Welch duo seal vacuum pumps...any info?

[tuckermtn]

came across this pump on craigslist...

http://nh.craigslist.org/tls/528465083.html

anyone know anything about their possible application in Maple? I did a little google search and looks like it can pull 5-6 cfm and some listings show 20-30" of HG...so might be okay for a small bush- 200-400 taps if you use the 1cfm per 100 tap ratio I saw from brookledge...no idea if its able to do continuous duty, etc...

thanks for any input...

-tuckermtn

[Teuchtar]

Tuckermtn
I did buy a Welch DuoSeal pump last year on eBay, and fiddled with it for while to adapt to my pipeline. But then I learned that the duoseal product works only for applications at "deep vacuum". It won't work well at all in the medium vacuum range 15"-25" like we're looking for in maple. Those Duoseal's are two-stage pumps with a really high compression ratio, and tend to develop high discharge temperatures at our vacuums. They will scorch and burn when pumping at medium vacuum.
I talked to Welch about the application, and they flat out told me, those pumps won't work for us.
They are really for Lab work, for metals refining in vacuum furnace, etc.

Now I'm using a rotary vane pump, then cycling a sapsucker on a float switch to pump the sap out of the releaser. Doesn't work worth a rat's a-- when system freezes, hey, but I'm havin' fun.

Good luck tinkering with vacuum. Thats all part of the fun.

[danno]

Teuchtar - what's your connection to Sutton (in your title). Now that's some beautiful country in the eastern townships.

[Teuchtar]

God put Sutton, Qc in the centre of the Maple World, and put me in charge.

Also, thats where we chose for our weekend cottage when we lived in Montreal. Nice and close. But now that big-ole GE moved me to the Schenectady plant, its a helluva commute. But since I'm gonna die stokin' my evaporator, I might as well hang on to this place till that time comes.

Saratoga's nice too. Good sailing on the Sacandaga when the syrup's done.

[sweetwoodmaple]

I used a Cenco Hyvac 14 last year (similar to Welch), and it worked pretty well. Yes, it is a 5-6 cfm pump and two stage (two rotors with two vanes each).

It did get hot, but it also is a flooded system with oil surrounding both bores. Holds about 1-1/2 quarts of oil. Put a fan on it and it was fine running 12+ hours at a time.

Cenco does sell a single rotor version of this pump. It is exactly the same body, just cut in half. Was thinking about just removing the vanes on the second stage to see if it runs better/cooler.

I agree, though, the 4 vane pumps with lower compression work better for what we do with them.

[tuckermtn]

thanks for the input...seems like I'll stick with dairy pumps and the old sap-sucker for now...

[sweetwoodmaple]

A bit more information on the Lab pumps.

My Dad just acquired a Welch 1397 pump. It is 17.7 cfm two stage with oil flood.

The reason Welch does not recommend these pumps is probably for two reasons.


1. The HP of the pump motor is not enough to support medium vacuum levels.

I.E. the Welch 1397 pump comes with only a 1 hp motor. if you use the usual "dairy" rule of 10, a 17 cfm pump at 15" vacuum would require 1.7 hp. Hence, in the Welch manual, it warns of tripping the overload on the motors when run over 10 torr (28" of vacuum roughly).

I can only guess that running a pump at deep vacuum requires less horsepower.


2. The difference with the lab pump is that people expect the lab pump to run for a long time without adding oil. That would be the case with deep vacuum as the pump is not moving that much air at those low levels.

As far as the heating goes, I think any pump (dairy or lab) pump is going to run hot at medium vacuum levels.

We sugarmakers realize that a delaval or whatever will loose oil out the exhaust and we will have to refill. Otherwise, you will burn up the pump. This agrees with the Welch manual as well (warns against excess oil consumption at high temps and med vacuum).


Anyway, sorry for beating this to death, but I wanted to find out what the deal was. I will probably try to run the 1394, but upsize the motor to 2 hp as I have a new motor already. I already have the fan to blow on the pump from last year.

Good luck all.

[gmcooper]

Sweetwoodmaple,

Give the pump a try. Might work very well for you.
Can you geta performance chart from the manufacturer. That might give you a good indication on the performance you can expect. I turned one down several years ago sounds like the same size. I do not remember exactly but thought the cfm dropped of rapidly after 18". Could be wrong.

