Title: Air/water seperator
Description: a/k/a the Franzinator
Franzİ - June 4, 2007 03:48 AM (GMT)
For the record, I didn't name it, somebody on the Hofart forum did years ago.
If you pay attention to nothing else in this posting, pay attention to this!
The Franzinator is a pressure vessel, and will operate in a very nasty environment of high pressure compressed air that is pulsating. If you aren't qualified to weld up a Franzinator with complete confidence DO NOT even attempt to weld one together. Improperly welded, the Franzinator has all the capability to blow apart and kill you! If it doesn't kill you, it will hurt you badly.
If you aren't competent to weld one together, you can still build a Franzinator using pipe fittings and threaded pipe. I'll post how to do that later.
There is one and only one Franzinator seperator, and I know because I developed it from a design given to me by an old timer. Over time, a lot of immitators have tried to duplicate and replicate the Franzinator. They have advanced their product and their concept of how it works. Some have even claimed to have improved upon the Mark I Franzinator. Unfortunately, they haven't been able to wrap their minds around everything that happens in the Mark I, let alone the Mark II water cooled Franzinator+.
My design has stayed the same for 30 years, because it works, and it works well. The specification and sizes are exact for a reason, they are what works. In all of the 30 years, I've only seen 1 person build his differently and get the same results as the Mark I model.
To begin, the Franzinator Mark I and Mark II are seperators. They are NOT dryers. Both devices accomplish the same function, but they do it entirely differently. Nearly all compressed air contains moisture as it leaves the compressor. A lot of energy is put into compressing enough cubic feet of free air into a cubic foot of air compressed to 100 psi, and some of that energy is converted to heat. Anybody who stayed awake during high school physics or meteorology remembers hot air can hold more humidity than cold air. Therein lies the first principal both Mark I and Mark II models work on. Chill the incoming airstream from the compressor as rapidly as possible, and force the compressed hot air to give up it's moisture.
The column of the Franzinator made from 2" pipe does this by forcing the airstream to impact the wall of the column immediately as it enters. The airstream enters the colum traveling in a downward direction, and begins cooling dropping water as it cools by expansion. Then, the airstream has to make a U turn since it can't leave the colum at a lower point than it entered, and must travel to the top of the colum to get to the receiver. In the process of this trip, the airstream expands. That minor expansion allows the airstream to act as a refridgerant gas, further cooling the column's housing.
The cooled airstream in the process of making the U turn drops a percentage of it's moisture by gravity into the sump of the column. Since the hot air stream is coming into the column at the coaxial center of the column, the air headed out has to flow along the walls of the column. This furtner cools the airstream, causing remaining moisture to condense into droplets on the wall.
Since the air is now even cooler, it cannot resorb the water from the inner wall of the column. The water that has condensed is also harder to pick back up because of the surface tension on the layer of water. There is also an unproven possibility that the column gains efficiency as the inner wall wets because of the affinity of water droplets to attach to the layer of water on the inside wall. As water accumulates on the surface, gravity carrys it to the sump.
The outside of the column cools by radiating its heat to the surrounding atmousphere. The trip thru the column takes between 10 and 20°f out of the compressed air stream before it leaves the column, and most of the water. Slower cooling of the airstream will not remove the same volume, even if the temperatures leaving the cooler match those of the Franzinator, because they do not employ the reversal of direction or the shock cooling of the column. Equal cooling by running the airstream thru a device such as an air conditioning coil leaves the compressed air in contact with the water longer, and allows a certain amount of resorption.
The dimensions of the Franzinator are somewhat critical. 2" pipe with a ½" elbow on the inlet provides optimum performance. A total column height of 36 to 38" also provides the greatest amount of seperation possible. Any water remaining in the airstream after leaving the Franzinator seems to condense on the inside of the receiver, and stay there.
A single column Franzinator is about perfect for a 2½ horsepower compressor running full out. Air volumes higher than that produced by 2½ hp need a second column piped paralell with the first.
The Franzinator MUST be plumbed into the system between the compressor and receiver, because that is where the maximum temperature differential can be acheived. For supercriticle situations, a secondary seperator of the same size and configuration can be employed to remove almost all condensate that finds its way out of the receiver.
Why the Franzinator is made from steel pipe- rather than copper tubing?
Very simply, steel and iron pipe radiate heat off to the surrounding atmousphere. Copper is not radiational. Copper can only transferr heat efficiently by conduction. If this design were set up as a water cooled seperator, copper would be more efficient. For an air cooled column, steel is best.
Why does the Mark II Franzinator use a wound copper coil around the steel column and not an all copper column?
Because it was what I had available when I built the Mark II, and because it worked far better than expected. I just wound a coil of 3/8 soft copper around the column with a greater coil density at the center and top than the sump end. My thinking was that maximum cooling was needed in the center where the hottest air enters the column, and minimal cooling was needed at the sump, with medium cooling at the top of the column. The coil is connected to an air conditioner coil via a tank and pump, much in the manner of a TIG torch cooler. Testing demonstrated a single Mark II removed as much volume of water from the airstream that a pair of Mark I columns could. When it works don't mess with it.
