Vacuum Setup Help

[Ed Scolforo]

My nephew was kind enough to drive 3 hours round trip to run a 220 line and wire my new Gast 1/4 hp pump. I was so excited! Now I'm having a problem getting good vacuum. I had ordered the filter that Surplus Supply recommends for the pump, and in spite of anything I do (epoxied the hose barb and other end to a close nipple, I still am losing vacuum. I'm using 3/8 blue compessor hose, except where that filter has a 1/2" barb at the bottom, and I adapted a compatible hose barb at the other end. I draw only about 12 inches with the filter in place and about 20 without it. I used lube and hose clamps to try keeping things tight. I can't imagine that the blue compressor hose is not sufficient. The rest of the setup is 1/4 NPT pipe that I used Rectorset pipe dope to help tighten the joints. Today I went to an auto parts place and bought a lawnmower in line filter. Same thing. I notice more vac if I put the sinctered? filter (breathing element) I got from Joewoodworker on the outlet end as opposed to keeping it open (and noisy). Is it a bad idea to restrict airflow on the outlet side? The rest of the setup is like what King Heiple demonstrated in Woodturning Design. Help will be greatly appreciated. Thanks.
Ed

[Dennis Peacock]

That's pretty odd there Ed. 24 without a filter and 12 with a filter. That sounds to me like the filter is too small to all enough volume to move. I'm only guessing as I don't have a filter on my vac setup yet either. I just turn it on and use it. Let me know what the solution is.

[Mark Cothren]

How about a picture of your setup? I'm bettin' somebody will be able to give some good advise to help solve your pressure loss.

[Jim Ketron]

Ed if your filter canister is like mine it has a large O-ring for the seal if I tighten mine too much it pinches the O-ring and losses its seal. After I clean out my filter I turn on my pump and tighten up the canister until I get a good seal and it really does not take much tightening to do that.
don't know if thats the problem but I agree with Mark some pictures would really help a lot!

[Andy Hoyt]

Hmmm. I wonder.

Compressor hose is designed to resist outward pressure on the walls.

Vac hose is designed to do the opposite.

Could this be a contributing factor?

[Dominic Greco]

Hmmm. I wonder.

Compressor hose is designed to resist outward pressure on the walls.

Vac hose is designed to do the opposite.

Could this be a contributing factor?

Don't think thats the case Andy. I have 10' of compressor hose along with an in line filter (with disposable liner) I purchased from McMaster Carr on my vacuum chuck set up and it works perfectly.

In addition, I have compressor quick disconnects on my shop built rotary union (also called a "rotary adapter"). I'm able to pull 22 to 24" of HG using my 220 V Gast Pump with no problem what so ever.

Like others have stated, I feel that the most likely culprit is the filter. It sounds like it is restricting air flow. Do that and the performance will always drop off.

[Bill Boehme]

You need to give a better description of your set up. I think that you are focusing on a hose leak and the problem is somewhere else. Here are some questions that would help:
Are you talking about "blocked port" vacuum? In other words, is the end of the hose that goes to your vacuum swivel adapter plugged? If not, then your test results may be invalid for diagnosing a problem.
Where is your vacuum gauge located? It should be located so that it is the first thing in the line as you go from the swivel adapter end of the hose towards the pump. Next, should be the inline filter (usually in a polycarbonate jar with an "O" ring seal), followed by a needle valve (make sure that that you are using a needle valve for this as other types of valves are too difficult to regulate) and the open side of the valve needs to have a filter -- a small inline pleated filter is usually good. And the last thing to have is a "T" with an inline ball valve to shut off the vacuum and another ball valve to draw outside air during the pump cool-down cycle -- it would be a good idea to put a filter on the open side of this valve also.
To answer your other question, the outlet side of your compressor should definitely have a sintered metal muffler type filter screwed into it -- that is what they are for -- muffling the noise.If you have been measuring the vacuum "downstream" of the inline filter (i.e., you have installed your gauge between the filter and the pump) and you have a "load" attached (swivel adapter, chuck and bowl) then there will be leaks and the reading that you get will be highly dependent upon where you install the gauge in the line. With air flowing in the system due to the leaks at the swivel adapter, the vacuum chuck, and the bowl, you will also see a vacuum drop across the filter because it presents a resistance to air flow. There will also be another vacuum drop at the bleed valve.

One parting thought is that 20 in-Hg for a blocked port vacuum is extremely low (it ought to be around 24 to 26) and it looks like the vanes on the pump that you bought are nearly worn out. The good news is that for a few shekeles, you can get a rebuild kit that consists of new gaskets and vanes and the pump will be back up to full speed again. Nevertheless, a blocked port test should give you the same reading at any point in the line and if it does not, then there is a leak at the "O" ring.

UPDATE: I have attached a sketch of the connections that I described.

