Vacuum pump flow rate

[sweetwoodmaple]

A question for all you vacuum pump weenies.

I purchased a two stage Cenco pump that is 5.6 cfm and has a 3/4 hp motor. The pump was in poor repair, so I had to rebuild. Unfortunately, between the time I tore it apart and when I iput it back together, I'm not sure I got the vanes back in the correct bore.

I made the assumption that, even though the bores were scored, it would be ok because of the oil bath (it holds 2-1/2 qts of oil).

When I turn the pump on, it seems fine, but I'm trying to do some experiments to make sure this pump pulls a good flow at 15"+ of vacuum. Stock, this pump should maintain 5.6 cfm all the way down to 28" or so. When I put my finger over the inlet, it goes immediately to 20-22"", but when I create a slight leak, it drops to 10-12". I'm thinking the pump should do better than this considering the specs of a new pump. I'm wondering if I should have went ahead and ground the vanes and bore?

Or, should I wait until things get worn in better? I don't want to spend $$ getting things perfect since I don't need 28".

Any advice would be appreciated.

[Maple Hill Sugarhouse]

post edited

[sweetwoodmaple]

Ummm...ok. 8O

This pump isn't junk. Even if it was, the stinking thing weights 80 pounds, so it would be worth a few cents anyway! :D

A new Hyvac 14 is $2 grand, and I paid $50 plus about $100 for parts so far.

Anyway, like a idiot, i should have got the vanes ground. Should know better after putting motors together.

I will do that and see where things are.

Thanks for all the help and useful information! :wink:

[Maple Hill Sugarhouse]

post edited

[sweetwoodmaple]

If you got the money, they make the parts for this unit. Again, they still make them brand new. They are mostly cast iron, including the vanes (not composite), hence their weight.

Yes, for the vanes like mine that are 3/8" thick, the end profile is important. I believe they have these in stock at hyvac, so I could get them in a pinch.

The pump the Bodie sent me was an old Hineman milking pump. Not even close to the same as far as quality of build. It has composite vanes as well.

http://www.hyvac.com/Products/Vacuum_pumps/Belt%20Drive%20Pumps/2Stage/HV2_45_descrip.htm

http://www.hyvac.com/PDFs/Exploded%20Views/HyVac%2014/DD_PDF_0036.PDF

[sweetwoodmaple]

Update: Spent valuable good weather time fooling around with the pump today.

Oh well. Anyway, took the bores off and vanes. Tried to match the scored vanes with the scored bores by feel, which worked and i did have two of them switched.

Also, i'm a little slow on the uptake on these pumps. There is a critical running clearance between the center rotor (that holds the vanes) and the bore itself. I am assuming this must be very close so as to allow the oil to plug this gap and allow the lowest possible vacuum and the least blow by or recirculation of air?

I matched the vanes and adjusted the bore and rotor clearance and now get a solid 24-26" of vacuum, plus it pulls down almost instantly and is quiet when I put my hand over the inlet. A sign of success according to Hyvac's troubleshooting guide.

[Parker]

When you say bore you mean the cylinder that the vanes spin around inside of? On the surge (what I have had apart) there is a cylinder that a billet with 3 groves cut in it turns indide of. The vanes ride in the groves in the billet. As the billet sipns the vanes ,by centrifical force, are pushed aginst the wall of the cylinder, there is a film of oil between the cylinder and the vane,,creating the vacume. Is this how you pump works? I am unclear on what you mean by "took the bores off and vanes",,wish I had a picture

[sweetwoodmaple]

See one of the earlier links the I posted for Kevin.

The bores that the vanes run inside are removeable. Hence me saying I removed them. The rotors can stay with the drive shaft and center section. Makes it convenient to grind the bore and vanes as you don't have to completely dissassemble the unit.

My vanes are spring loaded against the bore.

[Maple Hill Sugarhouse]

post edited

[sweetwoodmaple]

You don't need to tell me anything else...26" of vacuum is fine for me. :D

My pump only has two vanes on each rotor (or drum as you call it), but there are two rotors in series. Air is sucked in the first one, then sent to the second then out. There is also a small air relief on the second stage, some sort of purge I think.

Having two stage is overkill, and really not needed for what i'm doing, but the price was right.

[Maple Hill Sugarhouse]

So-You got er'

[sweetwoodmaple]

Yes, seems to be ok. Doing a timed pump down of a tank might be a good way to make sure.

I'll be hooking it up to my releaser soon, so I can do some testing then.

Put a dozen star tees in today to make sure I have enough capacity for my ladders. Eliminated the bypasses and put gage ports in instead. Also put drain valves at the bottoms of each ladder.

A lot of prep work for vacuum, I hope it's worth it.