The pump picks up cool fluid from the tank and delivers the cool fluid to the top of the column. The cold fluid enters the coil at the top, and is pumped down along the column cooling the steel pipe. The fluid exits the column coil and heads back to the tank by way of an air conditioner coil. As the fluid passes thru the AC coil, heat is removed by air being drawn thru the AC coil by a muffin fan. The fan is installed to suck air thru the fins to provide even airflow across all the cooling tubes. The fluid exits the coil and returns to the tank where the pump delivers it back to the Mark II. The pump and fan run constantly so they can gain cooling on the fluid when the compressor isn't running and delivering heat load to the column. The fluid system is sealed to minimize evaporation loss, and prevent animal consumption of the antifreeze solution. In a climate where no freeze potential exists, water could be used in the Mark II system.
The cooling coil on the Mark II column is wrapped tightly around the column, and soldered to the steel column for maximum thermal transferr. Galvanized pipe was used for the Mark II column to make the soldering easier.
Either the Mark I or Mark II system can be improved by adding autodrain to the columns for a high volume air consumption system. This would be accomplished by adding reverse acting solonoid valves to the drain ports in place of the draincocs, and connecting them via a time delay relay to the compressor motor. The timer would be set for a few seconds to allow the initial low pressure airstream from the compressor to evacuate accumulated condensate from the column's sump. As with any autodrain system on a compressor, the performence of the valves needs to be checked regularly as they all seem to plug up over time.
For a real crappy drawing, click the thumbnail. It was drawn with version 63.77 of LeTurneauCAD.
Franzİ - June 4, 2007 03:53 AM (GMT)
Franzinator Mark 1.02
In an attempt to build a more efficient column, prior to the Mark II, I built the Mark 1.02. Since I had a bunch of 1/16 x 1 flat laying around, I added 6 cooling fins to the Mark 1, running from the top to about 4" from the bottom. I borrowed an infrared thermometer, and did some comparison shell temperature readings on the Mark 1.01 compared to the Mark1. the concept didn't offer a degree of difference in readings between the Mark 1 and the Mark 1.01.
The Mark 1.02 evolved when I got the idea to wrap a shroud around the fins, and add a muffin type fan at the top of the column. By sucking air past the fins, the difference was about 6° of aditional cooling. Since the fan only needed to run when the compressor was running, and for a cooldown period after the compressor stops, I tied it into the compressor motor starter contacts with a timer that accomodated the post cool delay. There was a gain in the amount of water removed from the airstream.
My use patterns didn't really justify the Mark 1.02, somebody came along with cash in his hand and a desire to own it, so I sold it and replaced it with a Mark I.
Franzİ - June 4, 2007 04:04 AM (GMT)
Downline Seperators -
The same basic design of a seperator column works downline in the airstream from the compressor, BUT, it does NOT have the same efficiency. As previously stated, the Franzinator works by rapidly cooling the airstream. Since the downline air temperature is generally the same as room ambient temperature, temperature differential simply isn't present to be employed.
What is still available to work for you in downline seperators is gravity and reversal of flow direction. There is also a very minor gain available from the cooling of the air as it expands in the seperator column, but that is so minimal it's hardly worth discussing.
All that said, I find the Franzinator Mark 1, in a slightly downsized version is still worth installing between the air line and the hose going to paint guns or airtools. I also have one ahead of my Plasma cutter, and it has proven valuable in that use. I've even had a descicant dryer between the Franzinator and the plasma, and determined there wasn't sufficient gain in moisture collection to make the descicant dryer worthwhile.
Even with the column between the compressor and the receiver, a certain amount of water remains in the compressed air. Ideally, with a cooling method such as chilled fluid and a Mark II behind the Mark I more water could be removed prior to the water getting into the receiver. My air use simply doesn't justify such a system. My Mark I column removes so much heat from the airstream, the air entering the receiver is only a few degrees warmer than ambient air temperature. When the ambient temperature drops below 50° some more water condenses in the receiver. Ideally, this is drawn off by an autodrain. Generally, it isn't all removed, and some moisture enters the shop piping system.
This remaining moisture is far more difficult to remove. I've found secondary columns pretty effective in the removal, PROVIDED the geometry of the column is kept in the same ratio as the Mark I column. Ideally, I employ a secondary receiver after the secondary column primarily to act as a buffer tank in the airstream. 20# propane tanks serve ideally for this purpose. Locating the buffer tank above the airline and column provides the best efficiency, since any moisture reaching the buffer tank drains into the sump of the secondary column especially when air isn't being drawn off of the tank.
