The second problem I have had is with this plastic diaphragm itself developing a leak. I have had to replace two of these diaphragms because of leaks caused by screwing the pressure up to 150 pounds for the flash evap. This diaphragm has pressurized oil on the side to the pump housing and a spring against it on the outside where the pressure switsh is. The spring presses in and the oil pressure presses out, the diaphragm moves out/in enough to click the microswitch and turn the pump off/on. The problem is that to get 150 pounds the spring has to be realy preloaded by the adjuster screw, this puts a lot of pressure on the diaphragm material and it eventually gets cut or torn around the edge of the hole that it is mounted in.
This picture is of the diaphragm mounted in the pump housing.
pump_pressure_diaphragm_location__3_.JPG (24 Kb, 115 downloads)
This picture is of the diaphragm removed from the pump.
diaphragm_1__.JPG (20 Kb, 88 downloads)
This picture shows the type of damage being done to the diaphragm.
diaphragm_cut_3_.JPG (20 Kb, 88 downloads)
I like the shurflo pump for continuous unatended filtering so I have changed the manner of how the pressure cutoff switch is handled on my filter cart. Shurflo sells these same pumps without the cutoff switch, they simply put a blockoff plate over the diaphragm, I did the same thing.
This picture is of my home made 1/4 inch thick ABS plastic blockoff plate.
block-off_plate_3_.JPG (39 Kb, 105 downloads)
To avoid this problem I gave my evaporator a pressure tank after the pump- the pump should pressurise the tnak which should minimise hysterisis. I say 'should' because I got insanely busy a couple of months ago after building the thing, and haven't fired it up yet (it's not in a grease-friendly zone right now)
HMMM -- An accumulator tank. - OK - what is this tank using as the cushion, could be air without a bladder, or air with a bladder or hydraulic systems use a spring against a piston.
This problem is mostly associated with my continuous filter tank setup rather than the evaporator. I am only running prefiltered oil through the evaporator so should not have too big of a problem.
-BUT- I did have a problem with plugging the small hydraulic filter just before the orifice in the evaporator. I did not bother to clean this cintered brass filter last fall before putting everything away for the winter. It plugged during the second barrel of oil this spring. When I opened the filter to clean it I found it almost full of jelly, not dirt, looked like patrolium jelly. I was using the original very fine filter element that came with the filter, 10 micron from memory. The human eye is supposed to only see down to about 40 micron so a 10 micron cintered brass filter looks just the same as pollished brass, no porrosity is visable. I still have not gotten this element to flow freely even after weeks of solvent soaks and high pressure air blowouts. I had ordered a spare 90 nicron element when I ordered the filter origanally, you can see the porosity on this element, The 90 micron element has done several barrels of oil now with no problem but I clean it after every barrel (now I do). so far I have not seen any sign of plugging and it still passes air when blown out and it still looks like new.
Since there is no longer a pressure switch on my filter cart circulation pump I have added an industrial strength pressure switch on the pressure side of my filters. This pressure cutoff switch is the type used to turn air compressors on/off. This switch is rated to control up to a 5 HP motor at 110 volts AC so it should last forever on the tiny 6 amp 12 volt shurflo pump. If not, I am working on a setup using the diaphragm and mechanical portion of these air compressor switches as the analog pressure sensing element in a closed-loop PWM electronic pressure control (get these pressure switches for $5.00 each from my local salvage yard, never new so many air compressers got scrapped).
-- Update about the air compressor switch - 6-18-06 -- Works but with a restriction -- The shurflo pump can make pressure faster than this big switch can react if the pump is being powered with the full 12 volts. I heard the pump start cycling so went to check it out, glad I did because one of the water filter housings was leaking a tiny stream of oil through the housing gasket. From prior testing I know this happens at around 140 pounds pressure. I had set the pressure switch to click off at 120 pounds but the pump pulsations cause the pressure to reach around 150 pounds before the switch could shut it down. This happened no matter how I adjusted the spring adjuster on the pressure switch. This is only a problem when powering the pump with 12 volts, I normaly power it with the battery charger set to 6 volts anyway, at 6 volts it makes pressure slow enough that the switch works fine and the oil is still circulated at an aceptable rate. I normaly run the pump on 6 volts as it moves almost as much oil on 6 as it does on 12 due to the thickness of oil and on 6 volts the pumps electric motor stays a lot cooler, never had a problem with pressure on 6 volts either.
