The Super Sucker
Submitted by Dana Linscott
I find that water well pressure tanks (sometimes referred to as captive air pressure tanks) make an excellent WVO collection tank, mainly because they can often be obtained for free (or scrap value) from plumbers and domestic well drillers/installers in areas not served by a municipal water system. The ones made of steel are also lighter than most of the alternatives yet capable of holding a very high vacuum. Be aware that some fiberglass pressure tanks have been known to delaminate and implode under vacuum. An imploding tank is not dangerous, but it IS messy. Nearly any other steel pressure tank works, but thin wall water heaters have been known to crush under vacuum as do ordinary steel or plastic storage drums.
The pressure tank is used to contain a high vacuum, which "sucks" WVO into the tank. You can create a vacuum in several ways; I use a conventional refrigerator compressor. It lets me draw the vacuum at "home" where I have 120vac (house current) available. A refrigerator compressor can create a vacuum of around 27 "inches" (of Hg) in the tank and transport that vacuum to the WVO pickup point. A 30-gallon tank with a 27"Hg vacuum in it can draw in 10 gallons very quickly with a large enough hose (I like 1.5" "spa" or suction hose). Sucking in the first 10 gallons reduces the vacuum to around 22"Hg. With less vacuum, it takes about twice as long to suck in the next 10 gallons. The principle is, the lower the vacuum, the slower the flow. Given enough time and low enough viscosity VO, a 30-gallon tank can eventually fill to about 95%. There are ways to create a vacuum while you drive or are collecting WVO, like using the vacuum line on a gas engine, or using a 12VDC vacuum pump.
The basic "WVO sucker" uses a refrigerator compressor, like the water well pressure tank, you can usually acquire one for free or scrap value. Please purchase your compressor from a business that collects and recycles the refrigerant. The refrigerant is a very destructive gas to release into the atmosphere. It and may cause lung damage if you breathe it while trying to remove a compressor from a refrigerator yourself. You can also find Compressors in freezers, air conditioners, and dehumidifiers. So they are plentiful. The easiest way to find one is to call your local garbage collection service or recycling center and ask where you can dispose of an air conditioner or refrigerator. New refrigeration compressors are also sold by some appliance repair shops and occasionally on eBay. However, of course, a new compressor costs much more than a recycled one.
Once you find a source of recycled compressors, it would be a good idea to buy two. Used compressors may last for years, but about 10% of them seize up within a month. It is nice to have a spare handy if this happens. You can usually get two for the price of one if you haggle just a little. Select two that have several inches of the inlet and outlet tubing still attached. The small plastic box on the left side of the compressor with the wiring is also important; it contains circuitry to start the pump. Also, make sure that the base still has all four little rubber feet on it. These are vibration isolators, and without them, the compressor makes much more noise. They tend to drop out during transport. So be careful that you do not lose them on the trip home.
Usually, there should be a short power cord attached. Select two which have at least a few inches of this cord remaining. It makes connecting it to a wall plug much more manageable. You can also probably get a cord with the power plug thrown in for free since they are already on the refrigerator.
These compressors are very basic with an electric motor and either very simple (scroll or rotary) compressor inside the sealed outer shell. Typically, you find several small tubes exiting the housing. Only two should be open. One of these is the inlet and the other the outlet.
First, you want to splice in the cord w/power plug to the three wires that are sticking out of the plastic box on the compressor. If you feel uncomfortable wiring the compressor, ask an electrician or refrigerator repairman to help you. If this is not an option, use "wire nuts” to connect the wires. Then tightly wrap the connections with several layers of electrical tape to make a lumpy but secure connection.
Once you have a good wiring connection, plug in the power plug to a wall outlet and see if the compressor motor starts up. If it just wiggles around and then "clicks" and stops, unplug it and give it a few minutes to reset itself. If it has been a long time since the compressor ran last, it may be a bit hard to start. It may take four or five times before it works. Sometimes it gets a little closer to running smoothly with each attempt. If this does not work, warm the entire compressor to around 70°F and trying the procedure again. If you cannot get it to work, you can usually return or trade back a seized compressor for another one.
Once you have a smooth-running compressor, make a wooden base for it so you can keep it from "walking" around as it runs. To do this use a square of 3/4" to 2" thick board that is at least 2" wider and longer than the base of the compressor. Center the compressor on the board. Place a washer on top of each rubber foot and then secure the compressor to the base by running a wood screw through each of those washers through the foot and into the wood below. The head of the screw should be a little larger than the hole in the washers, and the screw should extend into the wood by at least 5/8". If possible, snug it up just enough so the washer cannot move around and rattle.
