Thread: OLD School DC issues

Watching with interest as there is one the same in the workshop at work (much better condition though) that has not been fired up in the time I have been around - we have no ducting for it so it has probably never been fired up at it's current location.

Originally Posted by Burnsy

Watching with interest as there is one the same in the workshop at work (much better condition though) that has not been fired up in the time I have been around - we have no ducting for it so it has probably never been fired up at it's current location.

I think this unit was a standard issue to WA schools and education institution in the 80's and 90's. While I would be OK for a home workshop it is not really appropriate for a school worksop unless it was just connected up to 1 or 2machines. I note that very large industrial grade cyclones are now being used at schools.

Originally Posted by BobL

The impeller is only a 12" straight vaned construction and these are known to be quite loud and sure enough it is.

At 50Hz it puts out 93dB at 1m, and draws 7.1A (that's not quite 3HP in my book, more like 2.5HP)
At 60Hz its 97dB and draws 12.1A which makes it closer to 4HP.
We will be putting this DC outside it in a noise enclosure anyway but its going to be tough to get those dBs down to something reasonable.

AT 50 Hz it's only 6.5" of WC while at 60 Hz it's 8.5" - there could have been some leaks in the system so I will repeat these tomorrow.
However, the impeller is too small and poorly designed so I doubt it will be much higher that this.

Update

Last night I was trying to think why the DC gave such low pressure readings and then I remembered I had not checked the fan rotation
On checking this morning - of course its running the wrong way!!
So rewiring to get it to run the right way and here updated data:

At 50Hz free running (i.e. bags connected) it now draws 10.5A which is ~3.4HP so that is good
I did not let if free run at 60Hz as I reckon it would draw too much current and trip the VFD

Then I blocked the inlet and checked the pressure and SPLs.
(with the inlet blocked the motor draws much less current so I can now test it at 60Hz no problems)

At 50Hz it's reading 7.2 " of WC with a db reading of 97 dB
At 60Hz its reading 9.6" with a reading of 102 dB

While these pressures are better than the first test they are still not as good as I was hoping for. I think I still have a small leak in my blocking pipe because the bags were still puffing up a bit more than I like to see - they should be almost flaccid if this test is being done correctly.

This is one hell of a noisy DC, we are going to have to build a decent enclosure for it of the neighbours will have something to say.

The one thing I forgot to add about this DC is that it does have a 9" intake which is surprisingly large.
Even at 7.2" of WC pressure the flow rate in a 9" pipe would be more than 2000 cfm, but of course serving machinery direct with a 9" duct is quite impractical and the real question would be if the impeller could still generate a decent (even 1000 cfm) under the extra resistance of smaller ducting and machine ports.

Just curious if a larger impeller, say 14' or 15" would fit in the existing housing and still work without mods? Or would it be too tight to the walls?

Pete

Originally Posted by QC Inspector

Just curious if a larger impeller, say 14' or 15" would fit in the existing housing and still work without mods? Or would it be too tight to the walls?

Pete

I havent measured it up but it look alike it would fit a 14" impeller. There are other problems with it though. I will take some pics next time I take the bags off to show what these are.'

As always Bob, interesting reading.




Pete

Originally Posted by pjt

As always Bob, interesting reading.
Pete

Cheers Pete,

Next thing I have to do is fit new wheels to the frame as the old ones were so badly corroded they did not swivel or even go around.
I ended up cutting them off and grinding away the stumps with an angle grinder.

Then I'll reassemble it all and take it over to the mens shed. Our new mens shed is still being built but I need to get the DC out of my yard before SWMBO complains about me using the outdoor table as a work bench - AGAIN!

Gee Bob ... Can I order a couple of those bag clamps ? They look great !

Originally Posted by Glenn.Visca

Gee Bob ... Can I order a couple of those bag clamps ? They look great !

They are dead easy to make.

Steel banding can be found in skips etc

The latches I got from the Trailerparts store (I went to the physical shop to look at them)
Look for the part numbers below on this page http://www.trailerparts.net.au/onlin.../1208418870/EL
I bought the medium size ($8) but the small ones would be fine ($6)

E0914 Cam Latch-adj & Lock : Small

E0915 Cam Latch-adj & Lock : Medium

You will need some 3/16" rivets and a 3/16" drill bit.

I riveted the latch direct to the steel band (there are 3 holes in the latch but only one central one so I drilled another along the centre line.
the catch is small and the holes are also not central so I riveted the catch to a small piece of ally and then rived that to other end of the band.
It takes a bit of finessing to get the length right but then it's quite easy.

Bob, u just 'happen' to have a surplus of VFD's? Not the sort of thing u generally keep a few of!

Originally Posted by johnredl

Bob, u just 'happen' to have a surplus of VFD's? Not the sort of thing u generally keep a few of!

Speaking for myself, it is necessary to have stuff (all those I might need that one day kinda things) with which to 'fiddle' with, I currently have 15 MSC3 Zener VSD and about 5 'others', all just right for 'doing something with' does't suprise me at all that Bob would just happen to have a spare VSD or two


Pete