Anyone who has ever had the misfortune of a blown head gasket knows that the old saying “oil and water don’t mix” is only partially true. When what’s coming out of the drain plug looks like a mocha latte, you know you’re about to have a very bad day.
[SpankRanch Garage] recently found himself in such a situation, and the result was this clever vacuum dehydrator, which he used to clean a huge amount of contaminated hydraulic fluid from some heavy equipment. The machine is made from a retired gas cylinder welded to a steel frame with the neck pointing down. He added a fill port to the bottom (now top) of the tank; as an aside, we had no idea the steel on those tanks was so thick. The side of the tank was drilled and threaded for things like pressure and temperature gauges as well as sight glasses to monitor the process and most importantly, a fitting for a vacuum pump. Some valves and a filter were added to the outlet, and a band heater was wrapped around the tank.
To process the contaminated oil, [Spank] glugged a bucket of forbidden milkshake into the chamber and pulled a vacuum. The low pressure lets the relatively gentle heat boil off the water without cooking the oil too badly. It took him a couple of hours to treat a 10-gallon batch, but the results were pretty stark. The treated oil looked far better than the starting material, and while it still may have some water in it, it’s probably just fine for excavator use now. The downside is that the vacuum pump oil gets contaminated with water vapor, but that’s far easier and cheaper to replace that a couple hundred gallons of hydraulic oil.
Never doubt the hacking abilities of farmers. Getting things done with what’s on hand is a big part of farm life, be it building a mower from scrap or tapping the power of the wind.
Very neat
Well, every pharmacist knows oil and water do mix, as long as you use an emulsifier when making creams.
And every cook knows oil and water mix, as long as you use egg yolks to make mayonnaise.
And after you mentioned the egg thing, now I can’t help but view water contaminated hydraulic or gear oil as forbidden hollandaise sauce.
Synthetic Mayo
Coincidentally, I just spent yesterday reading abut emulsions and how to create them with and without added emulsifiers. Now I’m curious whether the hydraulic pump might have had an emulsifying effect like a high-shear mixer does, and how stable the emulsion in the video was – how long would he have had to wait for it to separate on its own?
You don’t need chemical emulsifiers (egg yolk or otherwise) if the droplet size/density difference is small enough in a viscous fluid. Hydraulic systems become a homogenizer (eg. homogenized milk) pretty quickly with enough pressure and a few valves/orifices so there are plenty of companies selling you the same dewatering idea at whopping prices.
Could you not do this while the excavator is in operation?
Given enough time and money spent on the equipment, anything is possible. This hack was based on saving money, though.
If your low side pressure is low enough for that in operation, you may have a problem. You might be able to pump down, close it off, circulate the fluid, and pump again, or something like that?
I would expect to run this iteratively to clean the hydraulic fluid again. Kudos for the innovative approach.
How does so much water get into the hydraulic fluid in the first place?
The system isn’t 100% sealed, due to the fluid heating/cooling makes it subtly change volume.
Also hydraulic cylinder seals aren’t 100% sealing, especially on worn ones.
The seals around the pistons wear out over time and they aren’t air tight to begin with. I worked in a hydraulic/machine shop for a few months during covid shutdowns, and as precise as we were for a manual machine shop, there was a surprising amount of wiggle room when it came to the big pistons. Manifolds and pivots for excavators were often considered “wet components” that just leaked a little. They were always a little shiny with oil.
Plus there’s a lot of field maintenance that gets done, tanks get topped off, leaks, etc. I worked a boat once that had drip pans under some of its hydraulic pumps that we poured back into the reservoir every morning before startup. It was sketchy to say the least.
The only place I’ve seen near perfect hydraulic systems were in aircraft.
Nearly all hydraulic systems ‘breathe’ atmospheric air, to replace the oil that is being moved from the tank (reservoir) into e.g. a piston. The air is draw in through a filter to keep contaminants to a minimum. To minimize water vapor getting into the system, a breather filter with silica gel is often used. Btw. your hard drives also have these.
For systems that must be fully sealed for various reasons, a balloon can be placed in the reservoir to accommodate for the varying fluid level.
Also what the other guys said about seals, wear and tear.
really needs a moisture trap on the vacuum line before his vacuum pump
A surface condenser between the evaporator and the vacuum pump would be even better. This will drop out the moisture before it gets to your vacuum pump. Added benefit is it will help lower the vacuum as well. This is used in industrial evaporators to evaporate black liquor (pulp & paper) and caustic soda (chlor-alkali industry).
I am under the impression that when a gas ballast is used properly and the oily rotary vane pump is at a good warm temperature, the water ought to be making it out on its own. But if not, just use a different kind of pump, such as a multistage air venturi. If the fluid you’re taking the water out of is warm, you should be able to get the water out no problem with two stages of ~100psig, a bit like with home-grade refrigerant vacuum kits. Just takes a very inefficient amount of airflow, but who cares, you’re not doing this every day. And you can always use a dessicant or (if this is for some reason easier) a cold trap, to reduce the flow rate you need to pump out with either method.
Would a centrifuge be able to remove part of the water to reduce the load on your vacuum dryer?
he notes in the video that hydraulic oil evidently has emulsifiers that keep it from naturally settling out even after six months of sitting undisturbed; judging by that, I’m guessing a centrifugal separator would be less effective than you’re hoping. it would also have much smaller batch sizes in the same equipment-labor footprint and run far slower per-gallon of batch. this vacuum distiller will process 9 gallons in about 2-3 hours of minimal oversight, with fewer high-energy moving parts.
Still tired; A paint pot in a #10 tub of ice could help you trap the moisture and save the vacuum pump.
We use an oleophobic/ hydrophilic+ hydrioohobic/oleophilic T split filter on our injection molders. Mixed fluid goes in one port, Water comes out the o/H side, and oil come out the h/O side. Best part, the membranes are user serviceable. The o/H gets soapy water and water rinsed, the h/O side gets an alcohol rinse, air dry, then flushed with fresh hydraulic flud before reassembly.
I wonder if he could clean it further with an oil-water centrifugal separator. You could probably find a Navy or Coast Guard surplus one at a DLA Disposition Services auction (used to be called DRMO/DRMS/DISPO). Ships used them in engine rooms to pull oil out of bilge water before discharging it overboard.
No idea if it would worth the expenditure on electricity to run it though.
he notes in the video that hydraulic oil evidently has emulsifiers that keep it from naturally settling out even after six months of sitting undisturbed; judging by that, I’m guessing a centrifugal separator would be less effective than you’re hoping. it would also have much smaller batch sizes in the same equipment-labor footprint and run far slower per-gallon of batch. this vacuum distiller will process 9 gallons in about 2-3 hours of minimal oversight, with fewer high-energy moving parts.