You may notice that one of the steel tubes sticking out of the compressor is spitting out little droplets of oil when running. Unless you want to add a few drops of light machine oil to the compressor every few hours of operations, add a "re-oiler." Make one by taking a 1" section of small diameter (usually 1/4" or 5/16"id) rubber hose and sliding it over the end of the pipe spitting out oil. Now take a longer section (usually less than a foot) of flexible clear hose with an i.d. that allows it to slip tightly over the 1" section already on the pipe. Use a few heavy zip ties, or a small hose clamp make that connection leak free. Find a few feet of heavy wire (like coat hanger wire) and drill two small (1/8") holes 1" apart in the wood base near the spot under the outlet pipe. Bend the wire in two and stick the free ends in the two holes. Then secure the 1' section of flexible hose to this wire support with a few zip ties, so it points straight up. The clear tubing should collect most of the oil escaping the compressor while it is running and allow it to drain back into the compressor while it is idle. If no oil spits out of this pipe, add a few drops of light machine oil until you can notice that it is spraying on the inside of the clear oil catcher tube while the compressor is running.
Finally, we turn to the business end of the vacuum compressor, the remaining pipe sticking out of the compressor. DO NOT place your finger on the end of this pipe to see if there is a vacuum. If there is a vacuum, it can take a nice little "core sample" of flesh from your finger very quickly. If air is exiting the compressor, you can safely assume it is also being sucked in.
To connect the vacuum compressor to the "WVO sucker" tank, use a 3" section of rubber hose that tightly fits over the end of the inlet pipe on the compressor. This hose is the "connector" and works surprisingly well for connecting a longer section of small diameter clear plastic poly tubing. Clear plastic tubing is usually available for under a dime a foot and can connect a tank that is up to 100 feet away quickly and inexpensively. Make a second one for the compressor outlet so you can also pressurize the tank.
There are many ways to connect your vacuum pump to the vacuum tank. If you use a water well tank, remove the guts from the Shrader valve on top using a tire valve tool. Then use short sections of rubber hose to add a small valve (either ball valve or needle valve) to fit onto the tube that is left when you "gut" the Shrader valve. Secure the adapter with hose clamps and make another slip-on adapter the same way for the poly tube vacuum line. If your tank does not have a Schrader valve, you can drill a hole in the tank top and secure a small pipe stub in that hole with epoxy like JB weld or by having it brazed in.
Now for the sucker tank pickup line, you need to purchase a hose that can take 27" Hg of vacuum without collapsing. The hose may be the most expensive part of your WVO sucker. I recommend using a 1" i.d. hose, or larger if you have a very large tank. There are several types of vacuum hose most of which have an inner and outer semi-flexible liner with a wire spiral between the layers of plastic. Buy enough suction hose to reach to your WVO collection containers from your tank.
Once you decide on a size of suction hose, find a ball valve that fits it. Pay attention to the size of the hole through the ball valve. If it is significantly smaller than the inside of the hose, it can act as a restriction, slowing you down. Now find a reinforced clear hose that fits the valve and adds 4 to 5' of this to the ball valve side opposite the suction hose. The extension is the "business end" of the sucker that slides into the WVO and keeps the ball valve out of the oil. I prefer having this hose clear enough that I can see any air or water that is passing through to help determine if the end is too high or low in the collection drum/tank.
All that is left to do now is to create a place for the WVO to be sucked in and pushed out of the tank. The best way to do this is to either have a 1" to 2" (I like to use 1.5") pipe welded in so its interior opening is at the lowest point in the tank. Some examples:
Often an exhaust shop can do this for you AND supply the pipe that fits your suction hose. If it is a little too large or too small to fit tightly, they also have the equipment to stretch the end larger or smaller to fit tightly. Of course, you also need some large hose clamps to secure your suction and clear line to the tank and ball valve.
Almost ready to go get WVO now.
Only one more thing to do!
To create a vacuum in the tank simply start the vacuum compressor, open the valve, and slip the vacuum line onto the open valve end. The refrigerator compressor may take a long time to create a full vacuum, and if you have a large tank may even shut off to cool down a few times. When no more air exits the compressor outlet tube, it is indicating a full vacuum is present in the tank.
With a fully evacuated tank, you can now take it to your WVO collections tanks/drums and unroll the suction hose. Then slip the clear hose end about 6" below the surface of the WVO and SLOWLY open the ball valve all the way. If you open it too quickly, it tends to sink into the WVO as it gets suddenly heavier. By collecting only, the topmost oil, you avoid any free water or food chunks that may have settled to the bottom. Eventually, you may have to make a "crud run" to suck the crap from the bottom of your collection tanks/drums. You may be able to dump the crud at a compost or RV (sewer) drain station for a small fee.
Finally, when you get back home with a full tank of WVO, release any remaining vacuum by opening the small ball valve in the top of the tank. Then connect to the tank's suction line to your holding tank and hook up the pressure line from the compressor outlet. Open the large ball valve in the suction hose and turn on the compressor. As the pressure builds up in the tank, the WVO flows out faster and faster. Make sure to secure the suction hose end, since after the WVO drains, the air pressure behind it tends to make the hose fly around spraying the last of the WVO everywhere.
Sample Collection Tanks