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Blower Vac Setup

5/30/18       
Jon Member

Yesterday while I saw a blower setup where the pump had a filter in place to prevent chips from getting to the pump. Great plan but the person had tee'd the main intake off and air from behind the machine could bypass the filter and go straight through the pump. It's a 4 inch pvc pipe going to the machine with now 4 inches open also. Needless to say there is better vacuum when the tee is removed and not allowed to bypass. Is it safe for the blower system to not have this additional unplunmbed in the system. We get a lot more hold down when it's plugged. Just concerned the pump could get to hot. Any advice would help.

5/30/18       #2: Blower Vac Setup ...
JM

Not 100% sure what you're talking about, but I think you are referring to the pressure relief.

On that T you describe, there should be a relief valve, then a filter that is open to atmosphere. When the pump hits max vacuum, the valve should open slightly to take filtered air from the atmosphere so the pump does not operate beyond its capacity.

Pumps are only rated for a certain amount of vacuum. Go beyond this and you could damage the pump. The relief valve is there to prevent damage.

5/30/18       #3: Blower Vac Setup ...
Snaglpuss

I second the motion.
It is probably a pressure relief check valve so the pump doesn't dead head.
Does it have a filter on it?
It should so that when the relief valve opens your pump isn't sucking in fine dust.

5/30/18       #4: Blower Vac Setup ...
Jon Member

Here's what is really there. This pipe is unrestricted no filter ever seen this?


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5/30/18       #5: Blower Vac Setup ...
JM

That looks like the place the pressure relief and filter should be.

Image in the link shows the pressure relief and filter on the right side of the T.

Check this link

5/30/18       #6: Blower Vac Setup ...
Dropout Member

Is the end of the silver piece open or does it have a mesh?

5/30/18       #7: Blower Vac Setup ...
Snaglpuss

The big one looks like the filter housing off the main hose from the cnc bed.
Doesn't look like it has a relief valve or a filter for the relief valve. If this is just open no wonder it doesn't have much vacuum.

5/31/18       #8: Blower Vac Setup ...
Larry

I'm not understanding why a "pressure relief valve" is needed at all. As the pump approaches maximum vacuum the load on the motor approaches free running, no load. The motor would just spin at its synchronous speed. If you had some sort of process connected to the pump that could be harmed by high vacuum (not a CNC router!) Then a vacuum limiting valve would be needed. Definitely plug off the hole! The higher the vacuum the less work the motor needs to do. It won't get hot because of it.

5/31/18       #9: Blower Vac Setup ...
Jon Member

Thanks for all the input. There is no filter just a cap with holes in it. This thing sounds like a train. So I think we should measure the temp open for an hour and capped for an hour. Sound like a good approach?

6/1/18       #10: Blower Vac Setup ...
Jim

Website: http://totaalcutcnc.com

Jon,
It is a vacuum relief valve and it is necessary for proper operation of the pump. The motor could overheat due to excessive vacuum if it was not there. Due to it not having a filter on it, it may be full of trash and need to be cleaned and readjusted or simply replaced. I would not run the pump with this blocked off, unless i was prepared to send the pump in for repairs.

6/1/18       #11: Blower Vac Setup ...
Puzzleman Member

You probably need to clean out what came in through the relief valve.
I set up my relief valve in front of the filter so that this problem would not happen. did anyone else set up this way also?

6/4/18       #12: Blower Vac Setup ...
cabinetmaker

I am running a 40hp Travinni and it is filtered before the pump. Never thought I would need it until our spoil board get thin and crap gets on the phenolic bed Make sure it is filtered and the filter cleaned or checked daily.

6/4/18       #13: Blower Vac Setup ...
Larry

Jim, I'm not understanding what would make a motor run hot at full vacuum. The higher the vacuum the less work a motor would be doing. Basically spinning the impeller with no air resistance. What am I missing?

6/4/18       #14: Blower Vac Setup ...
Dropout Member

Needs air flow to cool it. No air flow no cooling.

6/4/18       #15: Blower Vac Setup ...
JM

Larry,
I think you have it backwards. As vacuum increases, the motor is working harder to pull the air.

Think of it like sucking air through a straw and slowly pinching it off. At max vacuum, no air is flowing and your lungs are working very hard.

6/4/18       #16: Blower Vac Setup ...
Larry

Drop out, the motor cooling is totally separate from the vacuum, it has its own cooling system.
JM, still beg to differ. At full vacuum the impeller is spinning in almost no air. So it isn't moving air just spinning freely. There isn't even any air to heat from friction. I don't buy the sucking on a straw comparison. We could do a test. Measure the amps being pulled with the pump blanked off. Then with the suction port wide open. Would you consider that a valid test? A motor typically draws about 1/2 of its full load amps when spinning freely. This will be my tomorrows project. Will you do the same? I have a good clamp on amp meter so I can measure each leg separately. I also have a 40hp Quincy pump. The pump in the picture looks like a regenerative blower. I've got one of those also but harder to get a good test on. See you tomorrow.

