Thread: 2hp DE Build

Originally Posted by BobL

If outside venting is not being considered because a shed is heated in winter what about setting up a simple diverter that sends unfiltered air outside when the shed is not being heated. This would lengthen the longevity of any filter by the ratio of unheated to heated time.

My current practice is to wheel the DE outside in warm weather. Bypassing the filter is a good idea though. Will look into that.

Originally Posted by BobL

What's the effective surface area of these filters...

226 sq ft. Not bad for the price.

Originally Posted by jack620

I have Pete. I got my blower plans from BP's website.



I'm afraid it's $675 each! The agent said the freight is a killer. They weight 7kg, but the volumetric weight is 54kg.

Opps. When threads get a few pages long I sometimes, no often, forget what was said in the beginning.

Bummer about the cost but you have at least found a good substitute. Have they said to what standard the filter is made to? MERV rating or similar?

Pete

I don't think MERV is a thing here. He said it was an 80/20 cellulose/polyester blend that filters 99.999% of particles down to 0.5 microns.
I suspect it's a Chinese version of the equivalent Torit filter. I found a supplier closer to me that sells Torit filters. Waiting on a price for the same size (TD large) filter in spun polyester. This one is washable. Not expecting it to be cheap.

Originally Posted by jack620

226 sq ft. Not bad for the price.

I agree about the price, but something else to think about.

According to BP a clean 600 sq ft filter will drop 0.2 "WC of static pressure so a 226 sqft will drop ~0.5" and will increase proportionally as the filter clogs.
ie when the 600 sq ft reaches a 0.4"WC loss, the 226 sqft filter will lose 1"

An important consideration is, given your impeller only generates 8"W and there is a cyclone inline, can a 1"W pressure loss be afforded?
One way to get around this is by using two of them which will halve the pressure losses.

FWIW the needle felt filter bags on 2HP DCs usually come in two types
A thinnish felt, with slightly higher initial flow but initially with low filtration efficiency like those on the Hare and Forbes machines
and
A thicker slightly lower initial flow with much better filtration like those on the Carbatech machines
In practice once either bags are conditioned they achieve similar levels of filtration, easily as good as pleated filters.
This is why I recommend anyone using a DC inside a shed condition brand new filters (including pleated filters) by taking the DC outside the shed, chucking a bucket full of fine sawdust into the plastic collection bag and running the DC for 20-30 minutes. The swirling of the dust will progressively mince the fine dust into even finer dust and condition the bags. This should not clog the filters as they are designed to hold a substantial amount of dust, but will improve their efficiency. If the filters look clogged a light clean with compressed air will fix that.

Vigorous cleaning of thinner filters (including pleated filters) can de-condtion the filters so they let through more fine particles again until the recondition. Thicker better quality filters can cope with a relatively vigorous clean and retain their condition. This is a non-issue when venting outside where there's no need to condition or recondition any filter.

I have not measured the static pressure losses of a 2HP filter but I have twin large thick needful bags on my system and they typically lose 0.25"W in a clean conditioned state. Provided I don't let the collection bags get more than 1/3rd full (they get quite heavy above that) the pressure loss is rarely above 0.4"WC. Some of this is because of my work materials and pattens, eg I cut a fair bit of Al with my TS which produces curly flakes that bulk out the sawdust and look like they reduce compaction of dust onto the filters. OTOH I do use MDF for jigs and rigs and that makes lots of finer dust.

Anyway enough for now.

Bob,
my new DE is just tall enough to fit two filters stacked on top of each other. It won't leave room for a clear-out or plastic bag at the bottom though.

I currently have a custom-made thick needle felt bag on my old DE. It works very well, but it won't work on the new DE because the air enters the filter from the top. I suppose I could cut the top out of the bag. One open end would attach to the outlet of the blower and the other end to a plastic bag via a suitable adaptor.

I could also have another bag made to suit the new DE, however I like the idea of the large surface area of pleated cartridges. If these $115 Chinese Torit copies work out, I think they will be an excellent solution. If they don't (i.e they don't cope with reverse flow), then a new needle felt filter might be my only affordable option.

Originally Posted by jack620

Bob,
my new DE is just tall enough to fit two filters stacked on top of each other. It won't leave room for a clear-out or plastic bag at the bottom though.

Could you make a short manifold that would allow them to sit side by side?

A manifold might be doable.

I measured the SP of the new blower today. 7 ¾ inches of water. Slightly worse than the original blower. Go figure.

I've attached a photo of the setup. Everything was sealed with duct tape. However, despite what I've seen on the internet, I don't think a tight seal is necessary for this test. Have a look at the photo of the blower inlet. I was still getting 7 ¾ inches with the test plate in that position.

Originally Posted by jack620

I measured the SP of the new blower today. 7 ¾ inches of water. Slightly worse than the original blower. Go figure.

I've attached a photo of the setup. Everything was sealed with duct tape. However, despite what I've seen on the internet, I don't think a tight seal is necessary for this test. Have a look at the photo of the blower inlet. I was still getting 7 ¾ inches with the test plate in that position.

It doesn't surprise me, the pressure distribution around a moving impeller is quite variable and may in places approach that of a a fully blocked impeller.

What is the distance between the top of the impeller blades and the impeller case, for each of the impellers?

Originally Posted by BobL

What is the distance between the top of the impeller blades and the impeller case, for each of the impellers?

The ends of the blades are about 12mm from the impeller case on the inlet side for both blowers. On the motor side I'd have to check.

Originally Posted by BobL

It doesn't surprise me...

Surprised the heck out of me! That inlet is nearly a quarter open.

I got a price on the Torit cartridge: $193.50 incl GST for a spun-bond polyester (washable) 323D x 660L open ends, inner guard.
That's from Filterfit in Moorabbin (VIC).

Originally Posted by jack620

The ends of the blades are about 12mm from the impeller case on the inlet side for both blowers. On the motor side I'd have to check.

Humm . . . I doubt the motor side matters. It’s sometimes a matter of air being able to move/leak back some how over the top of the impeller. But most likely it’s just that the same impeller blade is being used.

OK. Here's a pic.