The secondary columns I build are made from 1½" pipe 24" long. I use a 3/8 elbow as the inlet and 3/8 pipe size for the outlet. Air can be used directly from the top of the secondary column, or it can be further treated. In the refining business, seperators that function similarly to the Franzinator column are employed, followed by an additional unit called a polisher. While the actual piping in a refinery is probably far more sophisticated, I thought I'd give the idea a try. Polishing offers an opportunity to accomplish a couple things. The first is allowing the system to have another place for any compressed air to rest, cool, and deposit it's moisture on a cold surface. The second is adding cubic feet of capacity to the volume of stored compressed air.
egon - June 4, 2007 10:04 PM (GMT)
JT Metalworks - June 4, 2007 11:23 PM (GMT)
That tsunami design is essentially how my last aftercooler was made. It worked pretty good.
The area on the outer wall, where the tube was inside, was extremely hot; while the outlet tube was cool to the touch.
I still got a fair bit of condensate in the main tanks, but it was always dry at the tool.
I haven't decided what I'm going to do for my new IR. I found out it has a bad check valve, so I need to break into the plumbing where a cooler/separator would go anyways.
Franzİ - June 5, 2007 03:15 AM (GMT)
JT look up "Air Genie" I think WW Grainger still handles them. It replaces the check valve at the receiver.
The Genie vents the compressor to atmousphere for a couple seconds at startup so starting load on the motor is way less. Also minimizes torque loads on both the compressor and motor shafts.
Doesn't cost much more than a regular check valve, and is available from 1/4" pipe size up to 2" pipe size.
JT Metalworks - June 5, 2007 01:30 PM (GMT)
I picked one up. Looks like a slick little device.
I actually have an unloader valve on the pressure switch, and would only need to add a check valve with a port for it - but skipping all the fittings, let alone the time it would take to rig up the copper tubing was well worth the extra $8.
Franzİ - June 5, 2007 03:15 PM (GMT)
Load Genie is a little different from the unloader on the switch.
The switch unloader will be closed before the compressor makes a full revolution, ergo HIGH starting load.
The Genie stays open till the compressor is at speed ergo low starting loads. The $8- difference comes back real quick in longer machine life and for commercial power users lower demand charges.
JT Metalworks - June 5, 2007 11:08 PM (GMT)
I beg to differ Franz...
The vent port on the air genie is approximately 1/32". All it's doing is venting pressure when the pump is stopped, which is exactly what the unloader switched valve is doing. Otherwise, the genie is performing the same function as the check valve normally would.
It's a neat design, but it isn't magically saving machine life or electricity.
Franzİ - June 6, 2007 02:39 AM (GMT)
JT, read the damn Load Genie literature!
The vent port on the load genie only closes when the pressure from the compressor reaches a certain point, best I recall it's 30psi.
Then again, maybe you bought one of their controllers for a gas engine machine.
JT Metalworks - June 6, 2007 03:01 AM (GMT)
There's no indication of pressure needed to operate the valve, but it does have cfm requirements. This one is 15-46 cfm (or something close).
The first one I got decided to bind when I screwed it into the tank. Apparently, the body isn't very thick, so when I seated it to where I would normally thread a permanant fitting, it distorted and now hinders the movement of the valve. Time for a second attempt.
deadbodyman - April 25, 2009 03:43 AM (GMT)
Thats a lot more complicated than mine,I'll read it again and try to understand
deadbodyman - April 25, 2009 03:47 AM (GMT)
Man these are some old posts ,its all new to me but its all been said and done for you guys ,good information ,my seperators gonna git some modifications
deadbodyman - September 23, 2009 03:02 AM (GMT)
Franz that seperator of yours works better than the one I paid300.00 for Thanks I owe ya one
duke46 - July 10, 2011 09:52 PM (GMT)
Hi guys, After much info was given by a heck of a member I decided to re-work what I had did a few years back that worked ok I guess but just good enough and I also have another compressor that I am setting up for heavy blasting and then I will build the proper Franzinator + the smaller one for it.
First I had added the extra coils of copper and the fan and the fan would come on when the compressor would. Then I had a brain storm and built the water trap from the T down. It helped a lot also
Well after getting all the info I needed between this forum and another one + some help from an old short lived telephone splicer I did a swap around and changed the T direction and added the pipe above it and then to the tank.
Got it all plumbed back in and fired my compressor back up. Got my IR gun and took readings. The pipe stayed the same temp as my tank and I could follow the head from the compressor head through the copper coils and could see it dropping. After it shut off I drained about 1oz of water out of it. I had around 80 lbs of air in my 80 gal tank so to get that much water out in a short time was good I think.
So here is a picture of one heck of a mess after I had to relocate things like the copper tubing and it didn't want to bend worth a darn after being around so long.
This is made with 1 1/2 pipe and the added top is 1 1/4" Our Lowe's does not sell 1 1/2 any more :( so had to go with what they had.
The next ones will be built according to the org design.
Franzİ - July 11, 2011 05:16 AM (GMT)
Duke, is that coil of copper coming directly from the compressor or from the receiver the compressor is mounted on.
BTW, as a copper lover yourself I'm sure you remember one of the properties of copper being that it only likes to give off heat by conduction. Given that known, you need to get a lot of aluminum or steel fins on the coil to gain much from it.