spares after the seller recommended them. Will give them a call Monday. However -and probably like most on here - I like to understand what and why I am doing things.
Hopefully 200mm is too large, smaller would be better. I think the intake of the machine is 250mm. Not seen it yet so can't be sure but it's not less than 200
Looking at similar units the airflow is stated at 4250m3/h @178mm (7inches of water) Presumably the the filters etc contribute the that pressure so in reality quite a bit less than that flow.
My understanding is that the current increases with increased air volume. Restricting flow will reduce the load and hence little risk of overheating if little airflow.
Thanks for the replies guys. If I'm getting anything wrong please let me know.

 

[Inspector]

I played briefly with this calculator Duct Friction Loss and 8" duct, galvanized, 50' long at 2500CFM and 3 of 90º 5 piece elbows has a loss of almost 7". Same thing again with 10" and the loss is 2.4". Better to run the 10" and then use 3 machines with 6" ducts open at all times to feed it. If you want to use a 4" or two then leave two 6" ducts open. It has lots more suction than you need but if it isn't pulling the air it won't overheat or burn up. A restricted HVLP does less work because the air is spinning in the impeller housing and not doing as much work as when it is wide open. If you left a 6" port open high up like at the end of the "F" run it would scrub the air all the time and catch any dust not collected at the machine. Starting and stopping the motor too often is the hardest thing to do to a single phase DC. The current surge builds up heat that needs time to dissipate. ClearVue Cyclone in the US say to not start/stop more than 4 times and hour and their machine is a 5hp.

Pete

 

[stigg]

I played briefly with this calculator Duct Friction Loss and 8" duct, galvanized, 50' long at 2500CFM and 3 of 90º 5 piece elbows has a loss of almost 7". Same thing again with 10" and the loss is 2.4". Better to run the 10" and then use 3 machines with 6" ducts open at all times to feed it. If you want to use a 4" or two then leave two 6" ducts open. It has lots more suction than you need but if it isn't pulling the air it won't overheat or burn up. A restricted HVLP does less work because the air is spinning in the impeller housing and not doing as much work as when it is wide open. If you left a 6" port open high up like at the end of the "F" run it would scrub the air all the time and catch any dust not collected at the machine. Starting and stopping the motor too often is the hardest thing to do to a single phase DC. The current surge builds up heat that needs time to dissipate. ClearVue Cyclone in the US say to not start/stop more than 4 times and hour and their machine is a 5hp.

Pete

Hi,
those are the kind of figures I was getting too. Just need to make sure the flow doesn't drop too low to cause a build up. I have seen the figure 4000fpm as a minimum.
BTW this is a 3 phase 440v motor. Shouldn't have any problems starting. I also have an inverter to dive it if need be. Could probably push the frequency and get an increase in pressure. wouldn't want to go much past 10K rpm though! ;-)

Thanks.
Dan

 

[Inspector]

The calculator show the speed in the results so you can be sure you have enough. With that though is the understanding that if one uses a single 4" branch it will only flow about 400cfm so when it gets to the bigger main trunk it slows way down and drops the dust which will get picked up when bigger branches are opened at a future time. When that happens the lumps of settled dust can be picked up and go flying into the impeller.

Yes with a three phase there won't be the heat buildup especially if it is programmed to start over a few seconds. 10,000 eh. Good thing you are putting it outside. On the other hand you could run it slower with all ports open to scrub the room air if needed once in a while without as much noise as wide open.

Where you can opening the machines to bigger duct will improve capture a lot. I suspect you know that already.

Pete

 

[stigg]

Well I got it here. Three blokes and a forklift put it in my trailer (it only just fit). Just me to unload! It's going to have to go into storage in the garage until I have time to build it a shed and install ducting. I have a sash window and dormer to make and fit in the next couple of weeks. I'll save my Accoya purchasing woes for another day.
Inlet diameter is 265mm or about 10.5". Is that an odd size?
Here it is

 

[Inspector]

Big beastie. If you get a chance can you measure the impeller? Diameter, height and number of blades? I'm curious. I think the duct diameter would be about right for the 5.5kw /7.5hp motor it has. The ClearVue's CV1950 cyclones with a 3.7kw / 5hp motor and 16" impeller use 8" ducting.
Pete

 

[Jameshow]

Well I got it here. Three blokes and a forklift put it in my trailer (it only just fit). Just me to unload! It's going to have to go into storage in the garage until I have time to build it a shed and install ducting. I have a sash window and dormer to make and fit in the next couple of weeks. I'll save my Accoya purchasing woes for another day.
Inlet diameter is 265mm or about 10.5". Is that an odd size?
Here it is
View attachment 155876

Do you want some 8" ducting if any use?
Happy to meet half way (colne?) to hand over to you?

 

[stigg]

Big beastie. If you get a chance can you measure the impeller? Diameter, height and number of blades? I'm curious. I think the duct diameter would be about right for the 5.5kw /7.5hp motor it has. The ClearVue's CV1950 cyclones with a 3.7kw / 5hp motor and 16" impeller use 8" ducting.
Pete

The impeller is 400mm diameter and 100mm high. Sorry didn't count the blades. Think it is 8. Will check and update if not. They are arranged radially. The motor is marked 7.5HP and 2860rpm.

 

[stigg]

Do you want some 8" ducting if any use?
Happy to meet half way (colne?) to hand over to you?

Hi, Thank you, that might be very useful. What have you got?
Dan

 

[Inspector]

The impeller is 400mm diameter and 100mm high. Sorry didn't count the blades. Think it is 8. Will check and update if not. They are arranged radially. The motor is marked 7.5HP and 2860rpm.

Thank you. I appreciate you taking the time to measure it.

Pete

 

[Jameshow]

Hi, Thank you, that might be very useful. What have you got?
Dan

From memory I've got about 4 lengths about 6ft long.

I'll have to go and picture it tomorrow morning now.

Cheers James