6/5/18       #17: Blower Vac Setup ...
JM

We have a 20HP regenerative blower in our shop. We have had a meter on it in the past for troubleshooting other issues and I can tell you with certainty, the current draw is higher when there is a sheet of melamine on our table vs no sheet of melamine.

With no sheet, it basically just a big fan pulling air from the intake and pushing it out the exhaust. When a sheet is on the table, its more difficult to move the air (like pinching a straw) which causes the motor to work harder.

We do not reach absolute vacuum, where we start to lose things like air friction. We simply reach maximum vacuum.....maximum the pump is capable of, Then we need releif valves so we can keep the pump running at its maximum for prolonged/continuous use.

Look forward to seeing the results of your current draw.

6/5/18       #18: Blower Vac Setup ...
Larry

Testing 123: Quincy 40hp screw, 208V, When no air is being pulled, valve off at router, each leg measured 58A.
When we opened the valve for free air flow, 98A each leg. I checked the system and there is no relief valve. Pulls 26 inches blanked off. So when the rotor is spinning and just moving oil it takes a bit more than half the power than when free air is allowed in.

I looked up regenerative blowers. They do pull more power when at maximum vacuum levels. They also need to bleed off some vacuum to maintain air flow. So they do need a relief valve. But they are not very good to use on a CNC because of the low level of vacuum they can pull. In the USA the standard measurement is in "Hg. About 29"Hg at complete vacuum. My pump pulls a max. of 26" at the router and 20-22" when running a nest.

My regen blower is in storage so I can't give it a try. Regen blowers & screws are opposite in the way they consume power. So if your regen is idling free air most of the time it will cost you less electricity if you take as much time to get the next sheet on the router as what it takes to run it. But you will be paying more for each cu. ft. of air pulled and can't reach but about half the working level that a screw will pull. Regens are a lot cheaper to buy, so that's another trade off.

I had a 20hp Becker rotary vane on one of my machines. Relatively low cost, pulled good vacuum level when there was minimal leakage. But you need two of them for typical nesting. Maintenance costs are low, will run about 5,000 hours before vanes need to be replaced. While you've got it apart put bearings in it also.
My screw has 18,000+ hours on the meter, has never been apart other than oil & filter changes. But those are pretty expensive, every 6,000 hours. Pick you poison, no perfect solution.

6/5/18       #19: Blower Vac Setup ...
JM

I guess we were both right, just talking different vacuum types.

Regardless, this is all very good info.

6/6/18       #20: Blower Vac Setup ...
Larry

I've made my share of screw-ups. I had the vacuum pump wired 208 V. Motors pull a lot more amps at startup than running. I should have had it wired 480 like the router. You can hear the wires rattle in the conduit at start up now. Since one leg of a 208V 3 phase is 120 V, leg to ground, it isn't very likely to kill you if you accidentally come in contact. But a 480 circuit is 277 each leg, lethal! All of my European equipment is 380/400V, also lethal. Work safe.

6/22/18       #21: Blower Vac Setup ...
Jon Member

Ok so here's the follow-up in our world. First thanks for all the spirited input, advise and direction! We covered the bypass valve and it would have run until its cooked. It is currently set wide open because of the type of system it is and the way the maintenance department wants us to run. All of these decisions were made because of AMP load on the current building. Lucky us were moving where this restriction is no longer there. I found a really great explanation on the two types of pumps. This information was valuable and is provided to you. So I have one further question of this group. We are going to the Dekker 40hp pump and want to plumb it outside the building for heat/noise reasons. How far can I locate this pump from the machine with little to no effect on good vacuum? Once again thanks for all the sharing on this and I know I'm better equipped for it.
Thanks

Click the link below to download the file included with this post.

Vacuum_Explaination.pdf

6/22/18       #22: Blower Vac Setup ...
Larry

I looked up 40hp Decker pumps. Looks like it will have a 4" inlet on a liquid ring. We also put our Quincy screw outside, in an insulated shed, to avoid the heat and noise. In the summer it vents outside VIA a shuttered fan on a thermostat. In the winter we vent it into the shop with a fan that circulates shop air through the shed. When the pump is off the shed remains sort of warm so the oil in the pump remains fluid enough. There is an electric heater that will kick on if it becomes too cool due to our miserable cold winters. We plumbed our pump with 4" PVC plumbing DWV pipe. As with all air moving systems, try to keep the # of elbows to a minimum. Even at peak volume there isn't a huge amount of air moving. (500cfm)

6/22/18       #23: Blower Vac Setup ...
Jon Member

Larry how far away is the pump?

10/9/22       #24: Blower Vac Setup ...
kenwang

Website: http://dereike.com

It could be a pressure relief valve


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