Bill

[Gary DeWitt]

Hose I use is the one that came with the salvaged Gast pump, it's 3/8 Id clear tubing with a coil of wire, looks about 20 gauge steel, molded into the hose. Obviously designed for vacuum, not pressure.
One of the difficulties of finding leak(s) in a vacuum system is that they leak "inward". If there is some way you can hook up pressure to your system where the pump attaches, without the pump there, you could just spray soap solution all over it to find the leaks. Even low pressure from a bike pump would work. It seems to me you would have to have major leaks to get that kind of drop though. I typically get 23-24 in when I have a bowl on, plenty to hold it for even somewhat agressive turning.

Dennis - you may wear out the vanes in your pump pretty quick if you suck up some sawdust. I've seen pics on the web of homemade filters out of 3" sched 40 pvc filled loosely with steel wool or fiberglass insulation. Pretty easy and cheap to make. Pipe, end caps, barbs, no glue required as the vacuum pulls it together tighter.

[Ed Scolforo]

Thanks for the input, guys. Tomorrow I'll take some pics of the setup. BTW, I haven't made the connection yet from the tee near the gauge to the headstock adaptor yet. I figure if it's reading this low now, it'll only get worse once I add more hose.
Ed

[Bill Boehme]

Thanks for the input, guys. Tomorrow I'll take some pics of the setup. BTW, I haven't made the connection yet from the tee near the gauge to the headstock adaptor yet. I figure if it's reading this low now, it'll only get worse once I add more hose.
Ed

Ed,

Screw the vacuum gauge directly onto the pump with a pipe nipple to see what the read is. Next, add the filter, using another nipple and anything else necessary to see if there is a difference. There is a very slight chance that the gauge has a crack in its diaphram and is letting air leak through it.

Bill

[Dennis Peacock]

Hey Bill,

Nice drawing you got there. My setup is more simple than that though. Vac pump to hose to lathe headstock. ;) I really need to setup mine up properly and add in a filter, but hey....it works and I'll get to it when I get around to it. :o

Yup Ed...post us a pic or two and Bill has you headed in the right direction. Test it all one piece at a time to find the "trouble".

[Bill Boehme]

......... I really need to setup mine up properly and add in a filter, but hey....it works and I'll get to it when I get around to it......

Dennis,

If you do any sanding on thin wood (or some species don't need to be so thin) while on the vacuum rig, you might be amazed at the amount of dust that goes right through the wood. Along with it some of the abrasive from the sandpaper goes through. A filter is a lot cheaper than a rebuild kit for your pump. And forget about the fiberglass and steel wool "filter". It only catches the large stuff. Just like the dust that is the worst for your lungs, the "bad" stuff is the stuff that you can't see and the hommade filters can't handle.

Bill

[Ed Scolforo]

Ed,

Screw the vacuum gauge directly onto the pump with a pipe nipple to see what the read is. Next, add the filter, using another nipple and anything else necessary to see if there is a difference. There is a very slight chance that the gauge has a crack in its diaphram and is letting air leak through it.

Bill

Bill, I did that. It was reading around 28 directly off the pump and then dropped to 12 when I next added the filter. That's why I'm thinking it's either the filter or the tubing/hose barbs that are the problem. If I take the filter out and hook the rest of the plumbing up directly to the pump (which then goes up to the tee from which I connect to the headstock), I get a reading of 20. Some vacuum loss, but I don't know if that's to be expected? Anyway, I'll post some pics. Thanks, Ed.

[Bill Boehme]

Another question -- are all of the connectors the same type? There are pipe thread, flare, and compression and they don't seal properly if mixed. Use pipe dope to seal the connections. Contrary to rumor, don't use high vacuum grease -- it is not for sealing leaks, but for lubrication use in a vacuum environmement where ordinary grease would evaporate. The connections all need to be very tight.

Excuse my spelling -- I broke my glasses today.

Bill

[Ed Scolforo]

Another question -- are all of the connectors the same type? There are pipe thread, flare, and compression and they don't seal properly if mixed. Use pipe dope to seal the connections. Contrary to rumor, don't use high vacuum grease -- it is not for sealing leaks, but for lubrication use in a vacuum environmement where ordinary grease would evaporate. The connections all need to be very tight.

Excuse my spelling -- I broke my glasses today.

Bill
No, Bill. I used some LM and IM compressor fittings because they were bigger than the standard 1/4" barb.Hose clamps were also used. Some of the close nipples are copper/ brass, and some are regular pipe. All the plumbing up from the filter is regular pipe ( three 6" nipples) and sealed with Rectorset.
Ed

[Bill Boehme]

What I meant to ask was are the mating connectors the same type?

Also, as general information to anyone, if you put a hose over a threaded nipple and clamp it with a hose clamp, there will be a spiral leakage path along the screw threads.