This picture is of my filtering cart setup. --
The Shurflo pump is connected to the bottom of the vertical yellow hose, the pressure switch can be seen just above the top end of the yellow hose.
filter_tank_-_wide_1_.JPG (34 Kb, 146 downloads)
This picture is a closer view of the heavy duty pressure switch on the filter cart.
tank_switch_cu_2_.JPG (30 Kb, 96 downloads)
Ok -- Now back to the flash evap - Because of all this pump hassle I have been researching other pumps to use. I am seriously liking the oil pumps used to pump fuel oil through home oil burners. These pumps operate well within the flow rate and pressure range that fits about any size flash unit anyone might build and most have adjustable pressure regulators build right in, and they are silent. These are true gear type hydraulic pumps but not of the normal design, they are a bit like gearotor pumps but have much smaller lobes on the gears and the oil moves through them a bit differantly. They are not designed to operate at extremely high pressures so they do not need the very tight seals of a pump that might see 5-6000 pounds of pressure. They have only one small seal on the shaft so there is minimal drag on the shaft, this allows them to be turned with even small electric motors. The only problem is that there are over 600 different types of these pumps (so the Suntec website says) I am still trying to decipher all the part numbers and internal mechanisms to find the correct one to use. The one I am testing came from a burner on a steam cleaner, these seem to be redaly available on ebay for under about $30.00, unfortunatly they have to be modified before they will get even close to working. In the oil burners they want the oil to start/stop flowing instantly so the pumps have all sorts of internal flow sensing devices that bypass the output oil until the motor is within a couple hundred RPM.s of max etc. This is not how I want the pump to work.
I have made up a test pump driven with a small surplus 12 volt DC motor that originally powered a small childs electric ride-around-the-yard electric car. This motor draws about 6 amps at 12 volts and turns around 1000 RPM at 12 volts, way more than needed to make 150 pounds pressure at my flash units 5 G/H flow rate. I have figured out how to defeat the primary flow sensor in these pumps but the pressure regulator bypass piston is designed to leak oil until it sees a huge rise in pressure from the primary flow sensing device, I eliminated the primary device so to get the pump to put out pressure I have to smack it with a hammer or wrench to get the pressure piston to shift into the pressure regulating mode, not quite there yet with this pump, it sure works like a dream once it is working though.
This is an overview picture of the suntec pump I am testing. For size comparison, the base of the pump assembly is a short piece of 4 inch wide channel.
Grabbed_Frame_2.JPG (32 Kb, 140 downloads)
End view of the pump.
Grabbed_Frame_5.JPG (30 Kb, 99 downloads)
Side view of pump. The top hose is input oil, the bottom hose is the output for bypass return oil from the internal pressure regulator. The high pressure oil to the evap unit comes out of the 1/8 inch pipe nipple.
Grabbed_Frame_16.JPG (30 Kb, 100 downloads)
Now - condensing the flashed off oil/water vapor --
This is going to be a bit tough to describe. I will start with pictures.
This picture shows everything in place. I am pushing the vapors out of the flash tank with a small crossflow of air, the vapor moves out the tank through the horizontal pipe, on the top-right side of the flash tank, until it reaches the "T", The vapors are hot so they want to rise, they rise up into the 5 gallon tank until they hit the inside top of the tank where they start to cool due to contacting the cooler tank surface. The tank is cooled by the outside ambiant air over it's outside surface.
This picture is an overview showing the current prototype flash evap setup.
Grabbed_Frame_1.JPG (35 Kb, 176 downloads)
This is a closer view of the vapor outlet pipe and the condensing tank.
Grabbed_Frame_3.JPG (28 Kb, 132 downloads)
Now this is where it is going to get a bit tough to explain.
This picture is of the vapor output pipe but with the condensing tank removed.
Grabbed_Frame_12.JPG (32 Kb, 136 downloads)
The picture above shows a 1/2 inch pipe inside of a 1 inch pipe. This is used to seperate the oil vapor from the higher energy (hotter) water vapor.
The picture below is of the lower end of the vapor outlet pipe below the condensing bell. It has a 1 inch-to-1/2 inch pipe reducing bell on the bottom end. I re-tapped the inside of the bell so that the 1/2 inch internal pipe would screw into it from the inside. This bottom bell adapter has two 1/8 inch holes driller through its sides, these allows the condensed oil to run out into the condensed oil collection can.
The indentation in the oil directly below the pipe is caused by the slightly pressurizing vapor crossflow air exiting the unit, this is also where the water steam exits. The water steam does not condense, it flows out of the lower end of the 1/2 inch pipe as hot steam vapor and it rises out of the collection can and floats off into the surrounding air.
