I know we could try a bypass setup, but our 1HP pump from Murphy is a bit oversized for this and it would be better to just pump it in one pass into our fuel tank.
I just got off the phone with a rep for LMI pumps and was quoted some high prices for what he thought would be appropriate pumps $1700-2300. yikes!
Some useful info I took away from the conversation:
We should be looking for a continuous duty pump as we plan to push 350 gallon batches through 2 6' tall approx 16" dia fiberglass filter tanks at a max of 10gph. LMI makes a lot of pumps and apparently some of them are magnetically driven and perhaps not best suited for running 30 hours.
We need to figure out what pressure we need to pump, until we get our setup together and run a pressure test its just a guess at this point.
I was looking at these photos and accompanying info that Graydon posted a few years ago and in my conversation with the rep he said this pump would not be good for continuous duty. http://www.biodieselpictures.com/viewtopic.php?t=692
If pressure is higher than 30 PSI use an air diaphragm pump with a flow meter. We use this on all out 12 inch diameter and larger towers. Works very well. Very easy to rebuild if ever needed.
http://turnerbiodiesel.com/pumps scroll down the page to it to see specs
Around here, at the surplus store (princess auto) you can get nice bronze gear pumps for about 60 bucks, you can get a cheap Chinese VFD off ebay for less than 100 bucks and cheap 3phase motors(check any industrial surplus websites/stores) that will run from single phase power through the above mentioned drive. You could probably have a killer variable speed pump setup capable of high pressures for under 200 bucks.
Just a thought!
Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer
I am thinking this is for a dry wash system, and in that case pressure is actually not a good thing; what is needed is consistent flow rate. Metering pumps that go to the flow for dry wash systems aren't cheap,which is why I use a by-pass return to the tank where flow is controlled by leaving the return full open and cracking the flow valve (ball valve) just enough top get the rate I want.
Doesn't matter the flow rate of the pump itself as most of it returns to the tank unimpeded anyway; sort of the way return lines on a diesel engine work. The flow to the dry wash is controlled by the amount the ball valve is opened. To add pressure, if that is wanted, then throttle back the by pass valve a bit and that will automatically increase the pressure going to the dry wash flow.
** Biodiesel Glycerine Soap - The Guide
- on 5 continents helping people make & sell soap from the Biodiesel Glycerine.
I would think you could rig up a fairly cheap metering pump setup using a normal hydraulic gear pump turned at the appropriatly slow rate by a veriable speed DC motor. You would need to do a rough calculation on the actual flow needed and size the pump accordingly based on some max speed of the motor driving the pump. The motor can be one of the 1/4 HP 12 volt DC motors from harbor freight, or a surplus industrial 90 volt DC motor. Either can be speed controlled using a brute force veriable transformer (Variac) abd a four power diodes, or even a 90 volt DC motor and speed control electronics pulled from a salvage yard treadmill.
I use several small hydraulic gear pumps that are designed to pump the fuel for home oil furnaces, at 3400 rpm these can move over 10 G/H but I turn them VERY slowly using speed controlled vahicle windshield wiper motors, from 2 sec/rev down to 10 Seconds/rev, as metering pumps for my vegoil drip heater burners. I also turn one of these pumps up around 1500 rpm with a 12 volt DC motor and speed control electronics salvaged from a kids electric sidewalk scooter. The drip heater pumps run 24/7 durring the winter and the scooter motor unit ran for days at a time feeding my vegoil dewatering flash evaporator with 5 G/H vegoil at 150 pounds pressure.
I use s salvaged 1.5 HP treadmill motor and speed control to allow full torque adjustable speed of a drill press. The speed control has feedback of the actual speed to self-adjust the motor power as the load changes.
I'm with Tim Cook on this one - the larger oil furnace pumps are about the right size for a 10gph system. The pumps are usually still in good shape when a furnace is scrapped, so a used one ought to be cheap if you can find one.
Adding a low-pressure pressure relief valve will address the limitations of a column - the built-in pressure relief valves inside furnace pumps are too high, although replacing the spring might work after some experimentation.
Furnace fuel pumps - I have replaced the spring and had them regulate pressure down to about 10 pounds but the internal pressure relief plunger has an "O" ring on it that causes some resistance to movment with this light of a spring, I ocasionaly had to bang the pump to get the plunger to close and make pressure. With any spring that would make 25 or more pounds pressure I had no problem. Some of these pumps have internal flow control devices that keep the pressure from building until the pump speed hits about 3000 rpm, these are adjusted for the thickness of fueloil so the pressure build switch point changes with the viscosity of the fluid being pumped. These internal flow controls can be eliminated fairly easily, I have to remove them for my slow speed meterng pumps. I can point to other discussions with this info if anyone is interested.