Success!

I've read about it, but now I've seen it, so I can believe it!

Yesterday I changed two low pressure, slide on, clamp on hydraulic hoses at the bottom of a 5 gal reservoir. I had already, in the past, drained the reservoir to change some other bigger hoses and service the filter, and I didn't want to do it again.

I found the hose on my little old shop vac fit the filler hole on the reservoir quite well. I got a neighbor/farmer/friend to come operate the vacuum. He was skeptical. Now he's a believer too! I undid the bottom of the hoses first, and hardly got a drop! Apparently getting the vacuum level correct is the challenge, as we got more oil in the vacuum hose and tank, than we did on the ground. (I did this outside, just in case)

maybe partly safe with hyd oil. but I would not do it for safety reasons as fumes may be ignitable. about a year ago paper had article about man and his brother in law being killed and house destroyed when they tried to use shop vac to empty gas tank to change fuel pump. source of ignition was sparks from brushes min vac motor.

Be very careful. The use of a shop vac type vacuum and being very sure the liquid being controlled is not low in kindling (ignition temperature). Most oils with high viscosity are rather stable (some are very combustible). Turning the process into an experimental turbo jet Hoover has been done, and was not good. A vacuum (the suction, not the device) can cause the gassing out of volatilizes that migrated into the heavier oil to gas out. You were safe with new oil and a shop vac.
I post this response to inform others to be cautious in the adoption of the technology. Jim

It does work good. Did that a lot at the dealer I used to work for. A lot of time and cost to drain 100 gallons, sometimes much more, out of an excavator or big dozer, especially if you can't reuse the oil. Put a regulated vacuum on the tank, you could remove the hyd pumps even. You'd never think a little vacuum would hold back 100 gallons of oil, even after removing a 4 inch suction line from the bottom of the tank.

I do that on my Kubota, it's a hydrostatic transmission machine, I change the hydraulic filter that way. I saw the same method used in the factory to change hydraulic filters on machines, and they were very safety minded. Putting a vac on a fuel tank is a whole different issue.....

They make a tool (fitting) for that very thing.

You adapt it to your reservoir apply air pressure
Ad it creates a vacuum in the tank.
Tom

Must be sort of like the machine which uses shop air pressure, to create a vacuum, to evacuate air conditioning.

A venturi based evacuator is static free. Jim
one brand

That's kinda a different animal.
Used for venting a tank or something.

The one I have and lost was just a " T " type fitting that connected to the fill hole on the tank and you supplied air to one end.
As the air rushes pass a venture, and out the other end it creates
A vacuum and holds the liquid in.

Tom

Bob we do this all of the time on the hydraulic tanks on combines. If you have to replace a suction line draining all the oil and refilling it takes lots of time and labor. We made a intermediate bottle/bucket/trap to suck through so you do not get any oil in your vacuum cleaner at all. Just take an empty five gallon bucket that still has the lid. Remove the lid and put two PCV fittings in the lid that match the size of your vacuum cleaner hose. Make one of them go to almost the bottom of the bucket, this is your inlet from the tank. Put the lid back on the bucket. Hook the vacuum cleaner to the short fitting on the bucket. Then take another vacuum hose and hook it to the fitting with the longer tube. This hose you attach to your tank.

The fit to the tank needs to be fairly air tight but not perfect to work. I usually just duct tape the vacuum hose to the tank filler.

PS was doing this one time on a end loader with a 100 gallon hydraulic tank. It had a three inch suction line out the bottom we were replacing. Just about done and the shop vac trip the circuit breaker. Got quite the lap full of hydraulic oil real fast. LOL My pants and underwear sure did not rust for awhile. I slammed my hand over the fitting and another mechanic reset the breaker. We found out later that another mechanic had used the same circuit on large hand grinder. I finished the job had just went around back of the shop and stripped off everything below the waist. Made a kilt out of my work jacket to drive home in. I did not even try to wash the pants as they were so oil soaked.

Never tried it on a hydrualic tank, but many years ago when I worked in an appliance shop we did that to change lower heating elements without draining tank.