Good luck with it.
Mark

[saphead]

The vacuum pump talk peaked my curiosity so I got on the Welch Duo-seal web site today @ work.These lab pumps are designed to run @ 10 torr(29.5"hg) and below which means29.5"hg and above.The torr scale is opposite of the "hg scale.0 torr=29.92"hg,1 torr =29.88"hg,10 torr=29.5"hg,50 torr =27.9"hg,etc.
Cumberlandvacuum.com has a good chart on their site. According to Welch's
chart a 1397 will do about 13 cfm @ 10 torr,about 10 cfm @10 to -3 then it drops off as it gets to it's max. design of 10 to -4 torr. So in order to run these @ design and use them for sap,20"hg-24"hg, a vacuum breaker (relief) valve has to be put in between the releaser and the pump.fisherregulators.com/technical/vacuum/ explains this and has some cool diagrams etc. $ for these valves=? These pumps are $$ so investing in the proper controls to run the pump as designed may be worth the price of a valve.

[sweetwoodmaple]

Saphead - Thanks for the reply.

I already have a vacuum regulator in my system, but you could just use a small valve and create a leak as well.

Remember when looking at the welch chart that it is a log scale. The pump is rated at 17 cfm at atmosphere (760 torr) so that is the starting point on the graph. I will be wanting to run the pump at about 200 torr or 20" Hg. The graph doesn't seem to show much drop at 200 torr.

Fortunately, mine also has a large coffee can size outlet filter/reclaimer.

These pumps are about $5k new! (my price was free!)

[treefinder]

i was just looking @ those welch pumps online (ebay) and now i'm glad i didn't bid thanks for the info guys.

[sweetwoodmaple]

Yes, it's the age old story...money or time/effort.

You can modify these pumps or diary pumps to work (each have their issues), or you can fork over the cash and buy a liquid ring Sihi or whatever.

I just had the 1397 running yesterday for 2-1/2 hours. I put the larger motor on it and went to Synthetic multi-viscosity oil to deal with the extra heat. I lost very little oil in that time since mine came with an oil reclaimer/filter that lets the oil trickle back into the reservoir.

It definately puts out the CFM's, that's for sure.

I'll report back when the season is over.

[Haynes Forest Products]

The first year I tried vacuum was with the welch pump it was a 1/4 HP and it worked well on 75 taps just didnt have the CFMs. I did suck the sides in on a square tank no vac relief. Then went to a Gast oiless vane pump and that worked great no vacuum relief needed they can run all day at high vac and not hurt them just dont do it on a non vacuum tank (ya sucked that one flat too) If you dont want to mess with the dairy pumps and you have 110 volt near by use a gast vane pump Ebay has big ones every so often.

[Teuchtar]

I used a Gast vane pump last year, and ran it no problem for the season at about 20 to 22" mostly. I have it on my Zero tank, and don't want it running more than 20". I agree there's lots of Gasts on ebay. I bought this new-surplus pump without motor, but then had to configure the right motor and pulley ratio. Seems to me the Gasts are quite rugged.
I did buy a Sihi Liquid ring pump on ebay. Buyer beware bigtime. The person sold it as new, but turned out the impeller was knocked to pieces and unrepairable. Sihi service guy told me frankly the liquid ring pumps you find on the Used market will likely be unrepairable.

[Teuchtar]

Brian
To your comment about pump horsepower....
Pump work ( horsepower ) is the product of flowrate Q times pressure P across the pump.
At low vacuum, the pressure across the pump is near zero, and the mass flow is high, so with P so close to zero the work is low.
At high vacuum, this time P is high, but Q is low, since the density is vanishing. Again the product turns out very low.
But somewhere with moderate vacuum and moderate pressure, the PQ product reaches maximum.
This is how those duoseal pumps get away with such a low HP motor. They are rated only at very low vacuum where they're not doing much work. In the medium vacuum range, the motor works very hard for its little size, and there's a lot of heat to be dissipated within the pumping section.
The frame is comparitively massive, so it heats up slowly. But it does get awful hot running at medium vacuum for a long time.

[sweetwoodmaple]

I agree....the most hp required is in the mid vacuum range. Basically, almost were we need them to run! :-)

My rig worked well last year, but when it ran for 24 hours+...well let me just say I'm glad there were no plastic parts on the pump. Hot stuff and increased oil loss even with the small reclaimer.

I may attempt to cool it some other way for next year, but it is still a tank and works fine 90% of the time for the duty cycle required. Watching the oil level is the key.

And words like "free" make it nice too.