Seperation process -- The oil vapor condenses much easier than the lighter water steam, once the combined oil/water vapor hits the inside top of the tank the oil sticks to the inside of the tank and condenses, runs down the inside surface of the tank, down through the "T" (where it cools the incoming vapors somewhat, sort of a crude wierd reflux columb, sorta), the oil then runs down between the inside of the outer 1 inch pipe but outside of the inner 1/2 inch pipe. The oil outlet holes in the bottom reducer bell are small so this pretty much acts as an airlock to let condensed oil out but does not let outside air in.
The upper end of the 1/2 inch pipe sticks about half way up inside of the condensing tank. Because of this not much oil finds it's way into this center pipe but the entire inside area of the condensing tank is full of water steam that is being pushed in from the flash tank, it has to go someplace so it travels down the center of the center 1/2 inch pipe and exits out the bottom.
Grabbed_Frame_9.JPG (26 Kb, 131 downloads)
This picture is a bit wider view of the lower condensing pipe.
Grabbed_Frame_15.JPG (31 Kb, 109 downloads)
There is water vapor exiting ths steam outlet constantly, it increases/decreases by the second. I placed a mirror under the steam outlet and it fogged almost instantly even when no steam was visable to the eye, within a few seconds tiny water droplets were forming.
I will eventually add a 1/2 inch elbow onto the water vapor outlet and pipe it sideways away from the flash tank far enough so that I can place a second condensing tank next to the existing one for the water steam, hopefully this second tank will cool the water steam enough for it to condense, I would like to measure just how much water is being driven off the oil.
I dewatered 25 gallons of oil through the unit to get the amount of oil that is shown in the collection can, it measured to be 10 fluid ounces of condensed oil from the 25 gallons of dried oil, more than I expected but it sure explaines why my windshield was oily when I was letting all the combined oil/water steam float off into the air.
Source of vapor removing crossflow air -- I have been using compressed air for this up until now, it works but not reliably. The crossflow air realy has no pressure , maybe 1/10 pound, not much. I have been using a single stage air regulator to produce this from a standard air compressor, this does not work well. When I adjust the regulator to get a working airflow when the air compressor has high pressure the airflow stops when the compressor tank pressure drops a few pounds, if I set the airflow when the compressor tank pressure is low then I have way too much airflow when the compressor tank pressure is high.
I have just received a nice surplus tiny cast metal 12 volt DC blower. It seems to move more than enough air, I will try this out instead of the compressed air when dewatering oil the next time.
Grabbed_Frame_3.JPG (15 Kb, 103 downloads)
I have been enjoying this thread imensly. You will have to forgive me if I ask anything that has allready been adressed but there is ALOT of reading material in here. The 1st thing I wanted to mention is that I noticed in one part of the thread that you were looking for somthing that could creat some kind of a reliable mist and if you are still looking then I think I have the solution. Among other things I happen to be a painter. We use a spray gun and the tips we use come in many sizes (depending on the volume of paint you want to spray) They are about 30 bucks a piece and require a houseing also. the houseing screws on the end of the spray gun but caneasily be made to screw onto about anything w the riht thread size. I have many spray tips that I dont use anymore as wall as some houseings I believe, I would be more than happy to send you some if you think it may help. These tips are made to take several hindred pounds of pressure, also they are reversable, meaning that if they get cloged then they can be turned around to blow out the particulare that is cloging the tip. It atomizes the paint or wvo into tiny particles similar to that of an air brush but in much greater volume.
This brings me to another question. I was thinking of trying to create a similar contraption but instead of useing the kind uf pump you have I would use an extra airless paint sprayer I have. These machines are upright and have a wand that is submerged in the paint, it takes the paint (wvo through a series of filters, then through the line to the paint gun or what ever you have set up. On these rigs there is a pressure dial that is madde to adjust your pressure to a very particular pressure and doesnt vary from that pressure even a tiny bit. These pumps are called airless sprayers which means exactly what it implies. Through a piston it sucks up the product and pressurizes it through the lines w out any air (that is how it maintains perfect pressure). It seems like it may also be ideal since it may make the wvo a little less flamable under heat. I was thinking that it may be a good starting point for me to use one of these rigs and have it piped through a heater like you use w a thermostat on it but instead of useing a paint gun have it hooked to thermostat activated release. Does this seem like it has any merit? Also one of these pump units is ideal fore transfering and filtering wvo under pressure. The only modifacation would be removing the gun.
Here is a picture of what my rig looks like http://www.gritblasting.co.za/395.jpg
Here is a picture of the tip and houseing used
Again if I have covered a topic you hae allready adressed I am sory.
Thanks for the usefull info and keep up the good work
You can easily find used airless paint sprayers in the classifieds as well as the flea market for fairly cheap. New they start at about a grand but a good small used rebuilt one can be as little as 100 bucks. They maintain perfect constant perfect constant pressure.